DOT/FAA/AR-05/22 

Office of Aviation Research 

Washington, D.C. 20591

Fundamental Studies of Titanium 

Forging Materials—Engine 

Titanium Consortium Phase II 

June 2005 

Final Report 

This document is available to the U.S. public 

through the National Technical Information Service (NTIS), 

Springfield, VA 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
NOTICE 

This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The 

United States Government assumes no liability for the contents or use 

thereof. The United States Government does not endorse products or 

manufacturers. Trade or manufacturers names appear herein solely 

because they are considered essential to the objective of this report. This 

document does not constitute FAA certification policy. Consult your local 

FAA aircraft certification office as to its use. 

This report is available at the Federal Aviation Administration William J. 

Hughes Technical Center's Full-Text Technical Reports page: 

actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). 
 Technical Report Documentation Page

1. Report No.

DOT/FAA/AR-05/22

2. Government Accession No. 3. Recipient's Catalog No.

5. Report Date 

June 2005 

 4. Title and Subtitle 

FUNDAMENTAL STUDIES OF TITANIUM FORGING MATERIALS—ENGINE 

TITANIUM CONSORTIUM PHASE II 6. Performing Organization Code

7. Author(s) 

F. J. Margetan1

, E. Nieters2, L. Brasche1, L. Yu1, A. Degtyar3, H. Wasan3, M. Keller2, 

and A. Kinney4

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

1

Iowa State University 

 Ames, IA 

2

General Electric Aircraft Engines 

 Cincinnati, OH 

3

Pratt & Whitney 

 400 Main Street 

 East Hartford, CT 06108 

4

Honeywell Engines, Systems & Services 

 111 S. 34th Street 

 Phoenix, AZ 85072 

11. Contract or Grant No.

DTFA0398FIA029

13. Type of Report and Period Covered

 

 Final Report

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Aviation Administration 

Office of Aviation Research 

Washington, DC 20591

14. Sponsoring Agency Code

ANE-110 

15. Supplementary Notes

Federal Aviation Administration William J. Hughes Technical Center COTR was Cu Nguyen, Technical Monitors were Paul 

Swindell and Rick Micklos. 

16. Abstract

Because of their relatively low density and high strength at elevated temperatures, titanium alloys are often used in the 

manufacture of rotating jet engine components. To ensure safe operation, these components are ultrasonically inspected to detect 

defects such as hard alpha inclusions. A fundamental understanding of the ultrasonic properties of such components is necessary 

to improve inspection protocols. This report discusses measurements of ultrasonic velocity, attenuation, and backscattered grain 

noise in representative forged engine disks of Ti-6-4 alloy, with emphasis on the grain noise that acts to limit flaw detectability in 

practice. The manner in which the measurements can be used to design improved ultrasonic inspections is discussed. Other 

topics include the relationship between ultrasonic properties and forging strain, the effect of surface curvature on inspectability, 

and tests of models that predict ultrasonic flaw signals and grain noise levels. The manufacture of a representative forged disk 

containing synthetic hard alpha defects and flat-bottomed holes is also discussed. 

17. Key Words 

Titanium forging, Ultrasonic inspection, Probability of 

detection, Ultrasonic attenuation, Ultrasonic grain noise

18. Distribution Statement 

This document is available to the public through the National 

Technical Information Service (NTIS), Springfield, Virginia 22161.

19. Security Classif. (of this report)

 Unclassified 

20. Security Classif. (of this page)

 Unclassified

21. No. of Pages

 219 

22. Price

Form DOT F1700.7 (8-72) Reproduction of completed page authorized 
iii/iv

ACKNOWLEDGEMENTS 

The authors would like to acknowledge the Federal Aviation Administration for the support in 

funding this project. 

Research Team: 

 Iowa State University: 

 Lisa Brasche 

 Pranaam Haldipur 

 Anxiang Li 

Frank Margetan 

Bill Meeker 

R. Bruce Thompson 

Linxiao Yu 

General Electric Aircraft Engines: 

David Copley 

 Mike Keller 

 Richard Klaassen 

 Lat Koo 

 Mike Gigliotti 

 Edward Nieters 

 Thadd Patton 

 Lee Perocchi 

 Pratt & Whitney: 

 

 Andrei Degtyar 

 Anton Lavrentyev 

 Kevin Smith 

 Jeff Umbach 

 Harpreet Wasan 

 Honeywell Engines, Systems & Services: 

 Waled Hassan 

 Andy Kinney 

 Joel Schraan 
v

TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY xix 

1. INTRODUCTION 1-1 

1.1 Purpose 1-1 

1.2 Background 1-1 

1.3 Program Objectives 1-2 

1.4 Related Activities and Documents 1-2 

1.5 Approach 1-3 

2. DISCUSSION OF RESULTS 2-1 

2.1 Ultrasonic Properties of Forgings and Their Implications for Forging 

Inspections 2-1 

2.2 Coupon Selection Based on Grain Noise C-Scans, Macroetch, and Forging

Strain Information 2-1 

2.2.1 Pratt & Whitney Disk 2-4 

2.2.2 Basic Measurements of Backscattered Noise Level, Velocity, and 

Attenuation in the Forging Flow Line Coupons 2-24 

2.2.3 Relationship Between UT Properties and Forging Strain 2-33 

2.2.4 Identification of the High-Noise Coupons and Measurements of 

Grain Noise FOM 2-47 

2.2.5 Determination of Pulse Volume for #1/2 FBH Detection Sensitivity 2-55 

2.2.6 Other Measurements on the Forging Flow Line Coupons 2-61 

2.2.7 Summary 2-78 

2.3 Effect of Surface Curvature on Inspectability 2-81 

2.3.1 Effect of Surface Curvature on FBH Amplitudes 2-81 

2.3.2 Effect of Surface Curvature on Backscattered Grain Noise 2-87 

2.3.3 Summary 2-113 

2.4 Synthetic Inclusion Disk 2-115 

2.4.1 Approach 2-115 
vi

2.4.2 Results and Discussion 2-116 

3. SUMMARY 3-1 

4. REFERENCES 4-1 

APPENDICES 

A—Results of Backscattered Noise and Attenuation Measurements for the 

Forging Flow Line Coupons 

B—Synthetic Inclusion Disk Backscattered Noise C-Scans 

C—Ultrasonic Test Specimens 
vii

LIST OF FIGURES 

Figure Page 

1-1 Types of Property Measurement (or Forging Flow Line) Coupons 1-4 

1-2 Basic Geometry of Specimens Used to Study the Effect of Surface Curvature on 

Disk Inspections 1-5 

2-1 Examples of Possible Property Measurement Coupon Sites and Geometries 2-2 

2-2 Possible Shear-Wave Attenuation Measurement Setups 2-3 

2-3 Preferred Locations in Forgings for Property Measurement Blocks 2-3 

2-4 Computer-Aided Drawings of the P&W-Supplied Forged Disk 2-4 

2-5 Cross Section of the Sonic Shape of the P&W-Supplied Forging, With Inspection 

Surfaces Indicated 2-5 

2-6 Macroetch for the P&W-Supplied Forging 2-5 

2-7 Results of a DEFORM Calculation for the P&W Forging Showing How Small 

Circular Elements in the Billet are Deformed by the Forging Process 2-6 

2-8 Backscattered Noise C-Scan for the Shallowest Zone (0.20′′-0.56′′) Below Surface 

1 of the P&W Forging 2-7 

2-9 Backscattered Noise C-Scan for the Third Zone (1.54′′-2.21′′) Below Surface 2 of 

the P&W Forging 2-8 

2-10 Backscattered Noise C-Scan for the Fourth Zone (2.37′′-3.08′′) Below Surface 3 

of the P&W Forging 2-8 

2-11 Average Noise Levels in the High-Noise Regions of the P&W Forging 2-9 

2-12 Average and Peak Noise Levels for High-Noise Regions of the P&W Forging 2-9 

2-13 Ratio of Average Noise Levels in High- and Low-Noise Regions of the P&W 

Forging 2-10 

2-14 Ratio of Peak to Average Noise as a Function of Depth in the P&W Forging 2-10 

2-15 Sites for Eight Property Measurement Coupons Cut From the P&W-Supplied 

Forged Disk 2-11 

2-16 Radial-Axial Locations for the Eight Property Measurement Coupons in the 

P&W Disk, Superimposed on the DEFORM Strain Map From Figure 2-7(b) 2-11 
viii

2-17 General Appearance of the GE-Supplied Forged Disk Before the Bore Hole 

Was Cut 2-12 

2-18 Cross Section of the Sonic Shape of the GE-Supplied Forging 2-12 

2-19 Macroetch for the GE-Supplied Forging 2-13 

2-20 Results of a DEFORM Calculation for the GE Forging, Showing How Small 

Circular Elements in the Billet are Deformed by the Forging Process 2-13 

2-21 Relative Forging Strain Levels as Calculated by DEFORM for the GE Forging 

in Arbitrary Units 2-13 

2-22 Backscattered Noise C-Scan for the Shallowest Zone (0.06′′-0.6′′) Below Surface 

UG of the GE Forging 2-14 

2-23 Backscattered Noise C-Scan for the Second Zone (0.5′′-1.0′′) Below Surface UO 

of the GE Forging 2-15 

2-24 Sites for Property Measurement Coupons Cut From the GE-Supplied Forged Disk 2-15 

2-25 Average Noise Levels in the High-Noise Regions of the GE Forging 2-16 

2-26 Ratio of Average Noise Levels in High- and Low-Noise Regions of the GE 

Forging 2-17 

2-27 Ratio of Peak-to-Average Noise in the GE Forging 2-17 

2-28 Sites for Property Measurement Coupons Cut From the GE-Supplied Forged Disk 2-18 

2-29 General Appearance of the HW-Supplied Forged Disk 2-18 

2-30 Cross Section of the Sonic Shape of the HW Forging 2-19 

2-31 Macroetch of the HW-Supplied Forging 2-19 

2-32 Results of a DEFORM Calculation for the HW Forging, Showing How Small 

Circular Elements in the Billet are Deformed by the Forging Process 2-19 

2-33 Inspection Surfaces for the HW Forged Disk With Transducer and Setup Data 2-20 

2-34 Backscattered Noise C-Scan Acquired Through Surface D of the HW Forging 2-20 

2-35 Backscattered Noise C-Scan Acquired Through Surface F of the HW Forging 2-21 

2-36 Backscattered Noise C-Scan Acquired Through Surface A of the HW Forging 2-21 

2-37 Sites for Property Measurement Coupons Cut From the HW-Supplied Forged 

Disk 2-23 
ix

2-38 Coupon Locations for the HW-Supplied Forged Disk Superimposed on the 

DEFORM Strain Map 2-23 

2-39 Coupon Labeling Scheme for the GE-Supplied Ti-6-4 Forging 2-24 

2-40 Experimental Setup for Examining the Dependence of Backscattered Grain Noise 

on Position and Inspection Direction for Rectangular Ti-6-4 Forging Coupons 2-25 

2-41 Predicted Amplitudes for #1 FBH Echoes 2-26 

2-42 Pulse Volume Determination for the Focused Transducer Used in the Noise 

Measurements 2-27 

2-43 Backscattered Grain Noise C-Scans Through Four Surfaces of Coupon GE5 2-28 

2-44 Enumeration of the Eight Noise Measurements Categories for Each Forging 

Flow Line Coupon 2-28 

2-45 Peak and Average Noise Levels for the P&W Forging Coupons 2-29 

2-46 Peak and Average Noise Levels for the GE Forging Coupons 2-29 

2-47 Peak and Average Noise Levels for the HW Forging Coupons 2-30 

2-48 Setups Used for UT Velocity and Attenuation Measurements 2-31 

2-49 Measured UT Velocities for Propagation in the Radial (Through Side 1) and Axial 

(Through Side 2) Directions of the Forging Flow Line Coupons 2-32 

2-50 Measured Attenuation-Versus-Frequency Curves for Two Coupons From the HW 

Ti-6-4 Forging 2-33 

2-51 Measured UT Attenuation Values at 10 MHz for the Forging Flow Line Coupons 2-34 

2-52 In the Absence of Recrystallization, the Shapes of Macrograins in a Forging Will 

Vary With Position Due to the Varying Strain Levels 2-35 

2-53 DEFORM Calculation for the P&W Forging, Beginning With 5:1 Elliptical 

Volume Elements in the Billet 2-36 

2-54 Output of the DEFORM Calculation for the HW Forging, Beginning With 5:1 

Elliptical Volume Elements in the Billet 2-36 

2-55 Strain Diagram for the P&W Ti-6-4 Forging, Beginning With 5:1 Ellipses in the 

Billet Aligned With the Billet Axis 2-37 

2-56 Measured Properties of the Elliptical Macrograins in Forging Strain Maps, as 

Calculated Using DEFORM 2-38 
x

2-57 Definition of the Ellipse Projection Ratio for a Forging Macrograin, as Calculated 

Using DEFORM 2-38 

2-58 Correlation Between Grain Noise Anisotropy and Ellipse Projection Ratio for the 

P&W Forging 2-39 

2-59 Correlation Between Grain Noise Anisotropy and Ellipse Projection Ratio for the 

HW Forging 2-39 

2-60 Correlation Between Grain Noise Anisotropy and Ellipse Projection Ratio for the 

GE Forging, Beginning With Circular Macrograins in the Billet 2-40 

2-61 Measured and Fitted Grain Noise FOM Curves for the Lower Right Quadrant of 

Forging Coupon PW8, Assuming Macrograins With 7:1 Aspect Ratios in the 

Billet 2-42 

2-62 Measured and Predicted Grain Noise FOM Curves for Inspections Through Sides 

4 and 5 of Forging Coupon PW2, Based on Model Parameters Deduced by Fitting 

to Noise Data From Coupon PW8 2-42 

2-63 Measured and Predicted Average GPN Amplitudes for the Various Quadrants of 

the Forging Flow Line Coupons From the P&W Forging 2-43 

2-64 Gated-Peak Grain Noise C-Scan Image Resulting From a Rotational-Axial Scan 

of the Cylindrical Coupons From the High-Strain Regions of the Three Ti-6-4 

Forgings 2-44 

2-65 Comparisons of Measured and Predicted Angular Profiles for Backscattered Grain 

Noise in the Cylindrical Coupon From the Web Region of the P&W Ti-6-4 

Forging 2-45 

2-66 Measured and Predicted Average Gated-Peak Grain Noise Amplitudes for 

Various Quadrants of the Forging Flow Line Coupons From the P&W Forging 2-46 

2-67 Relationships Between Noise Anisotropy, Attenuation Anisotropy, and Total 

Forging Strain for Coupons Cut From Various Locations in OEM-Supplied Ti-6-4 

Forged Engine Disks 2-48 

2-68 Relationship Between Velocity Anisotropy and Local Total Forging Strain for 

Ti-6-4 Forging Flow Line Coupons 2-48 

2-69 Location and Backscattered Grain Noise C-Scan for the Highest-Noise Coupon in 

the GE-Supplied Ti-6-4 Forging 2-49 

2-70 Location and Backscattered Grain Noise C-Scan for the Highest-Noise Coupon in 

the P&W-Supplied Ti-6-4 Forging 2-49 
xi

2-71 Location and Backscattered Grain Noise C-Scan for the Highest-Noise Coupon in 

the HW-Supplied Ti-6-4 Forging 2-50 

2-72 Measured Attenuation Values and Power-Law Fit for the HW High-Noise 

Coupon 2-51 

2-73 The rms Backscattered Grain Noise Level Within the High-Noise HW Forging 

Coupon 2-52 

2-74 Deduced Grain Noise Capacity (FOM) for the High-Noise HW Forging Coupon 2-52 

2-75 Measured FOM Curve and Associated Power-Law Fit for the Highest-Noise 

Depth Zone Within the High-Noise Coupon From the HW Ti-6-4 Forging 2-53 

2-76 Measured Grain Noise FOM Values, as Functions of Frequency, for the GE and 

P&W High-Noise Forging Coupons 2-54 

2-77 Rule of Thumb Relating S/N Ratio to UT PV 2-56 

2-78 Noise-to-Signal Data for Three Ti Forging Specimens Used to Test the PV Rule 

of Thumb 2-57 

2-79 Noise-to-Signal Measurements for the Three High-Noise Forging Coupons 2-58 

2-80 Beam Diameter Determination for the 10-MHz F6 Transducer Focused at the 

FBH Depth 2-59 

2-81 Pulse Duration Determination for the 10-MHz F6 Transducer Focused at the FBH 

Depth 2-59 

2-82 Peak N/S vs the Square Root of PV for Measurements Performed on the HighestNoise Coupons Cut From the Three OEM-Supplied Ti-6-4 Forgings 2-60 

2-83 Inspection Direction Labels for Measurements by P&W Personnel 2-62 

2-84 Longitudinal Velocities for the Seven Rectangular P&W Forging Flow Line 

Coupons 2-63 

2-85 Average Longitudinal Attenuation Values at 10 MHz for the Seven Rectangular 

P&W Forging Flow Line Coupons 2-64 

2-86 Noise A-Scans for Axial Beam Propagation at Nine Positions in Coupon PW1 2-65 

2-87 (a) Measured rms Noise Curves, as Functions of Time Relative to the Front-Wall 

Echo (t=0), for the Seven Rectangular P&W Forging Coupons and (b) Tabular 

Comparisons of Measured and Predicted GPN Quantities 2-66 

2-88 Measured Absolute rms Noise Levels at a Depth of 0.7′′ for the Seven P&W 

Forging Flow Line Coupons 2-67 
xii

2-89 Measured Attenuation and FOM Values for Axial Beam Propagation in the Seven 

P&W Forging Flow Line Coupons 2-68 

2-90 Comparison of Two Measures of Backscattered Grain Noise Levels in the P&W 

Forging Flow Line Coupons 2-69 

2-91 Micrographs of the Surface Perpendicular to the Axial Direction for P&W 

Forging Coupons PW1 and PW8 2-69 

2-92 Number of Alpha-Phase Grain Aggregates per Unit Length, as Deduced From 

Micrographs of the Hoop, Radial, and Axial Surfaces of the P&W Forging 

Coupons 2-70 

2-93 Back-Wall Amplitude C-Scans of Three Ti-6-4 Forging Flow Line Coupons 

Acquired Using a 10-MHz Planar Transducer 2-71 

2-94 Experimental Setup for Attenuation Measurements 2-72 

2-95 Measured Amplitudes and Phases in Beam-Mapping Scans of a FQ Block and 

Ti-6-4 Forging Coupon HW7 2-73 

2-96 Attenuation Curves at Sites Having Strong and Weak Back-Wall Echoes in the 

HW7 Forging Coupon 2-74 

2-97 Measured Attenuation of Ti-6-4 Forging Coupon HW7 as Deduced From P/E 

Back-Wall Scans and From the TT Method 2-75 

2-98 Measured Attenuation of Ti-6-4 Forging Coupons PW2 and GE4 as Deduced 

From P/E Back-Wall Scans and From the TT Method 2-75 

2-99 Categories of UT Pressure-Field Distortions Treated in Signal Fluctuation Models 2-76 

2-100 Measured and Predicted Back-Wall Echoes and Spectra at Three Locations in a 

2′′ Thick Ti Alloy Billet Specimen 2-77 

2-101 Calculated Responses From 20-mil-Diameter FBHs Located Below Flat and 

Curved Surfaces in Ti-6-4 Forging Material (Beam Focused Near Surface) 2-83 

2-102 Calculated Responses From 20-mil-Diameter FBHs Located Below Flat and 

Curved Surfaces in Ti-6-4 Forging Material (Beam Focused Below Surface) 2-83 

2-103 Geometry of the Flat R88DT Curvature Correction Block 2-84 

2-104 Geometry of the R88DT Curvature Correction Block With a 10′′ Convex 

Curvature 2-85 

2-105 Geometry of the R88DT Curvature Correction Block With an 8′′ Concave 

Curvature and Pertinent Dimensions for the Other Concave Blocks 2-85 
xiii

2-106 Relative Efficiency Factors for Three Transducers Used for Measurements on the 

Curvature Correction Blocks 2-86 

2-107 Utrasonic Peak Responses From #1 FBHs in the Flat Curvature Correction Block 2-87 

2-108 Gains Required to Compensate for Surface Curvature as Measured Using a Set of 

Curvature Correction Blocks and Three Different Transducers 2-88 

2-109 Positions of the Noise Curvature Blocks Relative to the Original P&W Forging 2-89 

2-110 Appearances of the Six Noise Curvature Blocks and Regions Used for Subsequent 

Grain Noise Measurements 2-90 

2-111 Preliminary C-Scans Showing Gated-Peak Grain Noise Levels Measured 

Through the Flat Surfaces of the Six Noise Curvature Blocks 2-91 

2-112 Experimental Setup for Noise Measurements Using the Noise Curvature Blocks 2-92 

2-113 Examples of Noise Data (a) Raw Noise A-Scan at One Transducer Position, 

(b) Measured and Smoothed rms Noise-Versus-Depth Curves, and (c) C-Scan 

Images for Four Depth Zones 2-93 

2-114 Comparison of Measured and Predicted rms Grain Noise Levels for Inspections 

Through the Flat Surfaces of the Six Noise Curvature Blocks Using a 2.4′′ 

Water Path 2-95 

2-115 Comparison of Measured and Predicted rms Grain Noise Levels for Inspections 

Through the Flat Surfaces of the Six Noise Curvature Blocks Using a 1.0′′ 

Water Path 2-95 

2-116 Measured and Predicted Average Amplitudes in GPN C-Scan Images 2-96 

2-117 Measured and Predicted Maximum Amplitudes in GPN C-Scan Images 2-97 

2-118 (a)-(b) Microstructure Difference Factors, as Functions of Depth, Measured 

Using Water Paths of 2.4′′ and 1.0′′, Respectively and (c)-(d) a More Detailed 

View of the Microstructure Correction Factors for Two of the Blocks 2-98 

2-119 Average GPN Amplitudes Seen in C-Scans Through the Flat Sides of the Noise 

Curvature Blocks 2-99 

2-120 Average GPN Amplitudes Seen in C-Scans Through the Flat Sides of the Noise 

Curvature Blocks at a 2.4′′ Water Path, Before and After Correction for 

Microstructural Differences Between the Blocks 2-99 

2-121 Radial Profiles of the Noise C-Scans Through the Flat Sides of the Noise 

Curvature Blocks 2-100 
xiv

2-122 Polynomial Fit to the Average Radial Noise Profile Observed Through the Flat 

Sides of the Noise Curvature Blocks (After Normalization) 2-101 

2-123 Raw rms Noise-Versus-Depth Curves as Measured Through the Curved 

Surfaces of the Noise Curvature Blocks 2-102 

2-124 Average and Peak Values of Noise Amplitudes in C-Scans for Inspections 

Through the Curved Surfaces of the Noise Curvature Blocks at 1′′ Water Path 2-103 

2-125 Grain Noise Attributes for Measurements Through the Upper Surfaces Before and 

After Corrections for Microstructural Differences Between Coupons 2-104 

2-126 Flow Chart for Noise Model Calculations 2-105 

2-127 Predicted Incident Absolute Pressure Amplitudes at 10 MHz Within Three of 

the Noise Curvature Blocks for the Transducer Used in the Experiments 2-105 

2-128 Examples of Measured and Simulated GPN C-Scans 2-106 

2-129 Role of the Noise SCL in Model Calculations of Synthetic C-Scan Images 2-107 

2-130 Predicted Absolute rms Noise Levels and rms Noise Ratios for Inspections 

Through the Upper Surfaces of the Noise Curvature Blocks at Two Water Paths 2-108 

2-131 Effect of Surface Curvature on rms Noise-Versus-Depth 2-109 

2-132 Comparison of Measured and Predicted GPN Statistics for Noise C-Scans 

Measured Through the Upper Surfaces at 1.0′′ Water Path and 57 dB Gain 2-110 

2-133 Comparison of Measured and Predicted GPN Statistics for Noise C-Scans 

Measured Through the Upper Surfaces at 2.4′′ Water Path and 57 dB Gain 2-111 

2-134 C-Scans Through the Upper Surfaces of the Noise Curvature Blocks, Showing the 

FBHs at 1.5′′ Depth 2-113 

2-135 Etched Macrostructure of an As-Forged Disk of the Selected Design 2-116 

2-136 The SID As-Purchased From the Supplier 2-117 

2-137 The SID After Skim-Cut Machining 2-117 

2-138 Typical C-Scan of Disk After Light Skim Cut to Characterize Structural Noise 2-118 

2-139 Statistical Distribution of Seed Velocities 2-121 

2-140 Identification of Inspection Surfaces 2-121 

2-141 Approximate Dimensions of the SID in its Final Machined Form 2-122 
xv

2-142 C-Scan Images (Through Surfaces UH, UJ, UK, UL, and UM) of the SID 

After EDM Slicing 2-122 

2-143 Drilling Surface for Seed Targets 2-123 

2-144 An SID With Seed Holes Drilled 2-123 

2-145 Seed Locations as Viewed From Forward Side 2-124 

2-146 Seed Locations as Viewed From Aft Surface 2-124 

2-147 Placement of an SID Seed Into an Empty Hole 2-125 

2-148 Two Seeds in the SID 2-125 

2-149 An SID Cross Section With Embedded Seeds 2-126 

2-150 An SID Cross Section Showing Approximate Radial Positions of Embedded 

Seeds and FBHs 2-126 

2-151 Flat Bottom Hole Locations, Viewed From Aft Side 2-127 

2-152 Seed and FBH Locations, Viewed From Forward Side 2-128 
xvi

LIST OF TABLES 

Table Page 

1-1 Types of Specimens Fabricated and Studied 1-3 

2-1 Backscattered Grain Noise Statistics for C-Scans of the HW Forged Disk 2-22 

2-2 Comparison of Average and Maximum GPN Voltages 2-30 

2-3 Comparison of UT Properties for the High-Noise Coupons From the P&W, GE, 

and HW Ti-6-4 Forgings 2-54 

2-4 Measured Sonic PV and Peak N/S Ratios for the Highest-Noise Coupons From 

the Three OEM-Supplied Ti-6-4 Forgings 2-60 

2-5 Zoned Inspection Scheme to Achieve #1/2 FBH Sensitivity Throughout 3.9′′ of 

Depth in Ti-6-4 Forging Material 2-61 

2-6 Measured and Predicted Spectral Amplitude Characteristics 2-78 

2-7 Typical Values of Measured and Predicted GPN Ratios 2-112 

2-8 Synthetic Hard Alpha Seed Dimensions and Longitudinal- and Shear-Wave 

Sound Velocities 2-119 
xvii/xviii

LIST OF ACRONYMS 

2D Two-dimensional 

DAC Distance-amplitude correction 

EDM Electron discharge machining 

ETC Engine Titanium Consortium 

FOM Figure of merit 

FQ Fused-quartz 

FBH Flat-bottom hole 

FSH Full-screen height 

GE General Electric Aircraft Engines 

GPN Gated-peak noise 

HIP Hot isostatic press 

HW Honeywell Engines, Systems & Services 

ID Inside diameter 

ISU Iowa State University 

N/S Noise-to-signal 

NAR Noise anisotropy ratio 

NDE Nondestructive evaluation 

Ni Nickel 

OD Outside diameter 

OEM Original equipment manufacturer 

P&W United Technologies Pratt & Whitney 

P/C Pitch/catch 

P/E Pulse/echo 

PoD Probability of detection 

PV Pulse volume 

RF Radio frequency 

rms Root mean square 

S/N Signal-to-noise 

SCL Spatial correlation length 

SID Synthetic inclusion disk 

Ti Titanium 

TT Through-transmission 

UT Ultrasonic 
xix

EXECUTIVE SUMMARY

The Engine Titanium Consortium (ETC) Phase II Fundamentals Studies team was asked to 

investigate the fundamental ultrasonic (UT) properties of representative Ti-6-4 engine forgings, 

to explore the relationship of those properties to forging microstructure (e.g., flow line 

geometry), and to determine how the UT properties and surface curvatures of forgings impact 

inspectability. The team was also asked to use its data to determine how forging inspections 

could be improved four-fold in amplitude (from #1 flat-bottom hole (FBH) detection sensitivity 

to #1/2 FBH sensitivity). The approach adopted by the team involved the fabrication and study 

of four classes of test specimens. 

The first class of specimens, referred to as either the property measurement or forging flow line 

blocks, consisted of 26 small coupons, primarily rectangular blocks, which were cut from 

representative Ti-6-4 forged engine disks, one disk being supplied by each of the three aircraft 

engine manufacturers who were consortium members. The coupons were preferentially cut from 

regions of high grain noise and spanned a wide range of microstructures, as revealed by flow line 

geometries (via macroetch) and forging strain patterns (via DEFORMTM calculations (a computer 

software program that is used to evaluate strain-to-cracking for hard alpha defects in typical 

billets and forgings)). UT velocity, attenuation, and backscattered grain noise levels were 

systematically measured. Velocity variations were small (typically less than 1%), but variations 

in attenuation (0.2 to 2.7 dB/inch at 10 MHz) and backscattered grain noise levels (factor of 10 

change) were significant. At a given location in a forging, the direction in which measured noise 

was greatest was generally the direction in which the measured attenuation was smallest. This 

maximal noise, minimal attenuation direction generally occurred for beam propagation 

perpendicular to the macrostructure elongation direction (i.e., the flow line direction). The 

attenuation and noise variations were found to be well correlated with the shapes and orientations 

of model macrograins, as deduced from DEFORM simulations of plastic flow during forging, 

and that relationship was exploited to formulate a reasonably accurate model, which can be used 

to predict grain noise variations within forgings. Additional measurements were performed on 

the three highest noise coupons (one from each forging). In one such study, #1 FBH were drilled 

and signal-to-noise (S/N) ratio measurements were performed using several 10-MHz transducers. 

An expected relationship between S/N and the UT pulse volume was found to hold. Based on 

that relationship, it was determined that a 10-MHz forging inspection, which meets the #1/2 FBH 

sensitivity target, requires a beam diameter that does not exceed about 45 mils at any depth 

within a given inspection zone. 

Some sound-entry surfaces for forging inspections are curved, and the curvature modifies the 

interrogating sound beam, affecting both defect signal amplitudes and backscattered grain noise 

levels. To study these effects, two sets of blocks were fabricated. The first set, known as 

curvature correction blocks, were made from an ultrasonically neutral material (powder nickel 

alloy R88DT) and contained #1 FBHs at a series of depths. These blocks were used to study the 

effect of surface curvature on defect (FBH) echoes in the near absence of backscattered noise. 

The second set, known as the noise curvature blocks, were cut from a representative Ti-6-4 

forging and were used to study the effect of surface curvature on backscattered grain noise 

characteristics. Each set consisted of six blocks, with each block having a different concave or 

convex cylindrical curvature on its upper (sound-entry) surface. Three of the blocks in each set 
xx

had concave radii of curvature (0.75′′, 2.0′′, and 8.0′′), two had convex radii (4.0′′ and 10.0′′), and 

one block had a flat upper surface. Measurements of FBH amplitudes (in the curvature 

correction blocks) and backscattered grain noise properties (in the noise curvature blocks) were 

performed following typical 10-MHz inspection practices. The surface curvature had a strong 

influence on observed FBH amplitudes and grain noise levels. Results were found to be in 

generally good agreement with the predictions of Iowa State University models, indicating that 

the models can be used to estimate curvature corrections for both defect signal amplitudes and 

backscattered grain noise levels. 

The final specimen fabricated by the Fundamental Studies group was the synthetic inclusion disk 

(SID). This was constructed by taking a representative Ti-6-4 forged disk, slicing it in a plane 

perpendicular to the axis of rotational symmetry, inserting artificial defects, and then HIPping 

the two halves of the disk back together. The seeded internal defects were 40 synthetic hard 

alpha inclusions of two nominal sizes and two nitrogen impurity levels. These defects were 

cylindrical in shape, with the length along the cylinder symmetry axis nominally equal to the 

diameter. Nominal diameters (or lengths) were either 3/64′′ or 5/64′′, denoted here as #3 and #5 

respectively, using the usual notation for specifying FBH diameters in increments of 1/64′′. The 

two nitrogen impurity levels used for the defects, namely, 3% and 17% nitrogen by weight, are 

typical of those seen in the halo and core regions, respectively, of real hard alpha defects. The 

inclusions with the smaller diameter and smaller impurity level were expected to produce UT 

echoes of similar amplitude to #1/2 FBHs. After assembly and HIPping, 18 FBHs were drilled 

into the SID to serve as additional reference reflectors. After fabrication, the SID was forwarded 

to another ETC Phase II team for use in assessing various inspection methods aimed at achieving 

#1/2 FBH detection sensitivity. 

The research activities summarized in this report were the basis for seven scientific papers 

written for the open literature. 
1-1

1. INTRODUCTION. 

1.1 PURPOSE. 

The complex microstructures of titanium (Ti) alloys typically used in aircraft engine forgings can 

significantly modify the signal strength from flaws and produce competing backscattered noise 

signals, which interfere with the detection of the flaws [1]. An understanding of ultrasonic (UT) 

wave propagation in these systems is needed to guide the development and application of 

inspection systems with the highest possible sensitivity, to develop algorithms to most accurately 

interpret the acquired data, and to provide a basis for evaluating their capability, e.g., in the 

determination of probability of detection (PoD). 

1.2 BACKGROUND. 

Phase I of the Engine Titanium Consortium (ETC) effort focused on developing a solid 

fundamental understanding of the nondestructive evaluation (NDE) characteristics of Ti jet 

engine alloys and the effect of microstructure on the detectability of defects such as hard alpha 

inclusions. Cylindrical Ti billets typically contain columnar macrograins that tend to align with 

the billet axis and have dimensions on the order of several millimeters. The macrograins 

themselves are comprised of much smaller micrograins, which have preferred orientations for 

their crystalline axes. Fundamental property measurements were performed in Phase I to 

investigate the effects of that micro- or macrostructure on UT beam propagation. In those 

measurements, rectangular coupons were cut from representative Ti-17 and Ti-6Al-4V billets, 

and sonic beams were propagated through the coupons in the radial, axial, and hoop directions. 

For each propagation direction, three UT quantities were measured: 

• Velocity, which determines the rate of beam focusing and diffraction; 

• Attenuation, which describe the rate of decay of beam strength with penetration depth; 

• Noise figure of merit (FOM), which describes the capacity of the microstructure for 

generating backscattered grain noise. 

It was found that the direction of beam propagation relative to the billet macrostructure had a 

profound influence on the basic UT properties and, hence, on inspectability [2, 3, 4, and 5]. For 

example, grain noise levels were typically an order of magnitude smaller for propagation in the 

axial direction than in the radial or hoop direction. The columnar macrostructure was also found 

to distort the incident sonic beam, leading to significant excess signal attenuation and fluctuation 

effects. The severity of the distortion depended upon the beam propagation direction relative to 

the macrograin elongation direction, with the greatest distortions occurring when the beam 

traveled parallel to the elongation. In billet inspections, beam propagation is generally radially 

inward, approximately perpendicular to macrograin elongation; hence, beam distortion effects 

are minimized, but backscatter noise levels tend to be large. 

Flow lines in forged components are the counterparts of the elongated columnar macrograins in 

billets. It is, consequently, expected that the basic UT properties of forgings will depend 

strongly on the direction of sound propagation relative to the local flow line geometry. 
1-2

Fundamental property measurements are thus needed to quantify the effects of forging 

microstructure on beam propagation and the corresponding effect on inspectability. In addition, 

the surface curvatures of forgings are more complex than those of billets, requiring 

measurements to determine the effects of curvature variations on flaw signal amplitudes, grain 

noise levels and signal-to-noise (S/N) ratios. The UT property data is critical to determining the 

sensitivity and PoD of forging inspections. The data will be used to test aspects of the inspection 

simulation models developed under other ETC subtasks. The combined experimental and 

theoretical understanding of UT wave propagation in titanium forgings will provide the basis for 

the design of forging inspection systems with improved sensitivity and for the assessment of 

their capabilities as needed for life management studies. 

1.3 PROGRAM OBJECTIVES. 

The objectives of this program were 

• to gain the fundamental understanding of the UT properties of Ti forgings that is needed 

to provide a foundation for the development of reliable inspection methods that provide 

uniformly high sensitivity throughout the forging envelope. 

• to acquire the data necessary to relate the detectability of defects in forgings to 

component properties (i.e., flow line characteristics and surface curvature) and defect 

properties (i.e., size, shape, composition, location, and orientation) thereby providing a 

foundation for the design of improved inspections and the evaluation of inspection 

capability. 

1.4 RELATED ACTIVITIES AND DOCUMENTS. 

The ETC was established in 1993 and includes Iowa State University (ISU), General Electric 

Aircraft Engines (GE), Honeywell Engines, Systems & Services (HW), and Pratt & Whitney 

(P&W) in a partnership to perform research that contributes to improvements in flight safety. 

The Phase I program, which was completed in 1998, led to improvements in production 

inspection of Ti billet [6], improved physics models for UTs [7 and 8], and a feasibility study for 

phased array for UT inspection of billets [9]. In-service inspection efforts led to a commercially 

available portable scanner [10] and eddy-current probes [11], as well as improved probe designs 

[12] and eddy-current probe design tools [13]. Considerable progress was also made in 

development of a new approach [14] to quantifying inspection performance as reported in an 

Federal Aviation Administration (FAA) report “A Methodology for the Assessment of the 

Capability of Inspection Systems for Detection of Subsurface Flaws in Engine Components” 

[15]. A sound understanding of the manner in which the UT properties of Ti alloys affect billet 

inspections was developed during ETC Phase I, as detailed in a lengthy FAA report, 

“Fundamental Studies: Inspection Properties for Engine Titanium Alloys” [16]. 

The work summarized in this report was performed under ETC Phase II Fundamental Property 

Measurements for Titanium Forgings. The research results and the fabricated specimens were 

made available to two companion ETC Phase II research teams: Inspection Development for 

Titanium Forgings used the UT property data and specimens in the design and testing of 

improved forging inspections, and PoD of Ultrasonic Inspections of Titanium Forgings was to 
1-3

have used the UT property data in critiques of forging inspection schemes and probability of 

detection calculations, but that subtask was later suspended. 

1.5 APPROACH. 

The approach for this research effort consisted of the fabrication and study of the four classes of 

test specimens listed in table 1-1, which are briefly discussed below. Section 2 gives a more 

detailed discussion of the fabrication and uses of the test specimens. 

TABLE 1-1. TYPES OF SPECIMENS FABRICATED AND STUDIED 

Nomenclature 

Number of Specimens 

(Alloy) Uses 

Property measurement 

blocks (or forging flow 

line coupons) 

26 

(Ti-6-4) 

Measurement of basic UT properties of 

representative Ti-6-4 engine forgings. 

Study of the relationship between 

properties and forging flow lines 

(localized strain). Determination of sonic 

pulse volume requirements for improved 

forging inspections. 

Curvature correction 

blocks 

6 

(nickel alloy R88DT) 

To measure the effect of surface 

curvature on defect signal amplitudes and 

to test models that predict curvature 

correction factors for defect amplitudes. 

Noise curvature blocks 6 

(Ti-6-4) 

To measure the effect of surface 

curvature on backscattered grain noise 

levels and to test models that predict 

curvature correction factors for grain 

noise. 

Synthetic inclusion 

disk 

1 

(Ti-6-4) 

Full-round disk with internal flaws (FBHs 

and synthetic hard alpha inclusions) for 

assessing various forging inspection 

methods. 

FBH = Flat-bottom hole 

The first class consisted of small coupons, primarily rectangular prisms, cut from representative 

Ti-6-4 forged engine disks. Each of the three aircraft engine manufacturers (P&W; GE; and 

HW) supplied one forging for this purpose, and a total of 26 coupons were cut from high-noise 

regions of these forgings. These coupons are referred to as either property measurement or 

forging flow line specimens, and they were used to measure fundamental UT properties 

(velocity, attenuation, and backscattered grain noise) for typical Ti-6-4 forgings. Most of the 

property-measurement coupons were rectangular blocks, as illustrated in figure 1-1(a), with one 

face perpendicular to the beam propagation direction for a standard, normal-incident, 

longitudinal-wave disk inspection. However, one coupon from each disk was a cylinder, which 

was used to study the angular dependence of backscattered grain noise, as illustrated in 
1-4

figure 1-1(b). Since the coupons were cut at various angles to the forging flow lines (or local 

macrograin orientation direction), the relationship between UT properties and the directionality 

of the local disk microstructure could be studied. After basic UT measurements were completed 

on the suite of coupons, additional studies were performed using the three highest noise coupons 

(one from each disk), since high-noise regions generally pose the greatest inspection challenge. 

These latter studies were used to determine beam focal requirements for improving disk 

inspections from #1 FBH to #1/2 FBH sensitivity. 

Rectangular Cylindrical

Traditional

Inspection

Direction

or macrograin elongation direction

(a) (b)

Rectangular Cylindrical

Traditional

Inspection

Direction

Flow line or macrograin elongation direction

(a) (b)

FIGURE 1-1. TYPES OF PROPERTY MEASUREMENT (OR FORGING 

FLOW LINE) COUPONS 

Two classes of specimens were fabricated to study the effect of surface curvature on disk 

inspections. Both classes have the basic geometry shown in figure 1-2, i.e., a group of FBHs 

located below a curved entry surface. Specimens with both convex and concave upper surfaces 

were fabricated. Six specimens known as curvature correction blocks were made from an 

ultrasonically neutral material, i.e., fine-grained nickel (Ni) alloy R88DT. These were used to 

measure the effect of surface curvature on defect signal amplitudes and to test models that 

predict curvature correction factors for defect amplitudes. The R88DT material was chosen so 

that the effect of surface curvature on FBH amplitudes could be studied in the near absence of 

backscattered grain noise. 

To complement the curvature correction blocks, a second set of six blocks with curved upper 

surfaces were machined from a Ti-6-4 forged disk. These are referred to as noise curvature 

blocks and were primarily used to measure the effect of surface curvature on backscattered grain 

noise levels. The measurements were used to test the predictions of inspection simulation 

models that predict curvature correction factors for grain noise. 
1-5/1-6

FBH’s

Initial Shape

B

A

C

D

E

- 2”

- 4”

flat

4”

2”

Surface 

Basic Shape Progression

Types of

Upper Surfaces

concave

convex

FBH’s

Initial Shape

B

A

C

D

E

- 2”

- 4”

flat

4”

2”

Surface 

Basic Shape Progression

Types of

Upper Surfaces

concave

convex

FIGURE 1-2. BASIC GEOMETRY OF SPECIMENS USED TO STUDY THE EFFECT OF 

SURFACE CURVATURE ON DISK INSPECTIONS 

The final specimen fabricated under this effort was the Synthetic Inclusion Disk (SID). This was 

constructed by taking a representative Ti-6-4 forged disk, slicing it in a plane perpendicular to 

the axis of rotational symmetry, inserting artificial defects, and then hot isostatic pressing (HIP) 

the two halves of the disk back together. Internal defects were either FBH reflectors or spherical 

inclusions of synthetic hard alpha material. The SID was primarily fabricated for use in a 

companion Phase II study, Inspection Development for Titanium Forging, for assessing various 

forging inspection methods aimed at achieving #1/2 FBH sensitivity. 
2-1

2. DISCUSSION OF RESULTS. 

2.1 ULTRASONIC PROPERTIES OF FORGINGS AND THEIR IMPLICATIONS FOR

FORGING INSPECTIONS.

A chief goal of this study was to document the manner in which UT properties vary within 

representative Ti-6-4 forgings and to use that data to help design improved forging inspections. 

In particular, the Inspection Development for Titanium Forging intended to use the UT data to 

design forging inspections that improve defect detection sensitivity four-fold, from the current #1 

FBH level to a #1/2 FBH level. Since backscattered grain noise is primarily responsible for 

determining defect detection limits, an emphasis was placed on grain noise measurement and 

analysis. 

Each original equipment manufacturer (OEM) was asked to look through their inventory for 

potential forgings that could be used as sources for test samples. It was desired that the 

microstructures of the property measurement coupons be representative of the microstructures 

seen in typical forged engine components such as those studied in the Inspection Development 

for Titanium Forging. 

The OEMs supplied three typical forgings, and eight to ten coupons were cut from each. Coupon 

sites were chosen to provide a range of local microstructures based on backscattered noise, 

macroetch, and strain-map data. Measurements of UT longitudinal-wave velocity, attenuation, 

and backscattered noise were taken on the coupons and certain predictive models were 

developed to better understand the property data. The UT property data was also used to 

determine sonic beam-focusing requirements needed to achieve the # 1/2 FBH detection 

sensitivity target. This section describes that work. 

2.2 COUPON SELECTION BASED ON GRAIN NOISE C-SCANS, MACROETCH, AND

FORGING STRAIN INFORMATION. 

Coupon selection from each forging was based on four factors: part dimension, flow line 

information, backscattered UT noise C-scans, and model simulations of forging strain. Coupons 

cut from a forging had to be large enough to permit straightforward measurement of UT 

properties. Once suitable-sized forgings were identified, UT pulse/echo (P/E) inspections were 

performed to map out backscattered grain noise patterns. Since the high-noise regions are 

presumably harder to inspect, they were given priority in coupon selection. The OEMs also 

provided flow line information (macroetch photographs) so coupons could be selected from both 

high and low flow line density regions. In addition, each OEM worked with its respective 

forging supplier to acquire forging strain maps, as predicted using DEFORM software [17]. 

Prior to actual fabrication of the property measurement coupons, some general design 

methodologies were developed. The coupons were principally designed for measurement of 

longitudinal-wave properties in the axial-radial plane, which are the interest of the current study. 

However, the coupon geometry will also allow measurements of shear-wave properties in the 

axial-hoop plane. These may be of interest to future researchers. Figure 2-1 depicts a portion of 

a generic sonic shape disk, with possible coupon sites indicated. Four rectangular coupons 

(A, C, D, and E) are indicated, with each having an entry face perpendicular to the beam 
2-2

propagation direction for longitudinal-wave inspections (green arrows). The beam propagation 

direction for shear-wave inspections, if performed, is usually obtained by tilting the beam out of 

the plane of the page (e.g., into the Y Z plane for coupon E). 

...

...

...

...

CL

A C E

D

portion

of disk forging flow line

L-wave propagation

direction

...

...

...

...

CL

X (radial)

Y (axial)

Z (hoop)

A C E

D

portion

of disk forging flow line

L-wave propagation

direction

FIGURE 2-1. EXAMPLES OF POSSIBLE PROPERTY MEASUREMENT COUPON 

SITES AND GEOMETRIES 

As indicated in figure 2-1, it was desirable that coupons be cut from several locations in a 

forging with different local microstructures. Nearly all the coupons were chosen to be 

rectangular blocks with square cross sections in the radial-axial plane. This permitted 

comparative longitudinal-wave attenuation measurements to be performed for two propagation 

directions (e.g., axial and radial for coupon A) without complications arising from different 

thicknesses. In many cases, the two beam propagation directions were parallel and 

perpendicular, respectively, to the local flow lines. A small number of coupons with circular 

cross sections in the radial-axial plane were cut to better study the effect of flow line angle on 

backscattered noise. 

The rectangular coupons all had their longer dimension in the hoop direction. This design will 

permit future shear-wave attenuation measurements to be attempted using corner-trap echoes, as 

shown in figure 2-2 (left). If the use of corner-trap echoes proves to be problematic as is 

sometimes the case, a wedge could be cut (right) to facilitate shear-wave attenuation 

measurement. Both geometries shown in figure 2-2 have been used successfully in the past to 

measure attenuations in jet engine Ni alloys by comparison to a back-wall echo from a fusedquartz (FQ) reference block [18]. 

Inspections of Ti alloy forged disks typically reveal noise banding in the hoop (circumferential) 

direction, as illustrated in figure 2-3. In such cases, it was decided that property coupons would 

be cut from the high-noise regions of the disk, since defect detection is generally most difficult in 

such areas. 
2-3

FIGURE 2-2. POSSIBLE SHEAR-WAVE ATTENUATION MEASUREMENT SETUPS 

FIGURE 2-3. PREFERRED LOCATIONS IN FORGINGS FOR PROPERTY 

MEASUREMENT BLOCKS 

These design considerations guided coupon site selection in the OEM-supplied forgings. 

The following sections discuss how the coupon sites were specifically chosen for each of the 

three OEM-supplied disks. For the GE, P&W, and HW disks, in turn, the key elements of the 

data used in coupon selection will be displayed. The displayed materials include (1) drawings 

showing the axial-radial cross sections of each disk; (2) photographs of macroetches of the cross 

sections of nominally identical disks revealing flow line structures; (3) outputs of DEFORM 

calculations showing metal deformation during the forging process; and (4) selected examples of 

high noise quadrant

low noise quadran

h

t

igh noise quadrant

low noise quadrant

primary coupon sites

high noise quadrant

low noise quadran

h

t

igh noise quadrant

low noise quadrant

primary coupon sites

FQ Ti

BS1 CT1

45 shear wave

in metal

o

same water

path for both

Compare spectrum of corner-trap echo

 in Ti to that of back-wall echo in FQ

CT1

45 shear wave

in metal

Alternative

Geometry

Z (hoop)

Y (axial)

(typically)

o
2-4

C-scan images acquired by the OEMs during their respective inspections of the disks in question. 

The latter shows how backscattered noise levels vary with position within the forging. The 

specific coupon sites chosen for each forging will be indicated, and then the UT property 

measurements subsequently performed on the coupons themselves will be discussed. 

All the disk inspections performed to select coupon sites were focused-probe, normal incidence, 

P/E immersion inspections using longitudinal waves. It was noted that the three OEMs followed 

different protocols for inspecting disks, with each using different choices of transducers, 

inspection zones, and distance-amplitude correction (DAC) procedures. Thus, the noise C-scans 

supplied by different OEMs were not directly comparable to one another, although all could be 

used to infer the degree of noise banding and to identify the high-noise regions from which 

coupons were cut. After property measurement coupons were cut by the OEMs from their 

respective forgings, those coupons were shipped to ISU for UT measurements, which were all 

conducted following a uniform procedure. 

2.2.1 Pratt & Whitney Disk. 

The first disk considered was supplied by P&W. Figure 2-4 shows the general appearance of the 

disk (i.e., the sonic shape), and figure 2-5 shows the disk cross section with dimensional 

information. A macroetch of the cross section, revealing the flow line structure, is shown in 

figure 2-6. Figure 2-7 shows the results of a DEFORM simulation, which tracks plastic metal 

flow during the forging process. Small volume elements with circular cross sections in the 

radial-axial plane were specified in the billet blank, and these volume elements were then 

followed through the simulated forging process. As shown in figure 2-7(b), each circular 

element deformed into an ellipse, and areas of high forging strain have very elongated ellipses. 

FIGURE 2-4. COMPUTER-AIDED DRAWINGS OF THE P&W-SUPPLIED FORGED DISK 

(Its inner and outer diameters are approximately 4.2 and 17.8 inches, respectively.) 
2-5

FIGURE 2-5. CROSS SECTION OF THE SONIC SHAPE OF THE P&W-SUPPLIED 

FORGING, WITH INSPECTION SURFACES INDICATED 

FIGURE 2-6. MACROETCH FOR THE P&W-SUPPLIED FORGING 

Transducer: Nominal 3” focus, 3/8” diameter, 10 MHz Technisonic probe (N7135).

Surfaces: Three inspection surfaces.

Gating: Time interval between front and back wall echoes was divided into

4 time gates (different time gates for each inspection surface). 

Gain: Fixed waterpath with DAC. DAC set so that echoes from #1 FBHs in flat

calibration blocks were at 80% FSH. Then 15 dB of additional gain added.

Increments: 0.02” scanning increments in the scan and index directions.

C.L.

Surface 1

Surface 3

Surface 2

2.1”

6.8”

3.3”

Surface Gate Depth_Range

1 1 0.20” - 0.56”

1 2 0.56” - 0.93”

1 3 0.93” - 1.29”

1 4 1.29” - 1.62”

2 1 0.20” - 0.87”

2 2 0.87” - 1.54”

2 3 1.54” - 2.21”

2 4 2.21” - 2.88”

3 1 0.18” - 0.91”

3 2 0.91” - 1.64”

3 3 1.64” - 2.37”

3 4 2.37” - 3.08”

Surface Gate Depth_Range

1 1 0.20” - 0.56”

1 2 0.56” - 0.93”

1 3 0.93” - 1.29”

1 4 1.29” - 1.62”

2 1 0.20” - 0.87”

2 2 0.87” - 1.54”

2 3 1.54” - 2.21”

2 4 2.21” - 2.88”

3 1 0.18” - 0.91”

3 2 0.91” - 1.64”

3 3 1.64” - 2.37”

3 4 2.37” - 3.08”

Transducer: Nominal 3” focus, 3/8” diameter, 10 MHz Technisonic probe (N7135).

Surfaces: Three inspection surfaces.

Gating: Time interval between front and back wall echoes was divided into

4 time gates (different time gates for each inspection surface). 

Gain: Fixed waterpath with DAC. DAC set so that echoes from #1 FBHs in flat

calibration blocks were at 80% FSH. Then 15 dB of additional gain added.

Increments: 0.02” scanning increments in the scan and index directions.

C.L.

Surface 1

Surface 3

Surface 2

2.1”

6.8”

3.3”

C.L.

Surface 1

Surface 3

Surface 2

2.1”

6.8”

3.3”

Surface Gate Depth_Range

1 1 0.20” - 0.56”

1 2 0.56” - 0.93”

1 3 0.93” - 1.29”

1 4 1.29” - 1.62”

2 1 0.20” - 0.87”

2 2 0.87” - 1.54”

2 3 1.54” - 2.21”

2 4 2.21” - 2.88”

3 1 0.18” - 0.91”

3 2 0.91” - 1.64”

3 3 1.64” - 2.37”

3 4 2.37” - 3.08”

Surface Gate Depth_Range

1 1 0.20” - 0.56”

1 2 0.56” - 0.93”

1 3 0.93” - 1.29”

1 4 1.29” - 1.62”

2 1 0.20” - 0.87”

2 2 0.87” - 1.54”

2 3 1.54” - 2.21”

2 4 2.21” - 2.88”

3 1 0.18” - 0.91”

3 2 0.91” - 1.64”

3 3 1.64” - 2.37”

3 4 2.37” - 3.08”

Bore Web

Rim
2-6

 (a) 

 (b) 

FIGURE 2-7. RESULTS OF A DEFORM CALCULATION FOR THE P&W FORGING 

SHOWING HOW SMALL CIRCULAR ELEMENTS IN THE BILLET ARE DEFORMED 

BY THE FORGING PROCESS (a) BILLET SLICE BEFORE FORGING, WITH THE 

CROSS-SECTIONAL AREA DIVIDED INTO CIRCULAR ELEMENTS AND 

(b) RESULTS OF THE FORGING PROCESS 
2-7

For the P&W forging, normal incident C-scans were made through three surfaces with a 10-MHz 

transducer to map backscattered grain noise (see figure 2-5). A fixed waterpath was used for all 

scans, chosen to focus the sonic beam approximately 0.10′′ beneath the entry surface, and DAC 

was applied. The DAC was set so that echoes from #1 FBH in flat calibration blocks were at 

80% of full-screen height (FSH). An additional 15 dB of gain was then added for the C-scans to 

emphasize the backscattered grain noise. In some cases, noise values were saturated; for those 

cases, the gain was reduced by 6 dB, and the disk was rescanned. A total of 12 C-scans, four 

each from three surfaces, were completed. The disk used for these scans was missing a small 

annular slice that served as a registration point in the C-scan images. 

A typical C-scan image is shown in figure 2-8. It was taken through surface 1 and was gated to 

show only the region between 0.20′′ and 0.56′′ below the front surface. The full 360° C-scan is 

shown in the upper portion of the figure and enlarged views of two segments are shown below it 

(0° to 200° and 200° to 360°). In all C-scan images, regions of high and low average noise were 

located manually by the operator using the amplitude color bar as a guide. The low- and highnoise regions are labeled A and B respectively in figure 2-8. These analysis regions typically 

had an area of approximately 1 square inch on the sound-entry surface. The average and peak 

noise levels within each region were determined and reported as a percentage of FSH at 15 dB of 

additional gain. Note that the images in figure 2-8 have been compressed, and that the actual 

regions of high and low noise are not always exactly where they appear to be in the compressed 

image. The operator worked from the full images to identify the low- and high-noise regions, 

and then noted their approximate locations on the compressed image. For comparison with the 

shallow-zone scan shown in figure 2-8, deeper zones scans from surface 2 (figure 2-9) and 

surface 3 (figure 2-10) are also shown. 

FIGURE 2-8. BACKSCATTERED NOISE C-SCAN FOR THE SHALLOWEST ZONE 

(0.20′′-0.56′′) BELOW SURFACE 1 OF THE P&W FORGING 

Scan through Surface 1 at 15 dB higher than #1 sensitivity with DAC

Slice removed

from disk

0 to 200o

200 to 360o

Gate: 0.20” - 0.56”

 (1.62-4.62 uS)

Gate 1

A

B

Noise Stats :

 Ave / Peak

A: 21 / 46

B: 24 / 46
2-8

FIGURE 2-9. BACKSCATTERED NOISE C-SCAN FOR THE THIRD ZONE (1.54′′-2.21′′) 

BELOW SURFACE 2 OF THE P&W FORGING 

FIGURE 2-10. BACKSCATTERED NOISE C-SCAN FOR THE FOURTH ZONE 

(2.37′′-3.08′′) BELOW SURFACE 3 OF THE P&W FORGING 

The backscattered noise data taken from all three surfaces and all four depths were analyzed to 

determine the average and peak noise levels and the degree of noise banding. Figure 2-11 shows 

the average noise level in the high-noise region as a function of zone number (zone 

1 = shallowest, zone 4 = deepest) for each of the three surfaces inspected. A systematic increase 

in noise level with depth is readily apparent in the data from surfaces 2 and 3, which involved 

inspection of thicker cross sections. Because of the manner in which the DAC is applied here, 

the amplitude from a hypothetical FBH defect is expected to be independent of depth with a 

Scan through Surface 2 at 15 dB higher than #1 sensitivity with DAC

0 to 200o

200 to 360o

Gate 3 Gate: 1.54” - 2.21”

 (12.62 - 18.12 uS)

Noise Stats :

 Ave / Peak

A: 48 / 87

B: 52 / 97

B A

Scan through Surface 3 at 15 dB higher than #1 sensitivity with DAC

0 to 200o

Gate 4 Gate: 2.37” - 3.08”

 (19.44 - 25.24 uS)

A

B

Noise Stats :

 Ave / Peak

A: 100 / 169

B: 121 / 197

200 to 360o
2-9

constant amplitude of 450% FSH (i.e., 15 dB above 80%). Thus, the noise levels measured may 

be thought of as being noise-to-signal (N/S) ratios. Studies conducted during ETC Phase I have 

shown that for typical inspection scenarios, N/S tends to grow like the square root of the sonic 

pulse volume (PV) when the noise is microstructural in origin. Thus, N/S tends to be smallest 

near the focal zone of a sound beam, and to increase as one moves away from the focal zone, 

other factors (e.g., microstructure) being constant [16]. 

FIGURE 2-11. AVERAGE NOISE LEVELS IN THE HIGH-NOISE 

REGIONS OF THE P&W FORGING 

The dependence of noise level (or N/S) on inspection depth is more explicitly shown in 

figure 2-12. There the average and peak noise levels in the high-noise regions have been plotted 

as a function of the maximum depth within the inspection zone. The 12 values in figure 2-11 

have, thus, been replotted to produce the lower (blue) curve in figure 2-12, and the peak noise 

values are similarly plotted in the upper (red) curve. The general dependence on depth shown in 

figure 2-12 is believed to be principally due to the spreading of the sonic beam that was focused 

just below the entry surface for these measurements. 

FIGURE 2-12. AVERAGE AND PEAK NOISE LEVELS FOR HIGH-NOISE 

REGIONS OF THE P&W FORGING 

0

20

40

60

80

100

120

140

160

S1 S2 S3

Surface

Noise Level (% FSH)

Zone 1 Zone 2

Zone 3 Zone 4

0

50

100

150

200

250

0.0 1.0 2.0 3.0 4.0

Max Depth in Zone (inches)

Noise Level (% FSH)

Ave-High

Peak-High
2-10

The degree of noise banding in the circumferential direction was evaluated by plotting the 

average high-noise amplitude divided by the average low-noise amplitude for each zone of all 

three surfaces. The result, shown in figure 2-13, indicates that very little noise banding was 

observed in the P&W forging, with the high- to low-noise ratio ranging only from 1.0 to 1.2. 

FIGURE 2-13. RATIO OF AVERAGE NOISE LEVELS IN HIGH- AND LOW-NOISE 

REGIONS OF THE P&W FORGING 

The peak noise level observed within a region of a forging C-scan will always exceed the 

average noise level within that same region. The peak-to-average ratio is often of interest from a 

PoD standpoint, and this ratio is plotted versus zone depth in figure 2-14. For the P&W forging, 

the peak and average noise levels in a given 1-square-inch region typically differ by about a 

factor of 2. 

FIGURE 2-14. RATIO OF PEAK TO AVERAGE NOISE AS A FUNCTION OF 

DEPTH IN THE P&W FORGING 

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

S1 S2 S3

Surface

Ave-High / Ave-Low

Zone 1 Zone 2

Zone 3 Zone 4

0.0

0.5

1.0

1.5

2.0

2.5

0.0 1.0 2.0 3.0 4.0

Max Depth in Zone (inches)

Peak / Average

Low noise regions

High noise regions
2-11

The noise data were used to select positions for the property measurement test blocks. The noise 

C-scans of the P&W forging revealed a modest degree of banding, with the noise tending to be 

highest near the 260° angular position. Thus, it was decided that the test blocks would be cut 

from a wedge centered at 260° in the C-scan images. Eight test block sites were selected within 

this wedge, as indicated in figure 2-15. Seven of the test specimens were 1.25′′ by 1.25′′ by 2′′

rectangular blocks, while the eighth was a 1.25′′ diameter by 2′′ long cylinder. The positions of 

the eight specimens in the radial-axial plane were chosen to comprise a variety of local 

microstructures, based on the differences observed in the macroetch and the DEFORM 

simulation of forging strain (see figure 2-16). Note that coupons 2 and 3, which have different 

shapes but similar radial-axial positions, are expected to have similar microstructures. 

FIGURE 2-15. SITES FOR EIGHT PROPERTY MEASUREMENT COUPONS CUT FROM 

THE P&W-SUPPLIED FORGED DISK 

FIGURE 2-16. RADIAL-AXIAL LOCATIONS FOR THE EIGHT PROPERTY 

MEASUREMENT COUPONS IN THE P&W DISK, SUPERIMPOSED ON 

THE DEFORM STRAIN MAP FROM FIGURE 2-7(b) 

(The sonic shape is outlined in yellow.) 

2.2.1.1 General Electric Disk. 

The second disk was supplied by GE. Figure 2-17 displays the general appearance of the sonic 

shape, while figure 2-18 shows the disk cross section together with dimensional information and 

All coupons measure 1.25” x 

1.25” in the plane of the page, 

and 2.0” into the page. 

Coupon 3 is a cylinder 1.25” in 

diameter. The other 7 coupons 

are rectangular.

On average, the noisiest sector 

of the forging was centered near 

angular position 260o on the Cscan images. The coupons were 

cut from a wedge (approximately 

60o wide) centered at that 

angular position as shown at 

bottom left 

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

260 1 o

2

3

4

5

6

7

8

200o

(ref. gap)

All coupons measure 1.25” x 

1.25” in the plane of the page, 

and 2.0” into the page. 

Coupon 3 is a cylinder 1.25” in 

diameter. The other 7 coupons 

are rectangular.

On average, the noisiest sector 

of the forging was centered near 

angular position 260o on the Cscan images. The coupons were 

cut from a wedge (approximately 

60o wide) centered at that 

angular position as shown at 

bottom left 

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

260 1 o

2

3

4

5

6

7

8

200o

(ref. gap)

1

2

3

4

5

6

7

8 1

2

3

4

5

6

7

8
2-12

some UT inspection details. A macroetch of the cross section, revealing the flow line structure, 

is shown in figure 2-19. Figure 2-20 shows the results of a DEFORM simulation for plastic 

metal flow during the forging process. Again, small volume elements with circular cross 

sections in the radial-axial plane were specified in the billet blank, and these volume elements 

were followed through the forging process. Each OEM worked with a different forging supplier 

to perform DEFORM simulations and to document the outputs. Different suppliers were able to 

perform such calculations and display the results with differing degrees of sophistication. For 

example, the DEFORM results for the P&W disk shown in figure 2-7 have a different format 

than that shown in figure 2-20 for the GE disk. An alternative method for displaying DEFORM 

results is shown in figure 2-21, where the calculated forging strain magnitudes in the radial-axial 

plane are displayed as a function of position. 

FIGURE 2-17. GENERAL APPEARANCE OF THE GE-SUPPLIED FORGED 

DISK BEFORE THE BORE HOLE WAS CUT 

(Sonic shape is approximately 22′′ in diameter with a 9′′ diameter central hole.) 

FIGURE 2-18. CROSS SECTION OF THE SONIC SHAPE OF THE 

GE-SUPPLIED FORGING 

There were two inspection zones for all surfaces except

UK (Zone 1 only) and UG (Zones 1-4).

The zoning scheme was:

Zone 1, calibrated 0.06" to 0.5", gated 0.06" to 0.6".

Zone 2, calibrated 0.5" to 1.0", gated 0.4" to 1.1".

Zone 3, calibrated 1.0" to 1.5", gated 0.9" to 1.6".

Zone 4, calibrated 1.5" to 2.0", gated 1.4" to 2.1".

Two probes were used:

I3 (10 MHz, 0.375” dia. F= 3”) 

and

F8 (10 MHz, 1” dia. F= 8”) 

Zone 1 used I3 

Zone 2 used F8 (except UJ,UR,UZ)

Zones 3 & 4 used F8. 

US

Center

Line

UG

(3 3/4”)

UR

UP

UO

(1”)

UZ

(1 15/32”)

UM

(1 1/16”)

UL

UK

UJ

UH (1 15/16”)

6 9/16”

4.5”

US (11/16”)

7/16”

Lengths of selected

surfaces are indicated.

There were two inspection zones for all surfaces except

UK (Zone 1 only) and UG (Zones 1-4).

The zoning scheme was:

Zone 1, calibrated 0.06" to 0.5", gated 0.06" to 0.6".

Zone 2, calibrated 0.5" to 1.0", gated 0.4" to 1.1".

Zone 3, calibrated 1.0" to 1.5", gated 0.9" to 1.6".

Zone 4, calibrated 1.5" to 2.0", gated 1.4" to 2.1".

Two probes were used:

I3 (10 MHz, 0.375” dia. F= 3”) 

and

F8 (10 MHz, 1” dia. F= 8”) 

Zone 1 used I3 

Zone 2 used F8 (except UJ,UR,UZ)

Zones 3 & 4 used F8. 

US

Center

Line

UG

(3 3/4”)

UR

UP

UO

(1”)

UZ

(1 15/32”)

UM

(1 1/16”)

UL

UK

UJ

UH (1 15/16”)

6 9/16”

4.5”

US (11/16”)

7/16”

Lengths of selected

surfaces are indicated.

US

Center

Line

UG

(3 3/4”)

UR

UP

UO

(1”)

UZ

(1 15/32”)

UM

(1 1/16”)

UL

UK

UJ

UH (1 15/16”)

6 9/16”

4.5”

US (11/16”)

7/16”

Lengths of selected

surfaces are indicated.
2-13

FIGURE 2-19. MACROETCH FOR THE GE-SUPPLIED FORGING 

(The approximate boundary of the sonic shape is indicated.) 

FIGURE 2-20. RESULTS OF A DEFORM CALCULATION FOR THE GE FORGING, 

SHOWING HOW SMALL CIRCULAR ELEMENTS IN THE BILLET ARE 

DEFORMED BY THE FORGING PROCESS 

FIGURE 2-21. RELATIVE FORGING STRAIN LEVELS AS CALCULATED BY 

DEFORM FOR THE GE FORGING IN ARBITRARY UNITS 

(The as-forged cross section is shown with the white line 

indicating the boundary of the sonic shape.) 

Bore

Web

Rim

Billet Blank

GE Forging

0 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 

Radius (inches)

-1.2

0.0

1.2

2.4

3.6 4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Low Strain

(0.238)

High Strain

(5.411)

Height (inches)

GE Ti 6-4 Forging

0 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 

Radius (inches)

-1.2

0.0

1.2

2.4

3.6 4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Low Strain

(0.238)

High Strain

(5.411)

Height (inches)

0 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 

Radius (inches)

-1.2

0.0

1.2

2.4

3.6 4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Low Strain

(0.238)

High Strain

(5.411)

0 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 

Radius (inches)

-1.2

0.0

1.2

2.4

3.6 4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Low Strain

(0.238)

High Strain

(5.411)

Height (inches)

GE Ti 6-4 Forging
2-14

Normal incident C-scans were made through 11 surfaces of the GE forging (labeled UG-UZ in 

figure 2-18) to map backscattered grain noise. Two inspection zones, 0.060′′ to 0.5′′ (zone 1) and 

0.5′′ to 1.0′′ (zone 2), were used for all surfaces except UK (zone 1 only) and UG (zones 1-4). 

Two 10-MHz transducers were used: one with a 3′′ focal length for zone 1 and one with an 8′′

focal length for all the other zones. Waterpaths were adjusted to focus the sound beam at the 

middle of the zone being inspected, and DAC was then used across the zone. The echoes from 

#1 FBHs in flat calibration blocks were set at 80% of FSH. Additional gain ranging from 15 to 

27 dB was then added to better emphasize the grain noise variations. 

In all, 23 noise C-scans were completed and analyzed for the GE forging. Three examples are 

shown in figures 2-22 through 2-24. In each case, the horizontal axis represents angular position 

from 0° to 360° and the vertical axis represents probe travel in the axial-radial plane. For each 

C-scan image, regions of high and low average noise were located manually by the operator 

using the amplitude color bar as a guide. The low- and high-noise regions are labeled A and B 

respectively in the figures, with each box representing an area of approximately 1 square inch on 

the forging surface. The average and peak noise levels within each region were determined and 

reported as a percentage of FSH at the inspection gain. These values are labeled in figures 2-22 

through 2-24. 

FIGURE 2-22. BACKSCATTERED NOISE C-SCAN FOR THE SHALLOWEST ZONE 

(0.06′′-0.6′′) BELOW SURFACE UG OF THE GE FORGING 

A

B A= 10.5 / 18.8

B= 36.0 / 77.6

Ave. / Peak

A= 10.5 / 18.8

B= 36.0 / 77.6

Ave. / Peak
2-15

FIGURE 2-23. BACKSCATTERED NOISE C-SCAN FOR THE SECOND ZONE (0.5′′-1.0′′) 

BELOW SURFACE UO OF THE GE FORGING 

FIGURE 2-24. SITES FOR PROPERTY MEASUREMENT COUPONS CUT FROM THE 

GE-SUPPLIED FORGED DISK 

UOZ2F8.pcx 25May00 0.5” x 2” analysis regions

A

B

A= 10.9 / 23.5

B= 40.7 / 87.8

Ave. / Peak

UGZ4F8.pcx 25May00 0.25” x 4” analysis regions

A

B

A= 7.0 / 12.5

B= 42.3 / 85.4

Ave. / Peak
2-16

Like the example in figure 2-22 (zone 1 of surface UG), most of the noise-banding patterns have 

approximately 180° rotation symmetry. That is, for one complete revolution of the forging, one 

encounters a pattern of high-low-high-low noise. However, there are some interesting variations 

on this basic pattern. In some cases (e.g., UK zone 1 and UM zone 2) one of the high- or lownoise bands is suppressed, resulting in a pattern with a single dominant high-noise band and a 

single dominant low-noise band. In other cases, one can detect a subpattern with eight high- and 

eight low-noise bands within a full revolution; UP zone 1 and US zone 2 are of this nature. 

Backscattered noise data from all surfaces and depths were analyzed to determine average and 

peak noise levels and the degree of noise banding. All measured noise values were rescaled to a 

gain setting of 20 dB above #1 FBH calibration and are quoted in units of % FSH. Figure 2-25 

shows the average noise level in the high-noise regions as a function of depth for each of the 11 

surfaces inspected. Average noise levels in high-noise bands have a mean of about 40% FSH (at 

20 dB above #1 FBH), but vary considerably with inspection surface. Because the inspection 

procedure focuses the transducer at the center of each zone and then applies DAC, zone depth, 

per se, has very little effect on noise level. This is in contrast to the inspection of the P&W disk, 

where the transducer was focused near the surface for inspection of all zones. The variability 

evident in figure 2-25 suggests that the local flow line patterns and orientations have a significant 

influence on the noise level. 

FIGURE 2-25. AVERAGE NOISE LEVELS IN THE HIGH-NOISE REGIONS 

OF THE GE FORGING 

The degree of noise banding was evaluated using the same analysis that was applied earlier to the 

P&W forging data, i.e., plotting the average high-noise amplitude divided by the average lownoise amplitude for each zone of each surface. This data, shown in figure 2-26, indicates a 

higher degree of noise banding than was observed in the P&W forging. The ratio of these noise 

averages in the GE forging ranged from 1.0 to about 5, whereas the ratios ranged from 1.0 to 1.2 

in the P&W forging (see figure 2-13). For 12 of the 23 C-scans on the GE forging, the average 

noise level in the high-noise region is at least 3 times larger than the average noise level in the 

low-noise region. The degree of banding, as judged by this ratio, tends to be larger in the deeper 

inspection zones (zones 2-4). 

0

1

2

3

4

5

6

7

8

UG UH UJ UK UL UM UO UP UR US UZ

Surface

Ave-High / Ave-Low

Zone 1 Zone 2

Zone 3 Zone 4
2-17

FIGURE 2-26. RATIO OF AVERAGE NOISE LEVELS IN HIGH- AND 

LOW-NOISE REGIONS OF THE GE FORGING 

As was done earlier for the P&W forging, the ratio of peak-to-average noise was computed for 

each 1′′ square analysis region, as shown in figure 2-27 for the GE disk. In any given analysis 

region, the ratio of the peak noise pixel value to the average noise value was typically about 2. 

This was true for both the low- and high-noise regions. These results are very similar to those 

from the P&W forging (see figure 2-14), where the ratio varied from about 1.5 to 2.2. The one 

major exception was surface UL, zone 2, which has a region of elevated noise in a narrow 

angular range. 

Figure 2-27. RATIO OF PEAK-TO-AVERAGE NOISE IN THE GE FORGING 

As with the P&W forging, the GE noise data was used to select locations for the property 

measurement test blocks. Eight coupon sites were selected; their approximate locations are 

shown in figure 2-28. The data indicated that one angular section of the bore and web regions of 

the disk tended to have a higher noise level. All eight coupons were cut from this octant, as 

shown in figure 2-28. Seven of the coupons were rectangular prisms, while the eighth 

0

10

20

30

40

50

60

70

80

90

UG UH UJ UK UL UM UO UP UR US UZ

Surface

Noise Level (% FSH)

Zone 1 Zone 2

Zone 3 Zone 4

0

1

2

3

4

5

UG UH UJ UK UL UM UO UP UR US UZ

Surface

Peak / Average

Zone 1; Low Zone 2; Low

Zone 1; High Zone 2; High
2-18

(coupon 2) was a cylinder that was expected to have a similar microstructure to rectangular 

coupon #1. As for the P&W disk, the test coupon locations in the radial-axial plane were chosen 

using the macroetch and DEFORM results to provide a variety of flow line geometries relative to 

the beam propagation direction. 

FIGURE 2-28. SITES FOR PROPERTY MEASUREMENT COUPONS CUT FROM THE 

GE-SUPPLIED FORGED DISK 

2.2.1.2 Honeywell Disk. 

The last of the three Ti-6-4 forgings used as sources for property measurement coupons was 

supplied by HW. Figure 2-29 displays the general appearance of the sonic shape, while 

figure 2-30 shows the disk cross section, with dimensional information. A macroetch of the 

cross section, revealing the flow line structure, is shown in figure 2-31. Figure 2-32 shows the 

results of a DEFORM simulation of the forging process in the same spirit as the P&W and GE 

forgings. 

FIGURE 2-29. GENERAL APPEARANCE OF THE HW-SUPPLIED FORGED DISK 

(The ruler is about 6.5′′ long.) 

US

UG

UR

UP

UO

UZ

UM UL UK

UJ

UH

US

1

2

4

5

8

3

6

7

Coupons 1,4,5,6,7 are rectangles 

approx. 1.25” x 1.25” x 2.0”.

Coupon 3 is a rectangle approx. 

0.5” x 0.5” x 2.0”.

Coupon 8 is a rectangle approx. 

1.0” x 1.0” x 2.0”.

Coupon 2 is a cylinder approx. 

1.25” diameter by 2.0” long.

Note that each rectangular 

coupon has two sides the same 

length.

Sites for 8 coupons cut from 

the GE-supplied forging. 

Note that sites 1 and 2 are 

expected to have similar 

microstructures. All coupons 

are 2” long in the “hoop” 

direction.

Highest noise octant

of disk, as judged from 

UO, UM, UK C-scans

3

6

7

1

2 4, 5

8

US

UG

UR

UP

UO

UZ

UM UL UK

UJ

UH

US

1

2

4

5

8

3

6

7

US

UG

UR

UP

UO

UZ

UM UL UK

UJ

UH

US

1

2

4

5

8

3

6

7

Coupons 1,4,5,6,7 are rectangles 

approx. 1.25” x 1.25” x 2.0”.

Coupon 3 is a rectangle approx. 

0.5” x 0.5” x 2.0”.

Coupon 8 is a rectangle approx. 

1.0” x 1.0” x 2.0”.

Coupon 2 is a cylinder approx. 

1.25” diameter by 2.0” long.

Note that each rectangular 

coupon has two sides the same 

length.

Sites for 8 coupons cut from 

the GE-supplied forging. 

Note that sites 1 and 2 are 

expected to have similar 

microstructures. All coupons 

are 2” long in the “hoop” 

direction.

Highest noise octant

of disk, as judged from 

UO, UM, UK C-scans

3

6

7

1

2 4, 5

8 Highest noise octant

of disk, as judged from 

UO, UM, UK C-scans

3

6

7

1

2 4, 5

8
2-19

FIGURE 2-30. CROSS SECTION OF THE SONIC SHAPE OF THE HW FORGING 

FIGURE 2-31. MACROETCH OF THE HW-SUPPLIED FORGING 

FIGURE 2-32. RESULTS OF A DEFORM CALCULATION FOR THE HW FORGING, 

SHOWING HOW SMALL CIRCULAR ELEMENTS IN THE BILLET ARE 

DEFORMED BY THE FORGING PROCESS 

ID

AFT

FWD

OD

7.63′′

1.88′′

0.65′′

0.85′′

6.43′′

CL

1.55′′

1.93′′

Billet in Upset Dies After Finisher stage
2-20

C-scans of backscattered noise in the HW forging were made through each of the 11 surfaces 

labeled in figure 2-33. All surfaces were inspected using a 10-MHz, F=3′′ focused transducer 

with the water path chosen to position the focal spot at the entry surface. If the part thickness 

beneath the entry surface was greater than 0.5′′, a second inspection was performed using a 

10-MHz, F=6′′ transducer focused 0.25′′ beneath the entry surface. As in the P&W and GE 

disks, DAC was used to set the response from FBHs in flat test blocks to 80% FSH (independent 

of depth), with additional gain applied in some cases to emphasize the grain noise. 

FIGURE 2-33. INSPECTION SURFACES FOR THE HW FORGED DISK WITH 

TRANSDUCER AND SETUP DATA 

Results for three of the HW C-scans are shown in figures 2-34 through 2-36, with significant 

noise banding in two of those cases. Grain noise amplitude statistics were compiled for the full 

scan region and for smaller subregions chosen by the HW inspector. These statistics (minimum, 

maximum, average, and standard deviation) are listed in table 2-1. Overall, the degree of noise 

banding in the HW disk was similar to the GE forging. The ratio of peak-to-average noise 

amplitudes within the smaller subregions ranged from about 1.5 to 3, and was similar to peakaverage values observed for the P&W and GE disks. 

FIGURE 2-34. BACKSCATTERED NOISE C-SCAN ACQUIRED THROUGH 

SURFACE D OF THE HW FORGING 

(Surface D, gated from 0.100 to 0.500 inch.) 

A

B

C

D

E

F

H

J

G

K

L

INSPECTION SETUP:

SCANNER - IRT LS200

INSTRUMENT - IRT UPI50

TRANSDUCER for 0.100 to 0.500 inch metal travel: TLC, 

IS1010GA, F8, SN031703

• (10 MHz, focus = 3.0”, Ø 0.375”, Focused at 

surface, Waterpath = 3.0 inches, #2 FBH sensitivity, 

Bore was examined using right angle acoustic 

mirror.)

TRANSDUCER for metal travels > 0.5 inch metal travel: KB 

Aerotech, F12, S/N C01713

• (10 MHz, focus = 6.0”, Ø 0.500”, Focused at ~ 0.25 

inch metal travel, Waterpath = 2.0 inches, #2 FBH + 

18 dB sensitivity unless otherwise stated, 3 dB beam 

width @ 0.500” metal travel = 0.040”, index used 

0.020” )

A

B

C

D

E

F

H

J

G

K

L

INSPECTION SETUP:

SCANNER - IRT LS200

INSTRUMENT - IRT UPI50

TRANSDUCER for 0.100 to 0.500 inch metal travel: TLC, 

IS1010GA, F8, SN031703

• (10 MHz, focus = 3.0”, Ø 0.375”, Focused at 

surface, Waterpath = 3.0 inches, #2 FBH sensitivity, 

Bore was examined using right angle acoustic 

mirror.)

TRANSDUCER for metal travels > 0.5 inch metal travel: KB 

Aerotech, F12, S/N C01713

• (10 MHz, focus = 6.0”, Ø 0.500”, Focused at ~ 0.25 

inch metal travel, Waterpath = 2.0 inches, #2 FBH + 

18 dB sensitivity unless otherwise stated, 3 dB beam 

width @ 0.500” metal travel = 0.040”, index used 

0.020” )

0

FWD/ I.D.

AFT/ O.D.

AFT

FWD

D

0

FWD/ I.D.

AFT/ O.D.

AFT

FWD

D
2-21

FIGURE 2-35. BACKSCATTERED NOISE C-SCAN ACQUIRED THROUGH 

SURFACE F OF THE HW FORGING 

(Surface F, gated from a 0.100- to 0.500-inch C-scan shown aft looking forward.) 

FIGURE 2-36. BACKSCATTERED NOISE C-SCAN ACQUIRED THROUGH 

SURFACE A OF THE HW FORGING 

(Surface A, gated from 0.50 to 1.00 inch.) 

0° I.D.

O.D.

F

FWD

AFT

0° I.D.

O.D.

F

FWD

AFT

0°

I.D.

O.D.

FWD A

AFT
2-22

TABLE 2-1. BACKSCATTERED GRAIN NOISE STATISTICS FOR C-SCANS OF THE 

HW FORGED DISK 

Surface 

Gated Range 

in Inches 

Min. 

Amp. 

% FSH 

Ave. 

Amp. 

%FSH 

Max. 

Amp. 

%FSH 

Std. 

Dev. Notes 

A 0.100 to 0.500 7.8 21.1 70.5 1.9 Entire scan area (70.5 max. on 1 to 

3 individual pixels) 

A 0.100 to 0.500 7.8 21.1 34.5 1.9 Average clean area 

A 0.100 to 0.500 7.8 16.4 25.1 3.5 Low-amplitude area (1-area) 

B 0.100 to 0.500 16.4 26.6 46.2 1.9 Entire scan area 

B 0.100 to 0.500 16.4 24.3 30.5 1.1 Average clean area 

B 0.100 to 0.500 21.9 28.2 37.6 1.5 High-amplitude area (2-areas) 

C 0.100 to 0.500 10.9 21.5 32.1 1.9 Entire scan area 

C 0.100 to 0.500 18.8 25.4 32.1 1.9 Single line, high-amplitude area 

(1-area) 

D 0.100 to 0.500 9.4 26.2 98.4+ 7.0 Entire scan area 

D 0.100 to 0.500 14.1 23.9 58.8 3.9 Average clean area 

D 0.100 to 0.500 14.5 31.3 93.0 8.8 Average high-amplitude area 

(4-areas) 

E 0.100 to 0.500 7.8 22.3 72.9 5.4 Entire scan area 

E 0.100 to 0.500 9.4 20.0 48.6 3.5 Average clean area 

E 0.100 to 0.500 15.2 26.5 61.1 5.4 Average high-amplitude area 

(5-areas) 

F 0.100 to 0.500 18.0 33.3 97.2 6.6 Entire scan area 

F 0.100 to 0.500 23.5 29.8 47.8 1.9 Average clean area 

F 0.100 to 0.500 22.3 35.5 93.1 7.0 Average high-amplitude area 

(4-areas) 

G 0.100 to 0.500 13.3 22.7 36.8 1.5 Entire scan area 

G 0.100 to 0.500 14.7 22.5 39.4 1.5 Average high-amplitude area 

(4-areas) 

L 0.100 to 0.500 5.4 26.2 97.2 10.5 Entire scan area 

L 0.100 to 0.500 5.4 26.3 86.4 10.6 Average high-amplitude area 

(5-areas) 

A B C

D

E

F

H

J

G

K

L
2-23

As was the case for the P&W and GE disks, sites for property measurement coupons in the HW 

forging were based on the combined macroetch, forging strain, and grain noise data. The 

macroetch and strain data were used to select coupon locations in the radial-axial plane, and the 

hoop locations were chosen such that the measured grain noise was as large as possible. Coupon 

sites for the HW forging are shown in figure 2-37, with the guidelines used to choose the hoop 

coordinates. The radial-axial locations of the coupons relative to the computed forging strain 

map are shown in figure 2-38. In all, ten coupons were cut from the HW forging, with the 

majority again being 1.25′′ by 1.25′′ by 2.0′′ rectangular blocks. As before, one of the 

rectangular blocks (4) had a cylindrical counterpart (10) cut from an adjacent location in the 

hoop direction. 

FIGURE 2-37. SITES FOR PROPERTY MEASUREMENT COUPONS CUT FROM THE 

HW-SUPPLIED FORGED DISK 

FIGURE 2-38. COUPON LOCATIONS FOR THE HW-SUPPLIED FORGED DISK 

SUPERIMPOSED ON THE DEFORM STRAIN MAP 

(The sonic shape is shown in blue.) 

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

L

A

K

G

B

C

D

E

F

ID

H

J

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

L

A

K

G

B

C

D

E

F

ID

H

J

Figure at left shows only the radial/axial locations of the coupons. 

The location in the hoop (circumferential) direction is determined 

from noise C-scans.

The main objective is to cut each coupon from a high-noise 

band. A secondary objective is to try (if possible) to confine all of 

the coupons to one “sector” of the forging, so that the entire forging 

is not destroyed in the effort to get the coupons.

The table below indicates the primary C-scan surface to be 

consulted when choosing the angular position for each coupon. In 

some cases a second scan can also be consulted – indicated in 

parenthesis. If the two scans do not both have high noise bands at 

the same angular position, the primary C-scan should be used to 

assign a coupon location, and mark it for the machinist.

Coupon Primary (secondary) C-scan surface

1 F (G)

2 F

3 F

4 F (G)

5 D (F)

6 H (F)

7 L (A)

8 B (A)

9 L or J

10 F (G)

(The ensonification direction for the primary C-scan is always 

perpendicular to macrograin elongation. Macrograins in the billet 

are elongated in the axial direction with typical 5:1 aspect ratios. 

Thus the macrograins in the forging will have a shape similar to that 

obtained by stretching the ellipses seen in the DEFORM strain map 

by a factor of 5 in the axial direction.) 

All coupons have nominal dimensions of 1.25” X 1.25” x 2.0” 

except for #9 which is nominally 0.5” x 0.5” x 2.0”. 

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

L

A

K

G

B

C

D

E

F

ID

H

J

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1.75”

1.25” / 2

Sonic shape.

L

A

K

G

B

C

D

E

F

ID

H

J

Figure at left shows only the radial/axial locations of the coupons. 

The location in the hoop (circumferential) direction is determined 

from noise C-scans.

The main objective is to cut each coupon from a high-noise 

band. A secondary objective is to try (if possible) to confine all of 

the coupons to one “sector” of the forging, so that the entire forging 

is not destroyed in the effort to get the coupons.

The table below indicates the primary C-scan surface to be 

consulted when choosing the angular position for each coupon. In 

some cases a second scan can also be consulted – indicated in 

parenthesis. If the two scans do not both have high noise bands at 

the same angular position, the primary C-scan should be used to 

assign a coupon location, and mark it for the machinist.

Coupon Primary (secondary) C-scan surface

1 F (G)

2 F

3 F

4 F (G)

5 D (F)

6 H (F)

7 L (A)

8 B (A)

9 L or J

10 F (G)

(The ensonification direction for the primary C-scan is always 

perpendicular to macrograin elongation. Macrograins in the billet 

are elongated in the axial direction with typical 5:1 aspect ratios. 

Thus the macrograins in the forging will have a shape similar to that 

obtained by stretching the ellipses seen in the DEFORM strain map 

by a factor of 5 in the axial direction.) 

All coupons have nominal dimensions of 1.25” X 1.25” x 2.0” 

except for #9 which is nominally 0.5” x 0.5” x 2.0”. 

1

2

3

4

5

6

7 8

9

10

1

2

3

4

5

6

7 8

9

10
2-24

2.2.2 Basic Measurements of Backscattered Noise Level, Velocity, and Attenuation in the 

Forging Flow Line Coupons. 

One goal of this study was to document the manner in which UT properties vary within 

representative Ti-6-4 forgings and relate those properties to the forging microstructure. The 26 

coupons cut from the three OEM-supplied forgings were used for this purpose and are referred to 

as either the property measurement or forging flow line coupons. 

Prior to UT measurements, identification numbers were engraved into one corner of the hoop 

face of each coupon, as illustrated in figure 2-34. These identification numbers were P&W1-

P&W7, GE1-GE8, and HW1-HW10 for the three sets of coupons, respectively. The six sides of 

each rectangular coupon were then numbered 1, 2, ... 6 in indelible ink, as shown in figure 2-39. 

The normal vectors to sides 1, 2, and 3 generally point in the radial, axial, and hoop directions, 

respectively, with side 1 facing right, side 2 facing up, and side 3 facing the viewer in the 

standard drawings that show coupon locations within the forgings (e.g., figures 2-15, 2-28, and 

2-37). For tilted coupons, such as GE6 in figure 2-39, side 1 faces the lower right and side 2 

faces the upper right. In all cases, sides 4, 5, and 6 are always opposite to sides 1, 2, and 3, 

respectively. 

FIGURE 2-39. COUPON LABELING SCHEME FOR THE GE-SUPPLIED Ti-6-4 FORGING 

2.2.2.1 Backscattered Noise Measurements. 

The first group of experiments was designed to measure backscattered grain noise amplitudes in 

the coupons using a focused transducer with known focal properties. Recall that S/N ratios in Ti 

alloy inspections are generally found to be approximately inversely proportional to the square 

root of the sonic PV evaluated at the depth of the flaw [16 and 19]. By measuring backscattered 

Side 3

(hoop)

Side 1

(OD)

Side 2

(AFT)

engraved

label

Coupons GE1,3,4,5,8 Coupons GE6,7

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

6.6”

Side 3

(hoop)

Side 1

(OD)

Side 2

(AFT)

engraved

label

Side 3

(hoop)

Side 1

(OD)

Side 2

(AFT)

engraved

label

Coupons GE1,3,4,5,8 Coupons GE6,7

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

6.6”

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

6.6”
2-25

noise from the focal zone of the probe (relative to an FBH reference) and measuring the PV in 

the focal zone, one would then have the necessary data to estimate S/N values that would result 

for forging inspections using other transducers whose PVs were known. 

Twenty of the forging flow line coupons had nominally identical dimensions of 1.25′′ by 1.25′′

by 2.0′′, making them ideal for systematic studies of the manner in which UT properties depend 

on forging location and strain. All of these coupons could be inspected in a common manner 

using fixed experimental protocols, which were performed at ISU. The measurement setup used 

for backscattered grain noise studies is shown in figure 2-40. The transducer used was a 

15-MHz broadband probe with a nominal diameter of 0.5′′ and a nominal focal length of 90 mm 

(3.5′′). The transducer was characterized by beam-mapping experiments in water [20 and 21] 

and found to have an effective diameter of 0.48′′ and an effective geometric focal length of 

3.80′′. Since absolute grain noise levels tend to increase with inspection frequency, a 15-MHz 

probe was chosen rather than one of the 10-MHz transducers traditionally used for forging 

inspections. For each measurement trial, the beam was focused one-quarter of the way between 

the front and back surfaces, and gated-peak noise (GPN) data was then gathered from one-half of 

the coupon volume (the half nearest the transducer). No DAC was used. Thus, as discussed in 

reference 16, the measurement is most sensitive to backscattered noise from a plane of grains 

located near the focal plane (about 1.25′′/4 = 0.3125′′ deep). The graph in figure 2-40 shows the 

predicted manner in which noise sensitivity depends upon depth for a uniform microstructure, 

using the models described in Appendix B of reference 16. For normalization purposes, noise 

amplitudes were compared to the echo from a #1 FBH located 0.5′′ deep in a fine-grained IN100 

step-block, using the same inspection water path as employed for the noise measurements. 

FIGURE 2-40. EXPERIMENTAL SETUP FOR EXAMINING THE DEPENDENCE OF 

BACKSCATTERED GRAIN NOISE ON POSITION AND INSPECTION DIRECTION 

FOR RECTANGULAR Ti-6-4 FORGING COUPONS 

Transducer is:

15 MHz

-Diameter

F = 3.5”

Focused 1/4 way down.

Gated region for

C-scan images of 

gated peak noise.

Coupons measure

Each of the four 

large surfaces was 

scanned.

Relative inspection

sensitivity with depth

within gate.

(Via noise models.)

0.0 0.2 0.4 0.6 0.81.0

Transducer is:

15 MHz

-Diameter

F = 3.5”

Focused 1/4 way down.

Gated region for

C-scan images of 

gated peak noise.

Coupons measure

1.25′′ x 1.25′′ x 2.0′′.

Each of the four 

large surfaces was 

scanned.

Relative inspection

sensitivity with depth

within gate.

(Via noise models.)

0.0 0.2 0.4 0.6 0.81.0

Transducer is:

15 MHz

-Diameter

F = 3.5”

Transducer is:

15 MHz

0.5′′

F = 3.5”

Focused 1/4 way down.

Gated region for

C-scan images of 
2-26

A #1 FBH located 0.3125′′ deep in fine-grained Ti-6-4 would have been the ideal reference, but 

was unavailable. For the probe in question, the relationship between FBH amplitudes in the 

available IN100 block and the ideal Ti-6-4 block was estimated using ISU inspection simulation 

models [7]. Predicted #1 FBH peak amplitudes as a function of depth for both materials are 

shown in figure 2-41. These model calculations indicate that the response from a #1 FBH 

located 0.31′′ deep in fine-grained Ti-6-4 (top arrow in figure 2-41) would be about 3.1 times 

larger than a #1 FBH 0.50′′ deep in IN100 (bottom arrow in figure 2-41), for the transducer in 

question. Part of this difference (a factor of 1.7) arises mainly from the density difference 

between IN100 and Ti-6-4, which influences sonic transmission coefficients. The remainder is 

due to the locations of the FBHs relative to the focal zone. This translation factor of 3.1 will be 

used in the tabulation of normalized grain noise amplitudes. 

FIGURE 2-41. PREDICTED AMPLITUDES FOR #1 FBH ECHOES 

(15-MHz, 0.5′′, F = 90-mm probe) 

As indicated in section 2.3.1, measured noise amplitudes relative to an FBH reference will be 

different for different transducers, with the difference approximately proportional to the ratio of 

the square roots of the PVs of the transducers. For the focused transducer used in the noise 

measurements, the PV in the focal plane was determined by measuring (1) the lateral beam 

diameter (as estimated by scanning over a #1 FBH in IN100 and locating the -6 dB points) and 

(2) the pulse duration (as estimated by finding the -6 dB points of the envelope function of the 

rectified A-scan of the peak FBH echo). The PV measurement particulars are summarized in 

figure 2-42. Except for a minor correction for speed of sound differences, the PV in the focal 

zone is expected to be similar for IN100 and Ti-6-4. Based on these measurements, the PV in 

Ti-6-4 in the focal zone was estimated as 3.63E-4 cubic centimeters, or 2.21E-5 cubic inches. 

Using this value, the tabulated noise amplitudes for the forging coupons can be rescaled to 

provide estimated noise amplitudes for inspections with other transducers. 

0.00

0.05

0.10

0.15

0.0 0.2 0.4 0.6 0.8 1.0

Metal Depth (inches)

Rectified FBH Amplitude .

Ti 6-4; 3.2" water path

IN100, 3.2" water path

(Volts)

0.00

0.05

0.10

0.15

0.0 0.2 0.4 0.6 0.8 1.0

Metal Depth (inches)

Rectified FBH Amplitude .

Ti 6-4; 3.2" water path

IN100, 3.2" water path

(Volts)
2-27

FIGURE 2-42. PULSE VOLUME DETERMINATION FOR THE FOCUSED 

TRANSDUCER USED IN THE NOISE MEASUREMENTS 

Four C-scans were performed on each rectangular coupon, one each through sides 1, 2, 4, and 5 

(see figure 2-39), which each have nominal surface areas of 1.25′′ by 2.0′′. The results for a 

typical case are shown in figure 2-43. In the upper row of the figure, each C-scan is displayed at 

the gain setting actually used during data acquisition. In the bottom row, the C-scans have been 

rescaled to a common gain setting to facilitate visual comparison of the noise levels. C-scans for 

all 20 of the 1.25′′ by 1.25′′ by 2.0′′ forging flow line coupons can be found in appendix A, as 

well as additional information about cropping and labeling the C-scan images. 

Figure 2-43 shows that the grain noise levels for coupon GE5 are much larger for radial beam 

propagation than for axial propagation. It was found that noise levels are very sensitive to the 

orientation between the beam direction and the flow line (or macrograin elongation) direction. 

Generally speaking, the backscattered noise level is largest for beam propagation perpendicular 

to the macrograin elongation. 

For the suite of 20 coupons as a whole, the C-scan images generally show little variability from 

top to bottom (i.e., in the hoop direction). Some, however, show significant variability from left 

to right (i.e., in the axial or radial direction). For this reason, when noise statistics were 

tabulated, each image was split into its left and right halves, and average- and peak-noise 

amplitudes were computed for each half separately (see appendix A). Because there are four 

Estimated Pulse Volume for Noise Measurements

Lateral beam diameters at the focal 

plane are expected to be similar for 

IN100 and Ti 6-4.

The lateral beam diameter in the focal 

zone was measured by adjusting the 

waterpath to maximize the echo from 

the 0.5”-deep #1 FBH in IN100, and 

then scanning the FBH (Panel A) 

The average beam diameter at the 

-6 dB level (Panel B) was estimated 

as 0.0827 cm or 0.0325 inches.

The pulse duration (0.109 us) was 

estimated by finding the - 6 dB points 

of the envelope function of the peak 

FBH echo (Panel C). This leads to a 

pulse length in Ti 6-4 (v =0.62 cm/us) 

of 0.0676 cm 0r 0.0266” .

Based on these measurements, the 

pulse volume in Ti 6-4 in the focal 

zone is estimated as 3.63E-4 cm^3 or

2.21E-5 in^3.

0.1” x 0.1” scan area.

50 x 50 pixels, each 

0.002” x 0.002”

208 pixels (shown in 

black) are within 6 dB of 

max amplitude. Ave. 

beam dia. obtained from 

π*D*D/4 =208 sq. pixels

Signal from #1 FBH in Focal Zone

-0.12

-0.08

-0.04

0.00

0.04

0.08

0.12

0.4 0.5 0.6 0.7 0.8 0.9 1.0

Time (microseconds)

FBH Response (Volts) .

envelope

RF signal

At -6 dB

Δt = 0.109us

Panel A Panel B

Panel C

Estimated Pulse Volume for Noise Measurements

Lateral beam diameters at the focal 

plane are expected to be similar for 

IN100 and Ti 6-4.

The lateral beam diameter in the focal 

zone was measured by adjusting the 

waterpath to maximize the echo from 

the 0.5”-deep #1 FBH in IN100, and 

then scanning the FBH (Panel A) 

The average beam diameter at the 

-6 dB level (Panel B) was estimated 

as 0.0827 cm or 0.0325 inches.

The pulse duration (0.109 us) was 

estimated by finding the - 6 dB points 

of the envelope function of the peak 

FBH echo (Panel C). This leads to a 

pulse length in Ti 6-4 (v =0.62 cm/us) 

of 0.0676 cm 0r 0.0266” .

Based on these measurements, the 

pulse volume in Ti 6-4 in the focal 

zone is estimated as 3.63E-4 cm^3 or

2.21E-5 in^3.

0.1” x 0.1” scan area.

50 x 50 pixels, each 

0.002” x 0.002”

208 pixels (shown in 

black) are within 6 dB of 

max amplitude. Ave. 

beam dia. obtained from 

π*D*D/4 =208 sq. pixels

Signal from #1 FBH in Focal Zone

-0.12

-0.08

-0.04

0.00

0.04

0.08

0.12

0.4 0.5 0.6 0.7 0.8 0.9 1.0

Time (microseconds)

FBH Response (Volts) .

envelope

RF signal

At -6 dB

Δt = 0.109us

Panel A Panel B

Panel C
2-28

inspection directions, this yields eight sets of {average, peak} noise amplitudes for each coupon. 

These eight sets are enumerated 1-8 using the numbering scheme shown in figure 2-44. For 

example, measurement 5 refers to beam propagation through side 2, with noise statistics reported 

for the half of the C-scan image closest to side 4. 

FIGURE 2-43. BACKSCATTERED GRAIN NOISE C-SCANS THROUGH FOUR 

SURFACES OF COUPON GE5 

FIGURE 2-44. ENUMERATION OF THE EIGHT NOISE MEASUREMENTS 

CATEGORIES FOR EACH FORGING FLOW LINE COUPON 

(Four quadrants times two propagation directions.) 

The measured noise levels, relative to the amplitude from a (hypothetical) #1 FBH in finegrained Ti-6-4 at the same average depth, are summarized in figures 2-45 through 2-47. The 

upper set of bars indicates peak noise levels, while the lower set indicates average GPN levels. 

(The tabulated values can be found in appendix A.) Average noise values range from 0.2% to 

2.5% of the FBH response. Peak noise values range from 0.5% to 6.9% of the FBH response, 

with HW coupon 5 having the greatest peak noise level of any coupon (6.9%). 

0% 100%

1.3% / 3.2% 1.0% / 1.7% 3.3% / 12.0% 3.1% / 11.4%

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWDFWD

AFT

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWD

FWD

AFT

HOOP HOOP HOOP HOOP

15 dB

GE5

2

4

5

1 (3 = Hoop)

AFT

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBH

in IN100 at same waterpath & gain. 

0% 100%

1.3% / 3.2% 1.0% / 1.7% 3.3% / 12.0% 3.1% / 11.4%

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWDFWD

AFT

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWD

FWD

AFT

HOOP HOOP HOOP HOOP

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWDFWD

AFT

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

ID

ODOD

ID

AFT

FWD

FWD

AFT

HOOP HOOP HOOP HOOP

15 dB

GE5

2

4

5

1 (3 = Hoop)

AFT

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

GE5

2

4

5

1 (3 = Hoop)

AFT

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBH

in IN100 at same waterpath & gain. 

OD

(side 1)

1

8 7

5

4

3 2

6

BOT

(side 5)

ID

(side 4)

TOP

(side 2) TOP

ID OD

BOT

1

8 7

4

5

3 2

6

Side 1

Side 4

Side 2

Side 5

“Untilted” Case “Tilted” Case

OD

(side 1)

1

8 7

5

4

3 2

6

BOT

(side 5)

ID

(side 4)

TOP

(side 2)

OD

(side 1)

1

8 7

5

4

3 2

6

BOT

(side 5)

ID

(side 4)

TOP

(side 2) TOP

ID OD

BOT

1

8 7

4

5

3 2

6

Side 1

Side 4

Side 2

Side 5

TOP

ID OD

BOT

1

8 7

4

5

3 2

6

Side 1

Side 4

Side 2

Side 5

“Untilted” Case “Tilted” Case
2-29

FIGURE 2-45. PEAK AND AVERAGE NOISE LEVELS FOR THE 

P&W FORGING COUPONS 

FIGURE 2-46. PEAK AND AVERAGE NOISE LEVELS FOR THE 

GE FORGING COUPONS 

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

Noise Level

(100 = #1 FBH in Ti-6-4) 

Coupon, Inspection Direction and Quadrant

GE1

GE7 GE5 GE6 GE4

US

GE

GE

GE

GE

GE

AFT

FWD

ID OD

OD

(side 1)

1

8 7

5

4

3 2

6

FWD

(side 5)

ID

(side 4)

AFT

(side 2) AFT

ID OD

FWD

1 8

7

4 5

3

2

6

Side 1

Side 4 Side 2

Side 5

Red: Peak noise

Blue: Ave. noise

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

OD

(side 1)

1

8 7

5

4

3 2

6

BOT

(side 5)

ID

(side 4)

TOP

(side 2)

TOP

ID OD

BOT

1

8 7

5

4

3 2

6

S di e 1

S di e 4

Side 2

Side 5

1 2 345 678 1 2 345 6 7 8 1 234 5 6 7 8 1 2 34 5 6 7 8 1 2 3 4 56 7 8 1 234 5 6 7 8 1 234 5 6 7 8

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Noise Level 

(100 = #1 FBH inTi 6-4) .

Coupon, Inspection Direction and Quadrant

PW1

PW7 PW4 PW5 PW2 PW6 PW8

Red: Peak Noise

Blue: Ave. Noise

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

OD

(side 1)

1

8 7

5

4

3 2

6

BOT

(side 5)

ID

(side 4)

TOP

(side 2)

TOP

ID OD

BOT

1

8 7

5

4

3 2

6

S di e 1

S di e 4

Side 2

Side 5

1 2 345 678 1 2 345 6 7 8 1 234 5 6 7 8 1 2 34 5 6 7 8 1 2 3 4 56 7 8 1 234 5 6 7 8 1 234 5 6 7 8

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Noise Level 

(100 = #1 FBH inTi 6-4) .

Coupon, Inspection Direction and Quadrant

PW1

PW7 PW4 PW5 PW2 PW6 PW8

Red: Peak Noise

Blue: Ave. Noise
2-30

FIGURE 2-47. PEAK AND AVERAGE NOISE LEVELS FOR THE 

HW FORGING COUPONS 

A wide range of noise values was observed within each forging, but overall average noise levels 

were similar for the three forgings. This is illustrated in the first two numerical columns of 

table 2-2 where the mean and peak noise levels have been averaged over coupons and inspection 

directions. The last two columns list the ranges of measured values for average and peak noise 

in each forging. 

TABLE 2-2. COMPARISON OF AVERAGE AND MAXIMUM GPN VOLTAGES 

 <Average> <Peak> Range of Average Range of Peak 

GE 0.81% 2.03% 0.2%-1.9% 0.5%-6.1% 

P&W 0.83% 2.31% 0.4%-1.8% 0.7%-5.5% 

HW 0.88% 2.36% 0.4%-2.5% 0.6%-6.9% 

(#1 FBH in Ti-6-4 = 100%) 

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD OD

(side 1)

1

8 7

5

4

3 2

6

FWD

(side 5)

ID

(side 4)

AFT

(side 2)

OD

(side 1)

1

8 7

5

4

3 2

6

FWD

(side 5)

ID

(side 4)

AFT

(side 2)

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

Coupon, Inspection Direction and Quadrant

H1

H8

H3 H4 H2 H6 H5 H7

Noise Level 

(100 = #1 FBH in Ti 6-4) 

Red: Peak Noise

Blue: Ave. Noise

Honeywell Forging
2-31

2.2.2.2 Velocity and Attenuation Measurements. 

For the forging flow line coupons, UT longitudinal-wave velocity and attenuation measurements 

were performed using the same procedures established in Phase I for rectangular billet coupons 

[16]. The basic experimental setups are shown in figure 2-48. Measurements were made 

through sides 1 and 2 of each specimen, generally corresponding to beam propagation in the 

radial and axial directions, respectively. The UT measurement system consisted of a 

Panametrics 5052 pulser/receiver, a Lecroy 9400A digitizing oscilloscope, a Testek water tank 

with a motorized XY scanning bridge, a manual gimble-gimble goniometer for adjusting the 

transducer orientation, and a personal computer to control scanning and data acquisition. The 

A-scans (radio frequency (RF) waveforms) required for the attenuation measurements were 

digitized at a 100-MHz sampling rate. Because the forging microstructure can sometimes act to 

steer the beam slightly, the front-wall echo was used to normalize the beam on the entry surface. 

That is, the two transducer orientation angles were adjusted so that the front-wall echo amplitude 

was maximized. 

FIGURE 2-48. SETUPS USED FOR UT VELOCITY AND 

ATTENUATION MEASUREMENTS 

(A 10-MHz, 1/4′′ planar probe was used in each case. The water path was typically 5 cm.) 

The sound velocity near the center of the coupon was determined from the average time delay 

between the first three successive back-wall echoes, denoted BS1, BS2, and BS3, respectively, in 

figure 2-48. The time delay between two echoes was specifically defined as the time difference 

between the corresponding zero crossing points just preceding the dominant positive peaks in the 

RF waveforms. Results of the velocity measurements are shown in figure 2-49. Velocity 

variations were relatively small, with the measured values ranging from 0.617 to 0.622 cm/μsec, 

a spread of about 1%. Although the spread in measured values was small, some systematic 

variations were observed. For example, for the P&W coupons in figure 2-49, one sees that the 

difference between the velocities in the radial and axial directions tends to lessen as one moves 

from coupon HW1 (near the forging inside diameter (ID)) to coupon HW8 (near the forging 

outside diameter (OD)). It was also noted that the forging strain tends to decrease as one moves 

from the ID to the OD of the P&W forging (see figure 2-16). 

Scan 

-

Ti

Fused Quartz 

Ti 6 4 coupon Reference

Scan 

Attenuation Measurement

BS1 BS2 BS3

Velocity Measurement 
2-32

FIGURE 2-49. MEASURED UT VELOCITIES FOR PROPAGATION IN THE RADIAL 

(THROUGH SIDE 1) AND AXIAL (THROUGH SIDE 2) DIRECTIONS OF THE 

FORGING FLOW LINE COUPONS 

Unlike velocity, UT attenuation is typically a strong function of frequency. Attenuation-versusfrequency curves were measured by comparing the spectral amplitudes of the first back-wall 

echo in the Ti-6-4 specimen to a FQ reference block. (The method is described in detail in 

reference 16.) The macrostructure of engine Ti alloys acts to distort the pressure and amplitude 

profiles of a propagating sound beam. The details of these distortions vary from location to 

location within a coupon. As a consequence, back-wall amplitude C-scans tend to have a 

blotchy appearance rather than the uniform coloration of fine-grained metals. Stated in another 

way, the effective UT attenuation varies from point to point over relatively small distances. For 

this reason, the transducer was scanned in two dimensions above the specimen, and the 

attenuation values were measured at 100 or more locations within the central 1.5′′ by 0.75′′ area 

of each standard coupon. The quoted attenuation-versus-frequency curves for each specimen 

are, thus, area averages. 

Examples of measured average attenuation curves are shown in figure 2-50 for two of the 

coupons from the HW forging. The attenuation values are in Neper/cm units; if desired, multiply 

by 22.06 to change to dB/inch units. Measured values are most trustworthy in the frequency 

range from about 5 to 16 MHz where the spectral amplitudes of the back-wall echoes are largest. 

Similar attenuation-versus-frequency curves for the other forging flow line coupons can be found 

in appendix A. Forging inspections of Ti-6-4 engine disks with similar dimensions to those 

Measured Longitudinal-Wave 

Sound Velocities for the 

Forging-Flowline Coupons in 

cm/microsec Units.

HW: Velocity Vs. Coupon Number

0.614

0.615

0.616

0.617

0.618

0.619

0.62

0.621

0.622

0.623

HW1 HW2 HW3 HW4 HW5 HW6 HW7 HW8

Coupon Number

Velocity (cm/us)

Axial

Radial

GE: Velocity Vs. Coupon Number

0.615

0.616

0.617

0.618

0.619

0.62

0.621

0.622

GE1 GE4 GE5 GE6 GE7

Coupon Number

Velocity (cm/us)

Axial

Radial

PW: Velocity Vs. Coupon Number

0.616

0.617

0.618

0.619

0.62

0.621

0.622

0.623

PW1 PW2 PW4 PW5 PW6 PW7 PW8

Coupon Number

Velocity (cm/us)

Axial

Radial

Measured Longitudinal-Wave 

Sound Velocities for the 

Forging-Flowline Coupons in 

cm/microsec Units.

HW: Velocity Vs. Coupon Number

0.614

0.615

0.616

0.617

0.618

0.619

0.62

0.621

0.622

0.623

HW1 HW2 HW3 HW4 HW5 HW6 HW7 HW8

Coupon Number

Velocity (cm/us)

Axial

Radial

GE: Velocity Vs. Coupon Number

0.615

0.616

0.617

0.618

0.619

0.62

0.621

0.622

GE1 GE4 GE5 GE6 GE7

Coupon Number

Velocity (cm/us)

Axial

Radial

PW: Velocity Vs. Coupon Number

0.616

0.617

0.618

0.619

0.62

0.621

0.622

0.623

PW1 PW2 PW4 PW5 PW6 PW7 PW8

Coupon Number

Velocity (cm/us)

Axial

Radial
2-33

studied here generally use 10-MHz transducers. Measured attenuation values at 10 MHz for this 

suite of forging flow line coupons are shown in figure 2-51 in dB/inch units. Figures 2-50 and 

2-51 illustrate that attenuation variations across a forging can be considerable, with the 

attenuation being largest for radial propagation at some locations and largest for axial 

propagation at others. As will be discussed in the next section, certain aspects of the attenuation 

variations can be correlated with variations in forging strain. 

FIGURE 2-50. MEASURED ATTENUATION-VERSUS-FREQUENCY CURVES FOR 

TWO COUPONS FROM THE HW Ti-6-4 FORGING 

(Coupon HW1 (top panel) is from the mid-radius, aft region of the forging. 

Coupon HW7 (lower panel) is from the ID, forward region. The results 

are shown for both radial and axial sound propagation.) 

2.2.3 Relationship Between UT Properties and Forging Strain. 

The property measurement coupons were also used to study the relationship between the UT 

properties and the local forging microstructures. The microstructural data consisted primarily of 

the macroetch photographs and the forging strain maps calculated using DEFORM. Although 

flow line directions in the macroetches can be readily discerned, it proved difficult to define and 

extract other quantitative measures of the flow lines (such as flow line density) from the 

photographs. Thus, it was decided that it might be more fruitful to work directly with the 

DEFORM outputs rather than the macroetch photographs. 

Honeywell#7 Side1&2 Attenuation

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1

Att_Side2

Honeywell#1 Side1&2 Attenuation

0.00

0.03

0.06

0.09

0.12

0.15

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1

Att_Side2

radial

radial

axial

axial

Honeywell#7 Side1&2 Attenuation

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1

Att_Side2

Honeywell#1 Side1&2 Attenuation

0.00

0.03

0.06

0.09

0.12

0.15

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1

Att_Side2

radial

radial

axial

axial
2-34

FIGURE 2-51. MEASURED UT ATTENUATION VALUES AT 10 MHz FOR THE 

FORGING FLOW LINE COUPONS 

(The results are shown for propagation in the radial direction 

(through side 1) and axial direction (through side 2).) 

In Ti-6-4 billet materials, the ETC Phase I studies found that UT properties were correlated with 

the shapes and orientations of the large-scale microstructural elements known as macrograins. 

For example, backscattered grain noise levels tend to be largest when the beam travels 

perpendicular to the macrograin elongation direction, and effective attenuation values tend to be 

smallest for that beam propagation direction [16]. If little recrystallization occurs during the 

forging process, the macrograins in the billet will deform into associated macrograins in the 

forging, and these may largely control the UT properties of the forging. In billets, the 

macrograin elongation direction is predominantly along the billet axis. The situation will be 

more complicated in forgings since the local material deformation varies with position, as shown 

in figure 2-52. 

For each OEM-supplied forging, the results of DEFORM calculations were given, showing how 

circular volume elements in the billet deform into elliptical elements in the forging. (See figures 

2-7, 2-20, and 2-32.) However, since billet macrograins tend to be elongated along the billet 

axis, a more appropriate starting point for the current study would be DEFORM calculations in 

which the initial billet volume elements have elliptical cross sections. For the P&W and HW 

forgings, it was possible to work with the respective forging houses to carryout such calculations. 

However, similar calculations could not be obtained from Ladish, the source for the GE forging. 

PW: Attenuation at 10MHz Bar Graph

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

PW#1 PW#2 PW#4 PW#5 PW#6 PW#7 PW#8

Coupon Number

Attenuation (dB/inch)

Axial(S2)

Radial(S1)

GE: Attenuation at 10MHz Bar Graph

0

0.2

0.4

0.6

0.8

1

GE#1 GE#4 GE#5 GE#6 GE#7

Coupon Number

Attenuation (dB/inch)

Axial(S2)

Radial(S1)

HW: Attenuation at 10MHz Bar Graph

0

0.5

1

1.5

2

2.5

3

HW#1 HW#2 HW#3 HW#4 HW#5 HW#6 HW#7 HW#8

Coupon Number

Attenuation (Np/cm)

Axial(S2)

Radial(S1)

Measured Longitudinal-Wave 

Attenuation Values for the 

Forging-Flowline Coupons at 

10 MHz in dB/inch Units.

PW: Attenuation at 10MHz Bar Graph

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

PW#1 PW#2 PW#4 PW#5 PW#6 PW#7 PW#8

Coupon Number

Attenuation (dB/inch)

Axial(S2)

Radial(S1)

GE: Attenuation at 10MHz Bar Graph

0

0.2

0.4

0.6

0.8

1

GE#1 GE#4 GE#5 GE#6 GE#7

Coupon Number

Attenuation (dB/inch)

Axial(S2)

Radial(S1)

HW: Attenuation at 10MHz Bar Graph

0

0.5

1

1.5

2

2.5

3

HW#1 HW#2 HW#3 HW#4 HW#5 HW#6 HW#7 HW#8

Coupon Number

Attenuation (Np/cm)

Axial(S2)

Radial(S1)

Measured Longitudinal-Wave 

Attenuation Values for the 

Forging-Flowline Coupons at 

10 MHz in dB/inch Units.
2-35

FIGURE 2-52. IN THE ABSENCE OF RECRYSTALLIZATION, THE SHAPES OF 

MACROGRAINS IN A FORGING WILL VARY WITH POSITION DUE TO 

THE VARYING STRAIN LEVELS

The results of the DEFORM calculations beginning with 5:1 elliptical elements in the billet 

(elongated parallel to the billet axis) are shown for the P&W and HW forgings in figures 2-53 

and 2-54, respectively. One sees that both the elongations and orientations of the volume 

elements in the forgings are changed, compared to the predictions of the earlier DEFORM 

simulations. Note that the shapes and orientations of the volume elements in the forgings vary 

systematically with position. Also note that the forging volume elements tend to be elongated in 

the axial direction at some locations (e.g., near the forging OD) and tend to be elongated in the 

radial direction at other locations (e.g., near the forging ID). The elongations of physical 

macrograins in Ti forgings often exhibit a similar dependence on position, and it was assumed 

that the shapes and orientations of the volume elements in the DEFORM calculations 

approximate those of physical macrograins. 

In previous measurements of backscattered grain noise, it was found that noise levels varied 

significantly with location and inspection direction within forgings (see figures 2-45, 2-46, and 

2-47). Some aspects of the noise variations appear to be well correlated with the forging 

macrograin shapes and orientations predicted by the DEFORM calculations. Consider 

figure 2-55 whose upper portion shows the strain diagram for the P&W Ti-6-4 forging, 

beginning with 5:1 ellipses in the billet. Superimposed on the diagram are the locations of seven 

rectangular property measurement coupons. Recall that noise measurements on each coupon 

were made in two directions for each of the four quadrants in the radial-axial plane. The lower 

portion of figure 2-55 lists the values of the noise anisotropy ratio (NAR) for each quadrant of 

each P&W coupon. This ratio, which is sometimes called, simply, the noise anisotropy, 

compares the average grain noise level measured for axial propagation (numerator of ratio) to the 

radial propagation (denominator). Ratio values near unity indicate that the backscattered noise 

level is similar for the two inspection directions. For tilted coupon PW4, the noise levels were 

measured at normal incidence, and the noise value through the upper or lower face (i.e., the 

nearly axial face) appears in the numerator. 

Cast Ingot ReducedDiameter Billet

Forging

“Macrograins”:

large scale microstructure

Cast Ingot ReducedDiameter Billet

Forging

“Macrograins”:

large scale microstructure
2-36

FIGURE 2-53. DEFORM CALCULATION FOR THE P&W FORGING, BEGINNING WITH 

5:1 ELLIPTICAL VOLUME ELEMENTS IN THE BILLET 

1

2

3

4

5

6

7 8

9

10

1

2

3

4

5

6

7 8

9

10

1

2

3

4

5

6

7 8

9

10

1

2

3

4

5

6

7 8

9

10

FIGURE 2-54. OUTPUT OF THE DEFORM CALCULATION FOR THE HW FORGING, 

BEGINNING WITH 5:1 ELLIPTICAL VOLUME ELEMENTS IN THE BILLET 

(The approximate boundaries of the sonic shape and forging flow line coupons are also shown.) 

Volume 

elements 

with 5:1 

aspect ratio 

in the billet 

blank. (Full 

billet blank 

not shown)

Volume elements in the PW forging. 

Volume 

elements 

with 5:1 

aspect ratio 

in the billet 

blank. (Full 

billet blank 

not shown)

Volume elements in the PW forging. 
2-37

FIGURE 2-55. STRAIN DIAGRAM FOR THE P&W Ti-6-4 FORGING, BEGINNING 

WITH 5:1 ELLIPSES IN THE BILLET ALIGNED WITH THE BILLET AXIS 

Comparing the upper and lower portions of figure 2-55, one sees that (1) the forging volume 

elements tend to have about equal projections onto the two inspection directions in regions where 

the NAR is near unity; (2) the axial noise is larger than the radial noise (NAR > 1) in regions 

where the ellipses are elongated in the radial direction; and (3) the radial noise is larger than the 

axial noise (NAR < 1) in regions where the ellipses are elongated in the axial direction. Thus, 

overall, a coherent explanation of the noise anisotropy emerges if one assumes that forging 

macrograin geometries are primarily responsible for the noise, and that their shapes in the 

forging are determined by their shapes in the billet and the subsequent deformation during 

forging. The only major exception in figure 2-55 is for coupon PW5, which has relatively 

circular DEFORM elements throughout, but has a measured NAR that varies substantially from 

quadrant to quadrant. The macroetch revealed that this coupon is in a region with swirling flow 

lines; the relationship between noise and macrostructure may be more complicated there, or the 

DEFORM calculations may be less trustworthy in such a region. 

To carry the analysis further, tabulations were made of the macrograin shape and orientation 

characteristics, as calculated using DEFORM. As illustrated in figure 2-56, the computed 

elliptical volume elements were examined to determine (1) the length of the major axis, (2) the 

length of the minor axis, and (3) the (acute) orientation angle between the major axis and the 

radial direction of the forging (more generally, the direction normal to coupon sides 1 and 4). 

These quantities were measured near the center of each quadrant of each coupon, usually 

averaging the properties of neighboring ellipses to best estimate the values at the quadrant center. 

Attempts were then made to correlate attributes of the localized grain noise levels to the forging 

macrograin properties shown in figure 2-56. The best correlation discovered was between the 

NAR and the ellipse projection ratio defined in figure 2-57. Recall that the noise anisotropy is 

1

2

4

5

6

7

8

1.55 1.62

1.67 1.78

1.82 2.05

2.10 2.36

0.95 0.91

0.58 0.63

1.52 1.20

0.52 0.44

0.45 0.40

0.90 0.68

2.10 0.82

0.58 0.23

0.37 0.26

0.33 0.25

or

or

Tabulation of Noise Anisotropy

by Coupon Quadrant

(Axial Mean Noise / Radial Mean Noise)

1

2

4

5

6

7

8 1

2

4

5

6

7

8 1

2

4

5

6

7

8

1.55 1.62

1.67 1.78

1.82 2.05

2.10 2.36

0.95 0.91

0.58 0.63

1.52 1.20

0.52 0.44

0.45 0.40

0.90 0.68

2.10 0.82

0.58 0.23

0.37 0.26

0.33 0.25

1.55 1.62

1.67 1.78

1.82 2.05

2.10 2.36

0.95 0.91

0.58 0.63

1.52 1.20

0.52 0.44

0.45 0.40

0.90 0.68

2.10 0.82

0.58 0.23

0.37 0.26

0.33 0.25

or

or

Tabulation of Noise Anisotropy

by Coupon Quadrant

(Axial Mean Noise / Radial Mean Noise)
2-38

defined as the ratio of the average GPN values for C-scans made from two orthogonal directions. 

The ellipse projection ratio, as the name implies, is the ratio of the projections of the strain 

ellipses onto the same two inspection directions. A correlation between these two ratios is not 

unexpected, since the backscattered noise level from a local region will depend, in part, on the 

cross section that the macrograins present to the sonic beam [22]. 

FIGURE 2-56. MEASURED PROPERTIES OF THE ELLIPTICAL MACROGRAINS IN 

FORGING STRAIN MAPS, AS CALCULATED USING DEFORM 

Ave. Noise Seen From Axial Direction

Ave. Noise Seen From Radial Direction

Noise Anisotropy Ratio =

Y

X

Axial

Radial Ellipse Projection Ratio

= Y / X a

b

θ

Ave. Noise Seen From Axial Direction

Ave. Noise Seen From Radial Direction

Noise Anisotropy Ratio =

Y

X

Axial

Radial Ellipse Projection Ratio

= Y / X a

b

θ

FIGURE 2-57. DEFINITION OF THE ELLIPSE PROJECTION RATIO FOR A FORGING 

MACROGRAIN, AS CALCULATED USING DEFORM 

Comparisons between the grain noise anisotropy ratio (from earlier C-scan noise measurements) 

and the ellipse projection ratio (from DEFORM calculations) are shown in figures 2-58 and 2-59 

for the P&W and HW forgings, respectively. In each case, the assumed macrograins in the billet 

were 5:1 ellipsoids, elongated in the axial direction. There are four plotted points for each 

forging flow line coupon, corresponding to the four quadrants where measurements and analyses 

were made. For perfect correlation between grain noise anisotropy and the ellipse projection 

ratio, the plotted points in figures 2-58 or 2-59 would all lie along a diagonal line. This is 

approximately the case, although there is significant scatter about that ideal line, with the scatter 

being somewhat larger for the HW forging. The choice of 5:1 as an aspect ratio for the billet 

macrograins was a guess. If the billet aspect ratio is more properly chosen, one would expect 

that forging locations having circular macrograins would have a noise aspect ratio of unity, i.e., 

Ellipse properties directly measured from DEFORM outputs:

Length of the major axis;

Length of the minor axis;

The (acute) orientation angle θ with the “radial”

direction as shown above. 

“Radial” inspection θ

direction

(thru side 1 or 4) θ

6

These measurements were made at locations 

near the centers of the four quadrants of each 

coupon, indicated by the four white dots in the 

example at left (HW coupon # 6).

Ellipse properties directly measured from DEFORM outputs:

Length of the major axis;

Length of the minor axis;

The (acute) orientation angle θ with the “radial”

direction as shown above. 

“Radial” inspection θ

direction

(thru side 1 or 4) θ

6

These measurements were made at locations 

near the centers of the four quadrants of each 

coupon, indicated by the four white dots in the 

example at left (HW coupon # 6).
2-39

that the trendline in figures 2-58 or 2-59 would pass through the point (1, 1). This is not the case 

in either figure, although it is closer for the P&W forging. This suggests that it would have been 

better to begin with billet macrograins with a greater aspect ratio. Calculations for the P&W 

forging beginning with 7:1 ellipsoids in the billet were pursued and yielded a slightly better 

correlation between grain noise anisotropy and macrograin projection ratio. That work is 

documented in references 23 and 24. 

FIGURE 2-58. CORRELATION BETWEEN GRAIN NOISE ANISOTROPY AND 

ELLIPSE PROJECTION RATIO FOR THE P&W FORGING 

FIGURE 2-59. CORRELATION BETWEEN GRAIN NOISE ANISOTROPY AND 

ELLIPSE PROJECTION RATIO FOR THE HW FORGING 

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Ellipse Projection Ratio

NAR (Axial Noise / Radial Noise) 

sample#1 sample#2

sample#4 sample#5

sample#6 sample#7

sample#8

P&W Forging Coupons

Trendline

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Ellipse Projection Ratio

sample#1 sample#2

sample#4 sample#5

sample#6 sample#7

sample#8

P&W Forging Coupons

Trendline

0.0

1.0

2.0

3.0

4.0

5.0

0 1 2 3 4 5 6

Ellipse Projection Ratio

sample#1 sample#2

sample#3 sample#4

sample#6 sample#8

sample#5 sample#7

sample#9

Honeywell Forging Coupons

Horizontal coordinate is the projection of 

the ellipse onto the axial inspection 

direction divided by the projection onto 

the radial inspection direction.

Trendline

0.0

1.0

2.0

3.0

4.0

5.0

0 1 2 3 4 5 6

Ellipse Projection Ratio

NAR (Axial Noise / Radial Noise) 

sample#1 sample#2

sample#3 sample#4

sample#6 sample#8

sample#5 sample#7

sample#9

Horizontal coordinate is the projection of 

the ellipse onto the axial inspection 

direction divided by the projection onto 

the radial inspection direction.

Trendline
2-40

A similar comparison between grain noise anisotropy and ellipse projection ratio was performed 

for the GE forging, although the only forging strain map available was that which assumed 

circular volume elements in the billet. The result is shown in figure 2-60. The measurement of 

ellipse properties was hampered by the quality of the DEFORM outputs provided by the forger 

(Ladish). In particular, for some high-deformation regions of the forging, it was not possible to 

accurately discern the dimensions of the individual ellipses in the strain map. Nonetheless, there 

is still a positive correlation for the GE forging. 

FIGURE 2-60. CORRELATION BETWEEN GRAIN NOISE ANISOTROPY AND 

ELLIPSE PROJECTION RATIO FOR THE GE FORGING, BEGINNING WITH 

CIRCULAR MACROGRAINS IN THE BILLET 

In summary, a good understanding of the noise anisotropy in Ti-6-4 forgings can be obtained by 

assuming that it is controlled by the shapes of the macrograins in the forging, which, in turn, 

arise from the macrograin shapes in the billet and the forging strain pattern. In particular, the 

noise level at a given forging location tends to be largest for the inspection direction in which the 

model macrograins present the largest cross-sectional area to the incident sound beam. 

This finding motivated further research to try to correlate absolute grain noise levels in forgings, 

rather than just noise ratios, to the DEFORM outputs. An effort was made to develop simulation 

models to predict the variation of the absolute UT grain noise level within a forging. The models 

treat the forging as an effective medium containing scattering elements (macrograins) whose 

mean properties vary systematically with position. One model input is the local geometry of a 

scattering element, including its elongation and orientation with respect to the incident UT beam; 

as before, the local macrograin geometry is calculated using DEFORM. Two additional model 

inputs are the mean volume of a scattering element (V) and a parameter (<(δC33) 2>) that 

quantifies the mean elastic property variation between neighboring scatterers. These latter two 

global inputs are assumed to be fixed throughout the forging and are deduced by fitting to a 

0

1

2

3

4

5

0 2 4 6 8 10

Ellipsoid Projection Ratio (Y/X)

Noise Anisotropy

Sample #1

Sample #4

Sample #5

Smaple #6

Sample #7

GE Ti 6-4

Forging Coupons

Trendline

0

1

2

3

4

5

0 2 4 6 8 10

Ellipsoid Projection Ratio (Y/X)

Noise Anisotropy

Sample #1

Sample #4

Sample #5

Smaple #6

Sample #7

GE Ti 6-4

Forging Coupons

0

1

2

3

4

5

0 2 4 6 8 10

Ellipsoid Projection Ratio (Y/X)

Noise Anisotropy

Sample #1

Sample #4

Sample #5

Smaple #6

Sample #7

GE Ti 6-4

Forging Coupons

Trendline
2-41

limited amount of experimental data. Mathematical details of the noise models that were 

developed for Ti engine forgings can be found in references [24, 25, and 26]. They are based on 

earlier work by Rose for the backscattered noise power scattered from randomly orientated, 

equiaxed, single-phase [27] and multiphase [28] polycrystals, and on the work of Han and 

Thompson [22] who extended Rose’s theory to the cases of duplex microstructures containing 

elongated microstructural features or texture. 

Appearing in the models is a commonly used measure of a microstructure’s noise-generating 

capability known as the backscattering power coefficient η, i.e., the differential scattering cross 

section per unit volume in the backward direction [27 and 28]. Here, it was preferred to use the 

square root of η, the grain noise FOM, since it is directly proportional to the noise voltage 

observed on an oscilloscope during UT inspection. The grain noise FOM-versus-frequency 

curve, which depends only on the metal microstructure and beam propagation direction, is 

measured by comparing the average spectral components of noise A-scans to those of a frontwall or back-wall reference signal. The grain-noise FOM and its measurement are described in 

reference 16 and the references cited therein. 

The forging noise model comes in two forms, a simpler one, which ignores the effects on 

microstructural texture (preferentially oriented crystalline axes), and a more complex model, 

which treats texture. To develop and test the noise models, the P&W Ti-6-4 forging was chosen 

because a faster turn around of DEFORM calculations was available. Beginning with 7:1 

ellipsoidal elements in the billet, the usual DEFORM strain map was generated to determine the 

shapes and orientations of the macrograins within the forging, with these serving as one class of 

noise model inputs. For the untextured model, the remaining two global parameters (macrograin 

volume V and elastic constant anisotropy factor (<(δC33)2

>) were obtained by comparing 

predicted FOM-versus-frequency curves to the measured curves for one quadrant of one forging 

flow line coupon, i.e., the quadrant closest to sides 1 and 5 of coupon PW8 (located in the rim 

region of the forging). The two model parameters were adjusted to maximize the agreement 

between the measured and predicted FOM curves, as shown in figure 2-61. The optimal average 

scatterer volume was estimated as V = 1.328e-06 cm3

, and the optimal elastic property variation 

factor was estimated as <(δC33) 2> = 9.75 GPa2

. 

Once the model parameters were determined, backscattered noise predictions could be made for 

other locations and inspection directions throughout the forging. Examples of such predictions 

are shown in figure 2-62 for inspections in the axial and radial directions of coupon PW2, 

located in the web region of the forging. Note that coupons PW2 and PW8 have very different 

local flow line geometries, as shown in figure 2-62. Also note that for PW8, the measured noise 

level is highest for radial propagation, while for PW2, it is highest for axial propagation. This 

reversal of noise directionality is well-predicted by the model. 

The noise model was also used to predict the average GPN amplitudes (relative to the FBH 

reference), which were previously measured for C-scans over each quadrant of each P&W 

coupon. The procedure used to make such predictions is described in reference 24. It makes use 

of the fact that, to a good first approximation, the average GPN amplitude within a quadrant will 

be proportional to the average FOM value near the center frequency of the transducer. For 

selected coupons, measured FOM and GPN data were both available, and these were used to find 
2-42

FIGURE 2-61. MEASURED AND FITTED GRAIN NOISE FOM CURVES FOR THE 

LOWER RIGHT QUADRANT OF FORGING COUPON PW8, ASSUMING MACROGRAINS 

WITH 7:1 ASPECT RATIOS IN THE BILLET 

FIGURE 2-62. MEASURED AND PREDICTED GRAIN NOISE FOM CURVES FOR 

INSPECTIONS THROUGH SIDES 4 AND 5 OF FORGING COUPON PW2, BASED ON 

MODEL PARAMETERS DEDUCED BY FITTING TO NOISE DATA FROM COUPON PW8 

Bore Web

Rim Side 2

Side 5

Side 4 Side 1 8

Minmizing the Sum of Errors Square to fit the Exp. 

 V=1.328E-06cm^3, <deltaC^2>=9.75 Gpa^2

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

4 6 8 10 12 14 16

Frequency (MHz)

FOM(1/cm^0.5)

side1 Exp.

Side 5 Exp.

side1_fitting

Side5 Fitting

Bore Web

Rim Side 2

Side 5

Side 4 Side 1 8

Bore Web

Rim Side 2

Side 5

Side 4 Side 1

Bore Web

Rim Side 2

Side 5

Side 4 Side 1 8

Minmizing the Sum of Errors Square to fit the Exp. 

 V=1.328E-06cm^3, <deltaC^2>=9.75 Gpa^2

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

4 6 8 10 12 14 16

Frequency (MHz)

FOM(1/cm^0.5)

side1 Exp.

Side 5 Exp.

side1_fitting

Side5 Fitting

The Predict FOM on PW #2 S5&S4

 V=1.328E-06cm^3, deltaC^2=9.75 GPa^2

0.000

0.005

0.010

0.015

0.020

0.025

0.030

4 6 8 10 12 14 16 Freque ncy (M Hz)

FOM (1/cm^0.5)

side4_Exp

side4_prediction

Side5 Exp.

Side5_Prediction

Bore Web

Rim

2

8

Side 2

Side 5

Side 4 Side 1

Side 2

Side 5

Side 4 Side 1

Prediction Fit

The Predict FOM on PW #2 S5&S4

 V=1.328E-06cm^3, deltaC^2=9.75 GPa^2

0.000

0.005

0.010

0.015

0.020

0.025

0.030

4 6 8 10 12 14 16 Freque ncy (M Hz)

FOM (1/cm^0.5)

side4_Exp

side4_prediction

Side5 Exp.

Side5_Prediction

Bore Web

Rim

2

8

Side 2

Side 5

Side 4 Side 1

Side 2

Side 5

Side 4 Side 1

Prediction Fit

Bore Web

Rim

2

8

Side 2

Side 5

Side 4 Side 1

Side 2

Side 5

Side 4 Side 1

Bore Web

Rim

2

8

Side 2

Side 5

Side 4 Side 1

Side 2

Side 5

Side 4 Side 1 2

8

Side 2

Side 5

Side 4 Side 1

Side 2

Side 5

Side 4 Side 1

Prediction Fit
2-43

the scaling factor, relating average GPN to FOM at 10 MHz. Using this scaling factor, GPN 

amplitudes could then be predicted from the model FOM curves predicted for each coupon 

quadrant. Predicted GPN amplitudes are compared with the experiment for the P&W forging in 

figure 2-63, using the untextured version of the noise model. Each forging coupon yielded eight 

plotted points, corresponding to the combination of four quadrants and two inspection directions 

(axial and radial). The simplified model treatment ignores the fact that UT attenuation varies 

throughout the forging, and effectively ignores the frequency dependence of FOM. Nonetheless, 

one observes a good correlation between measured and predicted GPN amplitudes, which each 

vary by a factor of 5 within the forging. If the model were exact, the points in figure 2-63 would 

all lie along a diagonal line through the plot region. The largest departures from this ideal 

situation generally occurred for coupons 5 and 6, where, as noted earlier, the macroetch reveals 

flow lines having a swirling appearance. 

FIGURE 2-63. MEASURED AND PREDICTED AVERAGE GPN AMPLITUDES FOR 

THE VARIOUS QUADRANTS OF THE FORGING FLOW LINE COUPONS FROM THE 

P&W FORGING (RELATIVE TO A VALUE OF 100 FOR THE #1 FBH IN THE 

IN100 REFERENCE BLOCK) 

Recall that in addition to the rectangular coupons, one cylindrical coupon was cut from a highstrain region of each OEM-supplied forging. Backscattered noise measurements were performed 

using these three cylindrical coupons to investigate the variation of noise with rotation angle. 

Figure 2-64 shows the GPN C-scan obtained by stacking the three 1.25′′ diameter coupons atop 

one another and performing a rotational-axial scan using a 5-MHz cylindrically focused 

transducer. For a full rotation of each of the cylindrical forging coupons, one observes a pattern 

of low-high-low-high noise amplitude. 

Predicte d GPN Vs. Experime ntal GPN 

(Normalize d by #1FBH in 1N100 ), 

V=1.328E-06 cm^3, <de ltaC^2>=9.75GPa^2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Norm a lize d GPN by Pre diction

Norm alized GP N from Experim

PW#1 PW#2 PW#4

PW#5 PW#6 PW#7

PW#8
2-44

FIGURE 2-64. GATED-PEAK GRAIN NOISE C-SCAN IMAGE RESULTING FROM A 

ROTATIONAL-AXIAL SCAN OF THE CYLINDRICAL COUPONS FROM THE 

HIGH-STRAIN REGIONS OF THE THREE Ti-6-4 FORGINGS 

(A cylindrically focused, 0.5′′ diameter, 5-MHz transducer having a nominal 4-cm 

focal length was used. The inspection water path was 2.4 cm.) 

The cylindrical coupon from the P&W forging was used to further test the two-parameter 

(untextured) noise model. Measured and predicted angular noise profiles are shown in 

figure 2-65. The model curve is the predicted FOM profile (at 10 MHz) scaled to have about the 

same peak amplitude as the experimental curve. As before, the experimental and model 

quantities are expected to be approximately proportional to one another, although the scaling 

factor will be different from that used earlier because of the effect of the curved entry surface. 

The model (in this case, based on 7:1 ellipsoidal volume elements in the billet) successfully 

predicts the overall shape of the angular profile, but with somewhat sharper peaks than the 

experiment. The model tests, using the cylindrically focused transducer, are discussed in 

reference 24. 

The version of the grain noise model used in figure 2-61 through 2-65 did not account for metal 

texture that is known to be generated by forging processes [25]. Large deformations during 

forging are expected to cause partial alignment of crystallites by slip, twinning, or their 

combination. Such deformation-dependent texture will cause the elastic property variability 

factor, <δC332

>, to vary with position inside the forging. A second version of the model 

formalism was developed, which accounts for both strain and texture, and model predictions 

were similarly performed and compared with experiment. This more complex model is 

discussed in references 25 and 26. Figure 2-66, taken from reference 25, compares measured 

and predicted absolute grain noise levels in the P&W forging, in the style of figure 2-63. Taken 

PW3

GE2

HW10

Degrees

PW#3

GE#2

HW#10

PW3

GE2

HW10

Degrees

PW#3

GE#2

HW#10
2-45

as a whole, the collection of plotted points in figure 2-66, which used a texture effect, lie closer 

to the ideal diagonal line (representing perfect correlation between model and experiment) than 

figure 2-63 (noise model without a texture effect). 

FIGURE 2-65. COMPARISONS OF MEASURED AND PREDICTED ANGULAR 

PROFILES FOR BACKSCATTERED GRAIN NOISE IN THE CYLINDRICAL 

COUPON FROM THE WEB REGION OF THE P&W Ti-6-4 FORGING 

00 3600

C-scan Image of Gated-Peak Noise (GPN) from cylindrical coupon PW3

Bore Web

Rim

3

Angle

Angle Between Macrograin Major Axis and Inspection Direction (Degrees) Angular Profiles of Measured Average Gated- Peak Noise and Predicted FOM at 5 MHz.

Model

Experiment

00 3600

C-scan Image of Gated-Peak Noise (GPN) from cylindrical coupon PW3 C-scan Image of Gated-Peak Noise (GPN) from cylindrical coupon PW3

Bore Web

Rim

3

Angle

3

Angle

Angle Between Macrograin Major Axis and Inspection Direction (Degrees) Angular Profiles of Measured Average Gated- Peak Noise and Predicted FOM at 5 MHz.

Model

Experiment
2-46

FIGURE 2-66. MEASURED AND PREDICTED AVERAGE GATED-PEAK GRAIN 

NOISE AMPLITUDES FOR VARIOUS QUADRANTS OF THE FORGING FLOW 

LINE COUPONS FROM THE P&W FORGING 

(Absolute noise amplitudes are relative to a value of 100 

for the #1 FBH in the IN100 reference block.) 

The following briefly summarizes the model development work performed to better understand 

grain noise variability within forgings. 

A fairly simple two-parameter model was first developed that can predict grain noise variations 

within Ti-6-4 forgings. The model approximates the forging microstructure as an effective 

medium containing scattering elements, referred to here as macrograins, in which the average 

macrograin volume is constant throughout the forging, and the crystalline axes of the grains are 

randomly oriented relative to one another. The shapes and orientations of the macrograins were 

deduced from DEFORM simulations of material strain and, consequently, vary throughout the 

forging. The two global (constant) model parameters, the mean volume of the scattering 

elements and the elastic property variability, were obtained by fitting to noise data for one 

particular region of the P&W Ti-6-4 forging. Model testing was then done by comparing 

predictions with experimental data for (1) FOM-versus-frequency curves for selected rectangular 

coupons, (2) mean GPN amplitudes within the four quadrants of each of the seven rectangular 

coupons cut from different regions of the forging, and (3) angular dependence of grain noise for 

one cylindrical coupon cut from the web region of the forging. Reasonable agreement between 

experiment and theory was achieved, indicating the model captured the main factors that control 

the variability of backscattered grain noise within the forging. The simple two-parameter model 

neglects metal texture that develops in high-strain regions of the forging (i.e., preferentially 

oriented crystalline axes, as indicated by velocity anisotropy). A more complex model that treats 

texture effects was developed, which appears to produce slightly better agreement with 

experiment. (See references 24, 25, and 26 for more details.) Note that these modeling efforts, 

to relate UT grain to forging strain, are a work-in-progress, and the results in the present report 

are only preliminary. It is anticipated that future updated results should be available in the 

Measured and Predicted Gated Peak Noise in P&W Forging 

[ V=1.167E-06 cm^3, <deltaC^2_Opt>=14.25GPa^2 ]

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Predicted GPN Level

Experimental GPN Level

PW#1 PW#2 PW#4

PW#5 PW#6 PW#7

PW#8
2-47

PhD thesis of Linxiao Yu [26] and in planned publications in the open scientific literature, which 

will be based on that thesis. 

For the forging flow line coupons, the primary interest was the study of noise variability, since, 

in practice, backscattered grain noise is generally the key UT property that determines flaw size 

detection limits. However, noise and velocity variations in the forgings and their relationship to 

forging strain were examined. As with backscattered noise, there were correlations between the 

attenuation and velocity anisotropies and various measures of the forging strain, as shown in 

figures 2-67 and 2-68. In analogy with backscattered noise, the attenuation anisotropy for a 

given coupon was defined as the ratio of the attenuation values in the axial and radial directions 

at some fixed frequency. Then the anisotropy ratio was compared to a dimensionless measure of 

the total strain developed during forging at the location of the coupon. The strain measure used 

in figures 2-67 and 2-68 was based on the DEFORM calculations, which showed how circular 

volume elements in the radial-axial plane of the billet were deformed into elliptical elements in 

the radial-axial plane of forging. The circular element calculations were used because they were 

available for all three forgings. For these two figures, the simple ratio of the major to minor 

ellipse axes (averaged over the coupon volume) was used as the measure of the deformation 

strain amplitude, and noise and attenuation values for a given propagation direction were 

averaged over the coupon quadrants. As shown in figure 2-67, both noise and attenuation 

anisotropies were found be correlated to deformation strain amplitude, but in opposite manners. 

At sites where the radial noise exceeded the axial noise, it was generally found that the axial 

attenuation exceeded the radial attenuation. A similar behavior was observed in the ETC Phase I 

studies of Ti-6-4 billet coupons and was traced to the shapes of the macrograins in billets [16]. 

The current work further indicates that macrograin shape and orientation also play an important 

role in determining the UT attenuation variations within forgings. The velocity anisotropy of the 

forging coupons was also examined and found to be correlated with forging strain amplitude, as 

shown in figure 2-68, although the degree of correlation was somewhat less than for noise or 

attenuation. The quantity plotted on the vertical axis in figure 2-68 is the percentage difference 

in velocities measured in the axial and radial directions. The horizontal axis again displays the 

ratio of the major to minor ellipse axes of the deformed volume elements averaged over the 

coupon in question. Developing models to predict velocity and attenuation variations within 

forgings would be an interesting topic for future research. The measured UT properties of the 

forging flow line coupons and the related forging strain maps reported herein can serve as data 

for guiding the development and testing of such models. 

2.2.4 Identification of the High-Noise Coupons and Measurements of Grain Noise FOM. 

When designing UT inspections of forgings, the high-noise regions are of chief interest since the 

elevated grain noise levels there can mask echoes from small or weakly reflecting defects. For 

this reason, additional UT measurements were performed for the highest-noise coupon from each 

OEM-supplied forging. These additional measurements included determination of the 

attenuation and the backscattered grain noise capacity (FOM), both of which are frequencydependent quantities determined solely by the metal microstructure. Although all the forging 

flow line coupons were cut from high-noise quadrants of their respective forgings, some coupons 

had higher grain noise levels than others. The highest-noise coupon from each forging was 

identified by comparing backscattered noise C-scans, such as those contained in appendix A. 

All the rectangular coupons were examined, including a few that were smaller than the standard 
2-48

size (1.25′′ by 1.25′′ by 2.0′′). The highest-noise coupons from each forging were all found to be 

of standard size, i.e., coupons GE6, PW8, and HW5. The locations of these coupons within their 

respective forgings and the inspection directions producing the highest grain noise levels are 

illustrated in figures 2-69 through 2-71. Backscattered noise C-scan images are also shown. 

FIGURE 2-67. RELATIONSHIPS BETWEEN NOISE ANISOTROPY, ATTENUATION 

ANISOTROPY, AND TOTAL FORGING STRAIN FOR COUPONS CUT FROM VARIOUS 

LOCATIONS IN OEM-SUPPLIED Ti-6-4 FORGED ENGINE DISKS 

FIGURE 2-68. RELATIONSHIP BETWEEN VELOCITY ANISOTROPY AND LOCAL 

TOTAL FORGING STRAIN FOR Ti-6-4 FORGING FLOW LINE COUPONS 

Noise Anisotropy = 

Noise in Axial Dir. 

Noise in Radial Dir. 

Atten. Anisotropy = 

Atten. (10 MHz) in Axial Dir. 

Atten. (10 MHz) in Radial Dir. 

Attenuation Anisotropy Vs. Total Strain 

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10

Deformation Strain 

Attenuation Anisotropy

HW Coupons

GE Coupons

PW Coupons

Noise Anisotropy Vs. Total Strain

0

1

2

3

4

5

0 2 4 6 8 10

Deformation Strain 

Noise Anisotropy

HW Coupons

GE Coupons

PW Coupons

Noise Anisotropy Vs. Attenuation Anisotropy

0

1

2

3

4

5

0 0.5 1 1.5 2 2.5

Attenuation Anisotropy

Noise Anisotropy

HW Coupons

GE Coupons

PW Coupons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 2 4 6 8 10

Average Strain (Y/X)

Percentage Velocity 

Variation from Radial to Axial

HW Coupons

GE Coupons

PW Coupons
2-49

FIGURE 2-69. LOCATION AND BACKSCATTERED GRAIN NOISE C-SCAN FOR THE 

HIGHEST-NOISE COUPON IN THE GE-SUPPLIED Ti-6-4 FORGING 

FIGURE 2-70. LOCATION AND BACKSCATTERED GRAIN NOISE C-SCAN FOR THE 

HIGHEST-NOISE COUPON IN THE P&W-SUPPLIED Ti-6-4 FORGING 

Side labels for 

Coupon GE6

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

C-scan Thru

Side 1 (34 dB)

Hoop

Side 2Side 5

Side labels for 

Coupon GE6

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

4 2

5 1

(Hoop)

AFT

FWD

ID 3 OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

US

UG

UR

UP

UO

UZ

UM

UL

UK

UJ

UH

US

1

2

4

8 5

3

6

7

AFT

FWD

ID

OD

C-scan Thru

Side 1 (34 dB)

Hoop

Side 2Side 5

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

Side labels for 

Coupon PW8

2

4

5

1

(Hoop)

TOP

BOT

ID OD 3

C-scan Thru

Side 4 = ID (33 dB) BOT TOP

HOOP

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

Bore Web Rim

1

2

3

4

5

6

7

8

Top

Bottom

Side labels for 

Coupon PW8

2

4

5

1

(Hoop)

TOP

BOT

ID OD 3

Side labels for 

Coupon PW8

2

4

5

1

(Hoop)

TOP

BOT

ID OD 3

C-scan Thru

Side 4 = ID (33 dB) BOT TOP

HOOP
2-50

FIGURE 2-71. LOCATION AND BACKSCATTERED GRAIN NOISE C-SCAN FOR THE 

HIGHEST-NOISE COUPON IN THE HW-SUPPLIED Ti-6-4 FORGING 

The C-scans of the high-noise coupons from the P&W and HW forgings are reasonably uniform 

in amplitude over the inspected face; for these, average attenuation and FOM values were 

deduced from scans over the central regions of each coupon (away from edge effects). Because 

of the nonuniformity of the noise C-scan for coupon GE6, separate property measurements were 

made for the left and right halves of the coupon, as inspected through side 1, and those from the 

higher-noise (right) half will be quoted here. As noted in appendix A, two inspection systems 

were used to produce the C-scans shown in figures 2-69 through 2-71 (one for the GE and P&W 

coupons, and another for the HW coupons); therefore, the absolute noise levels in the images are 

not all directly comparable. 

Measurements of attenuation and FOM values, which required digitized back-wall or 

backscattered noise RF waveforms, were made using a different UT system than that used for the 

C-scan images. The same UT system used to measure the attenuation-versus-frequency curves 

for the forging flow line coupons was used for these measurements. Again, all required A-scans 

were digitized at a 100-MHz sampling rate. Attenuation was again measured by comparing the 

spectra of back-wall echoes in the coupon with those of a 1′′ thick FQ reference block, using a 

10-MHz, 0.25′′ diameter planar probe. FOM values were measured by comparing the spectra of 

grain noise echoes in the coupon with the spectra of the back-wall echo from a 1/2′′ thick FQ 

block. The 15-MHz, 0.5′′ diameter, F = 90-mm focused transducer was used for the FOM 

measurements, with the beam roughly focused 0.32′′ deep, i.e., near the center of upper half of 

the coupon thickness. Attenuation and FOM measurement procedures were essentially identical 

to those used during ETC Phase I, which are described in some detail in reference 16. All FOM 

values quoted in this report are in standard units of centimeters to the negative one-half power. 

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1

2

3

4

5

6

7 8

9

10

AFT

FWD

ID OD

Side labels for 

Coupon HW5

2

5

4

1 (Hoop)

AFT

FWD

ID OD 3

C-scan Thru

Side 4 (31 dB)

(Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1

2

3

4

5

6

7 8

9

10

AFT

FWD

ID OD

1

2

3

4

5

6

7 8

9

10

AFT

FWD

OD

1

2

3

4

5

6

7 8

9

10

AFT

FWD

ID OD

Side labels for 

Coupon HW5

2

5

4

1 (Hoop)

AFT

FWD

ID OD 3

Side labels for 

Coupon HW5

2

5

4

1 (Hoop)

AFT

FWD

ID OD 3

C-scan Thru

Side 4 (31 dB)

(Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)
2-51

The velocity and attenuation measurements (averaged over entry surfaces) that were performed 

for all the standard-sized forging flow line coupons. The results for the high-noise coupons PW8 

and HW5 were checked by repeating the measurements, and for coupon GE6, separate 

attenuation measurements were taken for the left and right halves of the side 1 entry surface. A 

power-law fit to the attenuation data for each high-noise coupon was then performed, as 

illustrated in figure 2-72 for the HW case. In that figure, average measured attenuation values 

are shown for scans over two areas of the coupon: a full scan region (central region measuring 

1.5′′ by 0.75′′ at the entry surface) and a reduced-area region (central 1.25′′ by 0.50′′). The 

measured attenuation values are very similar for the two regions. For GE6, there was little 

difference in measured velocity or attenuation for the two halves of the coupon, but the noise 

FOM values were found to be quite different, as expected from the noise C-scan image. 

FIGURE 2-72. MEASURED ATTENUATION VALUES AND POWER-LAW 

FIT FOR THE HW HIGH-NOISE COUPON 

Because the microstructure typically varies with depth, FOM values were deduced for a series of 

depths by using time gates with different centers and durations. The results of the procedure are 

shown in figures 2-73 through 2-75 for the high-noise HW coupon. Figure 2-73 shows the root 

mean squared (rms) grain noise level as a function of time for the scan above side 4. The rms 

noise level (deduced from noise A-scans described in references 16 and 29) depicts the manner 

in which the absolute grain noise level varies with observation time or, equivalently, with depth 

within the specimen. For uniform microstructures, the rms noise level tends to peak near the 

round-trip travel time to the focal zone. Six time gates spanning different depth zones are also 

shown in figure 2-73. FOM-versus-frequency curves were deduced separately from the grain 

noise echoes within each of these gates, and the results are shown in figure 2-74. The FOM 

extraction procedure [16] requires knowledge of the attenuation-versus-frequency curve, and the 

measured attenuation curve (which is actually an average over the coupon thickness) was used in 

the analysis. One sees in figure 2-74 that the deduced FOM curve depends somewhat on the 

time gate used. This dependence is believed to be primarily due to the forging microstructure 

0.00

0.01

0.02

0.03

0.04

0.05

4 6 8 10 12 14 16 18

Frequency (MHz)

Attenuation (Nepers/cm)

Full scan region

Reduced scan region

Power Law Fit

fit is 0.00082 x freq1.343
2-52

varying with depth. The highest FOM values for coupon HW5 in the 5-20 MHz range were 

obtained for gate 3, which was centered 0.56′′ beneath the entry surface. A power-law fit to the 

FOM-versus-frequency data for this gate was then made, with the results shown in figure 2-75. 

FIGURE 2-73. THE RMS BACKSCATTERED GRAIN NOISE LEVEL WITHIN THE 

HIGH-NOISE HW FORGING COUPON 

FIGURE 2-74. DEDUCED GRAIN NOISE CAPACITY (FOM) FOR THE 

HIGH-NOISE HW FORGING COUPON 

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0 1 2 3 4 5 6 7 8 9 10

Time after Front Wall Echo (usec)

RMS Noise (Volts)

Gate Center Duration

G1 2.61 us (0.32”) 2.55 us

G2 3.61 us (0.44”) 1.27 us

G3 4.61 us (0.56”) 1.27 us

G4 5.61 us (0.69”) 1.27 us

G5 6.61 us (0.81”) 1.27 us

G6 3.90 us (0.48”) 5.11 us

G4

G5

G1

G2

G3

G6

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0 1 2 3 4 5 6 7 8 9 10

Time after Front Wall Echo (usec)

RMS Noise (Volts)

Gate Center Duration

G1 2.61 us (0.32”) 2.55 us

G2 3.61 us (0.44”) 1.27 us

G3 4.61 us (0.56”) 1.27 us

G4 5.61 us (0.69”) 1.27 us

G5 6.61 us (0.81”) 1.27 us

G6 3.90 us (0.48”) 5.11 us

G4

G5

G1

G2

G3

G6

H5 Side 4 FOM (using meas. atten) 

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

5.0 10.0 15.0 20.0

Frequency (MHz)

FOM (std. units)

Gate #1 Gate#2

Gate#3 Gate#4

Gate#5 gate#6
2-53

FIGURE 2-75. MEASURED FOM CURVE AND ASSOCIATED POWER-LAW FIT FOR 

THE HIGHEST-NOISE DEPTH ZONE WITHIN THE HIGH-NOISE COUPON 

FROM THE HW Ti-6-4 FORGING 

Similar analyses were performed for the highest-noise coupons from the GE and P&W forgings. 

Measured FOM-versus-frequency curves for the same set of six depth zones are shown in 

figure 2-76. Again, for each coupon, a power-law fit was made to the FOM curve for the depth 

zone having the largest FOM values. The results for the three high-noise coupons are compared 

in table 2-3 for the depth zone having the highest noise capacity. Listed noise FOM values are 

conservative in the sense that they are the highest values measured for any depth zone in these 

coupons. The peak grain noise FOM value was largest for the HW forging and roughly similar 

for the GE and P&W forgings. Note that the differences in FOM values in table 2-3 are greater 

than the corresponding differences in average noise values listed in table 2-2. This is chiefly 

because, in the survey measurements leading to table 2-2, only GPN amplitudes were measured 

(relative to an FBH reference), and the focal spot of the transducer was not necessarily located in 

the depth zone where the noise capacity was greatest. For table 2-3 however, noise A-scan data 

were analyzed in a manner that identified the depth zone with the greatest noise capacity. In 

addition, the FOM measurement procedure accounts for the differences in attenuation of the 

various coupons, which also affect absolute grain noise levels. 

The UT properties listed in table 2-3 were originally compiled to support PoD computations 

planned under the suspended PoD of forgings subtask. These properties can be used as inputs to 

computer models that simulate UT inspections of forgings and estimate S/N ratios for defects of 

various types. Examples of such simulations for one proposed forging inspection scheme can be 

found in an article written for the 2001 QNDE conference held in Brunswick, Maine [23]. 

H5 Side 4 FOM (using meas. atten) 

y = 0.00415x1.07820

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

4 6 8 10 12 14 16

Frequency (MHz)

FOM (std. units)

Gate#3

Pow er (Gate#3)
2-54

FIGURE 2-76. MEASURED GRAIN NOISE FOM VALUES, AS FUNCTIONS OF 

FREQUENCY, FOR THE GE AND P&W HIGH-NOISE FORGING COUPONS 

TABLE 2-3. COMPARISON OF UT PROPERTIES FOR THE HIGH-NOISE COUPONS 

FROM THE P&W, GE, AND HW Ti-6-4 FORGINGS 

 P&W GE HW 

Velocity (cm/μsec): 0.622 0.618 0.621 

Density (gm/cc): 4.43 4.43 4.43 

Attenuation power law*: 6.83E-4*freq.1.79 4.31E-5*freq.2.26 8.20E-*freq.1.34

Attenuation at 10 MHz: 0.93 dB/inch 0.17 dB/inch 0.40 dB/inch 

FOM power law*: 1.61E-3*freq.1.25 2.93E-3*freq.0.896 4.15E-3*freq.1.078

Meas. FOM at 10 MHz: 0.027 0.021 0.047 

*For power laws, units are N/cm for attenuation, and cm-0.5 for FOM, with the frequency input in MHz. 

0.000

0.010

0.020

0.030

0.040

0.050

5 10 15 20

Frequency (MHz)

FOM (cm^-0.5)

Gate #1 Gate#2

Gate#3 Gate#4

Gate#5 Gate#6

PW8 Side 4 FOM

(Deduced With Measured Attenuation) 

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

5.0 10.0 15.0 20.0

Frequency (MHz)

FOM (cm^-0.5)

Gate #1 Gate#2

Gate#3 Gate#4

Gate#5 Gate#6

GE6_side1

(high noise half)

PW6_side4

0.000

0.010

0.020

0.030

0.040

0.050

5 10 15 20

Frequency (MHz)

FOM (cm^-0.5)

Gate #1 Gate#2

Gate#3 Gate#4

Gate#5 Gate#6

PW8 Side 4 FOM

(Deduced With Measured Attenuation) 

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

5.0 10.0 15.0 20.0

Frequency (MHz)

FOM (cm^-0.5)

Gate #1 Gate#2

Gate#3 Gate#4

Gate#5 Gate#6

GE6_side1

(high noise half)

PW6_side4
2-55

2.2.5 Determination of Pulse Volume for #1/2 FBH Detection Sensitivity. 

A key goal of the Inspection Development for Titanium Forging was to design an inspection 

scheme that achieves #1/2 FBH sensitivity in Ti-6-4 engine forgings. That is, for typical engine 

forgings such as the three studied in this report, the designed inspection should be able to reliably 

detect defects whose reflected amplitude equals or exceeds that of a 1/128′′ diameter FBH. As 

discussed below, flaw detection limits, as quantified by S/N ratios, are largely determined by the 

volume of the incident UT pulse that insonifies the defect. Thus, when designing a zoning 

scheme and choosing transducers, one of the key steps was to define the requirements on the UT 

PV. This is the approach that was taken here, and a new series of experiments was conducted 

using the three high-noise forging coupons to determine the PV requirements for #1/2 sensitivity. 

In a given P/E forging inspection, the absolute grain noise level and the absolute strength of an 

echo from a small defect depended on a number of factors, including 

• the transducer’s diameter and focal properties. 

• the sound hotness of the transducer (i.e., its efficiency for converting electrical energy to 

sound). 

• the inspection water path. 

• the surface curvature of the part being inspected. 

• the defect location with respect to the incident beam. 

• the UT attenuations of water and metal. 

• the inherent noisiness of the metal microstructure (i.e., the FOM value). 

• the inherent reflectivity of the defect (i.e., its so-called scattering amplitude). 

Simulation models have been developed over the years, which take into account all of the above 

factors, and endeavored to predict the absolute backscattered grain noise level and the absolute 

flaw signal amplitude in a given inspection. See, for example, reference 7 and Appendix B of 

reference 16. When such models are used to estimate S/N ratios, some of the above factors 

largely cancel, and a fairly simple rule of thumb can be developed by making a series of 

reasonable approximations to the model formalism. For example, material attenuation acts to 

decrease the defect echo and the echoes from nearby metal grains in much the same fashion, and 

thus, largely cancels when S/N is computed. 

Such a rule of thumb, developed in references 19 and 20, is illustrated in figure 2-77. It 

essentially says that for a fixed inspection frequency, S/N is proportional to 1 over the square 

root of the sonic PV at the flaw depth. The rule is specifically for S/N computed using the peak 

(on axis) flaw amplitude and the rms average grain noise level. However, other measures of 

noise (such as average GPN or maximum GPN within a specified scan area) are roughly 

proportional to the rms noise. Thus, the general form of the rule of thumb roughly applies for 
2-56

those other noise measures as well. If the probe center frequency changes, it is likely that the PV 

flaw scattering amplitude and microstructural FOM will all change. However, for an FBH defect 

in Ti engine alloys, both the FOM and the flaw-scattering amplitude are roughly proportional to 

frequency [16]. Thus, Aflaw/FOM is roughly independent of frequency, and one can argue that 

S/N remains roughly proportional to 1/square root of PV even for situations where the frequency 

changes. 

g

Flaw << beam size

Consider the case of a small 

flaw located somewhere along 

the beam’s central ray (but not 

necessarily at the focus):

Using “Gaussian Beam 

approximations”, one can 

show that the ratio of flaw 

signal amplitude to 

“localized rms grain noise” is 

approximately given by:

0

0

16 ( )

( )

flaw

metal x y

S A f

N v w w t FOM f π = Δ

pulse

duration lateral beam

widths at flaw 

depth

Noise FOM at 

center frequency

Flaw scat. ampl. at 

center frequency

Sonic pulse

Or: S

N Volume of

Ultrasonic Pulse

~

1 S

N Volume of

Ultrasonic Pulse

~

1

g

Flaw << beam size

Consider the case of a small 

flaw located somewhere along 

the beam’s central ray (but not 

necessarily at the focus):

Using “Gaussian Beam 

approximations”, one can 

show that the ratio of flaw 

signal amplitude to 

“localized rms grain noise” is 

approximately given by:

0

0

16 ( )

( )

flaw

metal x y

S A f

N v w w t FOM f π = Δ

pulse

duration lateral beam

widths at flaw 

depth

Noise FOM at 

center frequency

Flaw scat. ampl. at 

center frequency

0

0

16 ( )

( )

flaw

metal x y

S A f

N v w w t FOM f π = Δ

pulse

duration lateral beam

widths at flaw 

depth

Noise FOM at 

center frequency

Flaw scat. ampl. at 

center frequency

Sonic pulse

Or: S

N Volume of

Ultrasonic Pulse

~

1 S

N Volume of

Ultrasonic Pulse

~

1 S

N Volume of

Ultrasonic Pulse

~

1 S

N Volume of

Ultrasonic Pulse

~

1

FIGURE 2-77. RULE OF THUMB RELATING S/N RATIO TO UT PV 

Various tests of the simulation models and the rule of thumb were performed during ETC 

Phase I. One example is shown in figure 2-78, using backscattered grain noise data acquired by 

Howard and Gilmore [30]. The experiment setup is shown at the top of the figure. Howard and 

Gilmore made measurements on three rectangular Ti alloy forging specimens using nine 

different circular, spherically focused transducers having nominal center frequencies ranging 

from 5 to 10 MHz. The PV of each transducer was determined in two steps: (1) by measuring 

the time duration of a back-wall echo and (2) by measuring the lateral area of the focal spot. The 

latter was done by scanning the transducer over a #1 FBH in a reference block and analyzing the 

resulting C-scan image. Backscattered gated-peak grain noise C-scan images were then obtained 

for scans over the forging specimens using an 8-microsecond-wide time gate centered at the 

focal plane, and noise attributes normalized to the peak echo from the #1 FBH reference were 

plotted versus PV. The results for the average GPN amplitudes, as presented in the original 

reference, are shown in the left-hand graph in figure 2-78. The plotted points for each specimen 

are essentially N/S ratios, and as such, are expected to rise like the square root of the PV if the 

rule of thumb holds. In the right-hand graph in figure 2-78, the measured data and model 

predictions have been plotted versus the square root of the PV, and the N/S values have also been 

renormalized such that the nine measurements for each specimen have a mean N/S value of 

unity. The measured data are seen to rise approximately linearly with the square root of PV, as 

expected. Also shown in the right-hand panel of figure 2-78 are predictions for two versions of 
2-57

the inspection simulation models, before the approximations leading to the rule of thumb are 

made. Further details can be found in references 19 and 30. 

FIGURE 2-78. NOISE-TO-SIGNAL DATA FOR THREE Ti FORGING SPECIMENS USED 

TO TEST THE PV RULE OF THUMB 

To determine the PV requirement needed to achieve #1/2 FBH sensitivity for the representative 

Ti-6-4 forgings, a measurement and analysis procedure similar to that shown in figure 2-78 was 

followed. Each of the three high-noise coupons from the OEM-supplied forgings (i.e., coupons 

PW8, GE6, and HW5) were repeatedly scanned using four 10-MHz transducers with different 

focal characteristics to achieve a wide range of pulse volume values. These measurements were 

all performed at GE Quality Technology Center in Cincinnati. The transducers used had Fnumbers (focal length to diameter ratios) of F5, F6, F7, and F8, respectively. Their nominal 

diameters and focal lengths were (dia., foc.) = (1.2′′, 6′′), (1.0′′, 6′′), (1.0′′, 7′′), and (0.75′′, 6′′), 

respectively. The peak noise values in the C-scans, normalized by the amplitude from a #1 FBH 

reference, were then plotted versus the square root of the measured PV. Prior to the 

measurements, arrays of #1 FBHs were drilled into two of the high-noise coupons (PW8 and 

GE6), with one of the FBHs in coupon PW8 serving as the reference reflector. These holes were 

drilled approximately 0.15′′ deep into the noisiest faces of the coupons, resulting in an inspection 

depth of about 1.1′′ when insonified through the opposite face. In particular, six #1 FBHs were 

drilled into side 4 of PW8, and nine #1 FBHs were drilled into side 1 of GE6. At a later time, 

after the measurements described below were completed, six #1 FBHs were drilled into side 4 of 

coupon HW5. 

Pulse

duration

measurement

Beam spot

Size and FBH 

amplitude meas.

Noise measurement

focal plane

0

200

400

600

800

1000

0 200 400 600 800 1000 1200

Pulse Volume (units of 1E-6 cu. in.)

Mean Noise Amplitude

Ti-17A

Ti-17B

Ti-64

EXPERIMENT

#1 FBH = 204

N/S data of Howard and Gilmore

0.0

0.5

1.0

1.5

2.0

2.5

0 10 20 30 40

Sq. Root of Pulse Volume 

(units of 1E-3 cu. in.)

Mean N/S Ratio (Ave. = 1)

Ti-64

Ti-17A

Ti-17B

Theory-STB

Theory-BB

N/S data of Howard and Gilmore 

(replotted)
2-58

The C-scan data for one case is shown in figure 2-79. The transducer was the F6 probe, and the 

water path was chosen to focus the sound beam at the depth of the FBHs. The inspection gain 

was set such that the response from the #1 FBH reference hole would be at 320% FSH, or 

equivalent, and that the response from a #1/2 FBH would be approximately 80% FSH. The peak 

noise was measured for each of the high-noise coupons shown in the figure, resulting in 30.6%, 

43.0%, and 36% FSH for the P&W, HW, and GE coupons respectively. The time gate used for 

all C-scan measurements was 1.6 microseconds wide (corresponding to about 0.2′′ of metal 

depth), centered approximately at the FBH depth. 

FIGURE 2-79. NOISE-TO-SIGNAL MEASUREMENTS FOR THE THREE 

HIGH-NOISE FORGING COUPONS 

In addition to the N/S measurements, sonic PVs were also measured. First, the -6dB beam 

diameter at the FBH depth was determined from a fine-increment C-scan of the reference hole in 

the PW8 coupon. Figure 2-80 shows the beam diameter determination for the F6 example, 

leading to a value of 39.4 mils. Second, as shown in figure 2-81, the pulse duration was 

measured by finding the -6 dB points for the envelope function of the rectified FBH echo, then it 

was translated to a pulse length in metal. For the case shown, the pulse length was 36.7 mils, 

leading to a measured PV of (π/4)(39.4 mils)2

(36.7mils) = 44,600 cubic mils. 

Similar measurements of peak N/S amplitudes and sonic PVs were made for a total of nine 

configurations (transducer and water path combinations). For most transducers, measurements 

were made using more than one water path to vary the beam spot size at the FBH depth. For the 

F6 transducer, for example, three water paths were used: one chosen to maximize the amplitude 

from the reference FBH and two longer water paths for which the peak FBH amplitude was 

down by 3 and 6 dB, respectively, from the first case. Measured N/S amplitudes and sonic PVs 

#1/2 FBH ~ 80% 

HW5

Max noise

43%

GE6

Max. noise

36%

PW8

Max. noise

30.6%
2-59

for the nine measurement configurations are listed in table 2-4, and N/S is plotted versus the 

square root of PV, as shown in figure 2-82. For each coupon, the trend of the data approximately 

follows a straight line that passes through the origin, as expected from the rule of thumb. The 

slope of the line is different for each coupon; that slope is expected to be approximately 

proportional to the average FOM value within the time gate, although, strictly speaking, one 

would need to measure both the noise level and the FBH reference amplitude in the same 

specimen for this to be true. Coupon HW5 has the highest slope while the slopes for the PW8 

and GE6 coupons are similar. This ordering is in good agreement with the ordering of peak 

FOM curves near 10 MHz for these three coupons. 

FIGURE 2-80. BEAM DIAMETER DETERMINATION FOR THE 10-MHz 

F6 TRANSDUCER FOCUSED AT THE FBH DEPTH 

FIGURE 2-81. PULSE DURATION DETERMINATION FOR THE 

10-MHz F6 TRANSDUCER FOCUSED AT THE FBH DEPTH 

FBH C-scan

All pixels with amplitudes within 6 

dB of the maximum are located, 

and their joint area is measured.

Microseconds 

0

25

50

75

100

125

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Amplitude 

The full width of the 

envelope of the rectified 

FBH echo at the –6 dB 

level (50% of the maximum) 

is 0.150 microseconds.

F6-0dB-Rect

F6-0dB-Env
2-60

TABLE 2-4. MEASURED SONIC PV AND PEAK N/S RATIOS FOR THE HIGHEST-NOISE 

COUPONS FROM THE THREE OEM-SUPPLIED Ti-6-4 FORGINGS 

Peak N/S Ratio 

Transducer Location 

PV 

(cubic mils) 

PV 

(Sqrt) PW8 HW5 GE6 

F5 0 dB 20173 142.0324 25.0 29.0 25.0 

F5 -3 dB 26633 163.1952 29.8 41.5 31.3 

F5 -6 dB 34972 187.0091 39.0 50.9 39.2 

F6 0 dB 44613 211.2176 30.6 43.0 36.0 

F6 -3 dB 57029 238.8072 38.4 58.8 47.0 

F6 -6 dB 69354 263.3516 42.7 66.3 54.9 

F7 0 dB 51013 225.8606 40.8 43.9 37.6 

F7 -3 dB 68170 261.0929 48.0 67.5 52.5 

F8 0 dB 79673 282.2649 53.0 74.5 50.0 

FIGURE 2-82. PEAK N/S VS THE SQUARE ROOT OF PV FOR 

MEASUREMENTS PERFORMED ON THE HIGHEST-NOISE COUPONS 

CUT FROM THE THREE OEM-SUPPLIED Ti-6-4 FORGINGS 

As discussed in the ETC Phase II final report for the Forging Inspection Development subtask 

[31], a goal was set to develop and demonstrate #1/2 FBH detection sensitivity for zoned 

inspections of Ti-6-4 forgings. This was specifically taken to mean that within each inspection 

zone, the peak noise anywhere within a C-scan image should be at least 3 dB below the response 

from a #1/2 FBH located in that zone. The target inspection sensitivity is indicated by the 

magenta line in figure 2-82, which at 56.6% FSH, is 3 dB below the amplitude from a #1/2 

reference hole (80% FSH on the same scale). From the measurements one can conclude that 

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

0 100 200 300

Sqrt (Pulse Volume in cubic mils)

Peak-Noise-to-Signal (% FSH)

PW8

HW5

GE6

#1 FBH at 12 dB above 80%

or at 318.5% on this scale

F6 @ -3dB

F5 @ -3dB

56.6% (3 dB below 80%)

F6 @ 0dB

For each specimen,

Rule-of-Thumb would

predict a straight line

passing thru origin.

Slope dependent on FOM

F5 @ 0dB

F8 @ 0dB

1.6 usec time gate

#1/2 FBH

approx at 80%

on this scale.
2-61

choosing the square root of PV to be (250 mils)3/2 or smaller likely ensures that the peak noise is 

at least 3 dB below the response from a #1/2 FBH for the noisiest inspection directions in the 

nosiest forging flow line coupons cut from the three representative forgings. If the typical pulse 

duration is assumed to be equal to 37 mils (the average of the measured values), the limitation on 

the beam diameter would be about 45 mils. Thus, it was estimated that a forging inspection that 

meets the #1/2 FBH sensitivity target required a beam diameter that does not exceed 45 mils at 

any depth within a given inspection zone. 

One preliminary design for a zoned inspection scheme that meets the 45-mil beam diameter 

target is shown in table 2-5, with beam diameters at various depths calculated using ISU models. 

The design, implementation, and testing of zoned inspection schemes meeting the #1/2 FBH 

sensitivity target are discussed at length in reference 31. The scheme uses three transducers and 

has nine zones, each 7/16′′ wide. Each transducer covers three zones using three different water 

paths. Examples of the inspection simulation models to critique zoned inspection schemes are in 

reference 23. 

TABLE 2-5. ZONED INSPECTION SCHEME TO ACHIEVE #1/2 FBH SENSITIVITY 

THROUGHOUT 3.9′′ OF DEPTH IN Ti-6-4 FORGING MATERIAL 

Transducer 

No. 

Probe 

Diameter 

(in.) 

Probe 

Diameter 

(cm) 

Probe Radius of 

Curvature 

(in.) 

Probe Radius of 

Curvature 

(cm) 

1 0.92 2.34 5.77 14.66 

2 1.88 4.78 11.22 28.50 

3 2.80 7.11 16.70 42.42 

7/16′′ Zone Size, 3-Transducer Inspection, 4′′ coverage 

Zone 

From 

(in.) 

To 

(in.) 

Transducer 

No. 

Water 

Path 

(in.) 

Water 

Path 

(cm) 

Maximum Beam 

Diameter Within the Zone

(in.) 

1 0.0000 0.4375 1 4.8 12.19 0.046 

2 0.4375 0.8750 1 3.0 7.62 0.045 

3 0.8750 1.3125 1 1.2 3.05 0.045 

4 1.3125 1.7500 2 4.8 12.19 0.045 

5 1.7500 2.1875 2 3.0 7.62 0.044 

6 2.1875 2.6250 2 1.2 3.05 0.044 

7 2.6250 3.0625 3 4.8 12.19 0.045 

8 3.0625 3.5000 3 3.0 7.62 0.044 

9 3.5000 3.9375 3 1.2 3.05 0.044 

2.2.6 Other Measurements on the Forging Flow Line Coupons. 

Thus far, the following have been discussed: (1) the UT properties of the forging flow line 

coupons, (2) efforts to correlation those properties with forging strain, and (3) using the highnoise coupons to estimate PV requirements for improved forging inspections. These three 
2-62

studies largely fulfilled the intended uses for these coupons. However, a few other inquires were 

pursued using the forging flow line coupons, which are also worthy of mention. 

2.2.6.1 Additional Measurements on the P&W Forging Coupons. 

In addition to the systematic UT property measurements performed at ISU on coupons from all 

three forgings, some OEMs performed independent measurements on the coupons taken from 

their own forgings. The most complete study was conducted by P&W personnel who measured 

velocity, attenuation, and backscattered noise in three different inspection directions for each of 

the seven rectangular P&W coupons. The enumeration scheme they used for the radial, axial, 

and circumferential faces of the coupons is shown in figure 2-83. Note that it differs from the 

ISU measurements (figure 2-39). 

up

hub

1 (circumferential)

2 (radial)

3 (axial)

1

2

3 4

5

6

6

1

2

3

4

5

1 2

3 4 up

hub

1 (circumferential)

2 (radial)

3 (axial)

1

2

3 4

5

6

6

1

2

3

4

5

1 2

3 4

 FIGURE 2-83. INSPECTION DIRECTION LABELS FOR MEASUREMENTS 

BY P&W PERSONNEL 

(With velocity measurement positions indicated.) 

Longitudinal-wave velocities were deduced from measurements of the time delays between the 

first and second back-wall echoes using a 10-MHz, 3/8′′ diameter planar probe in immersion. 

For the radial and axial directions, the velocity was measured at six positions, as indicated in 

figure 2-83, and the results were averaged. In the circumferential direction, the velocity was 

measured at four positions. Measured velocities in the radial, hoop, and axial directions are 

shown in figure 2-84 for the seven P&W coupons. Both the average values (plotted points) and 

standard deviations (vertical bars) of the measurements are indicated for each inspection 

direction. The variability in the velocity throughout the suite of coupons was quite small, 

ranging from a low of 6.19 mm/μsec to a high of 6.24 mm/μsec, a range of about 0.8%. In the 

axial direction (i.e., the typical inspection direction), a clear trend was observed, with the 

velocity increasing by about 0.4% from the bore towards the rim. This same trend was observed 

in the ISU measurements (figure 2-49). 
2-63

1

2

3

4

5

6

7

8

Radial (2)

Axial (3)

Circumferential (1)

6.180

6.190

6.200

6.210

6.220

6.230

6.240

6.250

0 2 4 6 8 10

Test block

Velocity, mm/μs

radial

hoop

normal

0.4%

 

FIGURE 2-84. LONGITUDINAL VELOCITIES FOR THE SEVEN RECTANGULAR 

P&W FORGING FLOW LINE COUPONS 

Attenuation measurements performed by P&W personnel followed the general procedure 

developed at the ISU. The first back-wall reflection at a given point in the forging coupon was 

compared to the back-wall reflection from a low-attenuation block of similar thickness, in this 

case, a block of fine-grained Ni alloy IN1100. By comparing the spectra of the two back-wall 

echoes, the attenuation-versus-frequency curve for the metal specimen can be deduced within the 

bandwidth of the transducer [18]. For measurements on the seven rectangular coupons from the 

P&W forging, the 10-MHz, 3/8′′ diameter planar transducer was again used. For each inspection 

direction, attenuation curves were deduced at approximately 100 points by scanning the 

transducer over the central region of the entry surface. For measurements in the axial and radial 

directions, the scan area was 0.8′′ by 1.2′′. For measurements in the circumferential direction, the 

scan area was 0.5′′ by 0.5′′. As is generally the case for engine Ti specimens, for a fixed 

inspection direction, substantial variations were observed in the strength of the back-wall echo 

from position-to-position within a given coupon. For a given inspection direction, the 

attenuation-versus-frequency curves measured at the various scan locations were averaged, and 

the average curve was fit to a power law of the form 

Attenuation (N/cm) = (A)(Frequency in MHz)

1.5 (2-1) 
2-64

The curve fitting procedure was simplified by fixing the power-law exponent at 1.5, a typical 

value describing the measured rise rates of attenuation-versus-frequency curves near 10 MHz for 

such alloys. The measured and fitted attenuation curves are present in appendix A. The average 

deduced attenuation values at 10 MHz are shown in figure 2-85 for the suite of seven coupons. 

There are substantial differences between the average deduced attenuation values for different 

inspection directions in a given coupon. It was found that the attenuation measured in the axial 

direction tends to grow as one moves laterally from the ID (coupon P&W1) to the OD (coupon 

PW8); a trend was also observed for the ISU-measured values in figure 2-51. Overall, the 

measured attenuation was limited by about 1.4 dB/in. at 10 MHz for all coupon and direction 

combinations. 

1

2

3

4

5

6

7

8

up

hub 2 (radial)

3 (axial)

Attenuation in coupons at 10 MHz

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

S 1 S 2 S 4 S 5 S 6 S 7 S 8

Attenuation at 10 MHz, dB/in

axial (3) radial (2) circumferential (1)

1 (circumferential)

FIGURE 2-85. AVERAGE LONGITUDINAL ATTENUATION VALUES AT 10 MHz FOR 

THE SEVEN RECTANGULAR P&W FORGING FLOW LINE COUPONS

Backscattered grain noise measurements were also performed for all coupon and direction 

combinations, using a 10-MHz, 3/8′′ diameter focused probe, which was measured to have an 

effective diameter of 0.96 cm and a geometric focal length of 11.53 cm. The probe was focused 

just beneath the entry surface for all noise measurements. Full-noise A-scans were collected 

while scanning the transducer over the same surface areas used in the attenuation scans. To 

eliminate electronic noise, 150 waveforms were collected at each spatial position and averaged 

before storing the data. The rms grain noise, as a function of time, was then calculated from the 
2-65

data in the standard way [16 and 29]. For axial propagation, examples of noise A-scans are 

shown in figure 2-86, with the locations of the (truncated) front-surface (FS) and back-surface 

(BS) echoes indicated. The resulting rms averaged A-scan curves are shown in the top portion of 

figure 2-87. 

Example time-domain signals

-2.7

-2.4

-2.1

-1.8

-1.5

-1.2

-0.9

-0.6

-0.3

0.0

0.3

1.02E-04 1.04E-04 1.06E-04 1.08E-04 1.10E-04 1.12E-04 1.14E-04 1.16E-04

Time, sec

Amplitude, V

Pos 1

Pos 5

Pos 9

Pos 55

Pos 59

Pos 63

Pos 109

Pos 113

Pos 117

1 5 9

55 59 63

109 113 117

FS reflections BS reflections

Example time-domain signals

-2.7

-2.4

-2.1

-1.8

-1.5

-1.2

-0.9

-0.6

-0.3

0.0

0.3

1.02E-04 1.04E-04 1.06E-04 1.08E-04 1.10E-04 1.12E-04 1.14E-04 1.16E-04

Time, sec

Amplitude, V

Pos 1

Pos 5

Pos 9

Pos 55

Pos 59

Pos 63

Pos 109

Pos 113

Pos 117

1 5 9

55 59 63

109 113 117

1 5 9

55 59 63

109 113 117

FS reflections BS reflections

FIGURE 2-86. NOISE A-SCANS FOR AXIAL BEAM PROPAGATION AT NINE 

POSITIONS IN COUPON PW1 

The backscattered noise data gathered at P&W was also used to test aspects of grain noise 

models developed at ISU. At issue was whether the models could accurately translate between 

three types of noise quantities: (1) the rms noise level (as a function of time or depth), (2) the 

average GPN level within a C-scan, and (3) the maximum or peak GPN value within a C-scan. 

To test the noise models, these three noise quantities were measured at P&W for axial sound 

propagation in each of the seven coupons. Results of the comparison of between measured and 

computed noise attributes are shown in figure 2-87. The upper panel shows the measured rms 

noise curves for inspections using a 10-MHz transducer focused just below the entry surface. 

Since no DAC is applied, the rms noise level in a given coupon would be expected to peak near 

the focal zone (i.e., just beyond t=0) and to decrease systematically as one moves away from the 

focal zone if the microstructure were uniform with depth. This is the case for some (e.g., coupon 

PW5) but not all (e.g., coupon PW2), indicating that the microstructure varies with depth in 

some coupons. For a time gate covering the depth range from 0.25′′ to 1.00′′ in each coupon, the 

lower panel in figure 2-87 compares measured and predicted GPN attributes. In particular, the 

average and peak noise values from the C-scans are tabulated. The model predictions, using the 

measured rms noise curves as inputs, are also tabulated. One sees that the model does a good job 

of predicting the average GPN level, but underestimates the peak noise level in several cases. It 

was noted that the model assumes a laterally uniform microstructure within the scan region, 

therefore, the model estimates will be most accurate when this is the case. The bottom two rows 

of the tabulated information in figure 2-87 pertain to the lateral uniformity of the noise. The first 
2-66

(a) 

 Coupon 1 Coupon 2 Coupon 4 Coupon 5 Coupon 6 Coupon 7 Coupon 8 

Experimental summary. Time gate for C-scan extends from 0.25′′-1.00′′. All noise values are in Volts at fixed gain. 

Max. rms value in gate 0.0374 0.0370 0.0233 0.0371 0.0323 0.0405 0.0259 

Max. gated peak noise 0.1302 0.1606 0.0777 0.1454 0.2184 0.2343 0.1321 

Average gated peak noise 0.1044 0.1071 0.053 0.0892 0.0727 0.0952 0.0616 

 Averages 

Ratio max. gated peak/rms 3.48 4.34 3.34 3.92 6.76 5.79 5.09 4.7 

Ratio avg. gated peak/rms 2.79 2.89 2.28 2.40 2.25 2.35 2.38 2.5 

 

Theory predictions, using the rms_noise_vs_time curve on 0.25′′-1.00′′ as input. 117 probe positions in scan. 

Max. rms value in gate 0.0374 0.0370 0.0233 0.0371 0.0323 0.0405 0.0259 

Max. gated peak noise 0.1476 0.1499 0.084 0.1361 0.1181 0.1483 0.0938 

Average gated peak noise 0.099792 0.101675 0.050877 0.084498 0.070964 0.091534 0.058439 

 Averages 

Ratio max. gated peak/rms 3.94 4.05 3.61 3.67 3.66 3.66 3.62 3.7 

Ratio avg. gated peak/rms 2.67 2.75 2.18 2.28 2.20 2.26 2.25 2.4 

 

Comment on lateral uniformity 

of noise within coupon: Average Good Very Good Average Average Very Bad Bad 

Std,/Dev,/mean for ISU 0.246 0.228 0.197 0.260 0.247 0.387 0.310 

Gated-peak noise meas. 

(b) 

FIGURE 2-87. (a) MEASURED RMS NOISE CURVES, AS FUNCTIONS OF TIME 

RELATIVE TO THE FRONT-WALL ECHO (t=0), FOR THE SEVEN RECTANGULAR 

P&W FORGING COUPONS AND (b) TABULAR COMPARISONS OF 

MEASURED AND PREDICTED GPN QUANTITIES 

0.010 

0.015 

0.020 

0.025 

0.030 

0.035 

0.040 

0.045 

0.050 

0 2 4 6 8 10

Time after FS echo (μsec) 

RMS noise (Volts) 

Coupon 1 

Coupon 2 

Coupon 4 

Coupon 5 

Coupon 6 

Coupon 7 

Coupon 8 

Time gate Time gate for C-scans -scans(0.25′′-1.00 –1.00′′)
2-67

is based on the visual observation of the noise C-scan images (which resemble those shown in 

appendix A). The second lists a ratio (GPN standard deviation divided by the mean) that tends to 

be smaller when the noise is more uniform. It was noted that the C-scan image of coupon PW6 

was rated as having an average noise uniformity overall, but contained a pronounced hot spot 

that acted to boost the measured ratio of peak to average noise. One sees that the model 

prediction for peak noise tends to be more accurate when the noise level is fairly uniform within 

the C-scan. This study indicates that noise models, which assume a uniform microstructure, can 

be reliably used for predictions of average GPN levels, but that empirical data should be used for 

the ratio of peak and average noise. 

Measured rms noise levels are shown in figure 2-88 for all three inspection directions at a depth 

of 0.7′′ (i.e., near the coupon midplane for inspections in the radial and axial directions). In the 

axial direction, the noise is higher in the bore region compared to the rim region. The opposite 

trend is shown for radial propagation. Similar trends were observed for the earlier ISU 

measurements of average GPN amplitudes. This behavior is likely due to variations in the 

average cross-sectional areas that the forging macrograins present to the incident beam. 

FIGURE 2-88. MEASURED ABSOLUTE RMS NOISE LEVELS (IN VOLTS) AT A 

DEPTH OF 0.7′′ FOR THE SEVEN P&W FORGING FLOW LINE COUPONS 

The grain noise FOM at 10 MHz, as a function of depth (averaged over lateral position), was 

estimated from the measured rms noise-versus-time curves. The estimation method used was 

less exact than that employed earlier to deduced FOM-versus-frequency curves for various depth 

zones in the high-noise coupons (e.g., see figures 2-73 and 2-74). The approximate procedure 

assumes that (1) the FOM is approximately proportional to frequency at each depth and (2) the 

Rms noise in circumferendtial direction (1) at 18.5 

mm (0.7 in) depth

0.00

0.01

0.02

0.03

0.04

0.05

1

Rms noise, V

N1 N2 N4 N5 N6 N7 N8

Rms noise in radial direction (2) at 

18.5 mm (0.7 in) depth

0.00

0.01

0.02

0.03

0.04

0.05

1

Rms noise, V

N1 N2 N4 N5 N6 N7 N8

Rms noise in axial direction (3) 

at 18.5 mm (0.7 in) depth

0.00

0.01

0.02

0.03

0.04

0.05

1

Rms noise, V

N1 N2 N4 N5 N6 N7 N8
2-68

measured rms noise level at a given depth is directly proportional to the local FOM value 

(evaluated at the center frequency) at that depth. This approximate FOM estimation method is 

discussed in more detail in reference 32. The deduced FOM-versus-depth curves obtained in this 

manner may be found in appendix A. The FOM values at 10 MHz were found to be limited by 

0.025 1/cm1/2 in all cases and showed the same general behavior on inspection direction and 

coupon location as the rms noise values in figure 2-88. For axial beam propagation, figure 2-89 

compares the measured attenuation values with the measured FOM values near the coupon 

midplanes. One sees a clear inverse relationship between attenuation and noise attributes. This 

is reminiscent of the inverse correlation between attenuation and noise anisotropy in coupons 

from all three forgings in the ISU study (figure 2-67). 

FIGURE 2-89. MEASURED ATTENUATION AND FOM VALUES FOR AXIAL 

BEAM PROPAGATION IN THE SEVEN P&W FORGING FLOW LINE COUPONS 

In general, the UT property measurements performed by P&W personnel were found to be in 

good agreement with those reported by ISU researchers, when comparing the graphs in this 

section (and in appendix A) with those presented in figures 2-45, 2-49, and 2-51. Since different 

approaches were taken in the measurement of grain noise attributes, not all of the measured 

values could be directly compared. However, when direct comparison was not possible, 

quantities that were expected to be nearly proportional to one another were found to be so. An 

example is shown in figure 2-90 where two measures of backscattered grain noise levels in the 

P&W forging flow line coupons are compared. The vertical axis displays the noise FOM at 

10 MHz and a depth of 0.31′′, as estimated by P&W personnel using a 10-MHz focused probe. 

The horizontal axis displays the measured average GPN level, relative to a #1 FBH, as measured 

at ISU using a 15-MHz probe focused approximately 0.31′′ deep. Each plotted point represents 

one coupon inspected from one direction, with values averaged over the lateral area of the entry 

Attenuation in axial (3) direction at 10 MHz

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1

Samples

Attenuation, dB/in

S 1 S 2 S 4 S 5 S 6 S 7 S 8

Axial (3) direction: FOM at 10 MHz at 2 cm depth

0.000

0.005

0.010

0.015

0.020

0.025

0.030

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

radial

axial

circumferential

1

2

3

4

5

6

7

8

Attenuation in axial (3) direction at 10 MHz

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1

Samples

Attenuation, dB/in

S 1 S 2 S 4 S 5 S 6 S 7 S 8

Axial (3) direction: FOM at 10 MHz at 2 cm depth

0.000

0.005

0.010

0.015

0.020

0.025

0.030

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

radial

axial

circumferential

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8
2-69

surface in each case. For a given coupon and inspection direction, the average GPN value (ISU) 

and the FOM value at 10 MHz (P&W) are expected to be well correlated since both are average 

measures of the grain-scattering severity at the depth in question. A good correlation is shown in 

figure 2-90. 

FIGURE 2-90. COMPARISON OF TWO MEASURES OF BACKSCATTERED GRAIN 

NOISE LEVELS IN THE P&W FORGING FLOW LINE COUPONS 

In addition to the sonic measurements, P&W personnel produced electron beam micrographs 

revealing the local grain structure at isolated locations on three perpendicular surfaces of each 

coupon. Two of the micrographs, taken in the axial direction, are shown in figure 2-91. In the 

micrographs, aggregates of alpha-phase (hexagonal) grains appear as light-colored regions. The 

number of alpha-phase aggregates per unit length along lines drawn through the micrographs 

were measured, and the results are shown in figure 2-92. Both figures 2-91 and 2-92 indicate 

that for the axial viewing direction, the average cross-sectional areas of the aggregates tends to 

increase as one proceeds from the bore region (ID) of the forging to the rim (OD). This is 

believed to be due to the larger deformations experienced by the material in the bore region 

during the forging process and is consistent with the DEFORM calculations. 

FIGURE 2-91. MICROGRAPHS OF THE SURFACE PERPENDICULAR TO THE 

AXIAL DIRECTION FOR P&W FORGING COUPONS PW1 (BORE REGION) AND 

PW8 (RIM REGION) 

0.000

0.005

0.010

0.015

0.020

0.025

0.0 0.5 1.0 1.5 2.0

ISU Measured Average Gated-Peak Noise

(100 = #1 FBH in Ti 6-4)

P&W Measured FOM at 10MHz

 (cm ^ -0.5)

Side 2 (Axial)

Side 4 (Radial)

Sample 1 (ID) Sample 8 (OD)

0.575 mm
2-70

Average number of alpha-phase aggregates per 1 mm

0

5

10

15

20

25

30

35

Sample 1 Sample 2 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8

No. of aggregates, 1/mm

Plane A (3)

Plane C (2)

Plane B (1)

Analysis: 

Measure the average number of alpha-phase

aggregate boundary crossings per unit length

Average number of alpha-phase aggregates per 1 mm

0

5

10

15

20

25

30

35

Sample 1 Sample 2 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8

No. of aggregates, 1/mm

Plane A (3)

Plane C (2)

Plane B (1)

Analysis: 

Measure the average number of alpha-phase

aggregate boundary crossings per unit length

FIGURE 2-92. NUMBER OF ALPHA-PHASE GRAIN AGGREGATES PER UNIT 

LENGTH, AS DEDUCED FROM MICROGRAPHS OF THE (1) HOOP, (2) RADIAL, 

AND (3) AXIAL SURFACES OF THE P&W FORGING COUPONS 

2.2.6.2 Studies of Microstructure-Induced Beam Distortions. 

Research using the forging flow line coupons was also conducted with UT signal fluctuations 

that arise from beam distortion by the metal macrostructure. The UT property measurements on 

the forging coupons have demonstrated that the attenuation and grain noise capacity vary 

systematically within a given forging, with those variations evidently tied to variations in the 

shapes and orientations of the metal macrograins. When the macrograins are sufficiently large 

compared to the wavelength of sound, they can cause a propagating sound beam to become 

noticeably distorted, leading to UT signal fluctuations during inspection. For example, the 

amplitude of a back-wall echo may fluctuate noticeably over relatively short distances, giving 

back-wall amplitude C-scan images a speckled appearance. Similarly, the peak amplitudes from 

a collection of identical defects (e.g., an array of FBH reference reflectors confined within a 

small region of a component) may vary randomly about some mean value. Both of these effects 

were documented in the ETC Phase I studies of Ti alloy billet material [16]. The metal 

microstructure is believed to be responsible for such signal fluctuations. As a transducer is 

scanned across a component, the sonic beam insonifies a different collection of grains at each 

probe position, and small grain-to-grain velocity differences act to distort the amplitude and 

phase profiles of the beam in a manner that is different at each probe position. 
2-71

One effect of microstructure-induced beam distortions is to alter the apparent attenuation that is 

deduced using back-wall echoes, since the measured attenuation then has contributions both 

from energy loss (true attenuation) and beam distortion effects [16]. A series of experiments was 

performed at ISU to directly measure the energy-loss attenuation and to compare it to that 

deduced from back-wall echoes. Three of the 1.25′′ by 1.25′′ by 2.0′′ Ti-6-4 forging flow line 

coupons were selected for use in these studies: GE4 (from the mid-thickness OD region of the 

GE forging), HW7 (from the forward ID region of the HW forging), and PW2 (from the web 

region of the P&W forging). Back-wall C-scan images of these three coupons through the radial 

(side 1) and axial (side 2) faces are shown in figure 2-93. A 1/4′′ diameter, 10-MHz broadband 

planar transducer was used. Since all six back-wall images were acquired at the same gain 

setting and through the same nominal thickness (1.25′′), gross attenuation differences can be 

readily discerned. For example, axial beam propagation through coupon HW7 leads to the 

lowest average back-wall amplitude, indicating the highest attenuation of the six. For HW7 and 

PW2, back-wall attenuation is larger for axial propagation than for radial propagation; for GE4, 

this order is reversed. These attenuation differences are believed to stem from microstructural 

differences between the coupons, principally the sizes and shapes of the macrograins and their 

orientations relative to the axial and radial directions in the forgings. Within each C-scan image, 

a sound beam entering through side 1 (side 2) propagates in the radial (axial) direction of the 

original forging. Distance scales are in inches, as shown in figure 2-93. Local amplitude 

variations are shown, which arise from local variations in the metal microstructure. These 

amplitude variations led to differences in the measured attenuation values at different scan 

points. 

GE 4 side 2 HW7 side 2 PW2 side 2

GE 4 side 1 HW7 side 1 PW2 side 1

@ 15 dB

(axial)

@ 15 dB

(radial)

Low High

GE 4 side 2 HW7 side 2 PW2 side 2

GE 4 side 1 HW7 side 1 PW2 side 1

@ 15 dB

(axial)

@ 15 dB

(radial)

Low High

FIGURE 2-93. BACK-WALL AMPLITUDE C-SCANS OF THREE Ti-6-4 FORGING FLOW 

LINE COUPONS ACQUIRED USING A 10-MHz PLANAR TRANSDUCER 
2-72

For these test coupons, two methods of measuring attenuation were used. The first method, 

standard (P/E), is shown on the top of figure 2-94, and the second method, through-transmission 

(TT) is shown on the bottom of figure 2-94. In both C-scans, a 10-MHz, 1/4′′ diameter planar 

probe serves as the transmitter. In the P/E method, the first back-wall echo from the metal 

specimen is compared with a FQ reference block of similar thickness. This method was used to 

obtain attenuation-versus-frequency curves for all 20 1.25′′ by 1.25′′ by 2.0′′ coupons from the 

three Ti-6-4 forgings, and such curves (averaged over the sound-entry surface) can be found in 

appendix A. In the alternative pitch/catch (P/C) method, the same planar transmitting probe is 

fixed in position, and the beam emerging from a specimen is mapped in water using a small 

diameter (0.04′′) receiver known as a “pinducer.” The attenuation of the metal specimen is then 

deduced by comparing the through-transmitted signals for the metal specimen to the FQ 

reference block. In the first method, both energy loss and beam distortion effects contribute to 

the deduced attenuation. In the second method, the total energy carried by the emerging beams 

at a given frequency can be determined, leading to a deduced attenuation value from energy loss 

alone. By comparing the two methods, one can infer whether or not beam-distortion effects are 

contributing significantly to measured average attenuation values. The two methods are 

described in more detail in references 5 and 16. 

FIGURE 2-94. EXPERIMENTAL SETUP FOR ATTENUATION MEASUREMENTS 

(Top: Standard P/E setup. Bottom: TT P/C setup.) 

For each of the six specimens and side combinations studied, TT scans were made at two 

transmitter positions: one at a weaker than average back-wall echo in the P/E mode and one at a 

stronger than average echo. Examples of the TT beam-mapping results are shown in figure 2-95. 

Transmitter (fixed)

X

Y

Z1Ref

Pin-probe

(xy-scanned)

Z0Ref

Refer.

(FQ)

D

Z1Sample

Transmitter (fixed)

Z0Sample

Metal

Sample

X

Y

D

Transmitter/receiver

Z1Ref

Z0Ref

Refer. 

(FQ) Z1Sample

Transmitter/receiver

Z0Sample

Metal

Sample

Pin-probe

(xy-scanned)

Transmitter (fixed)

X

Y

Z1Ref

Pin-probe

(xy-scanned)

Z0Ref

Refer.

(FQ)

D

Z1Sample

Transmitter (fixed)

Z0Sample

Metal

Sample

X

Y

D

Transmitter/receiver

Z1Ref

Z0Ref

Refer. 

(FQ) Z1Sample

Transmitter/receiver

Z0Sample

Metal

Sample

Pin-probe

(xy-scanned)
2-73

There, for one frequency of interest, the amplitude and phase profiles of the received P/C signal 

are shown for propagation through both the 1′′ thick FQ reference block and the 1.25′′ thick 

HW7 coupon. A 0.25′′ diameter, 10-MHz transducer served as a transmitter, and the emerging 

beam was mapped by scanning a pinducer over a 0.8′′ by 0.8′′ area; the central 0.4′′ by 0.4′′ area 

is shown in the figure. One notes that the amplitude and phase profiles of the beam emerging 

from the FQ are approximately rotationally symmetric about the beam centerline, while those 

from the forging coupon are somewhat asymmetric (distorted). In figure 2-96, attenuationversus-frequency curves are displayed for the same specimen, as deduced using both the P/E and 

TT methods at two sites (strong echo site, weak echo site) for each propagation direction. As is 

always the case in such graphs, one can change from Neper/cm units (as shown) to dB/inch units 

by multiplying by 22.06. When the P/E method is used to deduce attenuation for a fixed 

propagation direction, a larger attenuation value is naturally obtained at the weak echo location. 

The TT method, however, is found to yield nearly identical attenuation values at the weak and 

strong echo sites. This indicates that the differences in back-wall amplitude (and deduced P/E 

attenuation) at the two sites is not due to a difference in the amount of sound energy reaching the 

back wall, but rather, due to beam distortion differences (principally, phase front distortion 

differences) at the two sites. 

FIGURE 2-95. MEASURED AMPLITUDES (TOP) AND PHASES (BOTTOM) 

IN BEAM-MAPPING SCANS OF A FQ BLOCK (LEFT) AND 

Ti-6-4 FORGING COUPON HW7 (RIGHT) 

(The results are for the 6-MHz component of the through-transmitted signal.) 

1”-thick FQ, 6 MHz Amplitude HW7 Side 1 (radial), 6 MHz Amplitude

1”-thick FQ, 6 MHz Phase HW7 Side 1 (radial), 6 MHz Phase

36 dB gain 44 dB gain
2-74

 

FIGURE 2-96. ATTENUATION CURVES AT SITES HAVING STRONG (Stg) AND 

WEAK (Wk) BACK-WALL ECHOES IN THE HW7 FORGING COUPON, 

AS MEASURED USING TWO METHODS 

For each of the forging coupons studied, automated two-dimensional (2D) scans were made to 

acquire back-wall RF echoes at several hundred locations, and the attenuation at each scan point 

was deduced using the standard P/E technique. The results for coupon HW7 are shown in 

figure 2-97 for two sound propagation directions: radial (left panel) and axial (right panel). The 

error bars extend one standard deviation on either side of the mean and typically bracket about 

68% of the measured attenuation values obtained with the pulse/echo method. Shown for 

comparison are the results of the TT method at two sites in HW7, namely, sites having strong 

and weak back-wall echoes respectively. One sees that the average P/E attenuation is in good 

agreement with the TT attenuation, except at the higher frequencies. Similar comparisons for the 

PW2 and GE4 forging flow line coupons are shown in figure 2-98. Again, the left and right 

panels display the results for radial and axial beam propagation, respectively. In all but one case, 

the average back-wall attenuation deduced from P/E scanning experiments is a reasonably good 

measure of the energy-loss (TT) attenuation and, hence, is suitable for use in calculating the 

average effect of attenuation on backscattered noise or defect echoes in Ti-6-4 forgings. The 

lone case in which the averaged P/E and TT attenuations disagreed noticeably (axial propagation 

in coupon GE4) was for a low-attenuation coupon (energy-loss attenuation of 0.5 dB/inch at 10 

MHz), displaying large back-wall amplitude fluctuations during scanning. Thus, in summary, 

the beam distortions caused the back-wall amplitude to be higher at some locations and lower at 

others but, on average, to be near that expected due to energy loss alone. 

As figure 2-93 showed, the forging microstructure can cause UT signal amplitudes from identical 

reflectors (in this case, flat back walls) to vary. Similar fluctuations can be expected to occur for 

small defects or reference FBH reflectors located at the same depth but different lateral positions. 

Such fluctuations are important from a PoD point of view. At present, no modeling tools are 

available to predict the fluctuation level for a given class of reflectors, using a given inspection 

scenario. However, basic work toward developing such modeling tools was begun during 

Phase II using available Ti-6-4 billet and forging coupons. The billet coupons (fabricated during 

Honeywell Coupon #7 Pulse/Echo Attenuation

at Strong and Weak Echo Positions

0.00

0.05

0.10

0.15

0.20

0.25

4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

PE_Att_Side 1 Stg Echo Site

PE_Att_Side 1 Wk Echo Site

PE_Att_Side 2 Stg Echo Site

PE_Att_Side 2 Wk Echo Site

Honeywell #7 Through-Transmission Attenuation

at Strong and Weak Echo Positions

0.00

0.05

0.10

0.15

0.20

0.25

4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

TT_Att_Side 1 Stg Echo Site

TT_Att_Side 1 Wk Echo Site

TT_Att_Side 2 Stg Echo Site

TT_Att_Side 2 Wk Echo Site

Honeywell Coupon #7 Pulse/Echo Attenuation

at Strong and Weak Echo Positions

0.00

0.05

0.10

0.15

0.20

0.25

4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

PE_Att_Side 1 Stg Echo Site

PE_Att_Side 1 Wk Echo Site

PE_Att_Side 2 Stg Echo Site

PE_Att_Side 2 Wk Echo Site

Honeywell #7 Through-Transmission Attenuation

at Strong and Weak Echo Positions

0.00

0.05

0.10

0.15

0.20

0.25

4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

TT_Att_Side 1 Stg Echo Site

TT_Att_Side 1 Wk Echo Site

TT_Att_Side 2 Stg Echo Site

TT_Att_Side 2 Wk Echo Site
2-75

FIGURE 2-97. MEASURED ATTENUATION OF Ti-6-4 FORGING COUPON HW7 

AS DEDUCED FROM P/E BACK-WALL SCANS (PLOTTED POINTS 

WITH ERROR BARS) AND FROM THE TT METHOD 

(AT STRONG AND WEAK ECHO SITES) 

FIGURE 2-98. MEASURED ATTENUATION OF Ti-6-4 FORGING COUPONS PW2 

AND GE4 AS DEDUCED FROM P/E BACK-WALL SCANS (PLOTTED 

POINTS WITH ERROR BARS) AND FROM THE TT METHOD 

(AT STRONG AND WEAK ECHO SITES) 

Attenuation of Coupon HW7 (Radial Propagation)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon HW7 (Axial Propagation)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon HW7 (Radial Propagation)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon HW7 (Axial Propagation)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon PW2 (Radial Propagation)

0.00

0.02

0.04

0.06

0.08

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon PW2 (Axial Propagation)

0.00

0.02

0.04

0.06

0.08

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon GE4 (Radial Propagation)

0.00

0.02

0.03

0.05

0.06

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon GE4 (Axial Propagation)

0.00

0.02

0.03

0.05

0.06

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon PW2 (Radial Propagation)

0.00

0.02

0.04

0.06

0.08

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon PW2 (Axial Propagation)

0.00

0.02

0.04

0.06

0.08

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon GE4 (Radial Propagation)

0.00

0.02

0.03

0.05

0.06

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 1

TT_Att_Stg_Site

TT_Att_Wk_Site

Attenuation of Coupon GE4 (Axial Propagation)

0.00

0.02

0.03

0.05

0.06

2 4 6 8 10 12

Frequency (MHz)

Attenuation (Nepers/cm)

P/E C-scan_Side 2

TT_Att_Stg_Site

TT_Att_Wk_Site
2-76

ETC Phase I) were preferred for some of the initial experiments because signal fluctuation levels 

tended to be larger and, thus, more easily measured. The underlying central concept for model 

development is that the fluctuations for different types of reflectors (e.g., back walls or FBHs) all 

stem from distortions of the propagating sound beam by the microstructure. Thus, if a few key 

statistical parameters that describe the nature and severity of the beam distortions can be defined 

and measured, then these can be used as inputs to models that predict the signal fluctuations. 

The distortion parameters currently being considered provide statistical descriptions of (1) the 

lateral drift of the center of energy about its expected position (beam skewing), (2) the distortion 

of pressure amplitude about its expected pattern, and (3) two types of wavefront distortion 

(wrinkling and tilting). The meanings of these beam distortion categories are illustrated in 

figure 2-99. 

FIGURE 2-99. CATEGORIES OF UT PRESSURE-FIELD DISTORTIONS TREATED IN 

SIGNAL FLUCTUATION MODELS 

An effort was initiated [33 and 34] to develop models that relate the fluctuations in back-wall 

amplitude C-scans (like those of figure 2-93) to sonic beam distortions as measured via TT beam 

mapping (like those of figure 2-95). First it was shown that the back-wall echo at a particular 

location in a Ti alloy specimen could be accurately predicted from TT beam-mapping data at that 

same location. This is illustrated in figure 2-100 for measurements made on a 2′′ thick block cut 

from a Ti-17 billet. The billet specimen was inspected in the axial direction using a 5-MHz, 

Distortions of sonic wavefronts

• Systematic tilting: ? .

• Phase “wrinkling”: ΔΦ .

Distortions of the lateral amplitude profile

• Drift of center of energy: ΔD.

• Amplitude “wrinkling”: ΔA/A0.

ΔA A0

?

ΔΦ

ΔD

Sonic field for a Homogeneous 

Microstructure

Distorted field for an inhomogeneous

Microstructure

Distortions of sonic wavefronts

• Systematic tilting: ? .

• Phase “wrinkling”: ΔΦ .

Distortions of the lateral amplitude profile

• Drift of center of energy: ΔD.

• Amplitude “wrinkling”: ΔA/A0.

ΔA A0

?

ΔΦ

ΔD

Sonic field for a Homogeneous 

Microstructure

Distorted field for an inhomogeneous

Microstructure
2-77

1/4′′ diameter planar transducer, and back-wall echoes at three locations are shown in the figure. 

The three echoes have significantly different amplitudes, as indicated by the listed peak-to-peak 

voltages (in millivolts), but each RF echo could be reconstructed with reasonable accuracy from 

knowledge of the through-transmitted beam map [33 and 34]. 

FIGURE 2-100. MEASURED AND PREDICTED BACK-WALL ECHOES AND SPECTRA 

AT THREE LOCATIONS IN A 2′′ THICK Ti ALLOY BILLET SPECIMEN 

A statistical model was developed that could be used to predict the back-wall signal fluctuations 

(mean and standard deviation) from a small number of key parameters that described the severity 

of the beam distortions and could be directly measured by a few beam-mapping experiments. 

The statistical model proved to be reasonably accurate in initial testing [33 and 34], as shown in 

table 2-6. The model was used to predict the mean and standard deviation of the 4.5-MHz 

component of the back-wall echoes during P/E C-scans of the 2′′ thick billet specimen. Two 

5-MHz transducers were used: a 1/4′′ diameter planar probe and a 3/4′′ diameter, F8 focused 

probe that was focused just above the back wall. In each case, the fluctuation level, defined as 

the ratio of the standard deviation to the mean of the back-wall echo amplitudes, was predicted 

with reasonable accuracy. Note that the fluctuation ratios are quite different for the two probes, 

and this large difference is well-predicted. 

3 different locations on

a Ti-billet sample

0 1 2 3 4 5 6 -100

-50

0

50

100

150

Ti Alloy B illet: Experimental and P redicted W aveform 

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

1400

1600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experim ental(Red) and Predicted Back(Blue) wall Spectrum

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

0 1 2 3 4 5 6 -30

-20

-10

0

10

20

30

Ti A lloy Billet: Experim ental and P redicted W aveform 

0 1 2 3 4 5 6 -60

-40

-20

0

20

40

60

80

Ti Alloy Billet: Experimental and Predicted W aveform 

0 2 4 6 8 10 12 14 0

100

200

300

400

500

600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

Time (us) Frequency (MHz)

12 3 456 2 4 6 8 10 12

-10 -30 -20 0 10 20 30 -20 -60 -40 0 20 40 60 80 -100 -50 0 50 100 150

Vpp = 58

Vpp = 122

Vpp = 205

The back-wall echo at 

each location was 

predicted from 

through-transmission 

beam-mapping data 

gathered at the same 

transmitter location. 

Experiment

Model

3 different locations on

a Ti-billet sample

0 1 2 3 4 5 6 -100

-50

0

50

100

150

Ti Alloy B illet: Experimental and P redicted W aveform 

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

1400

1600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experim ental(Red) and Predicted Back(Blue) wall Spectrum

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

0 1 2 3 4 5 6 -30

-20

-10

0

10

20

30

Ti A lloy Billet: Experim ental and P redicted W aveform 

0 1 2 3 4 5 6 -60

-40

-20

0

20

40

60

80

Ti Alloy Billet: Experimental and Predicted W aveform 

0 2 4 6 8 10 12 14 0

100

200

300

400

500

600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

Time (us) Frequency (MHz)

12 3 456 2 4 6 8 10 12

-10 -30 -20 0 10 20 30 -20 -60 -40 0 20 40 60 80 -100 -50 0 50 100 150

Vpp = 58

Vpp = 122

Vpp = 205

0 1 2 3 4 5 6 -100

-50

0

50

100

150

Ti Alloy B illet: Experimental and P redicted W aveform 

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

1400

1600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experim ental(Red) and Predicted Back(Blue) wall Spectrum

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

0 1 2 3 4 5 6 -30

-20

-10

0

10

20

30

Ti A lloy Billet: Experim ental and P redicted W aveform 

0 1 2 3 4 5 6 -60

-40

-20

0

20

40

60

80

Ti Alloy Billet: Experimental and Predicted W aveform 

0 2 4 6 8 10 12 14 0

100

200

300

400

500

600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

Time (us) Frequency (MHz)

12 3 456 2 4 6 8 10 12

-10 -30 -20 0 10 20 30 -20 -60 -40 0 20 40 60 80 -100 -50 0 50 100 150 0 1 2 3 4 5 6 -100

-50

0

50

100

150

Ti Alloy B illet: Experimental and P redicted W aveform 

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

1400

1600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experim ental(Red) and Predicted Back(Blue) wall Spectrum

0 2 4 6 8 10 12 14 0

200

400

600

800

1000

1200

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

0 1 2 3 4 5 6 -30

-20

-10

0

10

20

30

Ti A lloy Billet: Experim ental and P redicted W aveform 

0 1 2 3 4 5 6 -60

-40

-20

0

20

40

60

80

Ti Alloy Billet: Experimental and Predicted W aveform 

0 2 4 6 8 10 12 14 0

100

200

300

400

500

600

Frequency, MHz

Spectrum Amplitude

Ti ALloy Billet: Experimental(Red) and Predicted Back(Blue) wall Spectrum

Time (us) Frequency (MHz)

12 3 456 2 4 6 8 10 12

-10 -30 -20 0 10 20 30 -10 -30 -20 0 10 20 30 -20 -60 -40 0 20 40 60 80 -20 -60 -40 0 20 40 60 80 -100 -50 0 50 100 150 -100 -50 0 50 100 150

Vpp = 58

Vpp = 122

Vpp = 205

The back-wall echo at 

each location was 

predicted from 

through-transmission 

beam-mapping data 

gathered at the same 

transmitter location. 

Experiment

Model
2-78

TABLE 2-6. MEASURED AND PREDICTED SPECTRAL 

AMPLITUDE CHARACTERISTICS 

Probe Type Measured Predicted 

Mean (μ) 613.32 664.53 

STD (σ) 158.92 201.20 

Planar probe 

σ/μ 25.92% 30.28% 

Mean (μ) 1249.42 1056.65 

STD (σ) 73.25 53.75 

Focused probe 

σ/μ 5.87% 5.09% 

 STD = Standard deviation 

In addition, a parallel effort was begun to make use of a 2D computational model [35] that 

predicts sonic beam patterns in the presence of microstructures. For several types of model 

microstructures containing elongated grains, the 2D model was used to predict distorted beams 

for many ensembles of grains and to predict the back-wall amplitude for each grain ensemble. In 

experimental terms, this calculation would be equivalent to measuring the back-wall response for 

a P/E inspection at several hundred locations above a specimen, and then mapping the throughtransmitted beam (using a small-diameter receiver) at each location. The computed distorted 

beams were then analyzed to obtain the beam distortion severity parameters, which were input 

into the statistical model to predict the back-wall echo fluctuations. The predictions were found 

to be in generally good agreement with the characteristics of back-wall echoes, as calculated 

directly for each model microstructure [35]. Although all work to date for the statistical model 

has been for single-frequency components of the UT data, the extension to full RF signals should 

be possible. The details of the signal fluctuation model development were presented at the July 

2003 QNDE Conference in Green Bay, WI, see references 33 and 35. 

2.2.7 Summary. 

Each of the three OEMs selected a representative Ti-6-4 engine forging and performed focusedprobe, normal incident, P/E C-scans to map out backscattered grain noise patterns in the forging 

interior. Each OEM also provided a cross-sectional macroetch of the forging, revealing flow line 

patterns, and DEFORM calculations of metal strain, which developed during the forging process. 

From the noise maps, macroetches, and DEFORM calculations, coupon sites were selected 

within each forging. In the circumferential direction of each forging, coupons were cut from 

high-noise sectors since high-noise regions are generally the most difficult to inspect. Within the 

high-noise sector, coupon locations in the axial and radial directions were generally chosen to 

span the widest possible range of microstructures. A total of 26 such coupons were cut. The 

majority (20) being rectangular blocks of standard size with nominal dimensions of 1.25′′ by 

1.25′′ by 2.0′′ (radial by axial by hoop). Three of the coupons were cylinders used to study the 

dependence of grain noise on inspection direction. 

Systematic P/E, longitudinal-wave UT property measurements of the standard blocks were 

performed at two facilities. Velocity, attenuation, and backscattered noise measurements were 
2-79

performed at ISU for all 20 standard-sized coupons for beam propagation in the radial and axial 

directions (the usual propagation directions for longitudinal-wave forging inspections). Similar 

(but not always identical) measurements were performed for radial, axial, and hoop propagation 

on eight standard-sized coupons from the P&W forging by P&W personnel. The measurements 

at the two facilities were in good general agreement. 

For all three OEM forgings, sonic velocity variations were quite small, usually varying by less 

that 1 percent with position and inspection direction. Although the variations were small, 

systematic changes in velocity and velocity anisotropy was observed as one moved from the ID 

to the OD of a given forging. By themselves, these small variations in average sound speed are 

believed to pose no particular inspection difficulties. 

By contrast, variations of the UT attenuation and the average backscattered grain noise with 

position and inspection direction in the radial-axial plane were quite large, with either quantity 

varying significantly within a given forging by about an order of magnitude within the suite of 

forging flow line coupons. Measured attenuation values at 10 MHz ranged from 0.2 to 2.7 

dB/inch, and maximal GPN levels ranged from 0.5% to 6.9% of the amplitude of a #1 FBH 

reference reflector. The N/S values quoted above are specifically for an inspection using a 

focused transducer having a sonic PV of 2.2E-5 cubic inches; N/S ratios for other inspections can 

be estimated by using a rule of thumb that relates N/S to the square root of the PV. 

Variations of noise and attenuation with position and inspection direction were found to be 

related to one another and to the details of the local forging strain. At a given location in a 

forging, the direction in which the measured noise was greatest was generally the direction in 

which the measured attenuation was smallest. The maximal noise, minimal attenuation direction 

generally occurred for beam propagation perpendicular to the macrostructure elongation 

direction (i.e., the flow lines). The noise (or attenuation) anisotropy, defined as the noise (or 

attenuation) measured for axial propagation divided by that measured for radial propagation, was 

well correlated with the local forging strain, as calculated by the DEFORM software. More 

specifically, DEFORM calculations were performed in which circular or ellipsoidal volume 

elements in the billet (model macrograins) were tracked to determine their final shapes at the 

conclusion of the forging process. The noise or attenuation anisotropy was found to be well 

correlated with the ratio of the projections of the forging macrograins onto the two inspection 

directions. 

The clear relationship between noise anisotropy and forging macrograin geometry (as calculated 

using DEFORM) led to an effort at ISU to develop two models to predict the variation of 

absolute grain noise levels within a forging. The simpler model version treats the forging as an 

effective scattering medium described by two global parameters, which are the same at all points 

in the forging. One parameter describes the average size of the forging macrograins, and the 

other describes the average difference in elastic stiffness constants from one macrograin to the 

next. The model relies on DEFORM to calculate the shapes and orientations of the macrograins 

at various locations in the forging, assuming the initial macrograins in the billet are elongated in 

the axial direction. The simpler version of the model assumes the crystalline axes within the 

macrograins are randomly oriented. The more complex version of the model takes into account 

the preferred orientations (texture) that develop in high-strain regions. Both models were applied 
2-80

to predict noise variations throughout the P&W forging, showing reasonable agreement with 

experiment. This suggests that noise variations within forgings can be largely understood by 

following the shapes and orientations of the metal macrograins during the forging process. 

Backscattered grain noise can mask the echo from a small or subtle defect in a forging, thus 

playing a key role in determining the defect detection limits. Although all the forging flow line 

coupons were cut from high-noise sections of the OEM-supplied forgings, some coupons had 

higher grain noise levels than others. Additional measurements were performed on three 

coupons (one from each forging) having the largest absolute noise levels. In particular, the 

backscattered grain noise capacity (or FOM) was measured as a function of frequency for 

various depth zones and tabulated for the zone having the maximum FOM value. The values of 

velocity, attenuation, and noise FOM for these three worst-case microstructures can be used as 

inputs to inspection simulation models, which estimate the PoD for various forging inspection 

schemes. 

Current forging inspections are generally designed to #1 FBH sensitivity, i.e., to reliably detect 

any defect whose reflectivity exceeds that of a #1 FBH. A four-fold improvement in detection 

amplitude to a #1/2 FBH standard is desired for future forging inspections. The three high-noise 

coupons were used to determine beam focal requirements for achieving the #1/2 FBH detection 

sensitivity. As the sonic beam becomes better focused, the peak S/N ratio for a given defect 

tends to rise, being approximately proportional the reciprocal of the square-root of the sonic PV 

at the defect’s location. At the GE facility in Cincinnati, OH, S/N ratios for the three high-noise 

coupons were repeatedly measured using different 10-MHz transducers and various water path 

choices to span a wide range of PVs. #1 FBH reflectors were drilled into the high-noise coupons 

to facilitate these measurements. These results indicated that a typical 10-MHz forging 

inspection, which meets the #1/2 FBH sensitivity target, requires a beam diameter that does not 

exceed about 45 mils at any depth within a given inspection zone. This information was used in 

the Inspection Development for Titanium Forging Study to design improved forging inspection 

schemes. 

Selected forging flow line coupons were used to study UT signal fluctuations caused by the 

metal microstructure. For example, the amplitude of a back-wall echo can fluctuate noticeably 

over relatively short distances, giving back-wall amplitude C-scan images a speckled 

appearance. These fluctuations have important implications for PoD. To study the fluctuations, 

a small receiving transducer (pinducer) was used to map the amplitude and phase profiles of 

sonic beams that emerged after passing through Ti alloy and FQ blocks. It was shown that 

distortions of the profiles by the Ti microstructure were responsible for the variation in the backwall amplitude when the transmitting probe was scanned in P/E mode. The beam profile maps 

were also used to measure the energy-loss attenuation in selected forging flow line coupons. For 

these coupons, the average attenuation value deduced from planar probe P/E measurements of 

back-wall amplitude was generally close to the energy-loss value. Thus, the beam distortions 

caused the back-wall amplitude to be higher at some locations and lower at others, but on 

average, near that expected due to energy loss alone. 

Work was also begun on the development of a model that could predict the back-wall signal 

fluctuation level from several model parameters that described the nature and severity of the 
2-81

beam distortions, with those model parameters themselves measured via TT beam-mapping 

experiments. Initial tests of the model formalism, both experimentally and through computer 

simulations, appeared promising. 

2.3 EFFECT OF SURFACE CURVATURE ON INSPECTABILITY. 

Real-world forgings have complex geometries that can impact inspection sensitivity. If a 

component being inspected has a curved sound-entry surface, the shape of the sonic beam 

injected into the interior is altered compared to a flat-entry surface. For example, a focused 

sound beam may focus deeper or shallower under a curved surface, and the focal spot may have 

an elliptical rather than a circular cross section. Such modifications in the shape of the incident 

UT field affect inspections in two basic ways: (1) the sonic pressure field incident upon a flaw is 

altered, changing both the peak flaw amplitude and the shape and size of the defect image within 

a C-scan and (2) since the cross section of the sonic beam is changed, a different collection of 

metal grains will be insonified, thus altering the backscattered grain noise level. These two 

phenomena together determine S/N ratios and, hence, defect detection probabilities. 

Models have been developed at ISU to treat the effects of surface curvature on both defect signal 

amplitude [7] and backscattered grain noise characteristics. (See Appendix B of reference 16.) 

Two classes of specimens containing both convex and concave upper surfaces were fabricated to 

study the effect of surface curvature on disk inspections and to test model predictions. A set of 

six specimens known as curvature correction blocks were made from an ultrasonically neutral 

material, i.e., fine-grained Ni alloy R88DT. These were used to measure the effect of surface 

curvature on FBH signal amplitudes at various depths. The R88DT material was chosen so that 

the effect of surface curvature on FBH amplitudes could be studied in the absence of 

backscattered grain noise. A second set of six blocks with curved upper surfaces was machined 

from a representative Ti-6-4 forged disk. These blocks are referred to as noise curvature blocks, 

and were primarily used to measure the effect of surface curvature on backscattered grain noise 

levels. The measurements performed on both sets of blocks are discussed below along with 

comparisons to model predictions. 

2.3.1 Effect of Surface Curvature on FBH Amplitudes. 

Before curvature correction blocks were fabricated, the Consortium OEMs were surveyed to 

determine the range of surface curvatures likely to be encountered during inspections of the sonic 

shapes of current and future forgings. It was determined that convex radii with a curvature of 4′′

and larger and a concave radii of 0.75′′ and larger were of chief interest. The research team then 

decided that convex radii of 4.0′′ and 8.0′′ and concave radii of 0.75′′, 2.0′′, and 8.0 would be 

reasonable choices for the test block curvatures. Prior to fabricating the blocks, model 

calculations were performed to assess the likely effect of each curvature choice on inspectability. 

This was done to check that each selected curvature would lead to an easily measurable, but not 

overly extreme, change in defect amplitudes compared to a flat-entry surface. The inspection 

parameters assumed in the model simulations are listed below. Two commonly used inspection 

scenarios were examined, each of which used spherically focused, 10-MHz transducers. In the 

first case a 3/8′′ diameter transducer was focused near the entry surface; in the second case, a 

3/4′′ diameter transducer was focused well into the interior. Model defects were FBHs with 
2-82

20-mil diameters located at a sequence of depths down to 2′′. The specimens were assumed to be 

made from generic Ti-6-4 forging material, having velocity and attenuation values typical of 

those measured earlier in the forging flow line coupons. The responses from the FBHs were 

calculated using the Thompson-Gray measurement model with a Gauss-Hermite expansion for 

the incident sonic beam [7, 20, and 36]. 

• Transducers 

− 10 MHz, 3/8′′ diameter, 3′′ focal length. Focused near the entry surface. 

− 10 MHz, 3/4′′ diameter, 8′′ focal length. Focused 1′′ below the entry surface. 

• Surface Radii of Curvature 

− Flat 

− Concave: 0.75′′, 2.0′′, and 8.0′′

− Convex: 4.0′′ and 10.0′′

• Size of FBH: 0.020′′ diameter 

• Depth of holes was varied from 0.050′′ to 2.0′′ with 0.005′′ steps 

• ISU model applied (Thompson/Gray) 

• Ti-6-4 generic velocity and attenuation assumed 

Figure 2-101 displays the results of model calculations for the case where the sonic beam is 

focused near the entry surface. The upper panels in the figure show the predicted absolute FBH 

amplitudes (in arbitrary units) as a function of depth for a flat-entry surface and for each of the 

five assumed surface curvatures. The predicted amplitude for a (smaller) #1 FBH below a flat 

surface is also shown for comparison. The lower panels in figure 2-101 show the differences (in 

dB units) between the predicted FBH amplitudes beneath each curved surface and the FBH 

amplitude beneath a flat surface. As expected, the difference grows as the surface curvature 

becomes more severe, i.e., as the magnitude of the radius of curvature decreases. For the nearsurface focus case, the predicted amplitude differences, relative to the flat surface, range from 

about -10 dB to +10 dB. Figure 2-102 displays similar results for the other case considered, 

where the water path was fixed such that the nominal focus would occur about 1′′ deep for a flatsurface inspection. For the simulated inspection through the flat surface, the focal maximum is 

found to be somewhat inside the 1′′, due to both the effect of metal attenuation and the fact that 

the actual focal point of a transducer is always inside the geometric focal point (where the beam 

would focus in the absence of sound diffraction). For concave curvatures, the beam focuses at 

shallower depths, and for convex curvatures, it focuses at deeper depths. The departures of the 

predicted FBH amplitudes from the flat-surface case range from about -28 dB to +28 dB over the 

2′′ depth range. Again, the departures are larger when the surface curvature is more severe. It 

was noted that the predicted dB difference curves shown in figures 2-101 and 2-102 are 

relatively insensitive to the diameter of the FBH, so long as the hole is small compared to the 

lateral width of the beam. 
2-83

FIGURE 2-101. CALCULATED RESPONSES FROM 20-mil-DIAMETER FBHs LOCATED 

BELOW FLAT AND CURVED SURFACES IN Ti-6-4 FORGING MATERIAL (BEAM 

FOCUSED NEAR SURFACE) 

FIGURE 2-102. CALCULATED RESPONSES FROM 20-mil-DIAMETER FBHs LOCATED 

BELOW FLAT AND CURVED SURFACES IN Ti-6-4 FORGING MATERIAL (BEAM 

FOCUSED BELOW SURFACE) 

E ffect of c oncave su rface 

10 MHz , 3" focus p robe, focused near surface

0.0

10 .0

20 .0

30 .0

40 .0

50 .0

60 .0

0.0 0.5 1 .0 1.5 2.0

Hole Depth, in

Am plitude

#1F BH, flat

20 mils, flat

20 mils, 0.75" concave

20 mi ls, 2" c oncave

20 mi ls, 8" c oncave

E ffect o f concave surface 

10 MH z , 3" focus p robe, focuse d near surface

Amp litude change comp ared to flat

-15

-10

-5

0

5

10

15

0.00 0.50 1.00 1.50 2.00

Hole Depth, in

Amplitu de chang e, dB

0.75" concave

2" c oncave

8" c oncave

E ffect of co nvex surface 

10 MHz, 3" focus p robe, focused near surface

0

5

10

15

20

25

30

0.00 0.50 1.00 1.50 2.00

Hole Depth, in

Amplit ude

#1FBH, flat

20 mils , flat

20 mils , 4" convex

20 mils , 10" c onvex

Effect o f con vex surface 

10 MHz , 3" focu s probe , focus ed near surfac e

Am plitude cha nge compared to flat

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0.00 0.50 1.00 1.50 2.00

Hole Depth, in

Am plitude change, dB

4" convex

10" convex

Effect of concave surface 

10 M Hz , 8" focu s probe, focuse d @ 1"

0.000

0.002

0.004

0.006

0.008

0.0 0.5 1.0 1.5 2.0

Depth, in

FBH responce

flat s urfac e

0.7 5" co nca ve

2" concave

8" concave

Effect o f concave s urface 

10 MH z, 8" focus pro be, focused @ 1"

Am p litude change comp ared to flat

-30

-20

-10

0

10

20

30

0.0 0.5 1.0 1.5 2.0

De pth, in

Difference (convex-flat),

dB

0 .75" concave

2" co nca ve

8" co nca ve

E ffect of con vex surfac e 

10 MH z, 8" fo cus probe, focus ed @ 1"

0.00 0

0.00 1

0.00 2

0.00 3

0.00 4

0.00 5

0.00 6

0.00 7

0. 0 0. 5 1.0 1. 5 2. 0

D epth, in

FBH resp once

flat surfac e

4" c onvex

10" conve x

E ffect of con vex s urface 

1 0 M Hz , 8" focus probe, focused @ 1"

Amplitude cha ng e c om pared to flat

-10

-8

-6

-4

-2

0

2

0.0 0.5 1.0 1.5 2.0

Depth, in

D ifferen ce (convex -flat),

dB

4" c onve x

10" c onve x
2-84

On the basis of the model calculations, the research team agreed that the curvature correction 

blocks should be fabricated using the same set of five surface curvatures. #1 FBHs (1/64′′

diameter) would be used since these holes commonly serve as reference reflectors for forging 

inspections. Six test blocks were designed and fabricated by GE from a powder-metallurgy Ni 

alloy (R88DT). This fine-grained alloy was chosen to minimize backscattered UT noise. Three 

of the blocks had concave radii of curvature for the upper surface (0.75′′, 2.0′′, and 8.0′′), two had 

convex radii (4.0′′ and 10.0′′), and one block had a flat upper surface. Flat steps were machined 

into the bottom of each block at a sequence of depths ranging from 0.75′′ to 2.25′′ in 0.125′′

steps. A #1 FBH was then drilled into each step from underneath. Each hole was drilled in two 

stages to a total depth of about 0.25′′: a 50-mil-diameter pilot hole was first drilled to a depth of 

0.14′′, and an additional 0.11′′ deep #1 FBH was then drilled beyond the pilot hole. In each of 

the completed blocks, the FBH reflectors were located at 13 different depths below the top 

surface, ranging from about 0.5′′ to 2.0′′ in 0.125′′ steps. The block geometries are illustrated in 

figures 2-103 through 2-105. 

FIGURE 2-103. GEOMETRY OF THE FLAT R88DT CURVATURE CORRECTION BLOCK 

0.125"

1.5"

1.5"

8.5"

0.5"

0.75"

2.25"

2.5"

0.125"

1.5"

1.5"

8.5"

0.5"

0.75"

2.25"

2.5"

0.125"

1.5"

1.5"

8.5"

0.5"

0.75"

2.25"

2.5"
2-85

FIGURE 2-104. GEOMETRY OF THE R88DT CURVATURE CORRECTION BLOCK 

WITH A 10′′ CONVEX CURVATURE 

(See figure 2-103 for drilled holes.) 

FIGURE 2-105. GEOMETRY OF THE R88DT CURVATURE CORRECTION BLOCK 

WITH AN 8′′ CONCAVE CURVATURE AND PERTINENT DIMENSIONS FOR 

THE OTHER CONCAVE BLOCKS 

(See figure 2-103 for drilled holes.) 

1.5"

1.5"

8.5"

0.5"

0.75"

C = 0.098”

H = 2.348”

R = 8”

W

0.125"

2.50”

W 1.50 3.25 2.50

S 0.125 0.125 0.125

H 3.00 3.085 2.348

C 0.75 0.834 0.098

R 0.75 2.0 8.0

W 1.50 3.25 2.50

S 0.125 0.125 0.125

H 3.00 3.085 2.348

C 0.75 0.834 0.098

R 0.75 2.0 8.0

1.5"

1.5"

8.5"

0.5"

0.75"

C = 0.098”

H = 2.348”

R = 8”

W

0.125"

2.50”

1.5"

1.5"

8.5"

0.5"

0.75"

C = 0.098”

H = 2.348”

R = 8”

W

0.125"

2.50”

W 1.50 3.25 2.50

S 0.125 0.125 0.125

H 3.00 3.085 2.348

C 0.75 0.834 0.098

R 0.75 2.0 8.0

W 1.50 3.25 2.50

S 0.125 0.125 0.125

H 3.00 3.085 2.348

C 0.75 0.834 0.098

R 0.75 2.0 8.0

1.5"

1.5"

8.5"

0.5"

0.75"

0.078"

2.25"

0.125"

2.5"

10.0" Radius

1.5"

1.5"

8.5"

0.5"

0.75"

0.078"

2.25"

0.125"

2.5"

10.0" Radius
2-86

Measurements of FBH amplitudes in the six blocks were then performed using three different 

transducers. Two of the transducers were I3 probes (nominally 10 MHz, 3/8′′ diameter, 3′′ focus) 

of the kind typically used for near-zone forging inspections. The third transducer, denoted here 

as F10 (nominally 10 MHz, 1′′ diameter, 10′′ focus), was of the kind typically used for deeperzone inspections. Each transducer was characterized to determine its effective diameter and 

geometrical focal length, and its efficiency factor for the conversion of electrical energy to sound 

was also measured [7, 20, and 36]. The efficiency factors as functions of frequency, deduced 

from the analysis of the spectrum of an echo from a known reflector, are shown in figure 2-106. 

The two I3 transducers have quite different efficiencies; the probe designated I3-2 is the hotter of 

the two, producing larger FBH echoes for a given input stimulus than I3-1. The probe efficiency 

factor usually peaks near the designed center frequency (10 MHz), which is, approximately, the 

case for each of the three transducers. 

FIGURE 2-106. RELATIVE EFFICIENCY FACTORS (ARBITRARY UNITS) FOR 

THREE TRANSDUCERS USED FOR MEASUREMENTS ON THE 

CURVATURE CORRECTION BLOCKS 

Two-dimensional scans of the upper surfaces of the curvature correction blocks were performed 

at P&W to measure the peak amplitudes of each FBH. The measured peak amplitudes were then 

compared to the model predictions. The results for the flat block are shown in figure 2-107, with 

model predictions shown as solid lines having the same color as the plotted points representing 

the measured amplitudes. In figure 2-107, the vertical axis displaying the absolute receiver gain 

in dB units needed to bring the peak FBH amplitude to 50% FSH. Thus, high gain in the figure 

corresponds to weak FBH echoes. It was difficult to obtain accurate data on the deeper holes 

using the weaker of the two I3 probes (I3-1), because of the need to operate at very high receiver 

gains, thus boosting grain and electronic noise levels. For that probe, a second measurement trial 

(denoted I3-1a in figure 2-107) was conducted using a higher transmitter gain than is customary. 

This lessened the receiver gains needed to bring hole amplitudes to 50% FSH and improved hole 

resolution somewhat. Overall, the largest discrepancy between model and experiment was about 

1.5 dB, and the research team considered this as acceptable accuracy. 

0.00

0.05

0.10

0.15

0.20

4 6 8 10 12 14 16 18

Frequency, MHz

Efficiency

I3-1

I3-2

F10
2-87

FIGURE 2-107. ULTRASONIC PEAK RESPONSES (IN dB UNITS) FROM #1 FBHs 

IN THE FLAT CURVATURE CORRECTION BLOCK 

Measured and predicted curvature correction factors are compared for the various blocks in 

figure 2-108. Again, plotted points represent measured values, and solid curves are model 

predictions. The curvature correction is defined as the receiver gain that must be added to an 

inspection to compensate for the effect of surface curvature. The measured value plotted here is 

the gain required to bring an FBH at a given depth beneath a curved surface to 50% FSH minus 

the similar gain required for a hole at the same depth in the flat reference block. As shown in 

figure 2-108, the model calculations were found to predict the trends in the data well. The 

largest discrepancy between model and experiment was about 2 dB for the cases studied. The 

research team agreed that the model appeared sufficiently accurate to be useful as a tool for 

calculating curvature corrections in forging inspections. 

2.3.2 Effect of Surface Curvature on Backscattered Grain Noise. 

One limiting factor in the detection of small or subtle internal defects is backscattered grain 

noise, which arises from the scattering of sound by microstructural boundaries within the 

forging. In this report, the interplay between the observed grain noise level and the curvature of 

the forging surface was investigated. In P/E immersion inspections, any surface curvature will 

modify the incident sound profile within the forging, thus causing each metal grain to be 

insonified in an altered manner. This, in turn, changes the statistical properties of the 

backscattered grain noise. Six noise curvature blocks were fabricated to investigate the manner 

in which surface curvature influences inspection sensitivity in forgings. The principal use of the 

blocks was to test models developed at ISU that predict the characteristics of backscattered grain 

during forging inspections. Block fabrication and backscattered noise measurements were 

performed by P&W, and further analyses and model predictions were performed at ISU. 

30

35

40

45

50

55

60

65

70

75

80

0 0.5 1 1.5 2

Depth, in

Gain for #1FBH=50%FSH

I3-1

I3-1a

I3-2

F10
2-88

FIGURE 2-108. GAINS (IN dB UNITS) REQUIRED TO COMPENSATE FOR SURFACE 

CURVATURE AS MEASURED USING A SET OF CURVATURE CORRECTION 

BLOCKS AND THREE DIFFERENT TRANSDUCERS 

To isolate the effect of surface curvature on backscattered noise, it is necessary to have a suitable 

set of specimens. An ideal set of specimens would have identical, uniform, and homogeneous 

microstructures with each specimen having a different curvature on one surface. As depicted in 

figure 2-109, the specimens chosen were six blocks, each measuring approximately 1.6′′ by 5.9′′

by 2′′ (axial by radial by hoop), fabricated by P&W from the same Ti-6-4 forging used for the 

P&W forging flow line coupons. The location of each block within the forging cross section is 

shown in figure 2-109(a). The surface curvatures were the same values used for the R88DI 

curvature correction blocks. Three of the blocks had concave radii of curvature for the upper 

surface (0.75′′, 2.0′′, and 8.0′′), two had convex radii (4.0′′ and 10.0′′), and one block had a flat 

upper surface. The five curved blocks were machined first, and the flat block was machined at a 

later date from one of the remaining wedge-shaped scraps. The lower surfaces of each specimen 

were machined flat and had several small FBHs drilled into them. These 1/64′′ diameter, 0.10′′

deep holes did not play a role in the noise measurements, but may be of use as reference 

reflectors in future studies. Although each block was cut from the same position in the radialaxial plane of the forging, the blocks, of necessity, had different angular positions, as shown in 

8" concave block

-4

-2

0

2

4

6

8

10

0 0.5 1 1.5 2

Depth, in

Gain diference between curved and 

flat for #1FBH=50%FSH

I3-1

I3-2

F10

Si 1

2" concave block

-8

-4

0

4

8

12

16

20

24

0 0.5 1 1.5 2

Depth, in

Gain diference between curved and 

flat for #1FBH=50%FSH

I3-1

I3-2

F10

Si 1

0.75" concave block

-8

-4

0

4

8

12

16

20

24

0 0.5 1 1.5 2

Depth, in

Gain diference between curved and 

flat for #1FBH=50%FSH

I3-1

I3-2

F10

Si 1

10" convex block

-4

-2

0

2

4

6

8

10

0 0.5 1 1.5 2

Depth, in

Gain diference between curved and 

flat for #1FBH=50%FSH

I3-1

I3-2

F10

Si 1
2-89

figure 2-109(b). Since microstructural variations in the hoop direction of a forging are generally 

small, it was hoped that this construction method would produce six blocks with very similar 

microstructures. Figure 2-110 shows the finished blocks. 

FIGURE 2-109. POSITIONS OF THE NOISE CURVATURE BLOCKS RELATIVE TO 

THE ORIGINAL P&W FORGING (a) LOCATIONS IN THE RADIAL-AXIAL PLANE, 

(b) LOCATIONS OF CURVED BLOCKS IN THE RADIAL-HOOP PLANE, AND 

(c) SHAPE OF THE FLAT BLOCK IN THE RADIAL-HOOP PLANE 

260o

200o

(ref. gap)

Material not available

from this section

This side of the block

will be rounded to ensure 

that the length of the block is 6.8”

The interior 

edges may be 

lopped to ensure 

that all 5 blocks 

fit within the 

forging

concave 0.75

concave 2.0

concave 8.0

convex 4.0

convex 10.0

1

2

3

4

5

Small coupons for 

earlier property 

measurements

Flat block was 

later machined 

from one of the 

remaining 

wedges

2”

CURVED

SURFACE

1.64”

0.75”

1.5”

6.8”

3.4”

0.49”

0.49”

3.4”

#1 FBH

0.1”

ID OD

“Side 5” = “BOT”

“Side 2” = “TOP”

(a)

(b) (c)

260o

200o

(ref. gap)

Material not available

from this section

This side of the block

will be rounded to ensure 

that the length of the block is 6.8”

The interior 

edges may be 

lopped to ensure 

that all 5 blocks 

fit within the 

forging

concave 0.75

concave 2.0

concave 8.0

convex 4.0

convex 10.0

1

2

3

4

5

Small coupons for 

earlier property 

measurements

Flat block was 

later machined 

from one of the 

remaining 

wedges

2”

CURVED

SURFACE

1.64”

0.75”

1.5”

6.8”

3.4”

0.49”

0.49”

3.4”

#1 FBH

0.1”

ID OD

“Side 5” = “BOT”

“Side 2” = “TOP”

(a)

(b) (c)
2-90

FIGURE 2-110. APPEARANCES OF THE SIX NOISE CURVATURE BLOCKS (TOP) AND 

REGIONS USED FOR SUBSEQUENT GRAIN NOISE MEASUREMENTS (BOTTOM) 

2.3.2.1 Noise Measurements Through Bottom (Flat) Surfaces. 

Preliminary measurements of backscattered noise levels through the (lower) flat surfaces of the 

blocks were performed to check for block-to-block microstructural differences. In particular, 

noise C-scan data was gathered separately through the flat surfaces below the thick and thin 

regions of the noise curvature blocks. Selected results are shown in figure 2-111, and details 

about the focused transducer used and other inspection particulars are shown at the top of the 

figure. All C-scan images were acquired at the same gain, and average GPN levels, as a 

percentage of FSH, are shown at the margins of the figure. Ideally, the noise C-scans of the six 

blocks would have nearly identical appearances, indicating nearly identical microstructures. 

Although the average noise levels were generally similar from block to block, the differences 

were deemed to be large enough to require further measurement and documentation. In addition, 

the preliminary measurements revealed that the flat block, which was cut from the forging at a 

later date than the other five coupons, had been cutout upside down (i.e., with TOP and BOT 

faces reversed in figure 2-109(a). This error, and the fact that the noise level in the ID portion of 

the forging increases from TOP to BOT is responsible for the large difference in the right-hand 

portion of figure 2-111 between the noise level in the flat block and those of the other five 

coupons. Although unfortunate, this fabrication error was not deemed to be a major problem for 

testing the noise models. The principal noise measurements could be confined to the thicker 

zones of the blocks, and the flat block could simply be flipped when measurements were taken. 

This, in fact, was done. Therefore, subsequent references to the upper surface of the flat block 

ID

OD

8.0”

Concave

Flat 2.0”

Concave 0.75”

Concave

4.0”

Convex 10.0”

Convex

Radii of curvature are listed

ID

OD

8.0”

Concave

Flat 2.0”

Concave 0.75”

Concave

4.0”

Convex 10.0”

Convex

Radii of curvature are listed

Upper Curved Surface

Lower Flat Surfaces

(with #1 FBH’s)

Region used for

noise measurements

6.8”

1.6”

Upper Curved Surface

Lower Flat Surfaces

(with #1 FBH’s)

Region used for

noise measurements

6.8”

1.6”

ID

OD

8.0”

Concave

Flat 2.0”

Concave 0.75”

Concave

4.0”

Convex 10.0”

Convex

Radii of curvature are listed

ID

OD

8.0”

Concave

Flat 2.0”

Concave 0.75”

Concave

4.0”

Convex 10.0”

Convex

Radii of curvature are listed

Upper Curved Surface

Lower Flat Surfaces

(with #1 FBH’s)

Region used for

noise measurements

6.8”

1.6”

Upper Curved Surface

Lower Flat Surfaces

(with #1 FBH’s)

Region used for

noise measurements

6.8”

1.6”
2-91

generally means the upper surface after flipping, or the lower surface, as it appears in 

figure 2-109(a). Similarly, references to the lower (or flat) surfaces of the blocks mean the lower 

surfaces in figure 2-109(a) for the five curved blocks, and the upper surface in figure 2-109(a) 

for the flat block. Also note that the small FBHs drilled into one side of each block had no 

apparent impact on grain noise measurements through that surface. 

FIGURE 2-111. PRELIMINARY C-SCANS SHOWING GATED-PEAK GRAIN 

NOISE LEVELS MEASURED THROUGH THE FLAT SURFACES OF THE 

SIX NOISE CURVATURE BLOCKS 

A second round of noise measurements was made through the flat surfaces of the blocks (1) to 

carefully document the effect of microstructural differences between blocks and (2) to test noise 

model predictions for inspections through flat surfaces. This second round of measurements was 

made using a characterized 10-MHz, 3/8′′ diameter transducer whose effective focal properties 

were carefully determined (effective diameter = 0.344′′ and geometric focal length = 3.95′′). 

Figure 2-112 shows the measurement setup. Measurements through the flat surfaces of the 

blocks were made for two water paths: 2.4′′, which put the actual focal spot just under the entry 

surface, and 1.0′′, which put the focal spot approximately 0.5′′ deep in the metal. In each case, 

the probe was scanned over a 3′′ by 0.5′′ (radial by hoop) region using a step size of 0.015′′ in 

each direction. The noise A-scans acquired at each scan point were stored for off-line 

processing. For each day that noise data was acquired, a reference echo from a #1 FBH in a 

calibration block was also measured. The reference echo was later used to correct for minor 

Thinner region

Noise C-scans through the “Flat Surfaces” of the Six Specimens

Thicker region

10 MHz, 0.375′′D, focal depth in water = 2.65′′, Amp=7, Damping=1,Pulse Width = 20ns

Waterpath = 1.0in, Focus ≈0.5′′ deep, Gain = 57.0dB, Gate delay = 0.3in, Gate Range = 0.4in

10.0′′ Radius Convex Block

4.0′′ Radius Convex Block

Flat Reference Block

0.75′′ Radius Concave Block

2.0′′ Radius Concave Block

8.0′′ Radius Concave Block

OD ID

22.4%

18.8%

17.1%

22.9%

23.3%

19.9%

28.4%

14.1%

27.2%

32.8%

32.3%

30.5%
2-92

differences in measurement system efficiency from one measurement trial to the next. In 

addition, the electronic noise level was measured so that it could be properly accounted for when 

noise model predictions were compared with experiment. 

FIGURE 2-112. EXPERIMENTAL SETUP FOR NOISE MEASUREMENTS USING 

THE NOISE CURVATURE BLOCKS 

The types of grain noise data that were gathered are illustrated in figure 2-113. Raw noise Ascans were recorded and used to construct rms noise level curves and GPN C-scan images. The 

rms noise curves provided a convenient way of describing the manner in which the observed 

grain noise varies with depth. Their calculation from raw A-scan data is described in reference 

29. Since no DAC was applied, the rms noise curves tend to peak near the focal zone, as is the 

case in figure 2-113(b). GPN C-scans are commonly used in industrial settings to describe the 

lateral variation of the noise. As illustrated in figure 2-113(c), GPN C-scans were constructed 

for four time gates (or depth zones), having the same center but different durations, as listed. As 

the time gate is enlarged, there are more opportunities to observed large grain noise amplitudes, 

and the measured GPN amplitude consequently tends to rise, as shown in the figure. For each 

GPN C-scan image, the average amplitude, the peak amplitude, and the standard deviation of the 

amplitudes about the mean were computed. The four inspection gates (G1-G4) whose centers 

and extents are indicated in figure 2-113(c) were consistently used for all noise measurements 

through both the flat and curved sides of the coupons. 

scan

scan

Ti 6-4

Forging

Specimen

scan

Ti 6-4

Forging

Specimen

#1 FBH

in IN1100 

reference

block

Focused 

transducer had 

3/8” diameter, 

3.95” geom. 

focal length in 

water.
2-93

Ring-down of 

front-wall echo

Grain Noise Back-wall echo

Typical RMS-Noise-Versus-Depth Curve

Flat Block; Lower Surface; 1.0" Water Path

2

4

6

8

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Depth (inches)

RMS Noise Level

 (% FSH) .

rms

smoothed

Zone 1

Zone 2

Zone 3

Zone 4

0.8”-1.0”

0.7”-1.1”

0.6”-1.2”

0.5”-1.3”

Zone location

OD ID

2.0” Concave Block; 1” Water Path; Flat Side

(G1)

(G2)

(G3)

(G4)

Zone 1

Zone 2

Zone 3

Zone 4

0.8”-1.0”

0.7”-1.1”

0.6”-1.2”

0.5”-1.3”

Zone location

OD ID

2.0” Concave Block; 1” Water Path; Flat Side

(G1)

(G2)

(G3)

(G4)

(a)

(b)

(c)

Ring-down of 

front-wall echo

Grain Noise Back-wall echo

Typical RMS-Noise-Versus-Depth Curve

Flat Block; Lower Surface; 1.0" Water Path

2

4

6

8

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Depth (inches)

RMS Noise Level

 (% FSH) .

rms

smoothed

Zone 1

Zone 2

Zone 3

Zone 4

0.8”-1.0”

0.7”-1.1”

0.6”-1.2”

0.5”-1.3”

Zone location

OD ID

2.0” Concave Block; 1” Water Path; Flat Side

(G1)

(G2)

(G3)

(G4)

Zone 1

Zone 2

Zone 3

Zone 4

0.8”-1.0”

0.7”-1.1”

0.6”-1.2”

0.5”-1.3”

Zone location

OD ID

2.0” Concave Block; 1” Water Path; Flat Side

(G1)

(G2)

(G3)

(G4)

(a)

(b)

(c)

FIGURE 2-113. EXAMPLES OF NOISE DATA (a) RAW NOISE A-SCAN AT ONE 

TRANSDUCER POSITION, (b) MEASURED AND SMOOTHED RMS NOISE-VERSUSDEPTH CURVES, AND (c) C-SCAN IMAGES FOR FOUR DEPTH ZONES 
2-94

As illustrated in figure 2-113(b), rms noise-versus-depth curves averaged over the 0.5′′ by 3.0′′

scan regions tend to possess a noticeable statistical jitter. To better display the general trends of 

the curves, a simple smoothing operation was used to replace all values within a 0.5 μsec 

window (or 0.061′′ depth zone) by their simple average. Examples of raw and smoothed rms 

curves are shown in figure 2-113(b). The observed total rms noise is a combination of 

backscattered grain noise and electronic (equipment) noise, with the rms values related by 

 (RMStotal)

2

 = (RMSgrain)

2

 + (RMSelectronic)

2

 (2-2) 

The rms electronic noise was directly measured by acquiring noise A-scans without a specimen 

in the water tank. All absolute noise values reported here have been rescaled to a fixed, absolute 

equipment gain setting of 57 dB. At that setting, the measured rms electronic noise was 0.32% 

of the oscilloscope’s FSH. Equation 2-2 can then be used to determine the rms grain noise from 

the measured rms total noise. 

Experimental results were also corrected for measurement system efficiency differences. This 

was necessary because the noise data through the flat and curved surfaces of the various coupons 

were acquire on five separate dates over a 3-month period. The rms or GPN noise amplitudes 

acquired on different dates were multiplied by a correction factor (ranging from 0.93 to 1.09) 

that was based on the average strength of the spectral amplitude-versus-frequency curve for the 

echo from the #1 FBH reference reflector. 

The manner in which the rms grain noise level depended upon depth for measurements through 

each flat surface is shown in figures 2-114 and 2-115 for the 2.4′′ and 1.0′′ water paths, 

respectively. In the left-hand panels, the absolute rms noise levels, averaged over the lateral scan 

positions, are shown for each block after corrections for electronic noise and system efficiency 

variations. Block-to-block differences in noise levels are shown, which presumably resulted 

from variations in the forging microstructure with circumferential position. The right-hand 

panels of figures 2-114 and 2-115 show the rms noise levels predicted using an ISU model; these 

are compared to the average of the measured rms noise curves for the six coupons. The model 

assumes a uniform microstructure and requires UT velocity, attenuation, and grain noise FOM 

values as inputs. Initial guesses for the model inputs were obtained by averaging the values 

measured earlier for axial propagation in certain of the forging flow line coupons cut from the 

same forging (i.e., coupons PW4, PW5, PW6, and PW8). The estimated FOM value was then 

increased by 10% to bring the predicted rms noise level more into line with the average of the 

measurements on the six noise curvature blocks. Figures 2-114 and 2-115 show good agreement 

between the model prediction and the average experimental result in the central depth region, 

i.e., away from the influences of the front-wall and back-wall echoes. Also note that the location 

and width of the focal maximum in figure 2-115 is well-predicted by the theory. 

From the stored grain noise A-scans gathered through the flat sides of the coupons, other noise 

statistics could be readily computed. For example, figure 2-113(c) shows GPN C-scans 

reconstructed from the flat-surface A-scan data for one coupon for four choices of the time gate. 

Similar C-scan images were generated for all six coupons, and the average and maximal noise 

amplitude in each image was tabulated. The results are shown in graphical form in figures 2-116 

and 2-117, where they are compared to the predictions of the ISU noise model (rightmost portion 
2-95

of each plot). The model the does a good job of predicting the average GPN amplitude for each 

of the four gates. However, the theory tends to underestimate the maximum noise amplitude 

seen in a given C-scan. The noise model used in figures 2-116 and 2-117 again assumed a 

uniform average microstructure. The noise data indicate that the actual microstructure of a 

typical block varies only modestly with axial depth, but varies quite significantly with radial 

position, as shown in figure 2-113(c). Radial variations of noise FOM were incorporated into the 

noise model for later calculations. 

FIGURE 2-114. COMPARISON OF MEASURED AND PREDICTED RMS GRAIN NOISE 

LEVELS FOR INSPECTIONS THROUGH THE FLAT SURFACES OF THE SIX NOISE 

CURVATURE BLOCKS USING A 2.4′′ WATER PATH 

FIGURE 2-115. COMPARISON OF MEASURED AND PREDICTED RMS GRAIN NOISE 

LEVELS FOR INSPECTIONS THROUGH THE FLAT SURFACES OF THE SIX NOISE 

CURVATURE BLOCKS USING A 1.0′′ WATER PATH 

Noise Measurements thru Flat Entry Surfaces

2.4" water path; 57 dB

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Flat, FBHs in back Flat, FBHs in front

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx Theory 

Exp. values corrected for electronic

 noise and Ref signal differences

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

2.4" water path; 57 dB

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Theory Exp. Ave.

Exp. values correctedfor electronic 

noise and Ref signal differences

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

2.4" water path; 57 dB

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Flat, FBHs in back Flat, FBHs in front

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx Theory 

Exp. values corrected for electronic

 noise and Ref signal differences

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

2.4" water path; 57 dB

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Theory Exp. Ave.

Exp. values correctedfor electronic 

noise and Ref signal differences

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

1.0" water path; 57 dB

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Flat, FBHs in back Flat, FBHs in front

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx Theory 

Exp. values corrected

for electronic noise Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

1.0" water path; 57 dB

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Theory Exp. Ave.

Exp. values corrected

for electronic noise

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

1.0" water path; 57 dB

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Flat, FBHs in back Flat, FBHs in front

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx Theory 

Exp. values corrected

for electronic noise Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8

Noise Measurements thru Flat Entry Surfaces

1.0" water path; 57 dB

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Metal Depth (inches)

RMS Grain Noise (% of FSH) .

Theory Exp. Ave.

Exp. values corrected

for electronic noise

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25)

 Atten = 5.7E-4*freq^1.8
2-96

FIGURE 2-116. MEASURED AND PREDICTED AVERAGE 

AMPLITUDES IN GPN C-SCAN IMAGES 

(Results are shown for the four choices of the time gate 

(or depth zone) for each inspection water path.) 

2.3.2.2 Correcting for Microstructural Differences. 

The average noise characteristics, as reflected by the rms noise-versus-depth curves in 

figures 2-114 and 2-115, are somewhat different for the different blocks, indicating that the 

microstructures of the specimens are not identical. The differences in these flat-surface rms 

curves were used to determine microstructure difference factors, which were later used to 

approximately correct rms noise values measured through the curved surfaces. 

Noise Measurements from flat side, water path = 1"

Average Gated Peak Noise, Gain = 57 dB, I3 probe

0

5

10

15

20

25

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

THEORY

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Noise Measurements from flat side, water path = 2.4"

Average Gated Peak Noise, Gain = 57 dB, I3 probe

0

5

10

15

20

25

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0" convex 10.0"

convex

THEORY

% FSH

Gate1

Gate 2

Gate 3

Gate 4
2-97

FIGURE 2-117. MEASURED AND PREDICTED MAXIMUM 

AMPLITUDES IN GPN C-SCAN IMAGES 

(Results are shown for the four choices of the time gate 

(or depth zone) for each inspection water path.) 

For each block, the following four-step procedure was used to determine the depth-dependent 

microstructure difference factor from the flat-surface rms noise data. 

1. The measured rms noise-versus depth curve was adjusted to remove the (minor) effect of 

electronic noise. 

2. The six rms noise curves (one for each block) were averaged to determine the mean curve 

for the suite of coupons. This was done separately for each of the two inspection water 

paths (2.4′′ and 1.0′′). 

3. The rms noise curve for a given coupon was divided by the mean curve to determine the 

fractional deviation from the mean at each metal depth. As shown in figure 2-118, these 

difference factors were found to be nearly identical for the two inspections at different 

water paths, indicating that they do indeed arise from microstructural variations. 

Noise Measurements from flat side, water path = 1"

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe

0

20

40

60

80

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

THEORY

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Noise Measurements from flat side, water path = 2.4"

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe

0

20

40

60

80

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0" convex 10.0"

convex

THEORY

% FSH

Gate1

Gate 2

Gate 3

Gate 4
2-98

4. The difference factors measured for a given block using the 2.4′′ and 1.0′′ water paths 

were then averaged. In subsequence analyses of grain noise measured through the curved 

surfaces of the blocks, these difference factors were used (with the distance scale 

inverted) to correct noise quantities for microstructural differences. The correction 

procedure was relatively straightforward. In brief, if a measurement through the lower 

(flat) surface of a given coupon found the noise amplitude at depth Z to be 10% lower 

than the average for all coupons, then the noise amplitude measured at depth T-Z from 

the curved side was adjusted upward by 10%, where T denotes the coupon thickness. 

FIGURE 2-118. (a)-(b) MICROSTRUCTURE DIFFERENCE FACTORS, AS 

FUNCTIONS OF DEPTH, MEASURED USING WATER PATHS OF 2.4′′ AND 1.0′′, 

RESPECTIVELY AND (c)-(d) A MORE DETAILED VIEW OF THE 

MICROSTRUCTURE CORRECTION FACTORS FOR TWO OF THE BLOCKS 

Average GPN C-scan amplitudes could be corrected in much the same way. Figure 2-119 shows 

the average GPN amplitudes measured through the flat (bottom) sides of the specimens. If the 

microstructures of the six coupons were identical, each curve would be a horizontal straight line. 

There are systematic departures from this ideal state: for example the 8′′ concave specimen 

always has lower than average amplitude for each time gate and water path. To obtain rough 

microstructure correction factors for GPN, the noise amplitude for a given coupon was compared 

to the average overall six coupons (for a given gate and water path) to obtain a difference factor. 

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 2.4"

Normalized by average over six coupons.

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average

flat with FBHs in back

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

(5 and 0.62 dB corrections to "flat")

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 1"

Normalized by average over six coupons.

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average

flat with FBHs in back

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

RMS grain noise in Ti noise curvature blocks m easured from

 flat side, norm alized by average over six coupons.

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average .

4.0 cx- 1.0"

4.0 cx - 2.4"

4.0 cx - ave.

4.0” – Convex Specimen

RMS grain noise in Ti noise curvature blocks m easured from

 flat side, norm alized by average over six coupons.

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average .

0.75 cv - 1.0"

0.75 cv - 2.4"

0.75 cv - ave.

0.75” – Concave Specimen

(a) (b)

(c) (d)

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 2.4"

Normalized by average over six coupons.

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average

flat with FBHs in back

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

(5 and 0.62 dB corrections to "flat")

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 1"

Normalized by average over six coupons.

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average

flat with FBHs in back

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

RMS grain noise in Ti noise curvature blocks m easured from

 flat side, norm alized by average over six coupons.

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average .

4.0 cx- 1.0"

4.0 cx - 2.4"

4.0 cx - ave.

4.0” – Convex Specimen

RMS grain noise in Ti noise curvature blocks m easured from

 flat side, norm alized by average over six coupons.

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Depth (inches)

Coupon Noise / Average .

0.75 cv - 1.0"

0.75 cv - 2.4"

0.75 cv - ave.

0.75” – Concave Specimen

(a) (b)

(c) (d)
2-99

These difference factors are then averaged over water path and time gate choices. The averaged 

results are listed at the top of each plot in figure 2-119. For example, the value of 0.926 for the 

2′′ concave specimen means that the GPN level in that coupon tends to be about 7% below the 

average for the suite of six coupons. 

FIGURE 2-119. AVERAGE GPN AMPLITUDES SEEN IN C-SCANS THROUGH THE 

FLAT SIDES OF THE NOISE CURVATURE BLOCKS 

For the flat-side data for the 2.4′′ water path inspection, the effect of applying the simple 

microstructure correction procedure is shown in figure 2-120. All data for a given coupon is 

divided by a single correction factor (e.g., 0.926 for the 8′′ concave specimen). After correction, 

the average GPN amplitude is less dependent on the choice of coupon, but some residual scatter 

remains. 

FIGURE 2-120. AVERAGE GPN AMPLITUDES SEEN IN C-SCANS THROUGH 

THE FLAT SIDES OF THE NOISE CURVATURE BLOCKS AT A 2.4′′ WATER 

PATH, BEFORE (LEFT) AND AFTER (RIGHT) CORRECTION FOR 

MICROSTRUCTURAL DIFFERENCES BETWEEN THE BLOCKS 

Flat Side Inspection; 1.0" w.p.

Average GPN

0

5

10

15

20

25

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Flat Side Inspection; 1.0" w.p.

Average GPN

0

5

10

15

20

25

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4 Corrected for microstructural differences

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4 Corrected for microstructural differences

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4 Corrected for microstructural differences

Flat Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

14

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Microstructure Difference Factors:

0.969 1.136 0.926 0.992 1.046 0.931
2-100

Similar corrections were applied to GPN data acquired through the curved surfaces of the 

coupons. After correcting the grain noise properties for the microstructural differences between 

coupons, the remaining differences in noise properties are presumable due to surface curvature 

effects alone. 

In addition to the coupon-to-coupon differences, which presumably arise from microstructural 

variations in the hoop direction of the forging, the microstructure of each coupon varies 

significantly with radial position. These radial variations can also be quantified using the 

C-scans through the flat sides. To do this, the 1.0′′ water path case with the widest gate (Gate 4) 

was chosen since that combination leads to the highest average noise level. One such C-scan 

image is shown at top left of figure 2-121. A horizontal profile of the image is calculated, i.e., at 

each horizontal (radial) position the values for the vertical (hoop) row of pixels are averaged. 

The results are shown in the graph at the bottom of figure 2-121 for each coupon. Also shown 

(small circles) is the average profile for the suite of six coupons. 

FIGURE 2-121. RADIAL PROFILES OF THE NOISE C-SCANS THROUGH THE 

FLAT SIDES OF THE NOISE CURVATURE BLOCKS 

The averaged radial profile from figure 2-121 is shown again in figure 2-122, where it has now 

been normalized to have an average value of unity over the 3-inch-wide radial range shown in 

either figure. Also displayed is a fourth-order polynomial fit that summarizes the general trend 

of the data. This smooth variation of noise level with radial position will be assumed in certain 

model calculations. 

GPN Amplitude Profile

Flat Sides; 1.0" Water Path; Gate 4

0

5

10

15

20

25

30

35

40

45

0.0 1.0 2.0 3.0

Radial Position (inches)

Ave. GPN Amplitude (% FSH) .

Flat

0.75" concave

2.0" concave

8.0" concave

4.0" convex

10.0" convex

Average

8.0′′ concave block, flat side; 1.0′′ water path 
2-101

Flat Sides; 1.0" w. p.; Gate 4

y = 0.043329x4 - 0.106436x3 - 0.271504x2 + 

1.057836x + 0.237131

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Radial Position (inches)

Normed <GPN> Variation

Normed Average

Poly. (Normed Average)

FIGURE 2-122. POLYNOMIAL FIT TO THE AVERAGE RADIAL NOISE 

PROFILE OBSERVED THROUGH THE FLAT SIDES OF THE 

NOISE CURVATURE BLOCKS (AFTER NORMALIZATION) 

2.3.2.3 Noise Measurements Through Curved Surfaces. 

Thus far, only the noise properties measured through the flat sides of the noise curvature blocks 

have been discussed. Similar measurements were made through the curved sides by scanning the 

transducer at normal incidence, as indicated in figure 2-112. The same 10-MHz focused 

transducer was used for these 2D scans, and the scan areas again measured 0.5′′ by 3.0′′ along the 

curved entry surface. The same two water paths (1.0′′ and 2.4′′) were again used, and noise 

A-scan data were stored for off-line processing. As before, rms noise-versus-depth curves, 

averaged over the lateral scan area, were computed. The measured raw rms noise curves are 

shown in figure 2-123 before corrections for electronic noise, day-to-day changes in the 

measurement system efficiency, or microstructural differences between coupons. These curves 

may be compared to those shown in figures 2-114 and 2-115 for the flat-surface measurements. 

GPN C-scans were constructed from the stored curved surface data using the same four time 

gates as before (see figure 2-113(c)). These gates have the same center point but different 

durations, corresponding to depth zones of 0.8′′-1.0′′ (gate 1), 0.7′′-1.1′′ (gate 2), 0.6′′-1.2′′

(gate 3), and 0.5′′-1.3′′ (gate 4), respectively. For each C-scan image, the average amplitude, the 

maximal amplitude, and the standard deviations of the amplitudes about their mean were again 

computed. Examples of GPN C-scan properties, as measured through the curved surfaces, are 

shown in figure 2-124 for the 1′′ water path. Again, the properties are as measured prior to 

corrections. Average and peak noise amplitudes systematically vary as the surface shape 

changes from concave to flat to convex. 
2-102

Total RMS noise in Ti noise curvature blocks measured from 

curved side, water path = 1"

0

5

10

15

20

0.0 0.5 1.0 1.5 2.0

Depth, in

% of FSH

flat with FBHs in back

flat with FBHs in front

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

Total RMS noise in Ti noise curvature blocks measured from 

curved side, water path = 2.4"

0

5

10

15

20

0.0 0.5 1.0 1.5 2.0

Depth, in

% of FSH

flat with FBHs in back

flat with FBHs in front

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

Total RMS noise in Ti noise curvature blocks measured from 

curved side, water path = 1"

0

5

10

15

20

0.0 0.5 1.0 1.5 2.0

Depth, in

% of FSH

flat with FBHs in back

flat with FBHs in front

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

Total RMS noise in Ti noise curvature blocks measured from 

curved side, water path = 2.4"

0

5

10

15

20

0.0 0.5 1.0 1.5 2.0

Depth, in

% of FSH

flat with FBHs in back

flat with FBHs in front

0.75 cv

2.0 cv

8.0 cv

4.0 cx

10.0 cx

FIGURE 2-123. RAW RMS NOISE-VERSUS-DEPTH CURVES AS MEASURED 

THROUGH THE CURVED SURFACES OF THE NOISE CURVATURE BLOCKS 

The rms noise curves were corrected to remove the effect of electronic noise using equation 2-2. 

Both the rms noise curves and GPN amplitudes were corrected for measurement system 

efficiency difference, and for microstructural differences between the six coupons, in the manner 

described earlier in this section. In particular, for rms noise curves, the microstructure difference 

factors (as functions of depth) deduced from the flat-surface measurements (shown in 

figure 2-118) were used for the corrections, following the procedure on page 178. For GPN 

amplitudes, microstructural difference corrections were made in a similar way using the 

multiplicative factors shown in figure 2-120. 
2-103

Noise Measurements from curved side, water path=1"

Average Gated Peak Noise, Gain = 57 dB, I3 probe

0

5

10

15

20

25

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Noise Measurements from curved side, water path = 1"

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe

0

20

40

60

80

100

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Gate Depth in Metal

1 0.8” – 1.0”

2 0.7” – 1.1”

3 0.6” – 1.2”

4 0.5” – 1.3”

Noise Measurements from curved side, water path=1"

Average Gated Peak Noise, Gain = 57 dB, I3 probe

0

5

10

15

20

25

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Noise Measurements from curved side, water path = 1"

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe

0

20

40

60

80

100

Flat with

FBH in

back

Flat with

FBH in

front

0.75"

concave

2.0"

concave

8.0"

concave

4.0"

convex

10.0"

convex

% FSH

Gate1

Gate 2

Gate 3

Gate 4

Gate Depth in Metal

1 0.8” – 1.0”

2 0.7” – 1.1”

3 0.6” – 1.2”

4 0.5” – 1.3”

FIGURE 2-124. AVERAGE AND PEAK VALUES OF NOISE AMPLITUDES IN C-SCANS 

FOR INSPECTIONS THROUGH THE CURVED SURFACES OF THE NOISE 

CURVATURE BLOCKS AT 1′′ WATER PATH 

Examples of grain noise quantities before and after correction for coupon-to-coupon 

microstructural differences are shown in figure 2-125. These results are for inspections through 

the upper (curved) surfaces of the blocks at the 1.0′′ water path. The upper panels of the figure 

show the measured rms noise levels for each curved coupon, divided by the value seen at the 

same depth through the flat coupon; this ratio is a direct measure of the influence of surface 

curvature on the observed noise. Data values are most believable in the range from 0.3′′-1.3′′. 

Outside this range, the front- and back-wall echoes interfere with the noise data. The lower 

panels of figure 2-125 show average GPN amplitudes measured through the curved surfaces, 

both before and after the correction. 
2-104

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Corrected for microstructural differences

Effect of Curvature - 1.0" water path

(Corrected for E-noise and system diffs)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

RMS noise thru curve / RMS noise thru flat

(not corrected for microstructural differences)

Effect of Curvature - 1.0" water path

(Corrected for all other effects)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

1.0” water path 1.0” water path

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Corrected for microstructural differences

Effect of Curvature - 1.0" water path

(Corrected for E-noise and system diffs)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

RMS noise thru curve / RMS noise thru flat

(not corrected for microstructural differences)

Effect of Curvature - 1.0" water path

(Corrected for all other effects)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

1.0” water path 1.0” water path

FIGURE 2-125. GRAIN NOISE ATTRIBUTES FOR MEASUREMENTS THROUGH THE 

UPPER (CURVED) SURFACES BEFORE (LEFT) AND AFTER (RIGHT) CORRECTIONS 

FOR MICROSTRUCTURAL DIFFERENCES BETWEEN COUPONS 

2.3.2.4 Noise Modeling. 

Before displaying additional noise data for the curved surface measurements, the independent 

scatterer noise model whose predictions will be compared with experiment will be briefly 

discussed. The model assumes that the observed noise is an incoherent superposition of the 

direct echoes from the individual metal grains. Multiple scattering events are ignored. A flow 

chart for the model calculations is shown in figure 2-126. Reference 36 and the references cited 

therein describe the use of the basic model to predict the absolute rms noise level in a given 

inspection and the subsequent prediction of GPN amplitude distributions from rms noise-vs-time 

curves. The absolute noise level will depend on properties of the metal specimen and details of 

the inspection system. Metal UT properties that are input to the model include the density, sound 

speed, attenuation, and noise FOM. The latter is a frequency-dependent measure of the noisegenerating capacity of the microstructure, equal to the square root of the standard backscatter 

power coefficient. The surface curvature changes the sound pattern injected into the component 
2-105

by the transducer and, thus, determines which metal grains are insonified. This, in turn, impacts 

the backscattered noise characteristics. One step in the model calculations is the prediction of 

the incident sound pattern within the metal component. Examples of model calculations showing 

how the incident sound pattern is modified by surface curvature are shown in figure 2-127. 

Average UT 

properties obtained 

from fundamental 

studies coupons

(v, atten, FOM)

Measured

probe focal 

characteristics 

(diameter, GFL)

UT system 

efficiency 

deduced from 

FBH reference 

signal

RMS

Noise

Model

RMS grain noise 

level vs depth 

for average 

microstructure

Sonic pulse 

duration; 

Noise spatial 

correlation 

length

Empirical data 

on how noise 

varies with radial 

position

Gated

Peak

Noise

Model

Simulated 

noise 

C-scans; 

GPN 

statistics

Electronic 

noise level 

(measured)

Location and 

duration of 

time gate

Density = 4.43 gm/cm3

Velocity = 0.622 cm/usec

Attenuation(f in MHz) = 

0.00057 f 1.8 N/cm

FOM(f in MHz) = 

0.00062 f 1.25 cm –1/2

Average UT 

properties obtained 

from fundamental 

studies coupons

(v, atten, FOM)

Measured

probe focal 

characteristics 

(diameter, GFL)

UT system 

efficiency 

deduced from 

FBH reference 

signal

RMS

Noise

Model

RMS grain noise 

level vs depth 

for average 

microstructure

Sonic pulse 

duration; 

Noise spatial 

correlation 

length

Empirical data 

on how noise 

varies with radial 

position

Gated

Peak

Noise

Model

Simulated 

noise 

C-scans; 

GPN 

statistics

Electronic 

noise level 

(measured)

Location and 

duration of 

time gate

Average UT 

properties obtained 

from fundamental 

studies coupons

(v, atten, FOM)

Measured

probe focal 

characteristics 

(diameter, GFL)

UT system 

efficiency 

deduced from 

FBH reference 

signal

RMS

Noise

Model

RMS grain noise 

level vs depth 

for average 

microstructure

Sonic pulse 

duration; 

Noise spatial 

correlation 

length

Empirical data 

on how noise 

varies with radial 

position

Gated

Peak

Noise

Model

Simulated 

noise 

C-scans; 

GPN 

statistics

Electronic 

noise level 

(measured)

Location and 

duration of 

time gate

Density = 4.43 gm/cm3

Velocity = 0.622 cm/usec

Attenuation(f in MHz) = 

0.00057 f 1.8 N/cm

FOM(f in MHz) = 

0.00062 f 1.25 cm –1/2

FIGURE 2-126. FLOW CHART FOR NOISE MODEL CALCULATIONS 

1.5”

Thru 2” Concave Thru 4” Convex Thru Flat

0.6”

FIGURE 2-127. PREDICTED INCIDENT ABSOLUTE PRESSURE AMPLITUDES 

AT 10 MHz WITHIN THREE OF THE NOISE CURVATURE BLOCKS FOR 

THE TRANSDUCER USED IN THE EXPERIMENTS 

(A 1′′ water path is assumed, and the upper surfaces are assumed to be curved 

in the plane of the page.) 

The average UT properties (i.e., averaged over the 0.5′′ by 3′′ by 1.6′′ scan volume) assumed in 

the model calculations were largely determined from prior measurements on four of the smaller 

forging flow line coupons and are listed in the upper left portion of figure 2-126. The standard 
2-106

backscattered noise model discussed in references 1, 16, 19, 20, 29, and 36 assumes a uniform 

microstructure within the scan volume. That model was extended to treat microstructural 

variations of the type seen in the noise curvature blocks. More specifically, the extended model 

used here assumes that the microstructure does not vary in the axial or hoop directions but does 

vary in the radial direction. This is approximately the case for the noise curvature blocks 

themselves. At a given position in the scan pattern, the rms noise-versus-depth curve for the 

average (uniform and homogeneous) microstructure is first predicted, assuming a locally uniform 

microstructure that does not vary with depth. Then this predicted rms curve is scaled by a factor 

that depends on radial position. The assumed scaling factor was shown in figure 2-122, which 

was based on the average of the observed radial noise variations seen through the lower (flat) 

sides of the six coupons. At each scan position (image pixel), the portion of the scaled rms 

noise-vs-depth curve within the gate of interest is used to predict the GPN amplitude. A Monte 

Carlo approach is used, governed by Eq. (4) of reference 36. The process is repeated at each 

model pixel in the scan area, resulting in a simulated C-scan image, like those shown in the 

lower portion of figure 2-128. The average, maximum, and standard deviation of the GPN 

amplitudes in the simulated C-scan are then computed. For each surface curvature, water path 

choice, and time gate, 1000 simulated noise C-scans were calculated, and their statistics (mean, 

maximum, standard deviation) were averaged. The results were then compared with experiment. 

Exp. Flat Specimen; Zone 3: 0.6”-1.2”

Theory Flat Specimen; Zone 3: 0.6”-1.2”

(3 Simulated Noise C-scans)

FIGURE 2-128. EXAMPLES OF MEASURED (TOP) AND 

SIMULATED (BOTTOM) GPN C-SCANS 

(The examples are for a 2.4′′ water path.) 

Note that one additional parameter that must be specified when using the model to generate 

synthetic C-scan images is the noise spatial correlation length (SCL). This is the distance that 

one must move the probe laterally during scanning to get a different (statistically independent) 
2-107

noise A-scan. Based on measurements at ISU using 10-MHz focused transducers and other 

Ti-6-4 forging specimens, an SCL value of 0.045′′ was used in the model calculations. If a 

smaller SCL value is used (such as 0.015′′, which equals the scan step size for noise 

measurements), then the speckle pattern in the simulated C-scan images is too fine when 

compared with experiment. This is demonstrated in figure 2-129. 

One additional parameter which must be 

specified when using the model to generate 

synthetic C-scan images is the noise “spatial 

correlation length” (SCL). This is the distance 

that one must move the probe laterally to obtain a 

statistically independent noise A-scan. Based on 

measurements at ISU using 10-MHz focused 

transducers with other Ti 6-4 forging specimens, 

SCL= 0.045” has been used in our model 

calculations. 

If a smaller SCL is used (say 0.015”), then the 

“speckle pattern” in the simulated C-scan images 

is too fine compared with experiment (top image), 

as shown at left.

Exp. Flat Specimen; Zone 3: 0.6”-1.2”

Theory Flat Specimen; Zone 3: 0.6”-1.2”

(Simulated assuming SCL = 0.045” )

Theory Flat Specimen; Zone 3: 0.6”-1.2”

(Simulated assuming SCL = 0.015” )

(Above examples are for 2.4” water path)

Role of the Noise Spatial Correlation

Length in Model Calculations

One additional parameter which must be 

specified when using the model to generate 

synthetic C-scan images is the noise “spatial 

correlation length” (SCL). This is the distance 

that one must move the probe laterally to obtain a 

statistically independent noise A-scan. Based on 

measurements at ISU using 10-MHz focused 

transducers with other Ti 6-4 forging specimens, 

SCL= 0.045” has been used in our model 

calculations. 

If a smaller SCL is used (say 0.015”), then the 

“speckle pattern” in the simulated C-scan images 

is too fine compared with experiment (top image), 

as shown at left.

Exp. Flat Specimen; Zone 3: 0.6”-1.2”

Theory Flat Specimen; Zone 3: 0.6”-1.2”

(Simulated assuming SCL = 0.045” )

Theory Flat Specimen; Zone 3: 0.6”-1.2”

(Simulated assuming SCL = 0.015” )

(Above examples are for 2.4” water path)

Role of the Noise Spatial Correlation

Length in Model Calculations

FIGURE 2-129. ROLE OF THE NOISE SCL IN MODEL CALCULATIONS OF 

SYNTHETIC C-SCAN IMAGES 

2.3.2.5 Effect of Surface Curvature on rms Noise Levels: Experiment and Theory. 

Predicted rms noise-versus-depth curves, averaged over the 0.5′′ by 3.0′′ scan areas, are shown in 

figure 2-130 for each surface curvature and both inspection water paths. The two leftmost panels 

show the predicted absolute rms noise levels in the absence of electronic noise. One sees that the 

effect of a concave sound-entry surface curvature is to shorten the focal depth, thus enhancing 

the noise level at shallow depths and decreasing it deeper in the metal. The effect of convex 

curvature is just the opposite. The same trends are seen for both the 1.0′′ and 2.4′′ water paths, 

but the deviations from the flat-surface result are greater for the 1.0′′ water path. The rightmost 

two panels of figure 2-130 show the predicted rms noise levels for each curved coupon divided 

by the predicted value at the same depth for the flat coupon. This dimensionless ratio is a direct 

measure of the influence of surface curvature on the observed noise level. 

Figure 2-131 compares measured and predicted rms noise-versus-depth curves normalized by the 

flat-surface result at the same depth. The measured values have been corrected to account for the 

day-to-day differences in the measurement system efficiency and for specimen-to-specimen 

microstructural differences. In addition, electronic noise was subtracted from the measured total 

noise to obtain an experimental measure of backscattered grain noise alone. Given the rather 

simple method used to correct for microstructural differences between specimens, the overall 
2-108

level of agreement in figure 2-131 between experiment and theory is quite good. The manner in 

which surface curvature and water path influence the rms grain noise level is well-predicted. 

FIGURE 2-130. PREDICTED ABSOLUTE RMS NOISE LEVELS (LEFT) AND RMS NOISE 

RATIOS (RIGHT) FOR INSPECTIONS THROUGH THE UPPER (CURVED) SURFACES OF 

THE NOISE CURVATURE BLOCKS AT TWO WATER PATHS 

Predicted Absolute RMS Grain Noise 

Levels

( 2.4" Waterpath; 57 dB gain )

0

2

4

6

8

10

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Grain Noise (% FSH) .

 0.75" Concave

2" Concave

8" Concave

Flat

10" Convex

4" Convex

FOM = 6.16E-4*freq^1.25

Atten = 5.7E-4*freq^1.8

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

Predicted Absolute RMS Grain Noise 

Levels

( 1.0" Waterpath; 57 dB gain )

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Grain Noise (% FSH) .

 0.75" Concave

2" Concave

8" Concave

Flat

10" Convex

4" Convex

FOM = 6.16E-4*freq^1.25

Atten = 5.7E-4*freq^1.8

Predicted RMS Grain Noise Levels

( 1.0" Waterpath )

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex
2-109

FIGURE 2-131. EFFECT OF SURFACE CURVATURE ON RMS NOISE-VERSUS-DEPTH 

(Left: Experiment. Right: Model.) 

2.3.2.6 Effect of Surface Curvature on GPN: Experiment and Theory. 

Experimental and predicted values of GPN statistics in C-scan images are compared in 

figures 2-132 and 2-133 for inspections through the upper (curved) surfaces of the noise 

curvature blocks. The two figures show results for the 1.0′′ and 2.4′′ water paths, respectively. 

The upper panels of each figure display absolute average GPN amplitudes in %FSH units. The 

middle panels display the ratio of the standard deviation of the amplitudes to the average 

amplitude for each C-scan, and the lower panels display the ratio of the peak amplitude to the 

average amplitude. Again, experimental values were adjusted to correct for measurement system 

efficiency differences and for specimen-to-specimen microstructural differences. These 

adjustments do not alter the values of the experimental ratios shown in the figures, but do affect 

the absolute amplitudes shown in the upper panels. The model predictions were adjusted only to 

account for electronic noise. This was done by adding the measured rms electronic noise level to 

each predicted rms noise curve (using equation 2-2) before synthetic C-scans were generated. 

Effect of Curvature - 2.4" water path

(Corrected for all other effects)

0.4

0.6

0.8

1

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.4

0.6

0.8

1.0

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

Effect of Curvature - 1.0" water path

(Corrected for all other effects)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

(1.0” Water Path) 

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

1.0” water path

2.4” water path

Effect of Curvature - 2.4" water path

(Corrected for all other effects)

0.4

0.6

0.8

1

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.4

0.6

0.8

1.0

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

Effect of Curvature - 1.0" water path

(Corrected for all other effects)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

(1.0” Water Path) 

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

Effect of Curvature - 2.4" water path

(Corrected for all other effects)

0.4

0.6

0.8

1

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.4

0.6

0.8

1.0

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

Effect of Curvature - 1.0" water path

(Corrected for all other effects)

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Noise (flat = 1)

0.75 cv 2.0 cv

8.0 cv 4.0 cx

10.0 cx

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

(1.0” Water Path) 

Predicted RMS Grain Noise Levels

( 2.4" Waterpath )

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth (inches)

RMS Grain Noise

(1 = Flat Surface Value)

 0.75" Concave

2" Concave

8" Concave

10" Convex

4" Convex

(1.0” Water Path) 

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

RMS noise thru curve / RMS noise thru flat

(corrected for microstructural differences)

1.0” water path

2.4” water path
2-110

 Experiment Model 

FIGURE 2-132. COMPARISON OF MEASURED (LEFT) AND PREDICTED (RIGHT) GPN 

STATISTICS FOR NOISE C-SCANS MEASURED THROUGH THE UPPER (CURVED) 

SURFACES AT 1.0′′ WATER PATH AND 57 dB GAIN 

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Corrected for microstructural differences

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Std. Deviation / Average of GPN

0.0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. / Ave of GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Std. Dev. / Ave GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. of GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Maximum / Average GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max/ Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Max / Ave GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Corrected for microstructural differences

Curved Side Inspection; 1.0" w.p.

Average GPN

0

2

4

6

8

10

12

14

16

18

20

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Std. Deviation / Average of GPN

0.0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. / Ave of GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Std. Dev. / Ave GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. of GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Maximum / Average GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max/ Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 1.0" w.p.

Max / Ave GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4
2-111

 Experiment Model 

FIGURE 2-133. COMPARISON OF MEASURED (LEFT) AND PREDICTED (RIGHT) GPN 

STATISTICS FOR NOISE C-SCANS MEASURED THROUGH THE UPPER (CURVED) 

SURFACES AT 2.4′′ WATER PATH AND 57 dB GAIN 

Curved Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4 Corrected for microstructural differences

Curved Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Std. Deviation / Average of GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. / Ave of GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Std. Dev. / Ave GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. of GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Maximum / Average GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Max / Ave GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4 Corrected for microstructural differences

Curved Side Inspection; 2.4" w.p.

Average GPN

0

2

4

6

8

10

12

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Average GPN (% FSH)

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Std. Deviation / Average of GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. / Ave of GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Std. Dev. / Ave GPN

0

0.1

0.2

0.3

0.4

0.5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Std. Dev. of GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Maximum / Average GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4

Curved Side Inspection; 2.4" w.p.

Max / Ave GPN

0

1

2

3

4

5

0.75"

concave

2.0"

concave

8.0"

concave

flat 10.0"

convex

4.0"

convex

Max / Ave GPN

G1

G2

G3

G4
2-112

The average GPN amplitude shown in figures 2-132 and 2-133 depends significantly on surface 

curvature, tending to be largest for the near-flat curvatures. The dependence of GPN amplitude 

on curvature was more pronounced for the 1.0′′ water path than for the 2.4′′ water path. Note 

that the measured average noise amplitude for the 4.0′′ convex case appears to depart slightly 

from the general trend of the rest of data for the 2.4′′ water path. This is likely due to problems 

with data normalization. The original data set for the 2.4′′ inspection through the curved side of 

the 4.0′′ convex specimen was lost. The data for that one case was retaken a week later without 

recording a reference signal. Since no reference signal was available, the reference signal of the 

previous week was used in the analysis. 

For all cases shown in figures 2-132 and 2-133, the average GPN amplitude increased steadily as 

the time gate was enlarged, as expected, and the measured increases were close to those 

predicted by the model. The measured ratios of standard deviation/average GPN and 

peak/average GPN are relatively constant, showing no clear systematic dependence on surface 

curvature or water path. This relative constancy is also well-predicted by the model. In 

figures 2-132 and 2-133, the noise model does a good job of predicting the absolute GPN mean 

amplitudes and the manner in which they depend on surface curvature and water path. However, 

the model tends to slightly underpredict the ratios of standard deviation/average and 

peak/average. This may be, in part, because the model did not consider microstructure variations 

in the hoop and axial directions within the coupons. However, the extended model, which 

considered microstructural variations in the radial direction, did yield much more accurate 

predictions of GPN ratios than the older uniform microstructure model, as indicated in table 2-7. 

It was concluded that the Independent Scatterer Noise Model is sufficiently accurate to serve as a 

useful simulation tool for investigating and optimizing UT inspections of Ti-6-4 forgings. 

However, in inspection simulations, it is prudent to use the noise models only to predict average 

GPN amplitudes and to supplement the model with peak/average amplitude ratios that are based 

on measurement. For example, to estimate peak noise amplitudes in C-scans through curved 

surfaces, one could perform model calculations to predict the average GPN amplitude for the 

curved surface inspection, and multiply that value by the measured peak/average ratio typically 

seen in C-scans through flat surfaces of similar lateral area. 

TABLE 2-7. TYPICAL VALUES OF MEASURED AND PREDICTED GPN RATIOS 

 Standard Deviation/Average Peak/Average 

Experiment 0.40 ±0.10 3.0 ±0.5* 

Model-varying microstructure 0.37 ±0.02 2.4 ±0.1 

Model-uniform microstructure 0.19 ±0.01 1.8 ±0.1 

 * A few cases higher than 3.5 were observed. 

Note that the six noise curvature blocks each contained linear arrays of #1 FBHs at two depths. 

These FBHs played no role in the backscattered grain noise measurements, but may be of use in 

future studies. For example, figure 2-134 shows images of the holes in the thicker sections of the 

blocks, as observed in C-scans through the upper (curved) surfaces using a gate centered at the 

hole depth. For a given block, variations in peak FBH amplitudes can be seen, some of which 
2-113

are systematic (due to systematic attenuation variations with radial position) and some of which 

appear to be random. Such variations can be important when assessing detection reliability. 

FIGURE 2-134. C-SCANS THROUGH THE UPPER (CURVED) SURFACES OF THE 

NOISE CURVATURE BLOCKS, SHOWING THE FBHs AT 1.5′′ DEPTH 

(The inspection water path was 1.0′′.) 

Additional information about the noise curvature blocks and their use in testing backscattered 

noise models can be found in an article written for the Proceedings of the 2002 Conference on 

Quantitative NDE [37]. 

2.3.3 Summary. 

Some sound-entry surfaces for forging inspections are curved, which cause sound beams 

radiating into the forging to be altered. The sound beam will generally focus at a different depth 

and have different cross-sectional profiles compared to an inspection through a flat surface with 

the same transducer. Since the sound field impinging upon both defects and neighboring metal 

grains is altered, both defect signal amplitudes and backscattered grain noise levels will be 

changed. To study these changes, two sets of blocks were fabricated. The first set, known as the 

curvature correction blocks, were made from an ultrasonically neutral material (powder Ni alloy 

R88DT) and were used to study the effect of surface curvature on defect (FBH) echoes in the 

near absence of backscattered noise. The second set, known as the noise curvature blocks, were 

cut from a representative Ti-6-4 forging and were used to study the effect of surface curvature on 

backscattered grain noise characteristics. Each set consisted of six blocks, with each block 

having a different cylindrical curvature on the upper (sound-entry) surface. Three of the blocks 

in each set had concave radii of curvature (0.75′′, 2.0′′, and 8.0′′); two had convex radii (4.0′′ and 

10.0′′); and one block had a flat upper surface. 

10” convex

4” convex

8” concave

2” concave

flat
2-114

The curvature correction blocks each contained 13 #1 FBH reflectors, located at depths ranging 

from 0.5′′ to 2.0′′ beneath the upper (curved) surface. A series of experiments were performed in 

which 10-MHz transducers were scanned over the upper surfaces of the blocks and the peak 

amplitude of each FBH were measured. Three transducers were used, each with a fixed water 

path. Two of the transducers were I3 probes (nominally 10 MHz, 3/8′′ diameter, 3′′ focus) of the 

kind typically used for near-zone forging inspections. The third transducer, denoted as F10 

(nominally 10 MHz, 1′′ diameter, 10′′ focus), was of the kind typically used for deeper-zone 

inspections. Each transducer was characterized to determine its effective diameter and 

geometrical focal length, and its efficiency factor for the conversion of electrical energy to sound 

was also measured. By comparing peak FBH amplitudes for inspections through curved and flat 

surfaces, curvature correction values (in dB units) were determined. The curvature correction, 

which is a function of depth, is defined as the receiver gain that must be added to an inspection to 

compensate for the effect of surface curvature on FBH amplitudes. Curvature corrections over 

the 0.5′′-2′′ depth range studied ranged from about -2 to +22 dB for the three measurement trials. 

As expected, the curvature corrections tended to be largest for the surfaces having the most 

severe curvatures. Measured curvature corrections were compared to the predictions of the ISU 

models, with the largest discrepancy between model and experiment was about 2 dB for the 

cases studied. The research team agreed that the flaw signal model appeared sufficiently 

accurate to be useful for calculating curvature corrections in forging inspections. 

The six noise curvature blocks each measured approximately 1.6′′ by 5.9′′ by 2′′ (axial by radial 

by hoop) and were fabricated from the same Ti-6-4 forging that was the source of the P&W 

forging flow line coupons. The upper surface of each block was cylindrically curved, and the 

lower surface contained two flat steps into which several #1 FBHs were drilled. The holes 

played no role in the grain noise measurements. Preliminary measurements revealed that the flat 

block from the set had been cut upside down from the forging. This presented no real difficulties 

since the flat block could simply be flipped over, and the noise measurements were confined to 

the 1.6′′ thick regions of the blocks. 

For the noise curvature blocks, measurements of backscattered grain noise properties were 

performed using a well-characterized 10-MHz, 3/8′′ diameter focused transducer of the type 

generally used by P&W in forging inspections to depths of a few inches. Two inspection water 

paths were used: 2.4′′, which put the actual focal spot just under the entry surface, and 1.0′′, 

which put the focal spot approximately 0.5′′ deep in the metal. Raw noise A-scans were 

recorded and used to construct rms noise level curves and GPN C-scan images. The rms noise 

curves provide a convenient way of describing the manner in which the observed grain noise 

varies with depth, and GPN C-scans are commonly used in industrial settings to describe the 

lateral variation of the noise. GPN C-scans were constructed for four time gates (or depth zones) 

having the same center but different durations, and for each, the average amplitude, the peak 

amplitude, and the standard deviation of the amplitudes about the mean were computed. 

Noise measurements through the bottom (flat) surfaces indicated that the microstructures of the 

six noise curvature blocks were not identical to one another. The differences seen in the flatsurface measurements were used to determine microstructure difference factors, which were later 

used to approximately correct the rms and GPN noise values measured through the upper 

(curved) surfaces for block-to-block microstructural differences. In addition, the noise 
2-115

measurements through the lower (flat) surfaces revealed that the microstructures of the blocks 

varied systematically with radial position. The measured backscattered noise properties were 

found to depend significantly on surface curvature, with the deviations from the flat-surface case 

generally being more pronounced for the 1.0′′ water path than for the 2.4′′ water path. 

The measured (and corrected) rms noise-versus-depth curves and GPN properties were then 

compared to the predictions of the ISU models. The models were generalized to treat 

nonuniform microstructure in one direction (radial in this case) and to output simulated noise 

C-scan images. The noise model was found to do a good job of predicting (1) absolute rms 

noise-versus-depth curves for flat surface inspections, (2) the changes to rms noise-versus-depth 

curves that result from surface curvature, and (3) the average GPN amplitude seen in a C-scan, 

and the manner in which it depends on surface curvature, water path, and the choice of time gate. 

Although the model did a good job of predicting average noise properties, it tended to slightly 

underpredict the ratios of standard deviation/average and peak/average for noise C-scans. The 

research team concluded that the noise model is sufficiently accurate to serve as a useful 

simulation tool for investigating and optimizing UT inspections of Ti-6-4 forgings. However, in 

inspection simulations, it is prudent to use the noise models only to predict average GPN 

amplitudes, and then to supplement the model with peak/average amplitude ratios that are based 

on measurement. 

2.4 SYNTHETIC INCLUSION DISK. 

The capability of UT equipment and procedures to detect flaws is determined by inspecting 

blocks of representative material in which holes and notches have been machined [38]. 

Typically, the blocks are rectangular or cylindrical, and the holes are located to inspect the length 

of the hole or its top surface, such that they represent open cracks. With improved capabilities of 

inspection and the value of detecting ever-smaller flaws, there is a need to validate inspection 

capabilities with realistic defects located at all orientations within a part. Additionally, while 

machined holes and notches can represent cracks, flaws such as hard alpha inclusions in Ti have 

small reflectances [39], and there is a need for standardized referees at smaller target signal 

amplitudes [40]. An effort was undertaken, as summarized in this section, to embed synthetic 

hard alpha inclusions into a production aeroengine disk at various locations, sizes, and 

orientations—so that the disk could be used to assess the inspection capabilities on a part that 

would be representative of current industrial needs. The finished product was termed the 

synthetic inclusion disk. 

2.4.1 Approach. 

The approach selected was to obtain a disk, slice it on a plane perpendicular to its rotational axis 

of symmetry, embed hard alpha seeds, electron beam weld the disk pieces together on their 

periphery, and HIP the disk together. This approach had been previously used to make small 

seeded blocks [41]. The desired final disk would then be machined to the shape prescribed for 

UT inspection (sonic shape). 

Since the forging would lose some thickness from the cutting step, the forging was obtained asforged with no machining. In this way, machining to final shape and thickness would be done 

after HIP bonding. To minimize any warping during slicing, the forging would be stress-relief 
2-116

annealed. The seed locations would be selected after a UT scan of the forging to determine 

variability in grain noise. 

2.4.2 Results and Discussion. 

2.4.2.1 Measurements of UT Noise in an As-Forged Disk. 

The disk obtained was a production Ti-6-4 forging of the same general design as used for the GE 

forging flow line coupons. The disk shape was ideal since it would comprise a real forging 

geometry along with embedded, controlled reflectors. The directional, textured nature of the 

microstructure within the forging would permit measurements of how the UT beam interacted 

with microstructural features. Figure 2-135 shows the etched macrostructure of an as-forged 

disk of the design selected, with the sonic outline to be machined superimposed on the image. 

The forging flow lines are generally parallel to the as-forged surfaces and to the final sonic 

inspection shape, except for the bore where flow lines are perpendicular to the part surface. 

FIGURE 2-135. ETCHED MACROSTRUCTURE OF AN AS-FORGED DISK OF 

THE SELECTED DESIGN 

The forging was purchased from the supplier in the pre-heat-treated condition with the as-forged 

surface. Figure 2-136 shows the disk as-received. The disk was inspected using a 10-MHz, F8 

transducer (i.e., one having a focal length eight times its diameter) following a standard 

production inspection procedure. C-scans obtained were used to identify high- and low-noise 

regions and to plan the number and placement of targets. 

C-scan data were acquired before and after a light skim cut. The forged shape included a solid 

center since the bore had not yet been machined away. The inspection surfaces were neither flat 

nor concentric, and the surface finish was rougher than normally specified for UT inspection. 

The inspection could not achieve 0.06′′ near-surface resolution due to these limitations, and the 

signal gate was increased to 0.2′′ depth to avoid false alarm signals due to the rough entry 

surface. The OD was too irregular to be inspected at all. While noise patterns were detectable, 

confidence in the accuracy of the data was low due to poor surface conditions. 

Bore

Rim

AFT

FWD

ID OD
2-117

FIGURE 2-136. THE SID AS-PURCHASED FROM THE SUPPLIER 

(A 0° datum is marked on the disk in the lower left side of the image.) 

Machining was needed to render the surfaces of the as-received part more suitable for reliable 

UT inspection. Thus, a light skim-cut machining operation was performed, and the part was then 

re-inspected using the same probe and procedure. Figure 2-137 shows the disk after the skim 

cut. To allow for cleanup of the final forging geometry after defects were inserted and HIPped, a 

0.25′′ envelope was left on the OD and a 0.1′′ envelope left on other surfaces. Because of this 

0.25′′ envelope requirement, the OD had a small section that was not smoothed by the skim cut. 

This region on the OD can be seen near the bottom of the image in figure 2-137. Since this was 

only a small area, it did not significantly impact the set of noise C-scan images for this 

preliminary inspection. 

FIGURE 2-137. THE SID AFTER SKIM-CUT MACHINING 
2-118

The skim-cut inspection gave better near-surface resolution and produced higher quality C-scan 

images. Figure 2-138 shows a C-scan taken after the light skim cut. The other C-scans are 

contained in appendix B, together with a table summarizing the inspection particulars. The asforged C-scan data revealed no inherent defects. The regions of higher- and lower-material 

noise, as displayed in these higher-quality C-scans, were used to ensure that some synthetic seeds 

would be located in the high-noise regions and others in low-noise regions. 

FIGURE 2-138. TYPICAL C-SCAN OF DISK AFTER LIGHT SKIM CUT TO 

CHARACTERIZE STRUCTURAL NOISE 

2.4.2.2 Manufacture and Characterization of Synthetic Hard Alpha Targets. 

A series of 40 hard alpha seeds were embedded in the synthetic inclusion disk at five radial 

locations. Circumferential placement was based on C-scan data with targets in high- and lownoise regions. The seeds were right cylinders, approximately 3 wt.% and 17 wt.% N, and of two 

sizes equal to a #3 (0.047-inch (1.19-mm)) FBH and a #5 (0.078-inch (1.98-mm)) FBH. The 

length was equal to the diameter. Two seeds, each the same size but different nitrogen levels, 

were put at each location, about 1′′ apart. For example, a #5 (0.078-inch (1.98-mm)) 3 wt.% N 

and a #5 (0.078-inch (1.98-mm)) 17 wt.% N seed were placed together. 

Composition and size were based on a number of factors. Previous hard alpha studies [41] have 

shown that 3 wt.% N seeds are at the lower edge of reproducible detection and ETC Phase I [16] 

provided experience with this concentration. In addition, natural defects tend to have a 3 wt.% N 

halo around them [42, 43, and 44]. The higher wt.% N concentration was chosen because many 

natural defects have a core of 17 wt.% N. 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

Fwd

Aft

degrees CW from

datum looking at aft face
2-119

Grain noise, arising from localized anisotropy of sound velocity within Ti-6-4 grains, was an 

additional consideration for selecting a low-nitrogen composition. It was desirable to select a 

low-nitrogen composition whose reflectance relative to a mean velocity in Ti-6-4 would be 

similar to maximum sound reflectance between maximally misaligned grains. Gigliotti [16] 

measured sound velocity in large Ti-6-4 grains: a maximum velocity of 6712 m/s was measured 

parallel to the c axis (hexagonal symmetry axis) orientation, and a minimum velocity of 6063 to 

m/s was measured perpendicular to the c-axis. This anisotropy could give rise to a 5% 

reflectance. In work measuring sound velocities of Ti-N alloys [39], a composition of 3 wt.% N 

was calculated to have about a 5% reflectance in host Ti-6-4 metal. 

A #1/2 (0.0078-inch (0.20-mm)) FBH presents 1/36 (or 2.8%) of the reflecting area of a #3 

(0.047-inch (1.19-mm)) FBH. Therefore, an area-amplitude relationship would place the signal 

reflected by the #1/2 FBH target at 1/36 of the #3 FBH. However, the UT inspection of Ti disk 

forgings is typically conducted with 10-MHz, F8 transducers. Data sets acquired at 10 MHz on 

#1/2, #1, #2, and #3 FBHs show the signals reflected from the #1/2 FBH targets to fall within 

3.7% and 4.3% of the #3 FBH. A theoretical explanation of this observation is still under 

development. Data acquired at 10 MHz on 0.047-inch (1.19-mm) -diameter, 3 wt.%N synthetic 

hard alpha inclusions also show reflectivities approximately 4% of a #3 FBH. It, therefore, 

seems reasonable to state that 3 wt.% N 0.047-inch (1.19-mm) synthetic hard alpha inclusions 

are expected to closely approximate a #1/2 FBH with respect to reflected signal amplitude, even 

though the two targets are a factor of 36 different in reflecting area. 

Table 2-8 gives the dimensions and measured sound velocities for all 40 synthetic hard alpha 

seeds that were placed in the disk. The #3 (0.047-inch (1.19-mm) seeds were too small to 

accurately measure shear velocities. With reference to table 2-9, the longitudinal velocity (cL) 

measurements were made using a 1/4′′ diameter, 50-MHz transducer having a quartz buffer rod; 

the shear-wave velocities (cS) were measured with a 1/4′′ diameter, 20-MHz quartz buffer rod 

transducer. 

TABLE 2-8. SYNTHETIC HARD ALPHA SEED DIMENSIONS AND LONGITUDINALAND SHEAR-WAVE SOUND VELOCITIES 

Seed No. wt.% N 

Length 

(mm) 

Diameter 

(mm) 

cL 

(mm/μs) 

cS

(mm/μs) 

1 3 1.223 1.200 7.152 

2 17 1.216 1.197 8.492 

3 3 1.241 1.199 6.891 

4 17 1.202 1.164 8.435 

5 3 1.994 1.934 6.588 3.537 

6 17 1.955 1.994 8.323 4.915 

7 3 1.972 1.920 6.743 3.501 

8 17 1.953 1.978 8.328 4.901 

9 3 1.198 1.185 6.897 

10 17 1.211 1.188 8.398 

11 3 1.227 1.184 6.999 

12 17 1.219 1.204 8.471 
2-120

TABLE 2-8. SYNTHETIC HARD ALPHA SEED DIMENSIONS AND LONGITUDINALAND SHEAR-WAVE SOUND VELOCITIES (Continued) 

Seed No. wt.% N 

Length 

(mm) 

Diameter 

(mm) 

cL 

(mm/μs) 

cS

(mm/μs) 

13 3 1.982 1.911 6.678 3.576 

14 17 1.923 1.986 8.314 4.918 

15 3 1.995 1.939 6.619 3.542 

16 17 1.962 1.965 8.307 4.908 

17 3 1.251 1.207 6.923 

18 17 1.209 1.192 8.562 

19 3 1.192 1.185 6.819 

20 17 1.250 1.223 8.735 

21 3 1.982 1.929 6.653 3.628 

22 17 1.966 1.963 8.306 4.894 

23 3 2.021 1.985 6.551 3.513 

24 17 1.999 1.975 8.336 4.885 

25 3 1.211 1.227 6.881 

26 17 1.218 1.169 8.559 

27 3 1.198 1.188 6.768 

28 17 1.299 1.190 9.339 

29 3 1.983 1.925 6.645 3.632 

30 17 1.956 1.954 8.295 4.921 

31 3 2.002 1.910 6.638 3.539 

32 17 1.961 1.951 8.309 4.896 

33 3 1.231 1.210 7.010 

34 17 1.208 1.166 8.513 

35 3 1.236 1.213 7.112 

36 17 1.243 1.177 8.456 

37 3 2.003 1.950 6.619 3.351 

38 17 1.979 1.968 8.368 4.905 

39 3 2.011 1.938 6.570 3.505 

40 17 1.930 1.974 8.308 4.917 

Figure 2-139 shows a cumulative distribution probability plot for the seed velocities. This plot 

shows the velocities tightly bunched. The velocities of the #5 (0.078-inch (1.98-mm)) seeds are 

slightly lower than those of the #3 (0.047-inch (1.19-mm)) seeds. This is likely an artifact of the 

measurement process. The larger seeds were deburred after machining, while the smaller seeds 

were not. Since seed lengths were measured with a micrometer, the lengths of the smaller seeds 

may have a bias to positive error, since burr-to-burr length would be measured. 

2.4.2.3 Incorporation of Synthetic Hard Alpha Within the Disk. 

Using the C-scan images, regions of high- and low-grain noise below the flat inspection surfaces 

were identified in the forging. Figure 2-140 shows a schematic of the forging and the labeled 

scan surfaces, and figure 2-141 gives the forging dimensions. A single electron discharge 
2-121

machine (EDM) bagel cut was made through the disk at the midplane of the web in the 

horizontal direction, as shown in figures 2-140 and 2-141. Once the disk was cut, another set of 

C-scan images were taken, as shown in figure 2-142. For each of the images shown in 

figure 2-142, the horizontal direction denotes circumferential position, and the vertical direction 

denotes radial position, with the radial coordinate running from the bore side at the bottom of the 

image to the rim side at the top of the image. These images were compared to their precut 

counterparts and showed good agreement as to the locations of the high- and low-grain noise 

bands. Desired defect locations in high- and low-noise regions were marked on these images, 

reviewed by the research team, and then marked on the disk itself. 

FIGURE 2-139. STATISTICAL DISTRIBUTION OF SEED VELOCITIES 

FIGURE 2-140. IDENTIFICATION OF INSPECTION SURFACES 

(SID targets were aligned normal to flat-entry surfaces on the forward and aft sides.) 

12.205 dia.

18.110 dia.

40°

52°

60°

67°

0.652

1.067

1.345 1.175

1.721 1.472 2.012

0.856

4.108

22.66 dia.

Center

Line

Forward

Side

Aft

Side

12.205 dia.

18.110 dia.

40°

52°

60°

67°

0.652

1.067

1.345 1.175

1.721 1.472 2.012

0.856

4.108

22.66 dia.

12.205 dia.

18.110 dia.

40°

52°

60°

67°

0.652

1.067

1.345 1.175

1.721 1.472 2.012

0.856

4.108

22.66 dia.

Center

Line

Forward

Side

Aft

Side
2-122

FIGURE 2-141. APPROXIMATE DIMENSIONS OF THE 

SID IN ITS FINAL MACHINED FORM 

(The bold lines show machined surfaces, and the thin lines are 

as-forged surfaces, which were removed in the final part.) 

FIGURE 2-142. C-SCAN IMAGES (THROUGH SURFACES UH, UJ, UK, UL, AND UM) 

OF THE SID AFTER EDM SLICING 

Holes for the #5 (0.078-inch (1.98-mm)) and #3 (0.047-inch (1.19-mm)) seeds were drilled on 

the internal surface, as shown in figure 2-143, in locations based on the C-scan images in 

figure 2-142. Figure 2-144 shows the full disk cross section with holes drilled. Three holes are 

marked for reference. 

Center

Line

UM UL

UK

UJ

UH

UG

US

UR

UP

UO

Forward Side

Aft Side

Center

Line

UM UL

UK

UJ

UH

UG

US

UR

UP

UO

Forward Side

Aft Side

High noise Low noise

min max

0° 360°

CCW direction

UH

UJ

UK

UL

UM

Inner Radius

Outer Radius
2-123

FIGURE 2-143. DRILLING SURFACE FOR SEED TARGETS 

(Holes were drilled normal to the inspection surfaces along the internal 

side of the cut forging.) 

FIGURE 2-144. AN SID WITH SEED HOLES DRILLED 

(Three of the 40 total holes are marked.) 

For horizontal surfaces (e.g., UM at the bore), seeds normal to the forward side were also normal 

to the aft side (UO in this case). For sloped surfaces, half of the seeds were aligned normal to the 

forward surface (e.g., UL) and half were aligned normal to the aft surface (UP in this case). 

Normal seed alignment provides flat targets for area-amplitude calculations. Figure 2-145 

schematically shows the location of all the seeds as viewed from the forward side of the SID. 

Figure 2-146 shows the seed locations viewed from the aft side, using the seed numbers in 

table 2-8. Figure 2-147 shows a seed being placed in the SID. 

Center

Line

UM UL

UK

UJ

UH

Drilled this surface

Center

Line

UM UL

UK

UJ

UH

Drilled this surface
2-124

FIGURE 2-145. SEED LOCATIONS AS VIEWED FROM FORWARD SIDE 

(Scan surfaces are shown in gray.) 

FIGURE 2-146. SEED LOCATIONS AS VIEWED FROM AFT SURFACE 

(The locations are marked as x-y where x is the seed number in table 2-8 and 

y is the angular location. Note that 0° appears at the left.) 

Key:

1. #3, 3 wt%N

2. #3, 17 wt%N

3. #3, 3 wt%N

4. #3, 17 wt%N

5. #5, 3 wt%N

6. #5, 17 wt%N

7. #5, 3 wt%N

8. #5, 17 wt%N

* Seed from adjacent sloped

region may be visible here

as a tilted target.

† Seed normal to UR sloped

surface on AFT side.

‡ Seed normal to UP sloped

surface on AFT side.

8‡

1 2

3

4

5

6

7

8

1 2

3†

4†

5

6

7†

8† 1

2

3 4

5

6

7 8

2 1

3‡

4‡

5

6

7‡

1

2

3

4

5 6

7

8

UH

0°

UJ

UK

UL

UM

*

*

*

*

*

*

*

* * *

*

*

*

*

* *

8‡

1 2

3

4

5

6

7

8

1 2

3†

4†

5

6

7†

8† 1

2

3 4

5

6

7 8

2 1

3‡

4‡

5

6

7‡

1

2

3

4

5 6

7

8

UH

0°

UJ

UK

UL

UM

*

*

*

*

*

*

*

* * *

*

*

*

*

* *

1-12

2-20

3-110

4-118

5-132

6-139

7-244

0°

8-251

9-25

10-34.5

11-76 12-83

13-220

14-230

15-292

16-305

17-53.5

18-64

19-139

20-147

21-248 22-264

23-336

25-5

26-14.5

27-53

28-74 29-113

30-126

31-178

32-182

33-58

34-78

35-101

36-118

37-196

38-216

39-240

40-258

90°

180°

270°

24-346
2-125

FIGURE 2-147. PLACEMENT OF AN SID SEED INTO AN EMPTY HOLE 

(Another empty hole is visible at the lower left corner.) 

After the seeds were set in the disk, a prick-punch was used to wedge parent material around the 

hole to ensure the seeds would not fall out during handling. Figure 2-148 shows two seeds in the 

SID. 

FIGURE 2-148. TWO SEEDS IN THE SID 

(The prick-punch marks are the shiny spots at the upper 

left side of the seeds.) 

After the seeds were placed, the two forging halves were welded together via electron beam 

welding, leak checked, and sent for HIPping. The initial HIP failed, which was caused by a leak 

in the bore of the disk. The location was identified, welded again, and the disk was sent out for a 

second HIP. This time the HIP succeeded. Figure 2-149 schematically illustrates the state of the 

disk at this point, with the approximate radial positions of the synthetic hard alpha seeds shown. 

Note that the seeds at radial locations 2 and 4 are shown tilted, to be normal to the aft surfaces. 

Only half of the seeds had that orientation. The other half (not shown) was tilted normal to the 

forward surfaces. 
2-126

FIGURE 2-149. AN SID CROSS SECTION WITH EMBEDDED SEEDS 

The disk was then machined to its final shape (see the white line in figure 2-149 and the 

dimensional values in figure 2-141). Another C-scan inspection was conducted to verify HIP 

quality and seed locations. No problems were found. 

2.4.2.4 Machining of Flat Bottom Holes. 

The final step in the SID fabrication was drilling the FBH targets. A total set of 18 FBHs were 

drilled in the three flat surfaces on the aft side. Three radial positions were used, as indicated in 

figure 2-150. Note that the FBHs were drilled in the opposite side of the disk from that used for 

drilling the small holes into which seeds were inserted. This design allows for inspection of 

certain FBHs through the large UL surface on the forward side rather than through the narrow 

US surface on the aft side. 

FIGURE 2-150. AN SID CROSS SECTION SHOWING APPROXIMATE RADIAL 

POSITIONS OF EMBEDDED SEEDS AND FBHs 

Bore

Web

Rim

AFT

FWD

ID OD

1 2* 3 4* 5

UO UP

UR

US

UG

UJ

UH

UK UL

UM

Bore

Web

Rim

AFT

FWD

ID OD

1 2* 3 4* 5

UO UP

UR

US

UG

UJ

UH

UK UL

UM

Seed FBH

Bore

Web

Rim

AFT

FWD

ID OD

1 2* 3 4* 5

UO UP

UR

US

UG

UJ

UH

UK UL

UM

Seed FBH

Bore

Web

Rim

AFT

FWD

ID OD

1 2* 3 4* 5

UO UP

UR

US

UG

UJ

UH

UK UL

UM

Bore

Web

Rim

AFT

FWD

ID OD

1 2* 3 4* 5

UO UP

UR

US

UG

UJ

UH

UK UL

UM
2-127

Great care was taken when laying out the hole locations to ensure that none were put on top of a 

seed. At each radial location, one #5 (0.078-inch, 1.98-mm), one #3 (0.047-inch, 1.19-mm), and 

four #1 FBHs were drilled. For metal paths longer than a 10-to-1, length-to-diameter ratio, 1/4′′

diameter counterbores were used. At the bottom of the counterbore, the actual FBH was drilled. 

The #3 and #5 FBHs permit true equivalent reflectivity measurements with seeds of the same 

size. These size holes traditionally have good reproducibility, thus, replicates at each location 

were not needed. The #1 FBHs serve as small targets for inspection, and replicates were placed 

at each location due to lower reproducibility. No #1/2 FBHs were drilled because they have poor 

reproducibility, and they cannot be drilled deep enough to ultrasonically resolve the hole from 

the backwall or the counterbore shoulder. Figure 2-151 shows the hole location map for the SID. 

FIGURE 2-151. FLAT BOTTOM HOLE LOCATIONS, VIEWED FROM AFT SIDE 

(Scan surfaces are labeled in gray.) 

Holes were drilled in surface US all at the same radial location 0.75′′ in from the rim to an 

overall depth of 2.3875′′. Holes drilled in surface UK were put at a location centered radially to 

an overall depth of 0.3755′′. Holes drilled in surface UO were centered radially on the surface to 

an overall depth of 0.9155′′. Figure 2-152 shows a composite view of the SID with both seed 

and FBH locations marked. 

Key:

A1 #5 FBH US, 50°

B1 #3 FBH US, 65°

C1 #1 FBH US, 340°

C2 #1 FBH US, 270°

C3 #1 FBH US, 200°

C4 #1 FBH US, 160°

A2 #5 FBH UK, 320°

B2 #3 FBH UK, 290°

C5 #1 FBH UK, 305°

C6 #1 FBH UK, 230°

C7 #1 FBH UK, 110°

C8 #1 FBH UK, 30°

A3 #5 FBH UO, 350°

B3 #3 FBH UO, 335°

C9 #1 FBH UO, 310°

C10 #1 FBH UO, 290°

C11 #1 FBH UO, 145°

C12 #1 FBH UO, 30°

US

0°

UR

UK

UP

UO

A1

B1

C3 C4

C2

C1

A2

C5

B2

C6

C7

C8

C12 B A3 3

C9

C10

C11

US

0°

UR

UK

UP

UO

A1

B1

C3 C4

C2

C1

A2

C5

B2

C6

C7

C8

C12 B A3 3

C9

C10

C11
2-128

FIGURE 2-152. SEED AND FBH LOCATIONS, VIEWED FROM FORWARD SIDE 

(Scan surfaces are labeled in gray.) 

2.4.2.5 Summary. 

A production Ti-6-4 forging was purchased from a supplier in the as-forged, pre-heat-treated 

condition. A UT inspection was performed to identify high- and low-noise regions in the 

material. The disk was cut in half along the midplane with EDM, and a set of 40 synthetic hard 

alpha defects with 3 wt.% N and 17 wt.% N were placed in a variety of locations. The disk was 

HIPped, electron beam welded, heat treated, and machined to sonic dimensions. A set of 18 #1, 

#3 (0.047-inch 1.19-mm), and #15 FBHs were drilled in the disk to the midplane as calibration 

targets. The disk was used in the Inspection Development for Titanium Forgings Study to 

demonstrate #1/2 FBH inspection sensitivity in forging applications and to conduct PoD studies. 

Key:

A1 #5 FBH UH, 310°

B1 #3 FBH UH, 295o

C1 #1 FBH UH, 20o

C2 #1 FBH UH, 90o

C3 #1 FBH UH, 160o

C4 #1 FBH UH, 200o

A2 #5 FBH UK, 40°

B2 #3 FBH UK, 70o

C5 #1 FBH UK, 55o

C6 #1 FBH UK, 130o

C7 #1 FBH UK, 250o

C8 #1 FBH UK, 330o

A3 #5 FBH UM, 10o

B3 #3 FBH UM, 25o

C9 #1 FBH UM, 50o

C10 #1 FBH UM, 70o

C11 #1 FBH UM, 215o

C12 #1 FBH UM, 330o

1. #3, 3 wt%N

2. #3, 17 wt%N

3. #3, 3 wt%N

4. #3, 17 wt%N

5. #5, 3 wt%N

6. #5, 17 wt%N

7. #5, 3 wt%N

8. #5, 17 wt%N

8‡

1 2

3

4

5

6

7

8

1

2

3†

4†

5

6

7†

8†

1

2

3

4

5

6

7 8

2 1

3‡

4‡

5

6

7‡

1

2

3

4

5

6

7

8

UH

0°

UJ

UK

UL

UM

*

*

*

*

*

*

*

* * *

*

*

*

*

* *

A1

B1

C4 C3

C2

C1

A2

C5

B2

C6

C7

C8

C12

A3 B3

C9

C10

C11

8‡

1 2

3

4

5

6

7

8

1

2

3†

4†

5

6

7†

8†

1

2

3

4

5

6

7 8

2 1

3‡

4‡

5

6

7‡

1

2

3

4

5

6

7

8

UH

0°

UJ

UK

UL

UM

*

*

*

*

*

*

*

* * *

*

*

*

*

* *

A1

B1

C4 C3

C2

C1

A2

C5

B2

C6

C7

C8

C12

A3 B3

C9

C10

C11
3-1

3. SUMMARY. 

The Engine Titanium Consortium (ETC) Phase II Fundamental Studies team was asked to 

investigate the fundamental ultrasonic (UT) properties of representative Ti-6-4 engine forgings, 

to explore the relationship of those properties to forging microstructure (e.g., flow line 

geometry), and to determine how those fundamental properties and forging surface curvatures 

impact inspectability. The team was also asked to use its data to suggest how forging inspections 

could be improved four-fold in amplitude (from #1 flat-bottom hole (FBH) detection sensitivity 

to #1/2 FBH sensitivity) and to make recommendations. The approach adopted by the team 

involved the fabrication and study of the four classes of test specimens listed in table 1-1. 

The first class of specimens, referred to as either the property measurement or forging flow line 

blocks, consisted of 26 small coupons, primarily rectangular prisms, which were cut from 

representative Ti-6-4 forged engine disks. Each of the three aircraft engine manufacturers 

(United Technologies Pratt & Whitney (P&W); General Electric Aircraft Engines (GE); and 

Honeywell Engines, Systems & Services) supplied one forging for this purpose, and the coupons 

were used to measure fundamental UT properties (velocity, attenuation, and backscattered grain 

noise). Most of the property measurement coupons were rectangular blocks, having one face 

perpendicular to the beam propagation direction for a standard normal incident longitudinalwave disk inspection. However, one coupon from each disk was a cylinder used to better study 

the angular dependence of backscattered grain noise. Coupon locations in the axial-radial plane 

were chosen to span a wide range of microstructures, as revealed by flow line geometries (via 

macroetch) and forging strain patterns (via DEFORMTM calculations (a computer software 

program that is used to evaluate strain-to-cracking for hard alpha defects in typical billets and 

forgings)). In the hoop direction, coupons were cut from high-noise regions of the disks (as 

revealed by C-scans), since high-noise regions are generally the most difficult to inspect. Since 

the coupons were cut at various angles to the forging flow lines (or local macrograin orientation 

direction), the relationship between UT properties and the directionality of the local disk 

microstructure could be studied. 

All but three of the rectangular blocks were standard size, having nominal dimensions of 1.25′′

by 1.25′′ by 2.0′′ (radial by axial by hoop). Systematic measurements on these blocks were 

performed to measure UT velocity, attenuation, and backscattered grain noise levels, and to 

subsequently investigate the relationship of the UT property variations to the flow line geometry. 

For all three forgings, sonic velocity variations measured over lengths of an inch or more were 

quite small, usually varying by less that 1 percent with position and inspection direction and, by 

themselves, are believed to pose no particular inspection difficulties. By contrast, variations of 

the UT attenuation and the average backscattered grain noise level with position and inspection 

direction in the radial-axial plane were quite large, with either quantity varying significantly 

within any given forging and varying by about an order of magnitude within the suite of forging 

flow line coupons. Measured attenuation values at 10 MHz ranged from 0.2 to 2.7 dB/inch, and 

maximal gated-peak noise (GPN) levels ranged from 0.5% to 6.9% of the amplitude of a #1 FBH 

reference reflector. The signal-to-noise (S/N) ratios quoted above are specifically for an 

inspection using a focused transducer having a particular sonic pulse volume (PV) (2.2E-5 cubic 

inches); noise-to-signal (N/S) ratios for other inspections can be estimated by using a rule of 

thumb that relates the N/S ratios to the square root of the PV. 
3-2

Variations of noise and attenuation with position and inspection direction were found to be 

related to one another and to the details of the local forging strain. At a given location in a 

forging, the direction in which measured noise was greatest was generally the direction in which 

the measured attenuation was smallest. The maximal noise, minimal attenuation direction 

generally occurred for beam propagation perpendicular to the macrostructure elongation 

direction (i.e., the flow lines). The noise or attenuation anisotropy, defined as the value 

measured for axial propagation divided by that measured for radial propagation, calculated using 

DEFORM, was found to be well-correlated with the directionality of the local forging strain. 

More specifically, DEFORM calculations were performed in which circular or ellipsoidal 

volume elements in the billet (model macrograins) were tracked to determine their final shapes at 

the conclusion of the forging process. The noise or attenuation anisotropy was found to be wellcorrelated with the ratio of the projections of the forging macrograins onto the two inspection 

directions. The clear relationship between noise anisotropy and forging macrograin geometry 

led to the development of models that predict the variation of absolute grain noise levels within a 

forging. Two models were developed: a simpler one, which ignores metal texture, and a more 

complex one, which treats texture. The simpler model treats the forging as an effective 

scattering medium described by two global parameters that are the same at all points in the 

forging. One parameter describes the average size of the forging macrograins, and the other 

describes the average difference in elastic stiffness constants from one macrograin to the next. 

The model relies on DEFORM to calculate the shapes and orientations of the macrograins at 

various locations in the forging, assuming initial macrograins in the billet which are elongated in 

the axial direction. The simpler model assumes that crystalline axes within the macrograins are 

randomly oriented. The more complex version of the model takes into account the preferred 

orientations (texture) that develop in high strain regions. Both models were applied to predict 

noise variations throughout the P&W forging, and there was reasonable agreement with 

experiment. This suggests that noise variations within forgings can be largely understood from 

knowing the shapes and orientations of the elongated metal macrograins. 

Backscattered grain noise can mask the echo from a small or subtle defect in a forging, and, thus, 

plays a key role in determining defect detection limits. Although all the forging flow line 

coupons were cut from high-noise sections of the original equipment manufacturer-supplied 

forgings, some coupons had higher grain noise levels that others. Additional measurements were 

performed on the three coupons (one from each forging) with the largest absolute noise levels. 

The values of velocity, attenuation, and backscattered grain noise capacity (or figure of merit for 

noise severity) for these three worst-case microstructures were reported to the ETC, which were 

used as inputs to inspection simulation models that estimate the probability of defect detection 

for various forging inspection schemes. The three high-noise coupons were also used to 

determine beam focal requirements for achieving the #1/2 FBH detection sensitivity. As the 

sonic beam becomes better focused, the peak S/N ratio for a given defect tends to rise, being 

approximately proportional the reciprocal of the square root of the sonic PV at the defect’s 

location. The S/N ratios of the three high-noise coupons were repeatedly measured using 

different 10-MHz transducers and various water path choices to span a wide range of PVs. #1 

FBH reflectors were drilled into the high-noise coupons to facilitate these measurements. 

Measured S/N ratios were in good agreement with the PV rule of thumb. The results indicated 

that a typical 10-MHz forging inspection that met the #1/2 FBH sensitivity target requires a 

beam diameter that does not exceed about 45 mils at any depth within a given inspection zone. 
3-3

This information was used in a companion ETC study to design improved forging inspection 

schemes. 

The final use of the forging flow line coupons was to study UT signal fluctuations caused by the 

metal microstructure, such as the speckle that appears in back-wall amplitude C-scan images. 

Related fluctuations of FBH reference amplitudes or defect-signal amplitudes have important 

implications for probability of detection. To study the fluctuations, a small receiving transducer 

(pinducer) was used to map the amplitude and phase profiles of sonic beams that emerged after 

passing through titanium (Ti) alloy and fused-quartz blocks. It was shown that distortions of the 

beam profiles by the Ti microstructure were responsible for the variation in back-wall amplitude 

when the transmitting probe was scanned in pulse/echo mode. The beam profile maps were also 

used to measure the energy-loss attenuation in selected forging flow line coupons. For these 

coupons, the average attenuation value deduced from planar probe pulse/echo measurements of 

back-wall amplitude was generally close to the energy-loss value. Thus, the beam distortions 

caused the back-wall amplitude to be higher at some locations and lower at others, but on 

average, near that expected due to energy loss alone. Work was also begun to develop a model 

that could predict the back-wall signal fluctuation level from known model parameters, which 

described the nature and severity of the beam distortions, with those model parameters 

themselves measured via through-transmission, beam-mapping experiments. Initial tests of the 

model formalism, both experimentally and through computer simulations, appeared promising. 

The continued development and testing of signal fluctuation models, and their extension to small 

reflectors (e.g., FBHs), would be a useful avenue for future work. 

Some sound-entry surfaces for forging inspections are curved, and the curvature causes the 

interrogating sound beam to focus at a different depth and have different cross-sectional profiles 

compared to an inspection through a flat surface with the same transducer. Both defect signal 

amplitudes and backscattered grain noise levels are affected. To study these effects, two sets of 

blocks were fabricated. The first set, known as the curvature correction blocks, was made from 

an ultrasonically neutral material (powder nickel alloy R88DT) and was used to study the effect 

of surface curvature on defect (FBH) echoes in the near absence of backscattered noise. The 

second set, known as the noise curvature blocks, was cut from a representative Ti-6-4 forging 

and was used to study the effect of surface curvature on backscattered grain noise characteristics. 

Each set consisted of six blocks, with each block having a different cylindrical curvature on the 

upper (sound-entry) surface. Three of the blocks in each set had concave radii of curvature 

(0.75′′, 2.0′′, and 8.0′′); two had convex radii (4.0′′and 10.0′′); and one block had a flat upper 

surface. 

The curvature correction blocks each contained 13 #1 FBH reflectors, located at depths ranging 

from 0.5′′ to 2.0′′ beneath the upper (curved) surface. A series of experiments were performed in 

which 10-MHz transducers were scanned over the upper surfaces of the blocks, and the peak 

amplitude of each FBH were measured. By comparing peak FBH amplitudes for inspections 

through curved and flat surfaces, depth-dependent curvature correction values were determined, 

defined as the receiver gain that must be added to an inspection to compensate for the effect of 

surface curvature on FBH amplitudes. Curvature corrections over the 0.5′′-2′′ depth range 

studied ranged from about -2 to +22 dB for the three measurement trials using different 

transducers. As expected, the curvature corrections tended to be largest for the surfaces having 
3-4

the most severe curvatures. Measured curvature corrections were compared to the predictions of 

the Iowa State University (ISU) models, and the largest discrepancy between model and 

experiment was about 2 dB for the cases studied. The research team agreed that the flaw signal 

model appeared sufficiently accurate to be useful for calculating curvature corrections in forging 

inspections. 

The six noise curvature blocks were fabricated from the same Ti-6-4 forging, which was the 

source of the P&W forging flow line coupons. The upper surface of each block was 

cylindrically curved, and the lower surfaces were flat. Measurements of backscattered grain 

noise properties were performed through both the flat and curved surfaces using a 10-MHz 

focused transducer often used in forging inspections to depths of a few inches. Two inspection 

water paths were used to investigate two different focal conditions. Raw noise A-scans were 

recorded and used to construct root mean squared (rms) noise level curves and GPN C-scan 

images. The rms noise curves provided a convenient way of describing the manner in which the 

observed grain noise varies with depth, and GPN C-scans are commonly used in industrial 

settings to describe the lateral variation of the noise. GPN C-scans were constructed for four 

time gates (or depth zones) having the same center but different durations, and for each, the 

average amplitude, the peak amplitude, and the standard deviation of the amplitudes about the 

mean were computed. 

Measurements through the bottom (flat) surfaces of the noise curvature blocks were used to 

document block-to-block microstructural differences and to determine appropriate correction 

factors. Noise measurements through the upper (curved) surfaces were then corrected for 

microstructural differences to isolate the effects due to curvature alone. The effect of surface 

curvature on the measured noise was quite significant, with absolute noise levels altered by up to 

a factor of 3 compared to the flat-surface case. The measured rms noise-versus-depth curves and 

GPN properties were compared to the predictions of the ISU models. The noise models were 

generalized to (1) treat nonuniform microstructures and (2) output simulated noise C-scan 

images. The noise model did a good job of predicting (1) absolute rms noise-versus-depth 

curves for flat surface inspections; (2) the changes to rms noise-versus-depth curves that result 

from surface curvature; and (3) the average GPN amplitude in a C-scan, and the manner in which 

it depends on surface curvature, water path, and the choice of time gate. Although the model did 

a good job of predicting average noise properties, it tended to slightly underpredict the ratios of 

standard deviation/average and peak/average for noise C-scans. The team concluded that the 

noise model was sufficiently accurate to serve as a useful simulation tool for investigating and 

optimizing UT inspections of Ti-6-4 forgings. However, in C-scan simulations, it was prudent to 

use the noise models only to predict average GPN amplitudes, and then to supplement the model 

with peak/average amplitude ratios that are based on direct measurement. 

The final specimen fabricated by the Fundamental Studies task group was the synthetic inclusion 

disk (SID). This was constructed by taking a representative Ti-6-4 forged disk, slicing it in a 

plane perpendicular to the axis of rotational symmetry, inserting artificial defects, and then 

HIPping the two halves of the disk back together. The basic disk geometry was the same as the 

GE-supplied forging flow line coupons. The seeded internal defects were 40 synthetic hard 

alpha inclusions. These were right circular cylinders of two sizes (#3 and #5 diameters and 
3-5/3-6

lengths) and two nitrogen impurity levels (3% and 17% nitrogen by weight). The two impurity 

levels are typical of those in the halo and core regions, respectively, of real hard alpha defects. 

The inclusions with the smaller diameter and smaller impurity level were expected to produce 

UT echoes of similar amplitude to #1/2 FBHs. The inclusions were placed into a variety of 

locations, some having high-grain noise levels and some having low-grain noise levels, as 

identified by UT C-scans prior to slicing. After assembly and HIPping were successfully 

accomplished, 18 FBHs were drilled into the SID to serve as additional reference reflectors. 

These were of three sizes: #1 (12 holes), #3 (3 holes), and #5 (3 holes). After fabrication, the 

SID was forwarded to another ETC Phase II team for use in assessing various inspection 

methods aimed at achieving #1/2 FBH detection sensitivity. 

The research activities summarized in this report were the basis for seven scientific papers 

written for the open literature, namely, references 23, 24, 25, 33, 34, 35, and 38. The ETC 

specimens fabricated during this research program are listed in appendix C. 
4-1

4. REFERENCES. 

1. Margetan, F.J., Han, K.Y., Yalda, I., Goettsch, S., and Thompson, R.B., “The Practical 

Application of Grain Noise Models in Titanium Billets and Forgings,” Review of 

Progress in QNDE, 14B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New 

York, NY, 1995, pp. 2129-2136. 

2. Panetta, P.D., Margetan, F.J., Yalda, I., and Thompson, R.B., “Ultrasonic Attenuation 

Measurements in Jet-Engine Titanium Alloys,” in Review of Progress in QNDE, Vol. 

15B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 1996, 

p. 1735. 

3. Panetta, P.D., Margetan, F.J., Yalda, I., and Thompson, R.B., “Observation and 

Interpretation of Microstructurally Induced Fluctuations of Back-Surface Signals and 

Ultrasonic Attenuation in Titanium Alloys,” ibid., Vol. 16B, 1997, p. 1547. 

4. Margetan, F.J., Han, Kim, Y., Yalda, I., Goettsch, S., and Thompson, R.B., “The 

Practical Application of Grain Noise Models in Titanium Billets and Forgings,” ibid., 

Vol. 14B, 1995, p. 2129. 

5. Margetan, F.J., Han, K.Y., Yalda-Mooshabad, I., Goettsch, S., and Thompson, R.B., 

“The Practical Application of Grain Noise Models in Titanium Billets and Forgings,” 

Review of Progress in QNDE, Vol. 14B, D.O. Thompson and D.E. Chimenti, eds., 

Plenum Press, New York, NY, 1995, pp. 2129-2136. 

6. Howard, P., Copley, D., and Gilmore, R., “Transducer Design for High Sensitivity 

Ultrasonic Inspection of Titanium,” in Review of Progress in QNDE, Vol. 16A, D.O. 

Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 1997, pp. 893-900. 

7. Gray, T.A., “Application of Measurement Models to Specification of Ultrasonic 

Inspections,” in Review of Progress in QNDE, Vol. 16B, D.O. Thompson and D.E. 

Chimenti, eds., Plenum Press, New York, NY, 1997, pp. 2061-2068. 

8. Thompson, R.B., Margetan, F.J., Yalda, I., Chiou, C.-P., and Panetta, P.D., “Coupling 

Microstructure Outputs of Process Models to Ultrasonic Inspectability Predictions,” in 

Review of Progress in QNDE, Vol. 17B, D.O. Thompson and D.E. Chimenti, eds., 

Plenum Press, New York, NY, 1998, pp. 1847-1853. 

9. Umbach, J.A. and Roberts, R.A., “Ultrasonic Phased Array Transducers-Model and 

Experiment,” presented at ASNT Fall Conference, October 1997. 

10. Smith, K. and Brasche, L., “Successful Implementation of FAA Research Address the 

Disk Inspection Initiative,” in Proceedings of the 5th Annual FAA/NASA/DOD Aging 

Aircraft Conference, 2001. 

11. Filkins, R.J., Fulton, J.P., Patton, T.C., and Young, J.D., “Recent Advances and 

Implementations of Flexible Eddy Current Probe Technology,” in Review of Progress in 
4-2

QNDE, Vol. 17B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 

NY, 1998, pp. 1809-1816. 

12. Amos, J.M. and Chao, J.C., “Optimization of a Wide-Field Eddy Current Probe Using a 

Boundary Element Method Based Model,” in Review of Progress in QNDE, Vol. 17A, 

D.O. Thompson and D. E. Chimenti, eds., Plenum Press, New York, NY, 1998, pp. 275-

282. 

13. Chao, J.C., Nakagawa, N., Raulerson, D.A., and Moulder, J.C., “Boundary Element 

Method Based Probe Design Model Validation,” in Review of Progress in QNDE, Vol. 

16A, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 1997, pp. 

967-972. 

14. Meeker, W.Q., Chan, V., Thompson, R.B., and Chiou, C.-P., “A Methodology for 

Predicting Probability of Detection for Ultrasonic Testing,” in Review of Progress in 

QNDE, Vol. 20B, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, NY, 2001, 

pp. 1972-1978. 

15. Burkel, R.H., et al., “A Methodology for the Assessment of the Capability of Inspection 

Systems for Detection of Subsurface Flaws in Aircraft Turbine Engine Components,” 

FAA report DOT/FAA/AR-01/96, September 2002. 

16. Margetan, F.J., Gigliotti, M., Brasche, L., and Leach, W., “Fundamental Studies: 

Inspection Properties for Engine Titanium Alloys,” FAA Report DOT/FAA/AR-02/114, 

December 2002. 

17. DEFORM is a commercial software package produced by Scientific Forming 

Technologies Corporation, Columbus, Ohio. 

18. Haldipur, P.F., Margetan, F.J., Yu, L., and Thompson, R.B., “Ultrasonic Attenuation 

Measurements in Jet-Engine Nickel Alloys,” Review of Progress in QNDE, Vol. 20, D.O. 

Thompson and D.E. Chimenti, eds., AIP, Melville, NY, 2001, pp. 1338-1345. 

19. Margetan, F.J., Yalda, I., Thompson, R.B., Umbach, J., Suh, U., Howard, P.J., Copley, 

D.C., and Gilmore, R., “Ultrasonic Grain Noise Modeling: Recent Applications to 

Engine Titanium Inspections,” Review of Progress in QNDE, Vol. 16, D.O. Thompson 

and D. E. Chimenti, eds., Plenum Press, New York, NY, 1997, pp. 1555-1562. 

20. Margetan, F.J., Thompson, R.B., Yalda-Mooshabad, I., and Han, Y.K., “Detectability of 

Small Flaws in Advanced Engine Alloys,” ISU Center for NDE, July 1993. 

21. Yalda, I., Panetta, P.D., Margetan, F.J., and Thompson, R.B., “Characterization of 

Ultrasonic Focused Transducers Using Axial Scans and C-Scans,” Review of Progress in 

QNDE, Vol. 16, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 

1997, pp. 927-934. 
4-3

22. Han, Y.K. and Thompson, R.B., in Metallurgical and Materials Transactions, Vol. 28A, 

1997, p. 91. 

23. Yu, L., Margetan, F.J., Thompson, R.B., and Degtyar, A., “Survey of Ultrasonic 

Properties of Aircraft Engine Titanium Forgings,” Review of Progress in QNDE, Vol. 

21B, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, NY, 2002, pp. 1510-1517. 

24. Yu, L., Thompson, R.B., Margetan, F.J., and Degtyar, A., “Modeling Ultrasonic Grain 

Noise Within Ti-6Al-4V Forgings”, Review of Progress in QNDE, Vol. 22, D.O. 

Thompson and D.E. Chimenti, eds., AIP, Melville, NY, 2003, pp. 1339-1346. 

25. Yu, L., Thompson, R.B., and Margetan, F.J., “A Model Correlating Backsacttered 

Ultrasonic Grain Noise With Inhomogeneous Plastic Deformation in Ti-6Al-4V 

forgings,” (in preparation). 

26. Yu, L., “Understanding and Improving Ultrasonic Inspections of Jet Engine Titanium 

Alloys,” Ph.D. Thesis, Dept. of Materials Science and Engineering, Iowa State 

University, 2004. 

27. Rose, J.H., Review of Progress in QNDE, Vol. 11B, D.O. Thompson and D.E. Chimenti, 

eds., Plenum, New York, NY, 1992, p. 1677-1684. 

28. Rose, J.H., Review of Progress in QNDE, Vol. 12B, D.O. Thompson and D.E. Chimenti, 

eds., Plenum Press, New York, NY, 1993, pp. 1719-1726. 

29. Margetan, F.J., Thompson, R.B., and Yalda-Mooshabad, I., “Backscattered 

Microstructural Noise in Ultrasonic Toneburst Inspections,” Journal of Nondestructive 

Evaluation, Vol. 13, 1994, pp. 111-136. 

30. Howard, P.J. and Gilmore, R.S., “Ultrasonic Noise and the Volume of the Ultrasonic 

Pulse,” Review of Progress in Quantitative Nondestructive Evaluation, Vol. 15B, D.O. 

Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 1996, pp. 1495-1502. 

31. Margetan, F.J., Umbach, J., Roberts, R. Friedl, J., Degtyar, A., Keller, M., Hassan, W., 

Brasche, L., Klassen, A., Wasan, H., and Kinney, A., “Inspection Development for 

Titanium Forgings,” FAA report DOT/FAA/AR-05/46. 

32. Margetan, F.J., Haldipur, P., Yu, L., Thompson, R.B., Degtyar, A., and Wasan, H., 

“Backscattered Ultrasonic Noise Measurements in Jet-Engine Nickel Alloys,” Review of 

Progress in QNDE, Vol. 20, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, 

NY, 2001, pp. 1314-1321. 

33. Yu, L., Thompson, R.B., Margetan, F.J., and Wang, Y., “A Monte-Carlo Model for 

Microstructure-Induced Ultrasonic Signal Fluctuations in Titanium Alloy Inspections,” 

Review of Progress in QNDE, Vol. 23, D.O. Thompson and D.E. Chimenti, eds., AIP, 

Melville, NY, 2004. 
4-4

34. Yu, L., Thompson, R.B., Margetan, F.J., and Wang, Y., “Microstructure-Induced 

Ultrasonic Signal Fluctuations in Titanium Alloy Inspections,” (in preparation). 

35. Li, A., Yu, L., Roberts, R., Margetan, F.J., and Thompson, R.B., “A 2-D Numerical 

Simulation Study of Microstructure-Induced Ultrasonic Beam Distortions,” Review of 

Progress in QNDE, Vol. 23, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, 

NY, 2004. 

36. Thompson, R.B. and Gray, T.A., “A Model Relating Ultrasonic Scattering Measurements 

Through Liquid-Solid Interfaces to Unbounded Medium Scattering Amplitudes,” J. 

Acoust. Soc. Am., 74, 1983, p. 1279. 

37. Margetan, F.J., Thompson, R.B., Degtyar, A., and Wasan, H., “Effect of Surface 

Curvature on Backscattered Ultrasonic Grain Noise in Titanium Forgings,” Review of 

Progress in QNDE, Vol. 22, D.O. Thompson and D.E. Chimenti, eds., AIP, Melville, 

NY, 2003, pp. 1363-1370. 

38. Blessing, G.V., “An Assessment of Ultrasonic Reference Block Calibration 

Methodology,” NBSIR 83-2710, National Bureau of Standards, Washington, D.C., 1983. 

39. Gigliotti, M.F.X., Gilmore, R.S., and Perocchi, L.C., “Microstructure and Sound Velocity 

of Ti-N-O Synthetic Inclusions in Ti-6Al-4V,” Metallurgical Transactions, A, 25A (11), 

1994, pp. 2321-2329. 

40. Conrardy, W.P., Titanium-6Al-4V Low Density Inclusion Problem, Technical 

Memorandum MAA 66-20, Research and Technology Division, Air Force Systems 

Command, Wright Patterson Air Force Base, Ohio, July 1966. 

41. Gigliotti, M.F.X., Perocchi, L.C., Nieters, E.J., and Gilmore, R.S., “Design and 

Fabrication of Forged Ti-6Al-4V Blocks With Synthetic Ti-N Inclusions for Estimation 

of Detectability by Ultrasonic Signal-to-Noise,” Review of Progress in QDNE, Vol. 14, 

D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, NY, 1995, pp. 2089-

2096. 

42. Grala, Edward M., “Characterization of Alpha Segregation Defects in Ti-6Al-4V Alloy,” 

Technical report AFML-TR-68-304, Air Force Materials Laboratory, Wright Patterson 

Air Force Base, Ohio, September 1968. 

43. Yves Honnorat, “Issues and Breakthrough in the Manufacture of Turboengine Titanium 

Parts,” Materials Science and Engineering, A213, 1996, pp. 115-123. 

44. A. Mitchell, “The Electron Beam Melting and Refining of Titanium Alloys,” Materials 

Science and Engineering, A263, 1999, pp. 217-223. 
APPENDIX A—RESULTS OF BACKSCATTERED NOISE AND ATTENUATION

MEASUREMENTS FOR THE FORGING FLOW LINE COUPONS

The first section of this appendix, figures A-1 through A-5, displays noise C-scan images and 

tabulated noise statistics for the 20 nominally 1.25′′ by 1.25′′ by 2.0′′ forging flow line coupons 

cut from three original equipment manufacturer-supplied Ti-6-4 forgings, as measured at Iowa 

State University (ISU). See figures 2-15, 2-28, and 2-37 for coupon locations within the 

radial/axial plane of each forging. Due to an upgrade of ISU facilities, two scanning systems 

were used for these measurements: a SONIX system for the Pratt & Whitney (P&W) and 

General Electric (GE) coupons; and a UTEX system for the Honeywell (HW) coupons. Thus, 

there are some differences in the formatting of the images. 

The second section of this appendix, figure A-6, presents average attenuation-versus-frequency 

curves for the same 20 forging flow line coupons, as measured at ISU. The results shown are 

average curves for scans over the central region of each coupon, with side 1 measurements 

(generally) corresponding to radial propagation in the forging, and side 2 to axial propagation. 

Note that measured raw attenuation curves for the 1-20 MHz frequency range are shown in 

figure A-6; values are generally only trustworthy in the 4-16 MHz range where spectral 

amplitudes are sufficiently large to allow a proper measurement. 

The third section of this appendix, table A-1, lists grain noise statistics for the forging flow line 

coupons, as extracted from the backscattered grain noise C-scan images shown in figures A-4 

and A-6. 

The final section of the appendix, figures A-7 through A-9, summarizes attenuation and 

backscattered noise measurements performed by P&W personnel on the seven rectangular 

coupons from the P&W forging. 

A-1
For normalization purposes, noise amplitudes were compared to the echo from a #1 FBH 

located 0.5” deep in a fine-grained IN100 block, with the same inspection waterpath.[A #1 FBH located 0.3125” deep in fine-grained Ti 6-4 would have been the ideal reference.]

Transducer is:

15 MHz0.5”-Diameter

F = 3.5”

Focused 1/4 way down.

Coupons measure1.25” x 1.25” x 2.0”.Each of the four large surfaces was scanned.Gated region forC-scan images of gated peak noise.

Relative inspectionsensitivity with depthwithin gate.(Via noise models.)

0 0.

0 2.

0 4.

0 6.

0 8.

1 0.

For normalization purposes, noise amplitudes were compared to the echo from a #1 FBH located 0.5” deep in a fine-grained IN100 block, with the same inspection waterpath.[A #1 FBH located 0.3125” deep in fine-grained Ti 6-4 would have been the ideal reference.]

Transducer is:

15 MHz0.5”-Diameter

F = 3.5”

Focused 1/4 way down.

Coupons measure1.25” x 1.25” x 2.0”.Each of the four large surfaces was scanned.Gated region forC-scan images of gated peak noise.

Relative inspectionsensitivity with depthwithin gate.(Via noise models.)

0 0.

0 2.

0 4.

0 6.

0 8.

1 0.

Transducer is:

15 MHz0.5”-Diameter

F = 3.5”

Focused 1/4 way down.

Coupons measure1.25” x 1.25” x 2.0”.Each of the four large surfaces was scanned.Gated region forC-scan images of gated peak noise.

Relative inspectionsensitivity with depthwithin gate.(Via noise models.)

0 0.

0 2.

0 4.

0 6.

0 8.

0 0.

0 2.

0 4.

0 6.

0 8.

0 0.

0 2.

0 4.

0 6.

0 8.

1 0.

A-2

FIGURE A-1. REVIEW OF THE INSPECTION SETUP USED FOR BACKSCATTERED GRAIN NOISE 

MEASUREMENTS AT ISU 
GE1

FWD (41 dB)

OD

ID

HOOP

0% 100%

For the large rectangular coupons the scan area was 1.5” x 2.24” in steps of 0.02”. A typical result is shown above.Near the boundaries of the specimen, the noise amplitudes are affected by “edge effects”.

“Raw” C-scan for

GE1 (Bore Region Coupon)

Inspected thru FWD surface

The “edge effected” regions are cropped from the final images. The displayed area measures about 0.83” x 1.63” in this case.Note that in this example, radial flow lines can evidently be seen.

Inspectionsurfaceand gainsettingLabels for the adjacent surfaces which are parallel to the inspection direction“Hoop” (Side 3) is always at the bottom of the image

3.5% / 5.9%

Average and maximumgated-peak noise amplitude, as a percentage of the amplitude of the #1 FBH in IN100 at the same gain.

GE1

FWD (41 dB)

OD

ID

HOOP

0% 100%

For the large rectangular coupons the scan area was 1.5” x 2.24” in steps of 0.02”. A typical result is shown above.Near the boundaries of the specimen, the noise amplitudes are affected by “edge effects”.

“Raw” C-scan for

GE1 (Bore Region Coupon)

Inspected thru FWD surface

The “edge effected” regions are cropped from the final images. The displayed area measures about 0.83” x 1.63” in this case.Note that in this example, radial flow lines can evidently be seen.

Inspectionsurfaceand gainsettingLabels for the adjacent surfaces which are parallel to the inspection direction“Hoop” (Side 3) is always at the bottom of the image

3.5% / 5.9%

Average and maximumgated-peak noise amplitude, as a percentage of the amplitude of the #1 FBH in IN100 at the same gain.

A-3

FIGURE A-2. EXPLANATION OF CROPPING AND LABELING CONVENTIONS FOR NOISE 

C-SCANS OF THE P&W AND GE FORGING FLOW LINE COUPONS 
Backscattered Noise C-scans for Ti 6-4 Coupon GE1 (Bore Region)

AFT (37 dB) FWD (41 dB) OD (52 dB) ID (52 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (37 dB) FWD (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

0% 100%

4.1% / 11.3% 3.4% / 7.3% 0.9% / 1.6% 1.0% / 1.6%

15 dB

GE1

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE1

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon GE1 (Bore Region)

AFT (37 dB) FWD (41 dB) OD (52 dB) ID (52 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (37 dB) FWD (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (37 dB) FWD (41 dB) OD (52 dB) ID (52 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (37 dB) FWD (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

0% 100%

4.1% / 11.3% 3.4% / 7.3% 0.9% / 1.6% 1.0% / 1.6%

15 dB

GE1

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE1

GE1

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE1

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-4

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon GE4 (Far Rim Region; Mid Thickness)

0% 100%

AFT (45 dB) FWD (45 dB) OD (34 dB) ID (36 dB)

1.7% / 5.5% 1.4% / 3.5% 5.6% / 15.0% 3.6% / 8.8%

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (34 dB) FWD (34 dB) OD (34 dB) ID (34 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

15 dB

GE4

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE4

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon GE4 (Far Rim Region; Mid Thickness)

0% 100%

AFT (45 dB) FWD (45 dB) OD (34 dB) ID (36 dB)

1.7% / 5.5% 1.4% / 3.5% 5.6% / 15.0% 3.6% / 8.8%

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (34 dB) FWD (34 dB) OD (34 dB) ID (34 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (45 dB) FWD (45 dB) OD (34 dB) ID (36 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (34 dB) FWD (34 dB) OD (34 dB) ID (34 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

15 dB

GE4

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE4

GE4

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE4

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-5

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon GE5 (Far Rim Region, FWD Side)

0% 100%

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

1.3% / 3.2% 1.0% / 1.7% 3.3% / 12.0% 3.1% / 11.4%

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

15 dB

GE5

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon GE5 (Far Rim Region, FWD Side)

0% 100%

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

1.3% / 3.2% 1.0% / 1.7% 3.3% / 12.0% 3.1% / 11.4%

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (45 dB) FWD (48 dB) OD (36 dB) ID (36 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

AFT (36 dB) FWD (36 dB) OD (36 dB) ID (36 dB)

OD

OD

ID

ID

AFT

AFT

FWD

FWD

HOOP HOOP HOOP HOOP

15 dB

GE5

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

GE5

2

4

5

1

AFT

(3 = Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-6

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon GE6 (Rim Region, Aft Side, Tilted)

0% 100%

1.9% / 8.4% 1.5% / 4.0% 4.0% / 19.0% 2.7% / 12.3%

Side 2 (40 dB) Side 5 (43 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (34 dB) Side 5 (34 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

15 dB

GE6

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE6

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon GE6 (Rim Region, Aft Side, Tilted)

0% 100%

1.9% / 8.4% 1.5% / 4.0% 4.0% / 19.0% 2.7% / 12.3%

Side 2 (40 dB) Side 5 (43 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (34 dB) Side 5 (34 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (40 dB) Side 5 (43 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (34 dB) Side 5 (34 dB) Side 1 (34 dB) Side 4 (34 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

15 dB

GE6

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE6

GE6

2 4

5 1

AFT

(Hoop)

FWD

ID OD GE6

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE6

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-7

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon GE7 (Rim Region, FWD Side, Tilted)

0% 100%

3.2% / 8.3% 3.8% / 10.4% 1.5% / 3.0% 1.4% / 2.8%

Side 2 (37 dB) Side 5 (35 dB) Side 1 (45 dB) Side 4 (45 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (35 dB) Side 5 (35 dB) Side 1 (35 dB) Side 4 (35 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

15 dB

GE7

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE7

Ref. Scan

#1 FBH 

Backscattered Noise C-scans for Ti 6-4 Co

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

upon GE7 (Rim Region, FWD Side, Tilted)

0% 100%

3.2% / 8.3% 3.8% / 10.4% 1.5% / 3.0% 1.4% / 2.8%

Side 2 (37 dB) Side 5 (35 dB) Side 1 (45 dB) Side 4 (45 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (35 dB) Side 5 (35 dB) Side 1 (35 dB) Side 4 (35 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

3.2% / 8.3% 3.8% / 10.4% 1.5% / 3.0% 1.4% / 2.8%

Side 2 (37 dB) Side 5 (35 dB) Side 1 (45 dB) Side 4 (45 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Side 2 (35 dB) Side 5 (35 dB) Side 1 (35 dB) Side 4 (35 dB)

Side 1

Side 4

Hoop

Side 1

Side 4

Hoop Hoop Hoop

Side 2

Side 5

Side 5

Side 2

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

15 dB

GE7

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE7

GE7

2 4

5 1

AFT

(Hoop)

FWD

ID OD GE7

2 4

5 1

AFT

(Hoop)

FWD

ID OD

Scan area in each

image is 1.63” x 0.83”

Coupon GE7

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

A-8

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW1 (Bore Region)

TOP (42 dB) BOT (37 dB) OD (42 dB) ID (42 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (37 dB) BOT (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.4% / 6.3% 3.8% / 10.7% 1.8% / 6.3% 1.9% / 6.7%

17 dB

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

#1

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW1

Backscattered Noise C-scans for Ti 6-4 Coupon PW1 (Bore Region)

TOP (42 dB) BOT (37 dB) OD (42 dB) ID (42 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (37 dB) BOT (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.4% / 6.3% 3.8% / 10.7% 1.8% / 6.3% 1.9% / 6.7%

17 dB

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

#1

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW1

#1

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW1

A-9

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW2 (Web Region)

TOP (43 dB) BOT (37 dB) OD (46 dB) ID (43 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (37 dB) BOT (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.2% / 5.1% 3.8% / 11.4% 1.4% / 3.9% 1.5% / 5.3%

17 dB

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

#2

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW2

Backscattered Noise C-scans for Ti 6-4 Coupon PW2 (Web Region)

TOP (43 dB) BOT (37 dB) OD (46 dB) ID (43 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (37 dB) BOT (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (43 dB) BOT (37 dB) OD (46 dB) ID (43 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (37 dB) BOT (37 dB) OD (37 dB) ID (37 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.2% / 5.1% 3.8% / 11.4% 1.4% / 3.9% 1.5% / 5.3%

17 dB

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

#2

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW2

#2

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW2

A-10

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW4 (Mid-Radius, Top)

0% 100%

TOP (48 dB) BOT (48 dB) OD (40 dB) ID (40 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (40 dB) BOT (40 dB) OD (40 dB) ID (40 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

1.1% / 2.6% 1.4% / 3.2% 1.7% / 8.4% 1.8% / 8.4%

17 dB

#4

2

4

5

1

(3 = Hoop)

TOP

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW4

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon PW4 (Mid-Radius, Top)

0% 100%

TOP (48 dB) BOT (48 dB) OD (40 dB) ID (40 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (40 dB) BOT (40 dB) OD (40 dB) ID (40 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (48 dB) BOT (48 dB) OD (40 dB) ID (40 dB)

1.1% / 2.6% 1.4% / 3.2% 1.7% / 8.4% 1.8% / 8.4%

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (40 dB) BOT (40 dB) OD (40 dB) ID (40 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

1.1% / 2.6% 1.4% / 3.2% 1.7% / 8.4% 1.8% / 8.4%

17 dB

#4

2

4

5

1

(3 = Hoop)

TOP

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW4

#4

2

4

5

1

(3 = Hoop)

TOP

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW4

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-11

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW5 (Mid-Radius; Center)

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.5% / 6.9% 2.2% / 7.3% 3.5% / 12.4% 3.0% / 13.9%

17 dB

#5

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon PW5 (Mid-Radius; Center)

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.5% / 6.9% 2.2% / 7.3% 3.5% / 12.4% 3.0% / 13.9%

17 dB

#5

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW5

#5

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW5

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-12

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW6 (Mid-Radius, Bottom)

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.1% / 6.1% 1.8% / 5.4% 3.9% / 13.3% 3.4% / 14.5%

17 dB

#6

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW6

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon PW6 (Mid-Radius, Bottom)

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (41 dB) BOT (41 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.1% / 6.1% 1.8% / 5.4% 3.9% / 13.3% 3.4% / 14.5%

17 dB

#6

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW6

#6

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW6

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-13

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW7 (Rim Region, Top)

TOP (40 dB) BOT (40 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.7% / 8.0% 1.8% / 8.0% 4.1% / 14.5% 2.7% / 12.5%

17 dB

#7

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW7

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon PW7 (Rim Region, Top)

TOP (40 dB) BOT (40 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (35 dB) BOT (35 dB) OD (35 dB) ID (35 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

2.7% / 8.0% 1.8% / 8.0% 4.1% / 14.5% 2.7% / 12.5%

17 dB

#7

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW7

#7

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW7

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-14

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Backscattered Noise C-scans for Ti 6-4 Coupon PW8 (Rim Region, Center)

TOP (42 dB) BOT (42 dB) OD (35 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (33 dB) BOT (33 dB) OD (33 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

1.6% / 5.5% 1.5% / 4.6% 5.0% / 14.4% 5.1% / 17.0%

17 dB

#8

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW8

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

Backscattered Noise C-scans for Ti 6-4 Coupon PW8 (Rim Region, Center)

TOP (42 dB) BOT (42 dB) OD (35 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (33 dB) BOT (33 dB) OD (33 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (42 dB) BOT (42 dB) OD (35 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

TOP (33 dB) BOT (33 dB) OD (33 dB) ID (33 dB)

OD

OD

ID

ID

TOP

TOP

BOT

BOT

HOOP HOOP HOOP HOOP

0% 100%

1.6% / 5.5% 1.5% / 4.6% 5.0% / 14.4% 5.1% / 17.0%

17 dB

#8

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW8

#8

2

4

5

1

TOP

(3 = Hoop)

BOT

ID OD

Displayed area in each

image is 1.63” x 0.83”

Coupon PW8

Ref. Scan

#1 FBH 

0.5 inches deep

in IN100 block.

0.1” x 0.1” scan.

Mean / Max w.r.t. 100% = #1 FBHin IN100 at same waterpath & gain. 

A-15

FIGURE A-3. CROPPED AND ANNOTATED NOISE C-SCANS FOR EACH GE AND P&W COUPON (Continued) 

(In the upper row, each C-scan is displayed at the gain setting actually used during data acquisition. In the bottom row, 

the C-scans have been rescaled to a common gain setting to facilitate visual comparison of the noise levels.) 
Typical Noise C-scan: Image Labels and Statistics for HW Coupons

Table lists average and maximumgated-peak noise amplitude, as a percentage of the amplitude of the #1 FBH in IN100 at the same water path and gain.Amplitudes are computed for the reduced-area region (illustrated above) with “edge effects” cropped.

Side 2 - AFT

Side 5 - FWD

(Side 3 – hoop)

Thru OD Inspection entry 

surface

“Hoop” edge (Side 3) is always at the bottom of the image, allowing the other edges to be readily identified.

Specimen, inspection direction and absolute gain setting.

Info Appearing on Summary Figures

Tic marks are 0.5” apart

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

Cropped region used for noise statistics

Region scanned measures 1.6” wide by 2.5” tall in steps of 0.02”. Near the boundaries of the specimen, the noise amplitudes are affected by “edge effects”.

“Raw” C-scan for

HW Coupon #3 (AFT/OD region) 

Inspected thru OD surface

0% 100%

Typical Noise C-scan: Image Labels and Statistics for HW Coupons

Table lists average and maximumgated-peak noise amplitude, as a percentage of the amplitude of the #1 FBH in IN100 at the same water path and gain.Amplitudes are computed for the reduced-area region (illustrated above) with “edge effects” cropped.

Side 2 - AFT

Side 5 - FWD

(Side 3 – hoop)

Thru OD Inspection entry 

surface

“Hoop” edge (Side 3) is always at the bottom of the image, allowing the other edges to be readily identified.

Specimen, inspection direction and absolute gain setting.

Info Appearing on Summary Figures

Tic marks are 0.5” apart

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

Cropped region used for noise statistics

Table lists average and maximumgated-peak noise amplitude, as a percentage of the amplitude of the #1 FBH in IN100 at the same water path and gain.Amplitudes are computed for the reduced-area region (illustrated above) with “edge effects” cropped.

Side 2 - AFT

Side 5 - FWD

(Side 3 – hoop)

Thru OD Inspection entry 

surface

“Hoop” edge (Side 3) is always at the bottom of the image, allowing the other edges to be readily identified.

Specimen, inspection direction and absolute gain setting.

Info Appearing on Summary Figures

Tic marks are 0.5” apart

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

Cropped region used for noise statistics

Region scanned measures 1.6” wide by 2.5” tall in steps of 0.02”. Near the boundaries of the specimen, the noise amplitudes are affected by “edge effects”.

“Raw” C-scan for

HW Coupon #3 (AFT/OD region) 

Inspected thru OD surface

0% 100%

Region scanned measures 1.6” wide by 2.5” tall in steps of 0.02”. Near the boundaries of the specimen, the noise amplitudes are affected by “edge effects”.

“Raw” C-scan for

HW Coupon #3 (AFT/OD region) 

Inspected thru OD surface

0% 100%

A-16

FIGURE A-4. EXPLANATION OF LABELING CONVENTIONS FOR NOISE C-SCANS OF THE HW 

FORGING LOW LINE COUPONS 
A-17

H1 Side 1, 48dB

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

H1 Side 2, 32dB

Avg.: 4.20% 4.61% 4.36% 

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 1

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS 

Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 4, 48dB

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

H1 Side 5, 32dB

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 1

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

H1 Side 1, 48dB

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

H1 Side 2, 32dB

Avg.: 4.20% 4.61% 4.36% Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 4, 48dB

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

H1 Side 5, 32dB

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 1, 48dB

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

H1 Side 1, 48dB

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

H1 Side 1, 48dB

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

Avg.: 1.33% 1.24% 1.41% Peak: 2.37% 2.09% 2.37%

Fullimage

Lefthalf

Righthalf

H1 Side 2, 32dB

Avg.: 4.20% 4.61% 4.36% Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 2, 32dB

Avg.: 4.20% 4.61% 4.36% Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 2, 32dB

Avg.: 4.20% 4.61% 4.36% Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

Avg.: 4.20% 4.61% 4.36% Peak: 16.6% 16.6% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 4, 48dB

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

H1 Side 4, 48dB

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

H1 Side 4, 48dB

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

Avg.: 1.19% 1.21% 1.17% Peak: 2.22% 1.91% 2.22%

Fullimage

Lefthalf

Righthalf

H1 Side 5, 32dB

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 5, 32dB

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf

H1 Side 5, 32dB

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf

Avg.: 4.28% 4.03% 4.28% Peak: 15.9% 15.9% 11.3%

Fullimage

Lefthalf

Righthalf
A-18

H2 Side 1, 36dB

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

H2 Side 2, 34dB

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

H2 Side 4, 38dB

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

H2 Side 5, 37dB

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

Honeywell Ti 6-4 Forging Coupon # 2

H2 Side 1, 36dB

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

H2 Side 2, 34dB

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

H2 Side 4, 38dB

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

H2 Side 5, 37dB

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

H2 Side 1, 36dB

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

H2 Side 1, 36dB

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

H2 Side 1, 36dB

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

Avg.: 2.94% 2.64% 3.25% Peak: 11.9% 9.14% 11.9%

Fullimage

Lefthalf

Righthalf

H2 Side 2, 34dB

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

H2 Side 2, 34dB

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

H2 Side 2, 34dB

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

Avg.: 3.83% 3.90% 3.71% Peak: 14.6% 14.6% 10.2%

Fullimage

Lefthalf

Righthalf

H2 Side 4, 38dB

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

H2 Side 4, 38dB

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

H2 Side 4, 38dB

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

Avg.: 2.70% 3.02% 2.34% Peak: 7.62% 7.62% 6.78%

Fullimage

Lefthalf

Righthalf

H2 Side 5, 37dB

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

H2 Side 5, 37dB

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

H2 Side 5, 37dB

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

Avg.: 3.26% 2.71% 3.80% Peak: 11.0% 8.14% 11.0%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

Honeywell Ti 6-4 Forging Coupon # 2

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 
A-19

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 2, 38dB

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

H3 Side 4, 37dB

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

H3 Side 5, 38dB

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 3

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 2, 38dB

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

H3 Side 4, 37dB

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

H3 Side 5, 38dB

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 1, 37dB

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

Avg.: 2.58% 2.13% 3.03% Peak: 10.4% 6.11% 10.4%

Fullimage

Lefthalf

Righthalf

H3 Side 2, 38dB

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

H3 Side 2, 38dB

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

H3 Side 2, 38dB

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

Avg.: 2.78% 3.11% 2.50%Peak: 8.03% 8.03% 6.53%

Fullimage

Lefthalf

Righthalf

H3 Side 4, 37dB

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

H3 Side 4, 37dB

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

H3 Side 4, 37dB

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

Avg.: 2.22% 2.85% 1.63% Peak: 9.00% 9.00% 4.71%

Fullimage

Lefthalf

Righthalf

H3 Side 5, 38dB

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

H3 Side 5, 38dB

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

H3 Side 5, 38dB

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

Avg.: 2.22% 1.77% 2.66% Peak: 7.34% 4.80% 7.34%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 3

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 
A-20

H4 Side 1, 39dB

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

H4 Side 2, 35dB

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

H4 Side 4, 38dB

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

H4 Side 5, 35dB

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 4

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

H4 Side 1, 39dB

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

H4 Side 2, 35dB

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

H4 Side 4, 38dB

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

H4 Side 5, 35dB

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

H4 Side 1, 39dB

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

H4 Side 1, 39dB

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

H4 Side 1, 39dB

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

Avg.: 2.52% 2.59% 2.52% Peak: 8.84% 8.84% 6.69%

Fullimage

Lefthalf

Righthalf

H4 Side 2, 35dB

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

H4 Side 2, 35dB

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

H4 Side 2, 35dB

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

Avg.: 4.61% 4.50% 4.73% Peak: 13.0% 11.5% 13.0%

Fullimage

Lefthalf

Righthalf

H4 Side 4, 38dB

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

H4 Side 4, 38dB

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

H4 Side 4, 38dB

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

Avg.: 2.06% 2.18% 1.94% Peak: 7.78% 5.77% 7.78%

Fullimage

Lefthalf

Righthalf

H4 Side 5, 35dB

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

H4 Side 5, 35dB

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

H4 Side 5, 35dB

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

Avg.: 2.91% 2.62% 3.13% Peak: 11.3% 7.80% 11.3%

Fullimage

Lefthalf

Righthalf

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Honeywell Ti 6-4 Forging Coupon # 4

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 
A-21

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H5 Side1, 32dB

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

H5 Side 2, 46dB

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

H5 Side 4, 31dB

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

H5 Side 5, 45dB

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 5

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H5 Side1, 32dB

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

H5 Side 2, 46dB

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

H5 Side 4, 31dB

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

H5 Side 5, 45dB

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

H5 Side1, 32dB

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

H5 Side1, 32dB

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

H5 Side1, 32dB

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

Avg.: 7.24% 7.47% 7.08% Peak: 17.9% 15.2% 17.9%

Fullimage

Lefthalf

Righthalf

H5 Side 2, 46dB

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

H5 Side 2, 46dB

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

H5 Side 2, 46dB

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

Avg.: 1.41% 1.51% 1.32% Peak: 3.33% 3.33% 2.90%

Fullimage

Lefthalf

Righthalf

H5 Side 4, 31dB

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

H5 Side 4, 31dB

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

H5 Side 4, 31dB

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

Avg.: 7.69% 7.86% 7.51% Peak: 21.3% 17.9% 21.3%

Fullimage

Lefthalf

Righthalf

H5 Side 5, 45dB

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

H5 Side 5, 45dB

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

H5 Side 5, 45dB

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

Avg.: 1.40% 1.33% 1.45% Peak: 3.10% 2.52% 3.10%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 5

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 
A-22

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H6 Side 1, 39dB

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

H6 Side 2, 39dB

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

H6 Side 4, 44dB

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

H6 Side 5, 44dB

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 6

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H6 Side 1, 39dB

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

H6 Side 2, 39dB

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

H6 Side 4, 44dB

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

H6 Side 5, 44dB

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

H6 Side 1, 39dB

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

H6 Side 1, 39dB

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

H6 Side 1, 39dB

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

Avg.: 1.69% 1.62% 1.73% Peak: 4.13% 3.45% 4.13%

Fullimage

Lefthalf

Righthalf

H6 Side 2, 39dB

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

H6 Side 2, 39dB

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

H6 Side 2, 39dB

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

Avg.: 1.78% 1.76% 1.80% Peak: 3.92% 3.23% 3.92%

Fullimage

Lefthalf

Righthalf

H6 Side 4, 44dB

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

H6 Side 4, 44dB

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

H6 Side 4, 44dB

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

Avg.: 1.66% 1.68% 1.64% Peak: 4.65% 4.26% 4.65%

Fullimage

Lefthalf

Righthalf

H6 Side 5, 44dB

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

H6 Side 5, 44dB

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

H6 Side 5, 44dB

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

Avg.: 1.70% 1.72% 1.68% Peak: 3.86% 3.86% 3.80%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 6

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 
A-23

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H7 Side 1, 35dB

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

H7 Side 2, 45dB

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

H7 Side 4, 30dB

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

H7 Side 5, 46dB

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 7

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H7 Side 1, 35dB

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

H7 Side 2, 45dB

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

H7 Side 4, 30dB

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

H7 Side 5, 46dB

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

H7 Side 1, 35dB

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

H7 Side 1, 35dB

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

H7 Side 1, 35dB

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

Avg.: 3.98% 2.94% 4.90% Peak: 11.7% 8.61% 11.7%

Fullimage

Lefthalf

Righthalf

H7 Side 2, 45dB

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

H7 Side 2, 45dB

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

H7 Side 2, 45dB

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

Avg.: 1.14% 1.09% 1.17% Peak: 2.29% 1.95% 2.29%

Fullimage

Lefthalf

Righthalf

H7 Side 4, 30dB

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

H7 Side 4, 30dB

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

H7 Side 4, 30dB

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

Avg.: 4.85% 5.72% 3.97% Peak: 17.8% 17.8% 9.89%

Fullimage

Lefthalf

Righthalf

H7 Side 5, 46dB

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

H7 Side 5, 46dB

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

H7 Side 5, 46dB

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

Avg.: 1.09% 1.11% 1.08% Peak: 1.89% 1.74% 1.89%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 7

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.
A-24

FIGURE A-5. ANNOTATED NOISE C-SCANS FOR THE HW FORGING FLOW LINE COUPONS (Continued) 

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H8 Side 1, 45dB

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 2, 42dB

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

H8 Side 4, 43dB

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

H8 Side 5, 45dB

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 8

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

(Side 2 – AFT)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

Thru OD Thru FWD Thru AFT Thru ID

(Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop) (Side 3 – hoop)

(Side 2 – AFT)

(Side 5 – FWD)

(Side 5 – FWD)

(Side 4 – ID)

(Side 1 – OD)

(Side 4 – ID)

(Side 1 – OD)

H8 Side 1, 45dB

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 2, 42dB

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

H8 Side 4, 43dB

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

H8 Side 5, 45dB

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 1, 45dB

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 1, 45dB

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 1, 45dB

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

Avg.: 1.22% 1.33% 1.11% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 2, 42dB

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

H8 Side 2, 42dB

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

H8 Side 2, 42dB

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

Avg.: 1.59% 1.64% 1.51% Peak: 4.32% 4.32% 2.84%

Fullimage

Lefthalf

Righthalf

H8 Side 4, 43dB

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

H8 Side 4, 43dB

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

H8 Side 4, 43dB

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

Avg.: 1.36% 1.35% 1.37% Peak: 3.57% 3.57% 2.71%

Fullimage

Lefthalf

Righthalf

H8 Side 5, 45dB

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 5, 45dB

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

H8 Side 5, 45dB

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

Avg.: 1.31% 1.36% 1.25% Peak: 3.17% 3.17% 2.16%

Fullimage

Lefthalf

Righthalf

Honeywell Ti 6-4 Forging Coupon # 8

“Same day” reference C-scan at 17dB gain. Scan of #1 FBH 0.5” deep in IN100 block; 0.1” x 0.1” scan region with 0.002” step. This #1 FBH amplitude is defined as 100%.
A-25

FIGURE A-6. LONGITUDINAL-WAVE ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE 

FORGING FLOW LINE COUPONS IN Nepers/cm UNITS, AS MEASURED AT ISU 

PW#1 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#2 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#4 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#5 Side1&2 Attenuation

0.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#1 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#2 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#4 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#5 Side1&2 Attenuation

0.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2
A-26

FIGURE A-6. LONGITUDINAL-WAVE ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE 

FORGING FLOW LINE COUPONS IN Nepers/cm UNITS, AS MEASURED AT ISU (Continued) 

PW#6 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#7 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#8 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#1 Side1&2 Attenuation

0.100.080.060.040.020.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#6 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#7 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

PW#8 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#1 Side1&2 Attenuation

0.100.080.060.040.020.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2
A-27

FIGURE A-6. LONGITUDINAL-WAVE ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE 

FORGING FLOW LINE COUPONS IN Nepers/cm UNITS, AS MEASURED AT ISU (Continued) 

GE#4 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#5 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#6 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#7 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#4 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#5 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#6 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

GE#7 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2
A-28

FIGURE A-6. LONGITUDINAL-WAVE ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE 

FORGING FLOW LINE COUPONS IN Nepers/cm UNITS, AS MEASURED AT ISU (Continued) 

Honeywell#1 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#2 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#3 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#4 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#1 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#2 Side1&2 Attenuation

0.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#3 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#4 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2
A-29

FIGURE A-6. LONGITUDINAL-WAVE ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE 

FORGING FLOW LINE COUPONS IN Nepers/cm UNITS, AS MEASURED AT ISU (Continued) 

Honeywell#6 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#7 Side1&2 Attenuation

0.300.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#8 Side1&2 Attenuation

0.180.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#5 Side1&2 Attenuation

0.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side 2

Honeywell#6 Side1&2 Attenuation

0.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#7 Side1&2 Attenuation

0.300.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#8 Side1&2 Attenuation

0.180.150.120.090.060.030.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side2

Honeywell#5 Side1&2 Attenuation

0.250.200.150.100.050.00

0 2 4 6 8 10 12 14 16 18 20

Frequency (MHz)

Att (Np/cm)

Att_Side 1Att_Side 2
A-30 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum noise amplitudes

using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 flat-bottom hole (FBH) in the focal zone.) 

Tabular Form of the Noise Data for GE Forging Coupons 

Summary of Grain Noise Measurements on 

GE Ti-6-4 Forgings Specimens 

Raw data values on a scale of 0-254 

Normalized by 0.5′′ deep #1 FBH in 

IN100 = 100 (Measured FBH had 

peak response of 216 at 15 dB) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using ISU models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 GE1_S1_L 52 132.09 21.31 84 244 0.86 0.14 0.55 1.60 0.28 0.04 0.18 0.512 GE1_S1_R 52 149.64 20.75 100 244 0.98 0.14 0.65 1.60 0.32 0.04 0.21 0.513 GE1_S4_L 52 155.16 20.14 98 244 1.02 0.13 0.64 1.60 0.33 0.04 0.21 0.514 GE1_S4_R 52 137.92 19.73 86 227 0.90 0.13 0.56 1.48 0.29 0.04 0.18 0.485 GE1_S2_L 37 119.37 33.27 64 306 4.39 1.22 2.35 11.25 1.42 0.39 0.76 3.636 GE1_S2_R 37 102.46 34.60 36 241 3.77 1.27 1.32 8.86 1.22 0.41 0.43 2.867 GE1_S5_L 41 148.79 25.31 84 315 3.45 0.59 1.95 7.31 1.11 0.19 0.63 2.368 GE1_S5_R 41 145.53 23.15 84 244 3.38 0.54 1.95 5.66 1.09 0.17 0.63 1.831 GE4_S1_L 34 111.59 35.17 42 252 5.80 1.83 2.18 13.09 1.87 0.59 0.70 4.222 GE4_S1_R 34 102.45 33.40 42 288 5.32 1.73 2.18 14.96 1.72 0.56 0.70 4.833 GE4_S4_L 34 76.91 18.18 44 170 4.00 0.94 2.29 8.83 1.29 0.30 0.74 2.854 GE4_S4_R 34 60.66 16.28 30 158 3.15 0.85 1.56 8.21 1.02 0.27 0.50 2.655 GE4_S2_L 45 140.52 32.93 72 377 2.06 0.48 1.05 5.52 0.66 0.16 0.34 1.786 GE4_S2_R 45 93.01 20.90 54 320 1.36 0.31 0.79 4.68 0.44 0.10 0.26 1.517 GE4_S5_L 45 87.57 14.13 58 160 1.28 0.21 0.85 2.34 0.41 0.07 0.27 0.768 GE4_S5_R 45 100.23 21.13 60 241 1.47 0.31 0.88 3.53 0.47 0.10 0.28 1.141 GE5_S1_L 36 127.35 34.15 52 291 5.25 1.41 2.15 12.01 1.70 0.45 0.69 3.872 GE5_S1_R 36 31.80 10.70 18 118 1.31 0.44 0.74 4.87 0.42 0.14 0.24 1.573 GE5_S4_L 36 31.17 7.34 20 90 1.29 0.30 0.83 3.71 0.41 0.10 0.27 1.204 GE5_S4_R 36 118.21 29.99 60 275 4.88 1.24 2.48 11.35 1.57 0.40 0.80 3.665 GE5_S2_L 45 91.42 16.07 56 216 1.34 0.24 0.82 3.16 0.43 0.08 0.26 1.026 GE5_S2_R 45 80.67 12.93 48 148 1.18 0.19 0.70 2.17 0.38 0.06 0.23 0.707 GE5_S5_L 45 67.42 8.31 48 104 0.99 0.12 0.70 1.52 0.32 0.04 0.23 0.498 GE5_S5_R 45 70.70 9.29 46 116 1.04 0.14 0.67 1.70 0.33 0.04 0.22 0.55
A-31 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for GE Forging Coupons 

Summary of Grain Noise Measurements on 

GE Ti-6-4 Forgings Specimens 

Raw data values on a scale of 0-254 

Normalized by 0.5′′ deep #1 FBH in 

IN100 = 100 (Measured FBH had 

peak response of 216 at 15 dB) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using ISU models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 GE6_S1_L 34 39.05 21.50 18 178 2.03 1.12 0.94 9.25 0.65 0.36 0.30 2.982 GE6_S1_R 34 115.66 37.19 38 365 6.01 1.93 1.97 18.96 1.94 0.62 0.64 6.123 GE6_S4_L 34 74.64 27.09 26 236 3.88 1.41 1.35 12.26 1.25 0.45 0.44 3.954 GE6_S4_R 34 29.77 9.18 18 84 1.55 0.48 0.94 4.36 0.50 0.15 0.30 1.415 GE6_S2_L 40 81.93 29.01 38 322 2.13 0.76 0.99 8.38 0.69 0.24 0.32 2.706 GE6_S2_R 40 65.84 26.54 36 230 1.71 0.69 0.94 5.99 0.55 0.22 0.30 1.937 GE6_S5_L 43 81.57 14.04 50 144 1.50 0.26 0.92 2.65 0.48 0.08 0.30 0.868 GE6_S5_R 43 84.97 15.69 54 214 1.57 0.29 1.00 3.94 0.51 0.09 0.32 1.271 GE7_S1_L 45 102.71 18.88 60 202 1.50 0.28 0.88 2.96 0.49 0.09 0.28 0.952 GE7_S1_R 45 107.76 19.10 66 202 1.58 0.28 0.97 2.96 0.51 0.09 0.31 0.953 GE7_S4_L 45 98.81 17.13 58 170 1.45 0.25 0.85 2.49 0.47 0.08 0.27 0.804 GE7_S4_R 45 90.29 14.71 52 190 1.32 0.22 0.76 2.78 0.43 0.07 0.25 0.905 GE7_S2_L 37 73.11 22.67 32 204 2.69 0.83 1.18 7.50 0.87 0.27 0.38 2.426 GE7_S2_R 37 100.95 24.19 52 225 3.71 0.89 1.91 8.27 1.20 0.29 0.62 2.677 GE7_S5_L 35 104.24 26.01 46 225 4.83 1.20 2.13 10.42 1.56 0.39 0.69 3.368 GE7_S5_R 35 58.31 20.27 28 172 2.70 0.94 1.30 7.96 0.87 0.30 0.42 2.57

Note that some maximum signals were saturated in the original scans. These max signals were later redigitized at higher gain settings and rescaled to the original gain settings. 
A-32 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for P&W Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

P&W Ti-6-4 Forgings Specimens 

Raw data values on a scale of 0-254 

Normalized by 0.5′′ deep #1 FBH in 

IN100 = 100 (Measured FBH had 

peak response of 211.4 at 17 dB) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using ISU models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 PW1_S1_L 42 52.57 15.38 26 126 1.40 0.41 0.69 3.35 0.45 0.13 0.22 1.082 PW1_S1_R 42 79.31 20.88 38 236 2.11 0.56 1.01 6.28 0.68 0.18 0.33 2.033 PW1_S4_L 42 86.17 22.41 42 250 2.29 0.60 1.12 6.65 0.74 0.19 0.36 2.154 PW1_S4_R 42 59.25 20.56 24 202 1.58 0.55 0.64 5.37 0.51 0.18 0.21 1.735 PW1_S2_L 42 91.72 21.97 42 236 2.44 0.58 1.12 6.28 0.79 0.19 0.36 2.036 PW1_S2_R 42 86.36 21.66 44 233 2.30 0.58 1.17 6.20 0.74 0.19 0.38 2.007 PW1_S5_L 37 79.38 19.89 40 227 3.75 0.94 1.89 10.74 1.21 0.30 0.61 3.468 PW1_S5_R 37 80.90 20.26 38 206 3.83 0.96 1.80 9.74 1.23 0.31 0.58 3.141 PW2_S1_L 46 64.96 13.34 38 134 1.09 0.22 0.64 2.25 0.35 0.07 0.21 0.732 PW2_S1_R 46 99.10 24.40 48 233 1.66 0.41 0.81 3.91 0.54 0.13 0.26 1.263 PW2_S4_L 43 74.54 17.69 40 224 1.77 0.42 0.95 5.31 0.57 0.14 0.31 1.714 PW2_S4_R 43 49.56 11.74 28 144 1.17 0.28 0.66 3.41 0.38 0.09 0.21 1.105 PW2_S2_L 43 90.06 19.80 46 214 2.14 0.47 1.09 5.07 0.69 0.15 0.35 1.646 PW2_S2_R 43 94.47 20.19 54 216 2.24 0.48 1.28 5.12 0.72 0.15 0.41 1.657 PW2_S5_L 37 82.94 20.71 40 241 3.92 0.98 1.89 11.40 1.27 0.32 0.61 3.688 PW2_S5_R 37 78.33 17.36 42 180 3.71 0.82 1.99 8.51 1.20 0.26 0.64 2.751 PW4_S1_L 40 36.80 7.79 20 74 1.23 0.26 0.67 2.48 0.40 0.08 0.22 0.802 PW4_S1_R 40 69.12 25.97 30 250 2.31 0.87 1.00 8.37 0.75 0.28 0.32 2.703 PW4_S4_L 40 72.40 31.18 28 250 2.42 1.04 0.94 8.37 0.78 0.34 0.30 2.704 PW4_S4_R 40 36.65 7.10 22 72 1.23 0.24 0.74 2.41 0.40 0.08 0.24 0.785 PW4_S2_L 48 87.28 15.82 50 190 1.16 0.21 0.67 2.53 0.38 0.07 0.22 0.826 PW4_S2_R 48 84.49 16.45 48 192 1.13 0.22 0.64 2.56 0.36 0.07 0.21 0.837 PW4_S5_L 48 108.57 22.88 54 241 1.45 0.31 0.72 3.21 0.47 0.10 0.23 1.048 PW4_S5_R 48 105.65 20.78 56 214 1.41 0.28 0.75 2.85 0.45 0.09 0.24 0.92
A-33 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for P&W Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

P&W Ti-6-4 Forgings Specimens 

Raw data values on a scale of 0-254 

Normalized by 0.5′′ deep #1 FBH in 

IN100 = 100 (Measured FBH had 

peak response of 211.4 at 17 dB) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using ISU models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 PW5_S1_L 35 33.93 9.23 18 88 2.02 0.55 1.07 5.24 0.65 0.18 0.35 1.692 PW5_S1_R 35 84.56 26.53 32 208 5.04 1.58 1.91 12.39 1.62 0.51 0.61 4.003 PW5_S4_L 35 73.43 28.33 24 233 4.37 1.69 1.43 13.88 1.41 0.54 0.46 4.484 PW5_S4_R 35 28.10 6.73 16 64 1.67 0.40 0.95 3.81 0.54 0.13 0.31 1.235 PW5_S2_L 41 85.36 20.08 42 204 2.55 0.60 1.25 6.09 0.82 0.19 0.40 1.966 PW5_S2_R 41 81.07 20.05 42 232 2.42 0.60 1.25 6.92 0.78 0.19 0.40 2.237 PW5_S5_L 41 74.85 22.21 38 246 2.23 0.66 1.13 7.34 0.72 0.21 0.37 2.378 PW5_S5_R 41 75.67 19.35 40 238 2.26 0.58 1.19 7.10 0.73 0.19 0.39 2.291 PW6_S1_L 35 86.89 28.32 36 224 5.17 1.69 2.14 13.34 1.67 0.54 0.69 4.302 PW6_S1_R 35 43.88 17.16 18 162 2.61 1.02 1.07 9.65 0.84 0.33 0.35 3.113 PW6_S4_L 35 34.29 11.6 16 110 2.04 0.69 0.95 6.55 0.66 0.22 0.31 2.114 PW6_S4_R 35 80.92 25.84 34 244 4.82 1.54 2.02 14.53 1.55 0.50 0.65 4.695 PW6_S2_L 41 72.67 17.13 36 180 2.17 0.51 1.07 5.37 0.70 0.16 0.35 1.736 PW6_S2_R 41 70.03 18.53 36 204 2.09 0.55 1.07 6.09 0.67 0.18 0.35 1.967 PW6_S5_L 41 59.19 13.31 32 166 1.77 0.40 0.96 4.95 0.57 0.13 0.31 1.608 PW6_S5_R 41 61.32 15.19 34 158 1.83 0.45 1.01 4.72 0.59 0.15 0.33 1.521 PW7_S1_L 35 42.6 16.28 16 130 2.54 0.97 0.95 7.74 0.82 0.31 0.31 2.502 PW7_S1_R 35 94.07 25.06 42 244 5.60 1.49 2.50 14.53 1.81 0.48 0.81 4.693 PW7_S4_L 35 65.95 25.24 22 210 3.93 1.50 1.31 12.51 1.27 0.48 0.42 4.034 PW7_S4_R 35 26.27 7.57 14 72 1.56 0.45 0.83 4.29 0.50 0.15 0.27 1.385 PW7_S2_L 40 98.16 24.49 50 238 3.29 0.82 1.67 7.97 1.06 0.26 0.54 2.576 PW7_S2_R 40 61.87 21.69 22 230 2.07 0.73 0.74 7.70 0.67 0.23 0.24 2.487 PW7_S5_L 40 37.86 9.63 20 98 1.27 0.32 0.67 3.28 0.41 0.10 0.22 1.068 PW7_S5_R 40 65.98 20.9 30 238 2.21 0.70 1.00 7.97 0.71 0.23 0.32 2.57
A-34 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for P&W Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

P&W Ti-6-4 Forgings Specimens 

Raw data values on a scale of 0-254 

Normalized by 0.5′′ deep #1 FBH in 

IN100 = 100 (Measured FBH had 

peak response of 211.4 at 17 dB) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using ISU models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 PW8_S1_L 35 79.97 22.84 40 222 4.76 1.36 2.38 13.22 1.54 0.44 0.77 4.262 PW8_S1_R 35 88.26 23.85 44 241 5.26 1.42 2.62 14.35 1.70 0.46 0.85 4.633 PW8_S4_L 33 67.05 22.03 32 227 5.03 1.65 2.40 17.02 1.62 0.53 0.77 5.494 PW8_S4_R 33 69.79 20.2 32 176 5.23 1.51 2.40 13.19 1.69 0.49 0.77 4.265 PW8_S2_L 42 73.38 20.59 32 208 1.95 0.55 0.85 5.53 0.63 0.18 0.27 1.786 PW8_S2_R 42 46.06 10.81 26 116 1.23 0.29 0.69 3.09 0.40 0.09 0.22 1.007 PW8_S5_L 42 49.5 11.19 24 138 1.32 0.30 0.64 3.67 0.42 0.10 0.21 1.188 PW8_S5_R 42 62.11 14.91 34 174 1.65 0.40 0.90 4.63 0.53 0.13 0.29 1.49
A-35 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for HW Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

HW Forging Specimens H1-H8, by C-scan “halves” 

Raw data values on a scale of 0 to 0.25 Volts 

Normalized by 0.5′′ deep 

#1 FBH in IN100 = 100 

(after dB correction) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 H1_S1_L 48 0.095 0.014 0.063 0.160 1.24 0.18 0.82 2.09 0.40 0.06 0.27 0.672 H1_S1_R 48 0.108 0.017 0.068 0.182 1.41 0.22 0.89 2.37 0.45 0.07 0.29 0.773 H1_S4_L 48 0.093 0.012 0.063 0.146 1.21 0.16 0.82 1.91 0.39 0.05 0.27 0.614 H1_S4_R 48 0.090 0.012 0.055 0.170 1.17 0.16 0.72 2.22 0.38 0.05 0.23 0.725 H1_S2_L 32 0.056 0.024 0.012 0.201 4.61 1.98 0.99 16.55 1.49 0.64 0.32 5.346 H1_S2_R 32 0.053 0.019 0.020 0.137 4.36 1.56 1.65 11.28 1.41 0.50 0.53 3.647 H1_S5_L 32 0.049 0.018 0.021 0.193 4.03 1.48 1.73 15.89 1.30 0.48 0.56 5.138 H1_S5_R 32 0.052 0.016 0.023 0.137 4.28 1.32 1.89 11.28 1.38 0.42 0.61 3.641 H2_S1_L 36 0.052 0.015 0.023 0.180 2.64 0.76 1.17 9.14 0.85 0.25 0.38 2.952 H2_S1_R 36 0.064 0.025 0.027 0.234 3.25 1.27 1.37 11.88 1.05 0.41 0.44 3.833 H2_S4_L 38 0.075 0.023 0.033 0.189 3.02 0.93 1.33 7.62 0.98 0.30 0.43 2.464 H2_S4_R 38 0.058 0.016 0.029 0.168 2.34 0.65 1.17 6.78 0.75 0.21 0.38 2.195 H2_S2_L 34 0.061 0.017 0.031 0.229 3.90 1.09 1.98 14.64 1.26 0.35 0.64 4.726 H2_S2_R 34 0.058 0.017 0.027 0.160 3.71 1.09 1.73 10.23 1.20 0.35 0.56 3.307 H2_S5_L 37 0.060 0.015 0.033 0.180 2.71 0.68 1.49 8.14 0.88 0.22 0.48 2.638 H2_S5_R 37 0.084 0.024 0.035 0.242 3.80 1.09 1.58 10.95 1.23 0.35 0.51 3.531 H3_S1_L 37 0.047 0.016 0.016 0.135 2.13 0.72 0.72 6.11 0.69 0.23 0.23 1.972 H3_S1_R 37 0.067 0.026 0.025 0.230 3.03 1.18 1.13 10.41 0.98 0.38 0.36 3.363 H3_S4_L 37 0.063 0.023 0.029 0.199 2.85 1.04 1.31 9.00 0.92 0.34 0.42 2.904 H3_S4_R 37 0.036 0.011 0.016 0.104 1.63 0.50 0.72 4.71 0.53 0.16 0.23 1.525 H3_S2_L 38 0.077 0.022 0.037 0.199 3.11 0.89 1.49 8.03 1.00 0.29 0.48 2.596 H3_S2_R 38 0.062 0.018 0.031 0.162 2.50 0.73 1.25 6.53 0.81 0.23 0.40 2.117 H3_S5_L 38 0.044 0.011 0.023 0.119 1.77 0.44 0.93 4.80 0.57 0.14 0.30 1.558 H3_S5_R 38 0.066 0.018 0.033 0.182 2.66 0.73 1.33 7.34 0.86 0.23 0.43 2.37
A-36 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for HW Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

HW Forging Specimens H1-H8, by C-scan “halves” 

Raw data values on a scale of 0 to 0.25 Volts 

Normalized by 0.5′′ deep 

#1 FBH in IN100 = 100 

(after dB correction) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 H4_S1_L 39 0.072 0.021 0.033 0.246 2.59 0.75 1.19 8.84 0.83 0.24 0.38 2.852 H4_S1_R 39 0.070 0.019 0.037 0.186 2.52 0.68 1.33 6.69 0.81 0.22 0.43 2.163 H4_S4_L 38 0.054 0.013 0.029 0.143 2.18 0.52 1.17 5.77 0.70 0.17 0.38 1.864 H4_S4_R 38 0.048 0.014 0.021 0.193 1.94 0.56 0.85 7.78 0.62 0.18 0.27 2.515 H4_S2_L 35 0.079 0.020 0.037 0.201 4.50 1.14 2.11 11.45 1.45 0.37 0.68 3.696 H4_S2_R 35 0.083 0.023 0.037 0.229 4.73 1.31 2.11 13.04 1.53 0.42 0.68 4.217 H4_S5_L 35 0.046 0.010 0.027 0.137 2.62 0.57 1.54 7.80 0.85 0.18 0.50 2.528 H4_S5_R 35 0.055 0.014 0.029 0.199 3.13 0.80 1.65 11.34 1.01 0.26 0.53 3.661 H6_S1_L 39 0.045 0.009 0.027 0.096 1.62 0.32 0.97 3.45 0.52 0.10 0.31 1.112 H6_S1_R 39 0.048 0.010 0.027 0.115 1.73 0.36 0.97 4.13 0.56 0.12 0.31 1.333 H6_S4_L 44 0.083 0.019 0.049 0.211 1.68 0.38 0.99 4.26 0.54 0.12 0.32 1.384 H6_S4_R 44 0.081 0.019 0.045 0.230 1.64 0.38 0.91 4.65 0.53 0.12 0.29 1.505 H6_S2_L 39 0.049 0.009 0.027 0.090 1.76 0.32 0.97 3.23 0.57 0.10 0.31 1.046 H6_S2_R 39 0.050 0.010 0.029 0.109 1.80 0.36 1.04 3.92 0.58 0.12 0.34 1.267 H6_S5_L 44 0.085 0.017 0.047 0.191 1.72 0.34 0.95 3.86 0.55 0.11 0.31 1.258 H6_S5_R 44 0.083 0.016 0.051 0.188 1.68 0.32 1.03 3.80 0.54 0.10 0.33 1.231 H8_S1_L 45 0.072 0.014 0.047 0.172 1.33 0.26 0.87 3.17 0.43 0.08 0.28 1.022 H8_S1_R 45 0.060 0.009 0.043 0.117 1.11 0.17 0.79 2.16 0.36 0.05 0.26 0.703 H8_S4_L 43 0.058 0.011 0.037 0.154 1.35 0.26 0.86 3.57 0.43 0.08 0.28 1.154 H8_S4_R 43 0.059 0.010 0.037 0.117 1.37 0.23 0.86 2.71 0.44 0.07 0.28 0.885 H8_S2_L 42 0.063 0.012 0.039 0.166 1.64 0.31 1.02 4.32 0.53 0.10 0.33 1.396 H8_S2_R 42 0.058 0.010 0.033 0.109 1.51 0.26 0.86 2.84 0.49 0.08 0.28 0.927 H8_S5_L 45 0.074 0.013 0.047 0.172 1.36 0.24 0.87 3.17 0.44 0.08 0.28 1.028 H8_S5_R 45 0.068 0.010 0.047 0.117 1.25 0.18 0.87 2.16 0.40 0.06 0.28 0.70
A-37 

TABLE A-1. GRAIN NOISE STATISTICS FOR THE FORGING FLOW LINE COUPONS, EXTRACTED FROM 

FIGURES A-4 AND A-6 (Continued) 

(The last four columns are of chief interest and display the average, standard deviation, minimum, and maximum 

noise amplitudes using a scale in which 100 equals the peak amplitude from a Ti-6-4 #1 FBH in the focal zone.) 

Tabular Form of the Noise Data for HW Ti-6-4 Forging Coupons 

Summary of Grain Noise Measurements on 

HW Forging Specimens H1-H8, by C-scan “halves” 

Raw data values on a scale of 0 to 0.25 Volts 

Normalized by 0.5′′ deep 

#1 FBH in IN100 = 100 

(after dB correction) 

Normalized by #1 FBH in 

focal zone in Ti-6-4 = 100 

(Estimated using models) 

Index ISU Name 

dB 

Setting Ave. Noise Sigma Min. Max. Ave. Sigma Min. Max. Ave. Sigma Min. Max. 

1 H5_S1_L 32 0.097 0.022 0.053 0.197 7.47 1.69 4.08 15.17 2.41 0.55 1.32 4.89 2 H5_S1_R 32 0.092 0.020 0.053 0.232 7.08 1.54 4.08 17.86 2.28 0.50 1.32 5.76 3 H5_S4_L 31 0.091 0.021 0.047 0.207 7.86 1.81 4.06 17.88 2.54 0.59 1.31 5.77 4 H5_S4_R 31 0.087 0.022 0.035 0.246 7.51 1.90 3.02 21.25 2.42 0.61 0.98 6.85 5 H5_S2_L 46 0.098 0.018 0.057 0.217 1.51 0.28 0.88 3.33 0.49 0.09 0.28 1.08 6 H5_S2_R 46 0.086 0.016 0.051 0.189 1.32 0.25 0.78 2.90 0.43 0.08 0.25 0.94 7 H5_S5_L 45 0.077 0.013 0.049 0.146 1.33 0.22 0.84 2.52 0.43 0.07 0.27 0.81 8 H5_S5_R 45 0.084 0.015 0.047 0.180 1.45 0.26 0.81 3.10 0.47 0.08 0.26 1.00 1 H7_S1_L 35 0.054 0.015 0.027 0.158 2.94 0.82 1.47 8.61 0.95 0.26 0.47 2.78 2 H7_S1_R 35 0.090 0.025 0.045 0.215 4.90 1.36 2.45 11.72 1.58 0.44 0.79 3.78 3 H7_S4_L 30 0.059 0.016 0.029 0.184 5.72 1.55 2.81 17.83 1.84 0.50 0.91 5.75 4 H7_S4_R 30 0.041 0.011 0.020 0.102 3.97 1.07 1.94 9.89 1.28 0.34 0.63 3.19 5 H7_S2_L 45 0.063 0.009 0.039 0.113 1.09 0.16 0.67 1.95 0.35 0.05 0.22 0.63 6 H7_S2_R 45 0.068 0.011 0.043 0.133 1.17 0.19 0.74 2.29 0.38 0.06 0.24 0.74 7 H7_S5_L 46 0.072 0.010 0.047 0.11 1.11 0.15 0.72 1.74 0.36 0.05 0.23 0.56 8 H7_S5_R 46 0.070 0.010 0.045 0.12 1.08 0.15 0.69 1.89 0.35 0.05 0.22 0.61 

(Note: Measured “same day” FBH had a peak response of 0.216 volt for H1; 0.221 volt for H2, H3, H4, and H6; 0.216 volt for H8; and 0.231 volt for H5 and H7.) 
A-38

The remaining graphs in this appendix summarize the results of attenuation and backscattered 

grain noise measurements for the seven rectangular forging flow line coupons from the P&W 

forging, as measured by P&W personnel. Figure A-7 shows the coordinate system. For 

measurements in the axial and radial beam propagation directions, the scan area was 0.8′′ by 

1.2′′. For measurements in the circumferential direction the scan area was 0.5′′ by 0.5′′. (Refer 

to section 2.1.6 for additional details about the measurements.) 

FIGURE A-7. INSPECTION DIRECTION LABELS USED BY P&W PERSONNEL TO 

MEASURE THE FORGING FLOW LINE COUPONS 

up

hub

1 (circumferential)

2 (radial)

3 (axial)

1 (circumferential)

2 (radial)

3 (axial)
A-39

FIGURE A-8. MEASURED AND FITTED ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE P&W 

FORGING FLOW LINE COUPONS 

Attenuation in the circumferential direction (axis 1)

Ti-6-4, PWA 1215, Attenuation in circumferential (1) direction

December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PWA 1215, Attenuation in circumferencial (1) direction

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

1.5 (/) ( ) Np cm A f MHz α = ⋅

Sample # A1, Np/(cm·MHz1.5)

1 1.49·1032 1.52 ·1034 1.41·1035 1.97·1036 1.80·1037 0.97·1038 1.69·103

Experiment

Fit

1

2

3

4

5

6

7

8

Attenuation in the circumferential direction (axis 1)

Ti-6-4, PWA 1215, Attenuation in circumferential (1) direction

December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PWA 1215, Attenuation in circumferencial (1) direction

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

1.5 (/) ( ) Np cm A f MHz α = ⋅

Sample # A1, Np/(cm·MHz1.5)

1 1.49·1032 1.52 ·1034 1.41·1035 1.97·1036 1.80·1037 0.97·1038 1.69·103

Experiment

Fit

1

2

3

4

5

6

7

8 1

2

3

4

5

6

7

8
A-40

FIGURE A-8. MEASURED AND FITTED ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE P&W 

FORGING FLOW LINE COUPONS (Continued) 

Attenuation in the radial direction (axis 2)

Ti-6-4, PWA 1215, Attenuation in radial (2) direction

December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PWA 1215, Attenuation in radial (2) direction

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

1.5 (/) ( ) Np cm A f MHz α = ⋅

Sample # A2, Np/(cm·MHz1.5)

1 1.30·1032 1.23 ·1034 1.34·1035 1.77·1036 1.66·1037 1.16·1038 1.41·103

Experiment

Fit

1

2

3

4

5

6

7

8

Attenuation in the radial direction (axis 2)

Ti-6-4, PWA 1215, Attenuation in radial (2) direction

December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PWA 1215, Attenuation in radial (2) direction

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

1.5 (/) ( ) Np cm A f MHz α = ⋅

Sample # A2, Np/(cm·MHz1.5)

1 1.30·1032 1.23 ·1034 1.34·1035 1.77·1036 1.66·1037 1.16·1038 1.41·103

Experiment

Fit

1

2

3

4

5

6

7

8 1

2

3

4

5

6

7

8
A-41

FIGURE A-8. MEASURED AND FITTED ATTENUATION-VERSUS-FREQUENCY CURVES FOR THE P&W 

FORGING FLOW LINE COUPONS (Continued) 

Attenuation in the axial direction (axis 3)

1

2

3

4

5

6

7

8

1.5 (/) ( ) Np cm A f MHz α = ⋅ Ti-6-4, PWA 1215, Axial direction (axis 3) December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PW A 1215, Axial dire ction ("up" or a x is 3)

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

Sample # A3, Np/(cm·MHz1.5)

1 0.20·1032 0.24 ·1034 0.72·1035 1.00·1036 1.07·1037 0.75·1038 2.07·103

Experiment

Fit

Attenuation in the axial direction (axis 3)

1

2

3

4

5

6

7

8 1

2

3

4

5

6

7

8

1.5 (/) ( ) Np cm A f MHz α = ⋅ Ti-6-4, PWA 1215, Axial direction (axis 3) December 4, 2000

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, N/cm

Att1, N/cmAtt2, N/cmAtt4, N/cmAtt5, N/cmAtt6, N/cmAtt7, N/cmAtt8, N/cm

Ti-6-4, PW A 1215, Axial dire ction ("up" or a x is 3)

-0.05

0.200.150.100.050.00

5 10 15 20

Frequency, MHz

Attenuation, Np/cm

Sample 1Sample 2Sample 4Sample 5Sample 6Sample 7Sample 8

Sample # A3, Np/(cm·MHz1.5)

1 0.20·1032 0.24 ·1034 0.72·1035 1.00·1036 1.07·1037 0.75·1038 2.07·103

Experiment

Fit
A-42

FIGURE A-9. MEASURED GRAIN NOISE FOM-VERSUS-DEPTH CURVES FOR THE P&W FORGING FLOW LINE 

COUPONS, AND A COMPARISON OF MEASURED VALUES AT A 2-cm DEPTH 

Grain noise FOM at 10 MHz vs depth in 

the circumferential (1) direction

FOM A f = ⋅

Circum ferential (1) direction: FOM at 10 MHz at 2 cm 

depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

Circumferential (1) direction: FOM vs depth at 10 

MHz

0.060.050.040.030.020.010.00

0.0 1.0 2.0 3.0 4.0 5.0

Depth, cm

FOM, cm^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8

Grain noise FOM at 10 MHz vs depth in 

the circumferential (1) direction

FOM A f = ⋅

Circum ferential (1) direction: FOM at 10 MHz at 2 cm 

depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

Circumferential (1) direction: FOM vs depth at 10 

MHz

0.060.050.040.030.020.010.00

0.0 1.0 2.0 3.0 4.0 5.0

Depth, cm

FOM, cm^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8
A-43

FIGURE A-9. MEASURED GRAIN NOISE FOM-VERSUS-DEPTH CURVES FOR THE P&W FORGING FLOW LINE 

COUPONS, AND A COMPARISON OF MEASURED VALUES AT A 2-cm DEPTH (Continued) 

Grain noise FOM at 10 MHz vs depth in 

the radial (2) direction

FOM A f = ⋅

Radial (2) dire ction: FOM vs de pth at 10 M Hz

0.060.050.040.030.020.010.00

0.0 0.5 1.0 1.5 2.0 2.5

De pth, cm

FOM , cm ^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8

Radial (2) direction: FOM at 10 MHz at 2 cm depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

Grain noise FOM at 10 MHz vs depth in 

the radial (2) direction

FOM A f = ⋅

Radial (2) dire ction: FOM vs de pth at 10 M Hz

0.060.050.040.030.020.010.00

0.0 0.5 1.0 1.5 2.0 2.5

De pth, cm

FOM , cm ^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8

Radial (2) direction: FOM at 10 MHz at 2 cm depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8
A-44

Grain noise FOM at 10 MHz vs depth in 

the axial (3) direction

FOM A f = ⋅

Axial (3) dire ction: FOM vs de pth at 10 M Hz

0.060.050.040.030.020.010.00

0.0 0.5 1.0 1.5 2.0 2.5

De pth, cm

FOM , cm ^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8

Axial (3) direction: FOM at 10 MHz at 2 cm depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

Grain noise FOM at 10 MHz vs depth in 

the axial (3) direction

FOM A f = ⋅

Axial (3) dire ction: FOM vs de pth at 10 M Hz

0.060.050.040.030.020.010.00

0.0 0.5 1.0 1.5 2.0 2.5

De pth, cm

FOM , cm ^-0.5

FOM-1FOM-2FOM-4FOM-5FOM-6FOM-7FOM-8

Axial (3) direction: FOM at 10 MHz at 2 cm depth

0.0300.0250.0200.0150.0100.0050.000

1

FOM-1 FOM-2 FOM-4 FOM-5 FOM-6 FOM-7 FOM-8

FIGURE A-9. MEASURED GRAIN NOISE FOM-VERSUS-DEPTH CURVES FOR THE P&W FORGING FLOW LINE 

COUPONS, AND A COMPARISON OF MEASURED VALUES AT A 2-cm DEPTH (Continued) 
APPENDIX B—SYNTHETIC INCLUSION DISK BACKSCATTERED NOISE C-SCANS

Figure B-2 presents C-scan images of the synthetic inclusion disk (SID) following a light skim 

cut, but before disk slicing and defect insertion. These images were used to identify zones of 

high and low grain noise where defects would be placed. 

TABLE B-1. SYNTHETIC INCLUSION DISK INSPECTION DETAILS 

Summary of Scan Surfaces, Depth Zones, and Gain Levels

For Inspection of SID Disk Following Light Skim Cut 

Gain Levels (in dB relative to calibration of #1 FBH at 80% full scale) 

Surface Zone 1 Zone 2 Zone 3 Zone 4 

UG +12 +12 +12 +18 

UH +12 +18 

UJ +18 +12 

UK +18 

UL +18 +24 

UM +12 +12 

UO +12 +12 

UP +15 +15 

UR +15 +15 

US +12 +12 

Calibration:

Zone 1 calibrated 0.06′′ to 0.5′′, gated 0.06′′ to 0.5′′

Zone 2 calibrated 0.5′′ to 1.0′′, gated 0.4′′ to 1.1′′

Zone 3 calibrated 1.0′′ to 1.5′′, gated 0.9′′ to 1.6′′

Zone 4 calibrated 1.5′′ to 2.0′′, gated 1.4′′ to 2.1′′

Transducers:

I3 (10 MHz, 0.375′′ dia., 3.0′′ FL) 

F8 (10 MHz, 1.0′′ dia., 8.0′′ FL) 

Water Path:

All zone 1 scans: I3 transducer with 3.0′′ water path.

Zone 2, surfaces UJ, UR: I3 transducer with 3.0′′ water path. 

Other zone 2: F8 transducer with 5.65′′ water path.

Zone 3: F8 transducer with 3.5′′ water path.

Zone 4: F8 transducer with 1.8′′ water path. 

B-1
All Surfaces Except UG, UJ, UR

scan

(CCW rotate)

index

(OD to ID)

Datum

CW on part (looking at inspection surface)

OD 

to 

ID

datum

and scan start

Part C-scan Image

All Surfaces Except UG, UJ, UR

scan

(CCW rotate)

index

(OD to ID)

Datum

CW on part (looking at inspection surface)

OD 

to 

ID

datum

and scan start

Part C-scan Image

Surface UG

(O.D.)

aft

fwd scan

(CCW rotate)

index

(fwd to aft

datum (scan start) Datum CW on part (aft looking fwd)

Fwd 

to 

aft

Surface UG

(O.D.)

aft

fwd scan

(CCW rotate)

index

(fwd to aft

datum (scan start) Datum CW on part (aft looking fwd)

Fwd 

to 

aft

Surfaces UJ, UR

scan

(CCW rotate)

index

(ID to OD)

Scan start

(180 deg from datum)

Datum

(at 180 deg)

CW on part (looking at inspection surface)

ID 

to 

OD

datum

Surfaces UJ, UR

scan

(CCW rotate)

index

(ID to OD)

Scan start

(180 deg from datum)

Datum

(at 180 deg)

CW on part (looking at inspection surface)

ID 

to 

OD

datum

(a) 

(b) 

(c) 

FIGURE B-1. RELATIONSHIP OF SID INSPECTION SURFACES TO C-SCAN 

NOISE IMAGES, (a) ALL SURFACES EXCEPT UG, UJ, AND UR, 

(b) SURFACE UG, AND (c) SURFACES UJ AND UR 

B-2
Fwd

Aft

0 60 120 180 240 300 360 degrees CW from

datum looking at aft face

Region of as-forged surface

Fwd

Aft

0 60 120 180 240 300 360 degrees CW from

datum looking at aft face

Region of as-forged surface

C-scan of surface UG, Zone 1. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, OD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UG, Zone 2. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, OD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-3
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UG, Zone 3. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, OD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UG, Zone 4. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, OD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-4
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UH, Zone 1. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

High noise is

reflection from region

of as-forged surface

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

High noise is

reflection from region

of as-forged surface

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UH, Zone 2. Gain (rel. to #1 FBH) +18 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-5
Start at 180 deg

180 240 300 0 6 0 1 20 180

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UJ, Zone 1. Gain (rel. to #1 FBH) +18 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

Start at 180 deg

180 240 300 0 60 120 180

Fwd

Aft

degrees CW from

datum looking at fwd face

Start at 180 deg

180 240 300 0 60 120 180

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UJ, Zone 2. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-6
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UK, Zone 1. Gain (rel. to #1 FBH) +18 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UL, Zone 1. Gain (rel. to #1 FBH) +18 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-7
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face 0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UL, Zone 2. Gain (rel. to #1 FBH) +24 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face 0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UM, Zone 1. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-8
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face 0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at fwd face

C-scan of surface UM, Zone 2. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, FWD side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UO, Zone 1. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-9
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UO, Zone 2. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UP, Zone 1. Gain (rel. to #1 FBH) +15 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-10
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face 0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UP, Zone 2. Gain (rel. to #1 FBH) +15 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

Start at 180 deg

180 240 300 0 60 120 180

Fwd

Aft

degrees CW from

datum looking at aft face

Start at 180 deg

180 240 300 0 6 0 1 20 180

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UR, Zone 1. Gain (rel. to #1 FBH) +15 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-11
180 240 300 0 60 120 180

Fwd

Aft

degrees CW from

datum looking at aft face

180 240 300 0 6 0 1 20 180

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface UR, Zone 2. Gain (rel. to #1 FBH) +15 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface US, Zone 1. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-12
0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

0 60 120 180 240 300 360

Fwd

Aft

degrees CW from

datum looking at aft face

C-scan of surface US, Zone 2. Gain (rel. to #1 FBH) +12 dB, 10 MHz, F/8 transducer, AFT side. 

FIGURE B-2. C-SCANS OF SID PRIOR TO DEFECT INSERTION (Continued) 

B-13/B-14
APPENDIX C—ULTRASONIC TEST SPECIMENS

TABLE C-1. SPECIMENS FABRICATED UNDER THE ETC PHASE II FUNDAMENTAL 

STUDIES OF FORGINGS PROGRAM 

Specimen Type Number Comments 

Key Test 

Reference 

Forging Flow Line 

Coupons (Property 

Measurement Coupons) 

26 Small coupons cut from three Ti-6-4 forged 

disks (8, 8, and 10 from P&W, GE, and HW 

disks respectively). Twenty are rectangular 

blocks with nominal dimensions of 1.25′′ by 

1.25′′ by 2.0′′. Three are rectangular blocks 

with smaller dimensions. Three are 

cylinders 2′′ in length and 1.25′′ in diameter. 

Figure 2-15 

Figure 2-28 

Figure 2-37 

Curvature Correction 

Blocks 

6 Each block has a cylindrically curved upper 

(sound-entry) surface, below which are 13 

#1 FBHs at different depths, ranging from 

about 0.5′′ to 2.0′′. Three of the blocks have 

concave radii of curvature (0.75′′, 2.0′′, and 

8.0′′), two have convex radii (4.0′′ and 

10.0′′), and one block has a flat upper 

surface. Fabricated from powder Ni alloy 

R88ND. 

Figure 2-103 

Figure 2-104 

Figure 2-105 

Noise Curvature Blocks 6 Each block has a cylindrically curved upper 

(sound-entry) surface, below which are six 

#1 FBHs at each of two depths. Three of 

the blocks have concave radii of curvature 

(0.7′′, 2.0′′, and 8.0′′), two have convex radii 

(4.0′′ and 10.0′′); and one block has a flat 

upper surface. Blocks were cut from a 

Ti-6-4 forged disk. FBH depths are 0.75′′

and 1.5′′ below the center of the entry 

surface. 

Figure 2-109 

Figure 2-110 

Synthetic Inclusion Disk 1 Ti-6-4 forged disk containing 40 synthetic 

hard alpha (SHA) defects and 18 FBH 

defects. SHA defects are right cylinders 

with the same length and diameter (#3 and 

#5 sizes). SHA defects have either 3% or 

17% N contamination by weight. FBH 

defects are either #1 (12 each), #3 (3 each), 

or #5 (3 each) sizes. 

Figure 2-137 

Figure 2-141 

Figure 2-152 

C-1/C-2