NBSIR 76-984

Improved Ultrasonic Standard

Reference Blocks

G. F. Sushinsky, D. G. Eitzen, and D. J. Chwirut

Institute for Basic Standards

and

C. J. Bechtoldt and A. W. Ruff

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

November 1976

Final Report

Prepared for Air Force Materials Laboratory

National Aeronautics and Space Administration, and

Army Materials and Mechanics Research Center

NBSIR 76-984

IMPROVED ULTRASONIC STANDARD

REFERENCE BLOCKS

C. J. Bechtoldt and A. W. Ruff

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

November 1 976

Final Report

Prepared for Air Force Materials Laboratory

National Aeronautics and Space Adnninistration, and

Army Materials and Mechanics Research Center

U.S. DEPARTMENT OF COMMERCE. Elliot L. Richardson. Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Aricker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director

G. F. Sushinsky, D. G. Eitzen, and D. J. Chwirut

Institute for Basic Standards

and
III
IMPROVED ULTRASONIC STANDARD REFERENCE BLOCKS

(a)

G. F. Sushinsky , D. G. Eitzen, D. J. Chwirut,

C. J. Bechtoldt, and A. W. Ruff

ABSTRACT

A program to improve the quality, reproducibility

and reliability of nondestructive testing through

the development of an improved ASTM-type ultrasonic

reference standards system is described. Reference blocks

of aluminum, steel, and titanium alloys are considered. Equipment representing the stateof-the-art in laboratory and field ultrasonic equipment

was obtained and evaluated. RF and specral data on twenty-two sets of ultrasonic reference blocks were

taken as part of a task to quantify the variability

in response from nominally identical blocks. Techniques

for residual stress, preferred orientation, and

microstructural measurements were refined and applied

to reference blocks rejected by manufacturers during

fabrication in order to evaluate the effect of metallurgical condition on block response. The effects of

certain dimensional variables on block response were

studied and new fabrication techniques considered. A

study of the effects of measurement system variables on block response was carried out. A calibration service

for ASTM E127-type reference blocks has been established

and the development of a loaner service for calibration

blocks is under way.

Key Words: Aluminiim ultrasonic standards; ASTMtype reference standards; calibration; fabrication

variables; immersion testing; interim reference

standard; longitudinal waves; metallurgical variables;

nondestructive evaluation; pulse echo; steel ultrasonic

standards; titanium ultrasonic standards; ultrasonics.

(a)

Present Address, Institute for Applied Technology , NBS
1. INTRODUCTION

As the field of nondestructive testing and evaluation (NDT&E)

continues to increase in scope and importance, the problem of inadequate

or non-existent standards has shown itself to be a glaring weakness in

the measurement process. In particular, ultrasonic methods, which are highly dependent on reference standards, are characterized by inappropriate

and inconsistent reference artifacts, partly because of the demands for

defect size characterization brought on by materials shortages and fracture

mechanics technology. Standards originally developed for equipment

standardization began to be used for sensitivity setting and defect

sizing. Inconsistancies in standards used by different operational

groups result in uncertainties regarding the actual material condition.

These uncertainties lead to performance penalties due to increased

design uncertainties and either unnecessary piece rejection or inadequate service performance.

A program to improve the widely used system of ASTM-type standard

reference blocks for longitudinal ultrasonic testing was started at

NBS in January 1974. At that time, the procedures for fabricating and

checking these blocks were covered in two ASTM documents, E 127-64,

"Standard Recommended Practice for Fabricating and Checking Alxxminum

Alloy Ultrasonic Standard Reference Blocks" [1]*, and E 428-71, "Standard

Recommended Practice for Fabrication and Control of Steel Reference

Blocks Used in Ultrasonic Inspection" [2]. Both of these documents are widely referenced in government and industry purchasing specifications

and in many other ASTM documents. One of the above documents is also

sometimes used as a guide for the fabrication of titanium alloy ultrasonic reference blocks. The E 127 doctjment [1] was revised in 1975 [3].

However, both the authors and the users of these documents admit that the

documents contain serious shortcomings, but, partly because of other

^Figures in brackets indicate literature references at the end of this

paper.

2
corporate priorities and a lack of institutional mission, no one has

produced acceptable improvements through the voluntary standards systems.

The ASTM-type reference blocks are cylindrical blocks with flatbottomed holes drilled along the block axis, see Figure 1. A pulsed

stress wave produced by a piezoelectric transducer enters normal to the

undrilled end of the block and travels through the block. The flat end

of the drilled hole acts as a reflector and returns some of the energy to

the transducer, which converts this energy into an electrical signal.

This signal, displayed on a cathode ray tube (CRT), becomes a reference

signal for the evaluation of material of unknown condition. Sets of

reference blocks with different hole diameters and different lengths

are used to standardize ultrasonic measurement systems. Measurements

made with these systems then provide a basis for estimating flaw severity

and possible material rejection.

The problem with these reference blocks, simply stated, is this:

using a single ultrasonic measurement system, the ultrasonic responses

from nominally identical reference blocks vary unacceptably . Variations

of 40 percent are not uncoiranon. The problem becomes more acute when

different measuring systems are used. The extent of this variation has

been reported to be as great as 300 percent in standards produced from

titanium [4J

.

The objectives of the NBS program were to investigate systematically

the ASTM-type standard reference block system, to isolate if possible the causes of the variability, and to develop a new system of standards that

will allow different organizations to make consistent measurements

compatible with each other. It was envisioned that the output from this

program could take one of three forms:

1) New methods documents to revise or replace ASTM E 127 and E

428 that would allow the NDT community to fabricate standard

reference blocks that introduce acceptably small variability

into the measurement system.

3
HOLE A, BOTTOM MUST BE FLAT WITHIN

0.001 PER 0.125 DIA., AND FINISHED

SIZE MUSTBE THE REQUIRED DIA.t0.0005

ENTRY SURFACE

to

4-1

HOLE MUST BE STRAIGHT AND PERPENDICULAR

TO ENTRY SURFACE WITHIN 0°-30' AND

LOCATED WITHIN 0.010 OF LONGITUDINAL AXIS

BACK SURFACE

FLAT COUNTERBORE

0.250x0.062 DEEP

637^ EXCEPT AS NOTED

Figure 1- ASTM E-127 ULTRASO NIC STAND ARD REFERENCE BLOCK

ALL DIMENSIONS IN INCHESfl in = 25.4 mm).

A
2) a system whereby certified standard reference blocks would be

fabricated and sold by the National Bureau of Standards

through, for example, the Standard Reference Materials Program,

3) a calibration service whereby one set of blocks is defined

as THE STANDARD SET. Users' blocks could then be referenced

to this set following prescribed procedures.

The NBS program has moved forward in all three areas

1) NBS personnel have become active in the ASTM Sections working

on the reference block problem. Technical consultation,

editorial assistance, and experimental evaluation of proposed

changes have been supplied. Work is continuing on further

revisions of these documents.

2) A limited number of ASTM-type reference blocks are being

fabricated by NBS. These blocks will be carefully characterized

by comparison to appropriate references, and offered, on a loan

basis, to interested laboratories. These will allow an intercomparison of results between NBS and other laboratories. This

is also the first step in the formulation of a Measurement Assurance

Program (MAP) for this type of ultrasonic measurement system.

3) A calibration service, limited in scope and availability, has

been established at NBS for ASTM E 127-type reference blocks.

The details of this service are given in [5] and summarized in

Section 3.8 of this report. The service will be generalized.

This activity was performed in the Mechanics and Metallurgy Divisions

of the National Bureau of Standards with consultation and support from

other Divisions where appropriate.

2. PROGRAM OUTLINE

As envisioned at the outset, the NBS program was intended to affect

near-term improvements in the quality, reproducibility, and reliability

5
of the ultrasonic nondestructive measurement process. These Improvements

would result from the development of imposed ASTM-type reference blocks

and the methodology to accurately characterize these standards metallurgically, metrologically , and ultrasonically . The NBS program,

described herein, was a planned two-year effort including the following

nine tasks:

I Task 1. Literature- Search

A thorough search and review of all technical literature regarding

ultrasonic test standards will be conducted prior to commencement of

any major subsequent tasks. Results of the review will be used where

applicable to accelerate or modify subsequent tasks.

Task 2. Ultrasonic Measurement Facility

State-of-the-art ultrasonic equipment and associated electronics

appropriate for pulse-echo contact and immersion evaluations will be

obtained. This equipment will be evaluated using current standardization

methodology. This evaluation will be performed with a view towards the

establishment of standard methods which are more definitive than those

currently available. This equipment is intended to form the core of an ultrasonic reference block calibration facility, if established.

Task 3. Comparison of Nominally Identical Blocks

Nominally identical blocks from commercial sources and from the

field will be evaluated for the distribution of ultrasonic response

using the equipment of task 2. This task will serve to assess the

extent of variability of ultrasonic responses from nominally identical

blocks. The results of this evaluation will have an effect on the

methods used to identify the causes of the deviations in blocks.

Task A. Metallurgical Considerations

The current state of knowledge of the effects of the metallurgical

conditions of materials on their ultrasonic characteristics will be

reviewed. A limited number of confirmation experiments will be performed.

6
Additional tests on materials of other metallurgical consistency will

be undertaken to determine their ultrasonic response characteristics.

This knowledge will be applied to the selection of materials for the

fabrication of a master set of ASTM-type ultrasonic reference blocks.

Task 5. Fabrication Considerations

A number of nominally identical reference blocks with closely

controlled metallurgical properties and fabrication techniques will be

obtained. The blocks will be closely examined metrologically and the

distribution of ultrasonic response will be determined using the measurements laboratory of Task 2. Several forming techniques will be used

including the conventional drilling technique, the use of raw stock

formed by powder metallurgy, and the use of two-piece blocks. Comparison

of the distributions in response of these blocks with the results of the

evaluation of nominally identical field blocks (Task 3) will indicate

whether significant reductions in the deviation of ultrasonic response

of blocks can be anticipated in the near-term.

Task 6. Effects of Ultrasonic Measuring Systems

The results of previous round-robins on ASTM-type reference blocks

will be checked to determine whether different ultrasonic measuring

systems obtain the same ranking and distribution of ultrasonic response

from nominally identical blocks. An additional round-robin will be

performed, if necessary. The cooperation of interested NDT users will . be sought. The verification of the principle of standardization

associated with this task is a necessary step toward the establishment

of a rational calibration program.

Task 7. Master Reference Blocks

The results of the above tasks will be used to develop master ASTMtype reference standards for aluminum, steel, and titanium. The final

alloy selections for the master standards will be based on metallurgical

considerations, long-term availability, ultrasonic response, incidence

7
of structural use, and in consultation with the sponsors.

Task 8. A Single-Material Standard

An effort will be made to establish the feasibility of an improved

standards program through the us^e of a single-material master standard.

A candidate for the single-material standard is considered to be blocks

made of crown glass. This material can be controlled to have an impedance matching that of aluminum, has no crystalline structure, has a minimal defect count (which can be evaluated by light-scattering

techniques), and is amenable to the most sophisticated metrological

evaluation. Preliminary analyses arid tests will establish the feasibility of a one-material standard as the basis for determining the

ultrasonic response of reference blocks of various materials. Based

on appropriate feasibility indications the development of a basic

standard will be considered. Future work may then be proposed in order

to establish this standard.

Task 9. Calibration Service

An ASTM-type reference block calibration service will be initiated

if appropriate. A system will be established to quantify the responses

of blocks in terms of the NBS master standards, thus providing a common

basis for comparison and an objective evaluation. Blocks will be

evaluated in terms of the Master Reference Blocks of Task 7. It is

expected that any continuing calibration service will be self-supporting

through fees collected from the users.

3. TASK SUMMARY

3.1 Literature Survey

An extensive search and review of the open literature regarding

ultrasonic reference standards has resulted in a collection of several

hundred documents. The search has included four areas: general

background information, ultrasonic measurement techniques, previous

work directly on standards, and the relationship of metallurgical vari8
ables to ultrasonic response. Formal inputs to the search were received

from:

Nondestructive Testing Information and Analysis Center,

Defense Documentation Center,

National Technical Information Service, and

Smithsonian Science Information Exchange.

Of these the input from NTIAC was the most comprehensive. The number

of pieces of open literature requiring review was surprisingly large,

but few speak directly and conclusively to the problem.

In addition to the open literature, dozens of private documents

or communications have been analyzed. The search for unpublished or private communications has been more time consuming but often more

substantive. Important information regarding ultrasonic reference

standards has been obtained through exchanges with representatives

from the numerous government, industrial, and academic institutions

from the United States, Canada, United Kingdom, and West Germany.

An important objective of the literature search was the determination

of the major causes of the wide distribution of ultrasonic responsefrom nominally identical reference blocks examined with a single system.

No definitive conclusion could be drawn. There are significant, but

sometimes contradictory or self-serving statements indicating the material,

metallurgical, dimensional, or fabrication aspects as the chief cause. However, some positive conclusions were drawn from the review of previous

and on-going work. From work in the United Kingdom over the last twenty

years it is concluded that "calibrations" by a corrected comparison with

a standard set of aluminum blocks can be made to within + 1 dB, using

state-of-the-art equipment. Sufficient reductions in block disparity

to the point where corrections are not required will be difficult [5J.

Reports of work at Grumman [7] on reference blocks for titanium concluded

that two piece blocks may provide improved standards for this material.

Communications concerning work at Westinghouse and Automation Industries

indicate that there is a large disagreement about the size of the problem

with steel reference blocks. An additional, important conclusion is

9
that the most active concentrated help can be expected from members of

ASTM committee E-7.06. The aluminum producers were particularly

cooperat ive.

3.2 Ultrasonic Measurement Facility

Commercially available, state-of-the-art ultrasonic equipment and

accessories suitable for contact and immersion testing have been assembled.

Tliis equipment includes an immersion tank with a motorized scanning

bridge and precision manipulator, flaw detection equipment with associated

gating and amplifying circuitry, a spectrum analyzer, transducers,

ultrasonic reference blocks, and other accessory equipment. The laboratory

set-up is shown in Figure 2. Brief descriptions of this equipment are included below with more detailed specifications and characteristics

given in Appendix A of Reference 8.

3.2.1 Immersion System

The immersion system consists of a tank with transparent walls

and dimensions of approximately 38x21x18 in (97x53x46 cm)*. It is

equipped with a motorized bridge and carriage, search tube, motorized

manipulator, and mini-manipulator. It provides precision control of

search unit positioning in the X, Y and Z directions, as well as angular positioning in two vertical planes normal to the tank bottom.

A dry paper X-Y recorder is provided.

3.2.2 Flaw Detection Equipment

Two field inspection type flaw detection units were borrowed from

the Air Force Materials Laboratory and the Naval Research Laboratory.

These units were used primarily during the initial experimental stages

before the delivery of a third unit that was purchased with project funds.

All three units feature a tuned, narrow band pulse from a pulser/receiver

(P/R) module. With these three units, operating frequencies of 1.0,

2.25, 5.0 and 10.0 MHz are available. A video presentation on a CRT

is used for the signal display. Gating and amplifying modules are also

*Units for physical quantities in this paper are given in both the U.S.

Customary Units and the International System Units (SI).

10

available. The third unit, while similar to the two borrowed units, represents an improvement to the NBS ultrasonic measurement facility. In

addition to the above features, the third unit has a calibrated dB (decibel) sensitivity control, an improved CRT display, and improved gating

and amplifying circuitry. All three units are suitable for checking

ultrasonic reference blocks per the "Recommended Practice for Fabricating

and Checking Aluminum Alloy Ultrasonic St andard Reference Blocks," ASTM

Designation E127-75 [3].

A flaw detector suitable for collecting more detailed laboratory data

was also purchased. This unit consists of a power supply-frame, a broadband pulser/receiver , a stepless gate, and a peak detection and quantizing

module. Ultrasonic rf (radio frequency) signals are displayed on a 100-

MHz bandwidth storage oscilloscope equipped with two wideband amplifiers.

The stepless gate, peak detector, and quantizer provide flaw and transducer characterization. Signals are routed from the receiver through the

stepless gate. In the gate, unwanted signals are eliminated from the

repetitive pulse train and the desired wave packet is isolated. This isolated signal can then be used for spectrum analysis work or further processed through the peak detector and quantizer module. The peak detector

converts the positive peak amplitude of the signal to a proportional DC

voltage. This can then be quantized into discrete DC voltages based "on

incremental signal amplitude changes. An operational power supply amplifies the discrete DC voltages from the quantizer to provide the voltage

levels needed for the electrostatic C-scan recordings. An n- level grayscale C-scan recording, with the shade of gray proportional to the ultrasonic signal, can thus be obtained for studies such as transducer beam

profiling and attenuation measurements.

3.2.3 Spectrum Analyzer

The spectrum analyzer consists of a storage CRT display, and separate

if and rf plug- in modules. The frequency range extends from 0 to 100 MHz

with either a logarithmic or linear presentation.

Spectrum analysis is performed on ultrasonic signals received by the

transducer after initial processing through the gate circuitry. The signals usually analyzed are those reflected from special targets (e.g. steel

12
balls, flat quartz blocks, flat-bottom holes, etc.) or defects. This

information is necessary for the evaluation of transducer characteristics

and potentially helpful in determining defect size and orientation [9, 10].

3.2.4 Transducers { i Transducers were purchased from three manufacturers for use in this

program. Both contact and immersion transducers suitable for longitudinal

beam, pulse-echo testing were obtained. The transducers were chosen on

the basis of nominal crystal diameter and nominal center frequency to cover a representative range of transducers used in ultrasonic work.

These transducers are listed in Table 1. Special emphasis was placed on obtaining transducers suitable for work on standard reference blocks in

accordance with ASTM E127-64 [1] and ASTM E127-75 [3], as well as transducer size and frequency combinations suitable for establishing the data

base in Task 3.

3.2.5 Ultrasonic Reference Blocks

Seven sets of ultrasonic reference standards were purchased from

three different sources. These sets were comprised of three "Distance/Area

Amplitude (basic) sets, purchased from the Defense Supply Agency (the source of most Air Force field blocks), and four "Distance Amplitude sets.

The basic sets were all the product of one manufacturer. The Distance

Amplitude sets, purchased directly from the manufacturer, consisted of

two sets of "number 3"* blocks from a second manufacturer and one set

each of "number 5 and 8" blocks from the third manufacturer. This sample

will provide some measure of the inconsistency of products manufactured

by different producers as well as the variability of the standards produced by the same manufacturer. These sets constitute part of the data

base established at the NBS laboratory. In addition, these reference

blocks provide convenient working standards for the other activities in

the program.

*These reference standards are commonly referred to as "number x" blocks

where x represents the diameter of the "flat-bottomed hole in 64 THS of

an inch (1 in = 2.54 cm)."

13
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14
3.3 Comparison of Nominally Identical Blocks

Of major concern to the producers and users of ultrasonic reference

blocks is the large variability of response from "nominally identical"

standards. While this problem is widely acknowledged, the extent of the

problem is not well documented. The literature search produced only two

quantitative references to this problem. Reference [4] reported a 300%

variability in the response from nominally identical titanium standards

checked in a round-robin procedure. With regard to aluminum reference

blocks, a report by the Aeronautical Quality Assurance Directorate

(United Kingdom) [6] concludes that blocks could be fabricated and calibrated (by the assignation of correction factors with respect to a master

set) with an uncertainty of ± 1 dB. But ASTM E127-75 [3] recognizes a practical problem of greater magnitude and allows for a ± 2 dB variability

around a "nominal" value. The measurement of the extent of this variability was the primary intent of Task 3.

In order to establish a representative data base of the response

from ultrasonic reference blocks, the assistance of the NDT community

was sought. This was done through a personal appeal for the loan of

reference blocks to the members of ASTM E07.06, the ultrasonics subcommittee of the committee for nondestructive testing, an appeal to the

general NDT community through the NTIAC Newsletter, and through numerous

private communications. Reference blocks were received from the organizations listed in Table 2.

Pulse-echo response data were taken on all the block sets at the

test frequencies of 2.25, 5.0 and 10.0 MHz, using the immersion set-up,

broadband pulser/receiver , stepless gate, oscilloscope, and spectrum

analyzer described in Section 3.2. Additional data were obtained from

all but one block set using nominally identical 5.0 MHz, 0.375-in (0.952

cm) diameter quartz crystal transducers and the tuned, field-type, flaw

detection equipment described previously. The block sets evaluated, the

transducers used, and the number of data sets taken are summarized in

Table 3.

15
Table 2. Organizations Providing Reference Blocks for Task 3

Air Force Materials Lab

Aluminum Company of America

Battelle Memorial Institute - Columbus

Curtiss-Wright Corporation

Grumman Aerospace Corporation

LTV Aerospace Corporation

NASA Lewis Research Center

Naval Research Lab (NRL)

Ohio State University

Reynolds Metals Company

Westinghouse Electric Corporation

Wyman-Gordon Company

16
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During the data-taking process, all pulser/receiver settings were set

in repeatable positions. The system gain was generally set by standardizing the reflected signal from a steel ball. Some data sets were taken

using the quartz transducers standardized on the signal from a selected

reference block. The normal standardization points using steel balls are given in Table 4. These standardization points are only a basis for the

comparison of nominally identical blocks. They were chosen to give the

response closest to the response of a reference block with a 0.500-in

(13 mm) metal travel distance from the first set of blocks checked at NBS.

Photorecordings were made of the radio frequency (rf) signal reflected

from the flat-bottomed hole and the spectinjm of the gated rf waveform when

the broadband system was used. Only amplitude response data were recorded

using the tuned flaw detection system. Details of the mechanics of datataking, transducer characteristics, and typical waveform photographs are included in the first annual report [5].

3.3.1 Ultrasonic Reference Block Comparison

Nineteen sets of borrowed reference blocks were evaluated during the

two-year program along with the seven sets of blocks purchased by NBS.

The data taken from the distance amplitude (DAC) , area amplitude (AA)

,

and basic sets are shown in Figs. 3-22 for aluminum and steel reference

block sets. The mean values of response are plotted for nominally identical blocks evaluated under nominally identical conditions. The bars represent the spread in response from nominally identical blocks, and the numbers

indicate the number of blocks checked. The B-curve shown in figures 12-14

and later represents an increase in instrument gain for long metal distance

blocks in order to improve measurement resolution. Variations in the response

from nominally identical blocks was generally less than 40 percent (within the

+2 dB limits of E127-75) at the test frequencies from 2.25 to 10 MHz, but

variations in excess of 700 percent were also measured [8, Fig. 8]. The data

from this highly variant (700 percent) block set was not included in the

present data because it would only add to an already confused situation. There

is some background information that indicates that this particular set of

reference blocks was fabricated several years ago from drawn aluminum rod

rather than rolled rod as specified in [1] . While this fact may point to

metallurgical parameters as the major causes for the variation in response

in this case, the problems represented by a "normal" variation of 40 percent

cannot be dismissed as readily.

18
Table 4. Standardization Points for Reference Blocks in the NBS Data Base

Block Hole Size

0.047(#3)

0.047

0.047

0.078(//5)

0.078

0.078

0.078

0.078

0.078

mm

1.19

1.19

1.19

1.98

1.98

1.98

1.98

1.98

1.98

Material

Al

Al

Al

Al

Stl

Al

Stl

Al

Stl

Test

Frequency

MHz

2.25

5.0

10.0

2.25

, 2.25

5.0

5.0

10.0

10.0

Ball Diameter

m mm

0.0625

0.1875

0.2812

0.1250

0.0625

0.4375

0.2188

0.6250

0.2188

1.588

4. 762

7.144

3.175

1.588

11.112

5.556

15.875

5.556

Amplitude

V

1.20

1.20

0.60

1.28

1.20

1.20

1.50

0.60

0.60

0.125 (#8)

0. 125

0. 125

0.047

0.078

0.078

0. 125

3.18

3. 18

3.18

1.19

1.98

1.98

3.18

Al

Al

Al

Al

Al

Stl

Al

2.25

5.0

10.0

5.0*

5.0*

5.0*

5.0*

0. 3125

1.0000

1.0625

0.1250

0.3125

0.1250

0.6875

7.938

25.400

26.988

3.175

7.938

3.175

17.462

1.20

1.20

0.58

80% F.S,

80% F.S,

80% F.S,

80% F.S,

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39
The data presented in Figures 12, 13, and 14 were taken using the

procedures and standardization points recommended in E 127-75 [3]. Note

that there are several points that fall outside of the response limits of

+2 dB around the desired value. This indicates that some of the problems

associated with recommended practice E 127 were not resolved by the 1975

revision even within the large allowable tolerances. Clearly, a calibration

procedure with a well defined unit or primary standard would resolve much

of this problem.

A limited amount of data was also taken on titanium blocks. Two

2-piece, diffusion-bonded titanium reference blocks of the type described

in [7] were examined. These blocks contained defects measuring 1, 2, 3

and 5-64 in (0.40, 0.79, 1.19, and 1.98 mm) in diameter. One of the blocks

had metal travel distances of 0.25 and 2.75 in (6.4 and 69.9 mm) and the

other block had metal travel distancesof 1.50 and 1.50 in (38.1 and 38.1 mm).

Data were taken with a 10 MHz, 0.25 in (6.4 mm) diameter transducer and

the field-type flaw detection unit. Comparison of the amplitude response

with dB attenuation differences were made. The results were inconsistent.

Extraneous signals from the bond line severely affected the defect amplitude

measurements on all but the 0.25 in (6.4 mm) metal travel block. Some

of the noise was attributed to fabrication difficulties experienced in this

early attempt at a diffusion bonding process. Others are still working on

this technique, e.g. [11]. It is anticipated that reference blocks of this

type will be more closely examined in future efforts at NBS. The technique

seems to be particularily promising for steel and titanium reference blocks.

3.3.2 7075-T651 Reference Blocks

Six production runs of ultrasonic reference blocks were made from a

single lot of 7075-T651 extruded 2.25 in (57.15 mm) diameter rod material

40
supplied by NBS. This material was chosen over 7075-T6 rolled rod

material because it was from a single lot and was readily available.

Thus metallurgical variables were hopefully minimized. Three fabrication

runs were made by machinists at NBS and one run each was made by machinists

from the 3 leading block manufacturers. Each machinist was supplied with

a drawing from the ASTM-E 127 document (Figure 1 ) and asked to produce blocks

to the tolerances specified. Five of the 6 production runs consisted of

No. 3, 5, and 8 blocks (2 each) with a 3.00 in (76.20 mm) metal travel.

The sixth machinist was asked to produce No. 3, 5, and 8 blocks (4 each)

with a metal travel of 2.25 in (57.15 mm), and No. 5 blocks (6 each) with

metal travels of 0.50 in (12.7 ram), 3.00 in (76.20 mm), and 5.75 in (146.05 cm).

The ultrasonic responses from these blocks were measured at nominal frequencies

of 2.25, 5.0, 10.0 and 15.0 MHz. The average ultrasonic response from these

blocks was approximately 17 percent lower than the average response from

« the field blocks that were inspected, presumably due to the slightly different

metallurgy. The variation in response for the nominal frequencies of 2.25

and 5.0 MHz was about half that found in the field-type standards (see

Table 5). These two factors point to the significance of the metallurgical

aspects in improving the current reference standard, particularly the need

for a uniform lot of homogeneous material from which to produce standards.

3.4 Metallurgical Considerations

This task is concerned with the evaluation of the material from which

ultrasonic reference blocks are fabricated. Of particular concern are the

microstructural and metallurgical parameters that can affect the ultrasonic

response of reference blocks. Correlations were sought between ultrasonic

response anomalies and microstructural features. Techniques for residual

41
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42
stress measurements, preferred orientation measurements, and micros truetural

measurements were refined and applied in this task.

Alviminum, steel, and titanium alloys of the type used in reference

block production were studied. Two reference blocks, one 7075-T6 aluminum

alloy and one 4340 steel alloy, rejected by the manufacturer during

fabrication, were closely examined. Additional work was done on an NBS

fabricated block of 7075-T651 aluminum alloy and some titanium alloy

(Ti 6-4) sheet material [8] and steel sheet material.

3.4.1 Aluminvim Block

Studies were conducted of the microstructure of the extruded 7075-

T651 aliiminum block that was fabricated at NBS from commercial material.

Several surfaces produced by sectioning the block were examined. Determinations of the void content and the inclusion content were made on metallographically polished surfaces prior to etching. Figure 23 shows one

representative area on a polished surface with the voids and cavities

appearing dark. From the shape of some of the voids they appear to have

resulted either from original cavities forming at grain boundaries during

solidification or possibly from later void growth at grain boundaries

during fabrication. Another region on a different surface is shown in

Fig. 24. The void density found in the NBS block was not significantly

different from that found in the rejected aluminum block reported on

previously [8J. Some foreign phases also were found on the sections

examined. They are seen as lighter grey areas in Figs. 23 and 24. The

frequency of their appearance in the NBS block also is comparable to that

in the previously examined rejected aliominvim block.

Two different etching treatments were applied to the various aluminum

43
4 t

3

i

Fig. 23 NBS-fabrlcated aluminum block surface, as

polished. M » 400X.

Fig. 24 Another surface on NBS-fabrlcated block. M « 40QX.

44
surfaces studied in order to reveal the microstructural detail. Figure

25 is a region of one surface of the NBS block etched in a 10% NaOH

solution for 3 minutes at 140° F C60°C). Figure 26 shows the results

of a 5% HF etch for 10 sec. Either treatment brings out the grain

boundary structures and further enhances the foreign phase regions. Grain

size measurements were conducted using the intercept method. A value of

7.3 grain size (mean intercept 26 ym) was obtained on the NBS block which

was not significantly different from the grain size value of 7.5 determined

previously for the rejected block.

Electron beam microanalysis studies were conducted on surfaces from

both aluminum blocks to determine whether compositional inhomogenieties

could be detected. Figure 27 depicts a region on a polished surface of the

NBS block. X-ray spectra were obtained from two different areas within this

micrograph and are shown in Fig. 28. The copper peaks (arrow) in these

two spectra are nearly equal indicating no significant difference in

copper concentration in those two areas. Many other areas were visually

examined with the same result. Line scan studies were also conducted in

which the electron beam is scanned along a fixed line on the specimen

surface and the X-ray signal is stored during repeated scans. The white

line in Fig. 27 is such a scan line. The copper X-ray data corresponding

to that line is shown in Fig 29. While a small gradient decreasing to the

right is seen and is due to geometric factors, no significant local variation

in copper concentration could be detected. Other areas scanned also failed

to show any local concentration variations of significance in the NBS block.

The aluminum block surfaces were also examined in the etched condition

for variations in X-ray emission. Figure 30 shows a region on the NBS

block surface after etching for 10 sec. in 5% HF solution. The white line

45
* It

Fig. 25 NBS fabricated block etched in NaOH solution. M « 200X.

* r

t 4

Fig. 26 Another surface on NBS fabricated block, etched in HF

solution. M = 400X.

46
Fig. 27 NBS-fabrlcated block, as polished surface,

X-ray scan trace location is shovTn. M = 14QX.

f RST = •803628

188 SEC

080180 S:i

Fig. 28 X-ray spectra from two areas on surface shown

in Fig. 27.

47
SCftN 512 CH. 500 FS 50 SEC.

CURSOR= CH. 0257 000862 COUNTS

PRESET^ 1 SCANS TftLLV= 08018

Fig. 29 Copper X-ray line intensity recorded along

scan trace shown in Fig. 5. M = IIQX.

Fig. 30 Etched surface on NBS block. M = 13QQX.

48
locates the line scan trace. The copper X-ray signal intensity obtained

along this scan line is seen iii Fig. 31. Some local variations in signal

are seen and can be matched to scratches and etch topography on the surface

rather than to actual copper concentration variations. The rejected

alumintim block was also examined in the line scan mode after etching in

the HF solution. The area is shown in Fig. 32. The nonuniform etching

response is seen here; small patches of smooth surface are to be fotind

(arrow). Some cavities can also be seen in this area. Figure 33 shows

the X-ray signal from two different line scan regions on this surface —

one where the etched topography is uniform (upper) and the other where a

smooth slightly etched region is included in the scan line (lower). A

clear signal disruption is seen there, partially due to a variation in

copper content. This block had previously been found to have etching

characteristics interpreted to result from composition variations resulting from the solidification process.

Studies on the texture (crystalline preferred orientation) of the

rejected aluminum block were reported previously in {8] will not be

repeated here. Texture studies were made on one of the blocks made at

NBS from extruded aluminum rod on surfaces SI and S5/2, Fig. 34. Those

measurements were made using filtered copper radiation and the 200, 111,

and 220 peaks. The (100) pole figures for these two surfaces are included

in Figs. 35 and 36. There is a variation in the decrease of intensities

in these two pole figures indicating some lack of uniformity in the texture

along the block. The texture of these pole figures showed the rotational

symmetry usually found in a fiber structure. That is, the intensity levels

occur in bands aroimd the center. The intensities on these pole figures are

49
./' A

N 51

SOR=' C

2 CH. i H. 0207

:K FS , 58 S£:

800888 COUNTS' •

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S£T= 18 sm

Fig. 31 Copper X-ray line intensity recorded along

scan track shown in Fig. 8., M = 105CLK.

Fig. 32 Etched surface of rejected aluminum block.

Note smooth local regions (arrow) . M = 1300X.

50
SCrN / -5.12- :-aH.:588:;FS;-:^:: : 5e:-vS£C:;'

PRESET=. 18 SCANS TRLLV= 88883

Fig. 33 Copper X-ray line intensity recorded along

two lines in different regions on etched

rejected aluminiiin block. Note large signal

anomaly in lower trace. M = 1600X.

51
S1 S2/2

S2/1

S3/2

S3/1

S4/2

I S4/1 S5/2 I

S5/1 I

I

ii

:i

Fig. 34 SECTIONED NBS ALUMINUM BLOCK

52
Fig. 35. NBS Al Block Surface S5/2 (100) pole.

Intensity at center 100.

53
36 NBS Block Surface SI (100) pole. Maximum

intensity at center - 100.

54
plotted on a relative scale of 0 to 100, the strongest intensity being

assigned the value of 100.

The (100) pole figures have the maximum intensity in the center,

with a rapid decrease within 10° from the center. A secondary maximum

band is reached at approximately 20° from the center. The (100) pole

figure of the S5/2 surface showed a more pronounced variation in intensity

than did the (100) pole figure from the surface (SI). The (111) pole

figure, Fig. 37, showed a minimum at the center with maxima occurring near

35° and 55°. The maximum at 55° is related to the strong (100) texture of

that surface. The (110) pole figures, Fig. 38 and 39, showed a broad

maximum band between 20° and 55° with a crest near 30°. The occurrence

of that crest near 30° for the (110) pole and the secondary maxima near

35° for the (111) pole and near 20° for the (100) pole implies that

the rod has an additional texture component near (113) to (114) . The

observed rotational symmetry is to be expected for an extruded rod. The

detailed texture features depend on properties such as grain growth in

the ingot, alloy composition, temperature of extrusion, and the applied

thermal and mechanical treatments. Face centered cubic metals and alloys

show varied strong texture types from (100) to (111) components.

The texture of the rejected block, made of rolled rod, that was

previously studied, was characterized by an absence of rotational symmetry.

The (111) pole figure of that block (Fig. 20, [8J) showed evidence of

four-fold symmetry which was probably retained from the early fabrication

of the rolled rod. The same uniformity in texture as found in extruded

rod is not to be expected in swaged or rolled rod. From texture consideration, an extruded rod would probably give a more uniform response

55
Fig. 37 NBS Block Surface SI (111) pole.

56
57
39 NBS Mock Siirface SI (HQ) pole. Intensity

at center 15.

58
In ultrasonic attenuation than a rolled rod. As ultrasonic attenuation

is effected by crystal orientation, this texture would introduce variations in the ultrasonic response through the block.

Residual stress measurements were made on surfaces S4/1 and S5/2

(Fig. 34) as metallographically polished and after etching for three minutes

in hot( 140-149°F (60-65°C) ) 10% NaOH solution. The compressive stress on

the two surfaces after metallographical polishing was 26.1X10 Ibf/in

8 3 2 (1.8 X 10 Pa). After etching the values decreased to 6.2 and 6.8X10 Ibf/in

g (0.43 and 0.47 x 10 Pa) (see Appendix 1). This indicates that the stress

in the interior of the block is relatively low. The T-6 precipitation

anneal would be expected to reduce the quenching stresses in the 7075 alloy

and the reduction is dependent on the temperature and the time of the anneal.

3.4.2 Steel Block

The rejected steel block was also examined metallographically. A 5%

nital etch was used for 15 seconds. The observed structure on the original

surface containing the plugged hole is shown in Fig. 40. Several void and

cavity features are seen in this area. A higher magnification view of an

interior (cut) surface from the steel block is shown in Fig. 41. Two large

grains • can be identified, although the remaining grains in this field are

considerably smaller. However, even the few large grains found contained an

internal fine second phase structure that probably produced a much smaller

"effective" grain size. The interparticle separation was about 1 ym in

the steel specimen even though grains larger than 20 ym could be identified.

It appears that the microstructure of the steel block material is sufficiently

fine grained for it to behave ultrasonically in a fairly homogeneous manner.

The ultrasonic examination of this block prior to sectioning did not reveal

59
Fig. 40 Steel block, surface containing hole plug, after nital etch. M = 160X.

Fig. 41 Steel block, interior surface, after nital

etch. M = 800X.

60
any anomalies even though it was obtained after rejection for reference

block purposes.

Texture measurements were made on surfaces SI and S5/2, Fig. 42 of the

rejected steel block. Intensities were taken using the 111, 200, 211, and

220 peaks with filtered molybdenum radiation and a standard texture

goniometer. The intensities were relatively constant with orientation

showing less than ten per cent variation. These results indicate that

the rejected steel block had essentially a random orientation texture.

Sample intensities for the S5/2 surface are shown in Table 6.

Table 6 Texture measurement intensities on the S5/2 surface of the rejected

steel block.

Tilt Intensities for

Angle Various Poles

(deg) (110) (200) (211)

0 100.0 96.2 98.5

5 92.5 95.0 98.5

10 95.0 97.5 100.0

15 91.3 93.7 98.5

20 93.7 100.00 100.0

25 87.5 95.0 93.8

30 93.7 100.0 98.5

35 81.2 93.7 90.8

40 93.7 96.2 96.9

45 75.0 93.7 90.8

50 85.0 95.0 87.7

The [110] texture was essentially constant for both surfaces. A [IIOJ

texture is normally expected for bcc rod or wire materials.

Steel Block - Residual Stress

Residual stress measurements on the rejected steel block were made as outlined

in SAE TR-182 (amended) [12] . The determination of the peak maximum is done

differently. The alpha-1 peak is separated by using a modified method to

that outlined by Gangulee {13J . The new points are fitted to a parabola

and the parabola maximum is taken as the peak position. For this rejected

steel block, the 211 diffraction peak was measured with monochromatic

61
SI S2/2

c

£

S2/1

S3/2

I

S3/1

S4/2

] S4/1 S5/^

S5/1

Figure 42. SECTIONED REJECTED STEEL BLOCK

62
chromium radiation using a graphite crystal. The diffractometer was

scanned across the two-theta region of interest at the rate of one degree

in two-theta over a period of 240 seconds. Counts were taken at 20 second

intervals with a scalar containing a memory, permitting a new count to

start while the previous count was recorded' on tape. As the steel

block was essentially random in texture, no difficulty was encountered

in getting sufficient intensities at all angles. The residual stress

results are shown in Table 6 and with more detail in Appendix 2 for

the various surfaces and conditions. Deeply etched or electropolished

surfaces showed that the residual stress approached zero, indicating that

the steel block was in the annealed condition. The results (Table 7)

show that the stresses on the surface are affected by block history. The

results on the etched specimens may be effected by the relaxation of

stress on the roughened surfaces. The electropolished specimen retained

a smooth surface and therefore was not subject to this problem. For

some specimens, on slight electropolishing , a tensile stress appeared for

angle values approaching 60° inclination where X-ray penetration is less,

while intermediate angle values showed a compressive stress (Appendix 2).

Surface SI in the as received condition showed considerably lower stress

than surfaces S4/1 and S2/1 in the machined condition. After etching

surface SI with a nital solution, it was repolisked on silicon carbide

paper (through the 600 grit). The surface SI in this condition showed

the highest compressive stress measured.

Hardness measurement also were made on the S2/1 surface and were found

to be approximately HRA 61 (Rockwell Scale A). Results are given in Table 8.

63
Table 7. Residual Stress Values From the Sectioned Steel Block

Residual Stress

Location Stress , Fa Deviation Remarks

SI ' -2.2 X 10^ 2.6 X 10'' As received

-4.1 1.8 Met. papers

-2.4 0.6 Polished

-0.77 1.4 Polished and etched .001"

^- -0.35 1.3 Electropolished .002

S2/2 -3.1 , 0.7 ' Polished

0.08 1.1 Etched .001"

-0.03 1.2 Electropolished .002"

S2/1 -3.5 ' 1.9 Machined

S3/2 -2.6 0.5 V- Polished

-2.6 1.9 Etched, nital

S4/1 -3.8 2.7 Machined

-2.9 2.2 Polished

0.3 " 2.9 ' Electropolished .001"

-0.1 0.8 Electropolished .0018"

S5/2 -2.1 1.3 Polished

-0.1 -• 1.7 ^ Electropolished .001"

. -0.6 1.3 . Electropolished .0018"

64
Table 8 Hardness measurements from the S2/1 surface of the rejected

steel block.

Distance from

Edge HRA

1/8"

1/4"

3/8"

1/2"

5/8"

3/4"

7/8"

60 3/4, 61 1/4

60 3/4, 61

60 3/4

Center

61

61

61

61

61

These results also indicate that the steel block was in a soft,

annealed condition, imiformly through the cross section.

Measurements were also made on some specimens cut from a 4130 type

rolled steel sheet in order to indicate the texture that could be expected

in that form of material. The specimens were examined as rolled and

after the removal of various thicknesses of material by electropolishing.

The results showed a strong preferred orientation in the plane of the

sheet, in contrast to the random texture found in the steel block (rod)

just discussed. The pole figures after different treatments are shown in

Figs. 43-50.

Two areas related to the fabrication of reference blocks were

studied. The first area was concerned with the problem of meeting the

appropriate physical dimensions and machining tolerances. The specifications

in ASTM E 127 served as a reference. Specific help was requested from

the Dimensional Technology and the Optics and Micrometrology Sections of

NBS in the measurement of hole diameter, comer radius of the hole bottom,

3.5 Fabrication Considerations

65


68
69

71

73
parallelism of the hole bottom and the top surface of the block, and

surface finish of both the hole bottom and the top surface of the block.

The second area involved a feasibility study of the fabrication

of reference blocks from more than one piece of material.

3.5.1 Dimensional l^asurements

Fifty-four blocks fabricated from the supply of NBS 7075-T651

aluminum alloy, 3 blocks fabricated from fused quartz material, and 6

7075-T6 aluminum alloy blocks that were rejected by a block manufacturer

were checked for adherence to the hole diameter specifications of ASTM

E 127-75 (required diameter + 0.0005 in (0.0013 mm)). A mechanical

comparator that magnified the motion of a split-ball probe was used

in this effort. A dial gage readout with 0.0001 in (0.0025 mm) increments

provided diametral differences from an initial reading of a standard. Both

hole diameter and diametral variations (out of roundness) were measured.

Hole diameter differences from nominal values were as large as 0.0040 in

(0.1016 mm) with "roundness" deviations up to 0.0015 in (0.0381 mm). The

mean differences from the nominal values were more representative of the

specified tolerance at approximately 0.0007 in (0.0178 mm) with average

"roxindness" deviations of 0.0004 in (0.0102 mm). An attempt was made to

correlate hole diameter deviations and ultrasonic response deviations

(Section 3.3) but no obvious relationship was evident.

Pat McEleney of AMMRC has presented unpublished data to an ASTM

Committee that indicates that the ultrasonic response from a test piece

varies not only with the rms surface finish of the top surface of the test

piece but also with the different techniques used to produce the same rms

surface finish. This is an interesting result in view of the fact that

74
3 distinct finishing patterns were noticed on commercially supplied blocks

and the blocks produced from NBS-supplied material. Three of the purchased

blocks (2 from one manufacturer) were sent to the Optics and Micrometrology

Section at NBS for surface finish characterization by the arithmetic

average (AA) value and autocorrelation techniques. The procedures and

the equipment for this work are described in [14]

.

Two distinct machining patterns were visually evident on the 3

blocks whose entry surfaces were characterized. The entry surface of

two of the blocks were milled in a linear pattern while the third was

apparently turned on a lathe. A linear surface profile, 0.11 in (2.8 mm)

in length was taken near the center of each specimen. Typical surface

profiles, the amplitude density functions (histograms), and the autocorrelation functions are shown for the profiles of the 3 blocks (Figs.

51 to 55). Both across-the-grain and with-the-grain profiles are included

for the two milled specimens. An arithmetic average value (similar to rms

value) and an average characteristic wavelength were calculated for each

profile measurement. These values are listed in Table 9. Ultrasonic

reflection data (Table 9) were taken over the top surfaces of these 3 blocks

at 5 and 10 MHz. The variation in the amplitude of the energy reflected from the

top surfaces of the blocks was 7.7 percent in the worst case between the 2

machining processes - 4.4 percent between the similarly machined blocks.

No point-to-point correlations were made between surface finish and

ultrasonic reflection data.

Further work correlating the ultrasonic response at several frequencies

to the surface properties of test pieces is anticipated. Difficulties

have been encountered in the measurement of other dimensional parameters.

75
8x10

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SCAN DISTANCE, m

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PEAK HEIGHT

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Fig. 51 - SURFACE ROUGHNESS DATA (SCAN 1A) FOR SPECIMEN B-0121 (5-0012

REFERENCE BLOCK). THIS DATA WAS TAKEN NEAR THE CENTER PEA K OF THE

TURNED SURFACE.

76
0.4 X 10

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Fig. 52 - 'WITH THE GRAIN' SURFACE ROUGHNESS DATA FOR SPECIMEN 123

(8-0006 REFERENCE BLOCK). NOTE THE TWO DEPRESSIONS IN SCAN A.

77
0.4 X 10 ^

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Fig. 53 "ACROSS THE GRAIN" SURFACE ROUGHNESS DATA FOR SPECIMEN

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SCAN DISTANCE, m

Fig. 54. "WITH THE GRAIN' SURFACE ROUGHNESS DATA FOR SPECIMEN 123 (8-0012

REFERENCE BLOCK).

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Fig. 54 - CONT'D.

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AMPLITUDE DENSITY FUNCTION

PEAK HEIGHT

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Fig. 55 "ACROSS THE GRAIN" SURFACE ROUGHNESS DAT A FOR SPECIMEN

123 (8 -0012 REFERENCE BLOCK).

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82
such as the corner radius of the hole bottom, parallelism of the hole

bottom and the top surface of the block (except by ultrasonic methods)

and the surface finish of the hole bottom. A hole replication technique

t similar to that done at Curtiss-Wright by Michaelsohn or as outlined

in [2] has been tried at NBS. Such replicates seem to provide a

satisfactory media for the measurement of some of the flat-bottom hole's

characteristic dimensions of the larger diameter holes.

3.5.2 Multi-piece Reference Blocks

One new, promising concept in the fabrication of ultrasonic reference

standards involves the assembly of several pieces of material to produce

one reference standard. The main advantage to this procedure is the chance

to obviate the problems associated with dimensions of the reflector (e.g.

the comer radius, surface finish, etc. of the flat-bottom hole). Using

this concept, an ASTM type reference block might consist of two cylinders, "

one solid and one with a through hole, "bonded" together to form an

ultrasonic reference block.

Kettering at Grumman has fabricated multi-piece titanium standard by

sandwiching a thin titanium foil containing well-characterized defect

holes between two solid titanium blocks [7]. The 3 pieces are then diffusion

bonded. Pat on at Rockwell has similarly produced tltanixim and steel twopiece blocks with spherical and spheroidal cavities and forecasts that this

process will soon be feasible for aluminum and stainless steels 111]

.

Metallographic and ultrasonic examination diffusion bonded reference blocks

have confirmed the bond line quality and ultrasonic transparency in some

cases.

_Private communication to ASTM committee E 7.06.02.

83
The NBS activity in this area has concentrated on vrringing together

two pieces of material to produce a bond line which is almost ultrasonically

invisible. Initial experiments were performed on steel gage blocks,

aluminum cylinders, and quartz cylinders. These pieces had very flat

surfaces (0.5 fringe or better) and very fine surface finishes (2 y in

or better). The 2 steel gage blocks were "wrung" together using conventional

gage block techniques. Ultrasonic data was taken on the "wrving" steel

gage blocks at 5 MHz. The reflected energy received from the interface

was less than 10 percent of the back surface reflection. Two quartz discs,

one with a 0.125 in diameter through hole, were also "wrung" together.

The ultrasonic response from the interface was less than 5 percent of the

back surface reflection at 2.25, 5, 10, and 15 MHz. Usually this was

within the "noise" of the measurement system; the bond was essentially

"transparent". Attempts to wring the aluminum cylinders produced negative

results and surface finish damage to the cylinder faces.

The wrung quartz block was placed in a furnace in an attempt to fuse

the two pieces into one block. The procedure was not well controlled and the

resultant fused block contained areas of disbond at the interface. The

sections of this block that were fused produced no detectable ultrasonic

interface signal over the range of frequencies from 2.25 to 15.0 MHz.

Based on this data, it appears that "wrung" blocks may be feasible for steel

or quartz, but probably not for aluminum.

3.6 Effects of the Ultrasonic Measurement Systems

It is evident that the metallurgical and fabrication aspects of

ultrasonic reference block production can account for a significant

percentage of the variation in the response between nominally identical

84
standards. This is only part of the problem; several parts of the overall

measurement system can affect the response received from the same standard.

Consider as a basic ultrasonic measurement system one composed of a mainframe,

a pulser/receiver combination, a transducer, and an operator. Variations

in response arise by changing the electronic components (pulser, receivers,

mainframes, transducers, etc.), the operators, or some of the equipment

control settings. Changes to this basic test system were made in order to

document the effects of those changes on the measurement response of the

ultrasonic system.

The ultrasonic transducer is the one component of the basic ultrasonic

measurement system that is most likely to be broken, abused, or misplaced and,

therefore, need to be replaced by another "nominally identical" unit.

But what exactly do we mean by the term "nominally identical"? Certainly,

for a transducer, some basic characteristics should be within appropriate

limits. The ASTM E 127-75 document [3] contains a section listing the

characteristics that a transducer must possess to be suitable for checking

the response from aluminum reference standards. The important parameters

in that list include the center frequency, the distance-amplitude curve

shape, the location of the landmark, and the beam profiles at the Y^"*"

and landmarks.

Five "nominally identical" 5.0 MHz center frequency, 0.375 in (9.52 mm),

quartz crystal transducers were evaluated according to the guidelines in

[3J. Three of these 5 transducers (designated as Lab Standards, LS-1,

LS-2 , and LS-5) were produced by one manufacturer, while the other 2

(LS-3 and LS-4) came from a competing firm. The transducer pairs LS-1

LS-2 and LS-3, LS-4 were presumably produced consecutively as they were

delivered in pairs with sequential serial number^. Some measured characteristics

85
of these 5 transducers are listed In Table 10. Based on the data in

Table iQ the 5 transducers are reasonable facsimiles of each other in

frequency, beam size, and axial profile shape, but LS 1 and LS 3 are

not suitable for checking the response from aluminum reference standards

according to ASTM E 127-75. The peak height differences at the Y

~

point (LS-1) and the location of the point (LS-3) are not within

the tolerances specified in [3J.

The E 127-75 procedure uses the response from a steel ball and a

"qualified" transducer to establish the measurement system gain for

checking the response from aluminum reference blocks. The relating

ball-to-block response was measured for one No. 3, 5, and 8 reference

block with a 0.50 in (13 mm) metal travel blocks using all 5 transducers.

The results (Table 11) of the ball-to-block comparison differed by 14

to 18 per cent for the 5 transducers. This practical result should

also be considered in qualifying "nominally identical" transducers.

Combining the information in Tables 10 and 11 only LS-3 and LS-4 are

nominally the same.

Other discriminating characteristics need to be specified in order

to accurately characterize a transducer. One good technique appears to be

the measurement of the relative power output versus excitation frequency

curve for a transducer. These curves for the 5 quartz transducers are

shown in Figures 56 to 60.* Again LS-3 and LS-4 are a good match.

Because of the consistent similarities in all characteristics measured,

LS-3 and LS-4 were considered the best among the five and were chosen

for use in the limited calibration service described in 3.9.

*These measurements were taken in the Auditory Acoustics Section at NBS.

Further information about the procedure can be obtained from F. R. Breckenridge

or C. E. Tschiegg, Auditory Acoustics Program Team, National Bureau of

Standards, Washington, D.C. , 20234.

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Table 11. Effects of Different Transducers on Relative

Ball-to-block Response.

1/8" Ball

3-0050 Block

LS-1

80

94

LS-2

80

82.5

TRANSDUCERS

LS-3 LS-4

80

98

80

95

LS-5

80

89

SPREAD

AVG. , %

16.90%

5/16" Ball 80 80

5-0050 Block 79.5 75

80

89.5

80

86.5

80

?9.5 17.68%

11/16" Ball 8Q

8-0050 Block 81

80

78

80ao80

87.5

80

80.5 14.39Z

All 5.0/0.375 quartz immersion transducers

water path = 3.5"

All numbers average of at least 3 readings

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The practical limitations of using a ball-to-block transfer response

are evident from the data in Table 11. Table 12 demonstrates the effect of

changing transducers for a block-to-block transfer. The overall effect

is a 13 percent variation which represents an improvement over the ballto-block results. The important fact to note is the less than 3 percent

variation in response between the LS-3, LS-4 pair.

The effects of changing some of the other system parameters were also

investigated. For example the variability in response that can exist

between different laboratories and different operators had been previously

documented [8J. Data showing the variability in response that can occur

by changing the pulser/receiver iinit is presented in Table 13. These

results were obtained using a ball-to-block transfer mechanism.

Other variations can arise from more subtle equipment changes.

Cable length and type can affect the center frequency

and signal amplitude of the signal received by the ultrasonic system.

This data is presented in Table 14 for a 10 MHz, 0.25 in (6.4 mm) ceramic

transducer. The effect of changes to the gain reference level ("cal" pot)

of the receiver and the pulse length of the pulse were demonstrated for

both a ball-to-block and block-to-block relative response. These data

are presented in Tables 15 and 16 respectively. In each case the relative

block-to-block comparison is affected less by these adjustments.

Figure 61 demonstrates graphically the effect of evaluating the

response from one set of No. 5 reference blocks using the same electronic

system. The 2 transducers (LS-3 and LS-4) selected for use in the calibration

service were used by 3 different NBS operators on 9 relative block-to-block

comparison rvins. These 9 data sets showed very little variation (generally

94
Table 12. The Effects of Different Transducers on Relative Block-to-Block Response

TRANSDUCER

3-0050

5-0125

8-0325

LS-1

80

91.5

70

LS-2

80

94

75.5

LS-3

80

92

75

LS-4

80

97

79.5

LS-5

80

95.5

77.5

SPREAD

AVG. %

5.85%

12.58%

All numbers average of 4 readings

All 5/0.375 quartz immersion transducers

water path - 3.5"

95
Table 13. The Effects of Different Pulser/Receiver Units

on Relative Ball-to-Block Response.

Block

3/16" ball

8-0300

7-0300

6-0300

5-0300

A-0300

3-0300

2-0300

1-0300

P/R

Transducer

Ampl Ampl Ampl Ampl

100 100 100 100

90 75 84 70

70 55 ^ 63 52

53 41 50 38

36 27 33.5 25

25 18 . 23 17

13 10 11 9

5 3 4.5 3

0.5 0 1 0

5 10 5 10

LS-1 LS-1 LS-2 LS-2

96
Table 14. Effects of Different <Cable Lengths and Types on Frequency

CABLE CABLE CENTER SIGNAL

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less than 4 percent) in ultrasonic response for the block-to-block comparison.

The response from this set on the NBS system with LS-3 or LS-4 is now "well

characterized". At least 9 data runs were also made on the No. 3 and

No. 8 reference block sets owned by NBS using the same measurement system.

The results were similar to the data displayed in Figure 61. The response

from these sets on the NBS system are also "well-characterized". Figure

62 presents similar data from several different No. 5 reference block sets

including the data shown in Figure 61. The variation in response can still

be as great as 40 percent, but now the response from these other sets can

be referenced to the response from this well characterized data taken

previously. A slight extension of this idea leads naturally to a "calibration"

procedure.

All of the preceeding results were considered and used in the establishment

of the procedures for the limited calibrated service (3.9). Not only was

a relative block-to-block comparison used, but procedures were established

that would limit the control adjustment that affected either a ball-toblock or block-to-block comparison.

' 3.7 Single Material Standard

The concept of using a single-material for the production of ultrasonic

standards was well received by the participants at the NBS - NDE Public

Review and Workshop in December, 1974. An amorphous material with low

attenuation would be a good candidate material. In addition, a material

that can be suitably inspected for anomalous characteristics by other than

ultrasonic methods (e.g. optical inspection) is desirable. Fused quartz

or crown glass are two such materials.

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101
Three reference blocks were machined from two 2 in (51 mm) diameter

ingots of fused quartz. The block ends were ground flat and parallel

and checked both optically and ultrasonically . Some preliminary photoelastic data displayed a similar internal stress pattern in all 3 cylinders.

Despite these undesirable stress patterns, the reflected amplitude from the

back surface of the 3 cylinders varied by less than 5 percent for the

frequencies from 2.25 to 15 MHz. Stress-free quartz ingots are also

commercially available at a slight increase in material cost.

Flat-bottomed holes were machined into the 3 cylinders to produce

No. 3, No. 5, and No. 8 reference blocks with a 3 inch (76 mm) "metal"

travel. Hole diameter measurements were within ASTM E 127 tolerances on

the No. 5 and No. 8 blocks but 0.0015 in (.0381 mm) oversized on the No. 3

block. "Out-of-roundness" was less than +0.001 in (0.0025 mm) for all

three blocks.

The area-amplitude response relationship between the 3 quartz blocks

was determined using the theoretical response differences, expressed in

decibels as given by: '<

dB difference = 20 log —rj—

2

where V^and are the signal amplitudes (voltages) received from the

reflectors. The theoretical difference between a No. 8 and a No. 5 hole

is 8.16 dB, and the measured value was 8.5 dB. The theoretical difference

between a No. 5 and a No. 3 hole is - 8.87 dB, but the measured value was

only - 5.1 dB.

There are several disadvantages in producing single-piece quartz

blocks. Material and machining costs are high. Each of the three

102
blocks costs in excess of 260 dollars to produce, reflecting mostly the

difficulty of maching quartz without cracking or crazing the material.

Despite the care taken in producing the blocks, comer radii and small

cracks were evident at each hole tip.

Despite these difficulties, the concept of a quartz single material

standard should not be completely discoxmted. The results on the wrung

two-piece quartz blocks (see Section 3.5) were particularly encouraging.

While it is not presumed that such standards would replace the field-use

reference blocks, two-piece quartz blocks may be of value as master or

primary transfer standards used for equipment standardization and interlaboratory measurement system comparisons.

3.8 ASTM Participation

The NBS investigators have continued their active association with

the ASTM Committee E 7 on Nondestructive Testing, Sub Committee E 7.06

on Ultrasonics, and particularly E 7.06.02, the working group on Aluminum

Reference Blocks. Close contact has been maintained with several members

of E 7.06.02 regarding the revision of the E 127 document that took place

in 1975. Experiments were performed at NBS to verify the validity of

comparing the response from different size (hole diameter) reference

blocks on a single (universal) distance-amplitude curve. The data from

three sets of blocks, one each set of No. 3, 5, and 8, when plotted on a

universal distance-amplitude curve, are shown in Figure 30 of I8J . The

scatter between these data appears to be no worse than the scatter between

data from different sets of blocks of the same size (Figures 3 to 22).

Data taken at NBS, as well as several other labs, were used to determine

the appropriate equivalent ball sizes for sensitivity setting when checking

103
reference blocks. NBS is currently participating in ASTM sponsored

studies of material attenuation and curved entry surface reference blocks,

and is working on the problem of ultrasonic instrument linearity. Continued

participation in activities of mutual interest to ASTM and NBS is planned.

3.9 Calibration Service

Several problem areas have been identified in measuring the response

from ASTM-type ultrasonic reference standards. These problem areas arise in

the standard itself and the ultrasonic measurement system. While work

continues to eliminate these problems, NBS has undertaken the task of

establishing a calibration service for ASTM E 127-type reference blocks.

3.9.1 The Measurement Process '

The primary goal is the establishment of a proper measurement process

for measuring the response of ASTM E 127-type ultrasonic reference blocks.

Using the measurement system established at NBS, the difference between

the amplitude of response of users' blocks and a reference artifact

maintained by NBS is quantified.

In order to formulate a "proper" measurement process, it is necessary

to operationally define the measurement unit . Since the quantity of interest,

the ultrasonic response of reference blocks, is not derived from any SI

base xmits, there is, in principle, a great deal of arbitrariness in its

definition. To emphasize this arbitrariness, the reference artifact

maintained by NBS will be considered our Interim reference standard, subject

to change as the state-of-the art advances. It is anticipated that initially

this service will be of most value as a means for comparing the values of

different users' blocks. However, as the NBS defined unit becomes accepted

(e.g., in contractual agreements), the process can be interpreted in terms

104
of an "absolute" measurement.

3.9.2 Calibration Service Limitations

The calibration seirvice offered by NBS will, initially, be narrow

in scope. The set of measurands to be included is restricted to 7075

aluminum alloy, E 127 type reference blocks with metal travel distances

ranging from 0.50 in (13 mm) to 6.5 in (165 mm) and flat-bottomed hole

diameters from 1 to 8 64ths. The procedures will closely parallel that

prescribed in I3J with the major exception of eliminating the ball-toblock response transfer mechanism. A block-to-block calibration transfer

will be used. The measurement system variables will be closely controlled

and a master standard will be maintained by NBS against which all comparisons

will be made. Check standards are also maintained to insure the performance

of the NBS measurement system. As improvements to the measurement process

are realized, they will be implemented.

The measurement approach is to quantify the difference in relative

response between the blocks being calibrated and the master standard.

At present these measurements are primarily comparative. This is a

limitation imposed by the lack of a precise mathematical model that describes

in a physically meaningful way the complex interaction that is taking place.

The development of such a model would be the necessary step in the development

of an "absolute" measurement process.

A detailed description of the development and implementation of the

NBS calibration service can be found in [5J

.

There are several logical improvements to this outlined measurement

system. The measurement process should eventually be extended to include

steel and titanium blocks and possibly the interpretive model siiauld be

105
improved so that the set of measurands can include blocks of any material

and so that some of the process restrictions can be removed (e.g. use

different frequencies). The system can be further improved by "replicating"

the "master" reference and making these available for use with field

measurement systems on field reference blocks.

Approximately ten sets of blocks are being produced with a minimum

of variability. The remaining variability will be carefully quantified.

A set of blocks will be transmitted to a requesting user. On return the

set will be recalibrated. This loaner service is scheduled to begin in

early 1977.

To keep the measurement system under control, this loaner service should

be generalized to a Measurement Assurance Program (MAP) , emphasizing feedback

to NBS from the user community to insure that good measurements are being

made in the field.

4. CONCLUSIONS

The NBS program described herein is devoted to achieving near-term

improvements in the reliability of ultrasonic measurements by improving

the ASTM-type reference standards system. This report describes work

performed in the first two years of a continuing effort. Based on this work

the following conclusions are drawn:

1) If the block sets evaluated by NBS to date are typical of the

reference block sets available to the NDE conmiunity, than a normal variation

in ultrasonic response of 20 percent can be expected between nominally

identical blocks. However, variations in block response of about 40

percent are not uncommon, and variations as high as 700 percent have been

recorded. These variations were measured on the same system but with different

operators.

106
2) The variability between data taken by three operators using the

same blocks and the same equipment was measured to be less than about

5 percent. The deviations between readings from two operators using

the same blocks and the same search unit but different systems was less

than 10 percent.

3) Efforts to manufacture reference blocks from 2 pieces of material

have shown this process to be feasible. The particular NBS effort on

wrung two-piece blocks has met with mixed success with wrung twopiece quartz, steel, and aluminum blocks. Of these a two-piece quartz

standard appears to be the most promising.

4) One-piece quartz blocks were fabricated by NBS from fused quartz

ingots. The machining of this material is difficult and the resultant

problems associated with the machining processes are evident in the

ultrasonic response from these block. A two-piece quartz standard

appears to be a more promising candidate for a "single-material" master

standard.

5) One-piece aluminum blocks have been fabricated at NBS from a uniform

lot of 7075-T651 extruded rod. The spread among nominally identical

blocks was less than 10 percent for three different sets.

Five sets of 6 blocks each were fabricated from the same lot of

7075-T651 extruded rod by 2 NBS machinists and the machinists from 3

leading block manufacturers. The variability in the ultrasonic responses

of nominally identical blocks was about half of the variability among

field blocks. This points to metallurgy as an important variable

contributing to field block variability.

6) Metallurgically , an extruded rod will usually contain a uniform

107
texture across the cross section. The final texture (for the case of

face centered cubic material) tends from strong (100) texture with

rotational symmetry.

The same xiniformity of texture is usually not found in rolled or

swaged rod. While texture at the rod center may approach that of extruded

material, the outer layers will invariably contain orientations not found

in the center. The rejected aluminum block studied here also showed a

strong (100) texture but lacked the rotational symmetry found in the

NBS block (extruded rod). It contained a duplex four-fold symmetry which

gave the cross section a nonuniformed texture. To the extent that ultrasonic attenuation is affected by crystal orientation, this texture coxild

contribute to variations in such measurements across the block.

The micros true ture and residual stresses appeared to be comparable

between the two blocks studied. The differences observed in ultrasonic

measurements did not appear to arise from these causes. However, the

residual stresses on the surfaces can vai^y between blocks of the same

rod depending on machining practices and polishing techniques. If

extruded rod is used for ultrasonic test blocks, care should be exercised

in the selection of material as the metallurgical structure can vary

along the length of the extrusion.

Only a single rejected steel block was examined metallurgically.

Texture studies indicated it had a nearly random texture. No (110) preferred

texture was observed. All tests including ultrasonic examination,

indicated that this specimen was uniform across the cross section. In

electropolished sections, the residual stresses were low, approaching

the experimental uncertainty. The specimen was in the annealed condition.

108
No reasons for the rejection of this block were found from metallurgical

examination. Studies on rolled steel plate, in contrast, showed a

strong orientation texture associated with the fabrication method.

7) A study of the effects of various equipment characteristics

has shown that several standard adjustments, notably pulse length and

attenuation "cal" adjustment, significantly affect relative ball-toblock response and slightly affect relative block-to-block response.

For the NBS calibration service, a block has been selected as the primary

reference rather than the ASTM practice of using steel balls.

8) NBS has established a calibration service for ASTM E 127 -

type reference blocks. This system compares the responses of the blocks

being calibrated to the response of an interim standard reference block

using prescribed equipment and procedures.

9) Plans for a "loaner service" of well characterized blocks, to

be available to the ultrasonic community, are underway. This will be

formalized into a Measurement Assurance Program to assess the adequacy

of the entire measurement system.

109
5 . ACKNOWLEDGEMENTS

The following people have made helpful contributions to this program.

Their assistance is gratefully acknowledged.

Gary D. Boswell and Robert G. Elmer, Engineering Mechanics Section

NBS - laboratory assistance.

Martin Greenspan, Sound Section, Carl Tschiegg, and Frank Breckenridge,

Auditory Acoustics Section, NBS - consiiltatlon on equipment and transducers.

E. Clayton Teague and Fred Scire, Optics and Mlcrometrology Section,

NBS - surface finish measurements.

Ralph Veale, Dimensional Technology Section, NBS - hole diameter

measurements.

James A. Lechner, Statistical Engineering Section, NBS - statistical

support for calibration service.

Hyong, Jun Coi, guest worker. Micros tructure Characterization

Section, NBS - metallurgical laboratory assistance.

Carolyn Stull, Auditory Acoustics Section, NBS - manuscript preparation.

Sponsorship and financial assistance have been received from the

Air Force Materials Laboratory, National Aeronautics and Space Administration

(Lewis Research Center) , and the Array Materials and Mechanics Research

Center. These organizations were technically represented by Lee R. Gulley,

Jr., Robert L. Davies , and George Darcy, respectively. The work was

administered through the Air Force Materials Laboratory with Lee R. Gulley,

Jr. as project monitor.

110
6. REFERENCES

Anon. , Standard Recommended Practice for Fabricating and Checking

Aluminum Alloy Ultrasonic Standard Reference Blocks , ASTM

Designation E 127-64, 1974 Annual Book of ASTM Standards , Part 11

(Am Soc Test Mat, Philadelphia, 1974), p. 229.

Anon., Standard Recommended Practice for Fabrication and Control of

Steel Reference blocks Used in Ultrasonic Inspection, ASTM Designation

E 428-71, Ibid, p. 489.

Anon. , Standard Recommended Practice for Fabricating and Checking

Aluminum Alloy Ultrasonic Standard Reference Blocks, ASTM Designation

E 127-75 (available from Am Soc Test Mat, 1916 Race St., Philadelphia,

PA, 19103).

Gulley, Lee R. , NDE Horror Stories, in Proceedings of the Interdisciplinary

Workshop for Quantitative Flaw Definition, Report No. AFML-TR-7 4-238

,

for Air Force Materials Laboratory by Rockwell International Science

Center, Thousand Oaks, CA, January 1975.

Chwirut, D. J., Sushlnsky, G. F, , and Eitzen, D. G. , Procedures for the

Calibration of ASTM E 127-Type Ultrasonic Reference Blocks, Report

No. NBS TN 924, National Bureau of Standards, Washington, D. C ., September

1976.

Millman, I. , An Improved Facility for the Calibration of Aluminum

Alloy Ultrasonic Reference Blocks, Report No. AQD/NDT 1369, AQD Labs,

Harefield, Uxbridge, Middlesex, U.K.

Ill
[7J Kettering, D. D. , Ultrasonic Nondestrictive Testing (NDT)

Calibration Standards, Report No. ADR 14-04-75.2, Gruimnan Aerospace

Corporation, Bethpage, NY, July 1975.

[8] Eitzen, D. G. , et al. Improved Ultrasonic Standard Reference Blocks,

Report No. NBSIR 75-685, National Bureau of Standards, Washington,

D.C. , April 1975.

{9J Chaskelis, H. H. , Transducers - Fact and Fiction, Non-Destructive

Testing, December 1971, p 375.

[10] Reynolds, P. M. (editor). Proceedings of the Symposivim on The Future

of Ultrasonic Spectroscopy, sponsored by the British Non-Ferrous Metals

Research Assoc., London, England, Oct 14, 1970.

[11] Paton, N. E. , Ultrasonic Saii5)les Using Diffusion Bonding Techniques,

in Proceedings of the ARPA/AFML Review of Quantitative NDE, Report

No. AFML-TR-75-212 , for Air Force Material Laboratory, by Rockwell

International Science Center, Thousand Oaks, CA, January, 1976.

[12] Christenson, A. L. , Measurement of Stress by X-rays, Report No. SAE

TR-182 (as corrected by enata sheet dated March 11, 1964), Society

of Automotive Engineers, New York, NY, 1960.

[13] Gangulee, A., Separation of '^^~'^2 in X-ray Profiles, J.

Appl. Cryst. 3, 111 (1970).

[14J league, E. Clayton, Evaluation, Revision and Application of the NBS

Stylus/Computer System for the Measurement of Surface Roughness,

Report No. NBS TN 902, National Bureau of Standards, Washington,

D.C. , April 1976.

112
Appendix 1

Residual Stress Measurement, NBS Aluminum Block

RESIDJAL STRESS MEASUREMENTS

NBS AL. BLOCK, SURFACE S^i/l, METALLCGHAPH IC ALLY POLISHED

YOUNG'S MODULUS = 7.2E-H0 N/Mtg; 7.3E+03 KG/MMt2i 1 .04E+07 PD/IN»2

PCISSCN'S RATIO " .33

STRESS COMPONENT = -l .1 E+08 N/M!2; -I .2E+01 KG/MMI2; -1.7E*04 PD/IN!2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE J DEL 2TH = ( 1 .11 93 5 )* (S IN PSI ) 12 C-5. 74014E-2 ) ANGLE OF

INCLINATION 2-THETA SIN»2 DEL 2TH LSE FIT

0 1 55.405 .000 .000 -.057

IS 1 55.476 .067 .071 .018

30 1 55 .563 .250 .1 58 .222

45 155. 7ie .500 .313 .502

60 1 56.330 .750 .92 5 .782

PROBABLE ERROR OF LINEAR FIT = .101

STANDARD DEVIATION OF STRESS = 2 .5E*07 N/Mt2

RELATIVE STAND. DEV. OF STRESS = 21.3 PER CENT

RESIDUAL STRESS MEASUREMENTS

NBS AL. BLOCK, SURFACE S4/1, ETCHED 3 MIN, 10% NAOH, 60-65 DEGS C.

YOUNG'S MODULUS - 7.2E+10 N/Mt2J 7.3E*03 KG/MMtp; 1.04E*07 PD/IN.2

POISSCN'S RATIO « .33

STRESS C0MP0NENT = -4.3E>07 N/M!2; -4.4E*00 KG/MMf2; -6 .2E*03 PD/IN!2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE:

DEL 2TH » < .418597 )*CS1N PSI ) t8 C . 1 t 90 1 9 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 1 55.357 .000 .000 .119

15 1 55.497 .0 6 7 .140 .147

30 1 55.743 .2 50 .386 .224

45 155.737 .500 .380 .326

60 1 55.755 .750 .398 • 433

60 1 55.737 .750 .380 .433

raCBABLE ERROR OF LINEAR FIT .073

STANDARD DEVIATION OF STRESS » 1.5E+07 N/M»2

RELATIVE STAND. DEV. OF STRESS 35.1 PER CENT

A-1
RESIDU-^L STRESS MEASUREMENTS

MBS AL. BLOCK* SURFACE S5/2* METALLCGRAPH IC ALLY POLISHED

YOUNG'S MODULUS «- 7.2E + I0 N/M»2; 7.3E+03 KG/MMI2; 1.04E+07 PD/lNt2

POISSON'S RATIO « .33

STRESS C0KP0NENT«=-1 .2E*0fl N/Kf2; -1.2E-^0l KG/MMI2; -1.7E+04 PD/1NI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH «: ( I .141 78 )*(SIN PSI )»2 (-.038433 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 1 55.422 .000 .000 -.038

15 1 55.51

.067 .089 .038

30 1 55 .630 .2 50 .208 .247

45 1 55.778 .500 .356 .532

60 1 56.366 .750 .944 .81 8 PROBABLE ERROR OF LINEAR FIT = .0 89 1^

STANDARD DEVIATION OF STRESS »= 2.2E*07 N/M»2

RELATIVE STAND. DEV. OF STRESS «= I P. 6 PER CENT

RESIDUAL STRESS MEASUREMENTS

NBS AL. BLOCK, SURFACE S5/2> ETCHED 3 KIN, lOt NAOH, 60-65 DEGS C

YOUNG'S MODULUS » 7.2E*iO N/Mf2; 7.3E+03 KG/MMt2; 1.04E+07 PD/INf2

POISSON'S RATIO = .33

STRESS C0MP0NENT=-4 .7E*07 N/M!2; -4.8E+00 KG/MMI2; -6.9E+03 PD/IN12

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA S*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH - ( .462704 >*(SIN PSI ) t2 (-2 . 212I2E-2 ) ANGLE OF

INCLINATION 2-THETA SINf2 - DEL 2TH LSE FIT

0 I 55.400 .000 .000 -.022

15 1 55.507 .067 .107 .009

30 I 55.414 .2 50 .014 .094

30 I 55.410 .2 50 .010 .094

45 1 55.601 .500 .201 .209

60 1 55.776 .750 .376 .325

PROBABLE ERROR OF LINEAR FIT - .0 55

STANDARD DEVIATION OF STRESS - 1 .3E+07 N/M»2

RELATIVE STAND. DEV. OF STRESS 27.9 PER CENT
Appendix 2

Residual Stress Measurement on Rejected Steel Block
4 -re
RESIDUAL STRESS MEASUREMENTS

STEEL BLCX;K SURFACE SI* AS RECEIVED

YOUNG'S MODULUS = 2.1E-M1 N/Kt2; 2.1E+04 KG/MM»2; 3.00E*07 PD/INt2

PCISSCN'S RATIO .30

STRESS CCMP0NENT = -2 .2E-^08 N/KI2; -2.3E401 KG/MMI2; -3.2E*04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH «: < .739685 )*{SIN PSI ) '2 + ( 4. 69848E-2 )

ANGLE OF

INCLINAT ION 2-THETA S INt2 DEL 2TH LSE FIT

0 155.518 .000 .000 .047

15 1 55.625 .067 .107 .097

30 I 55.778 .2 50 .260 .232

45 1 55.991 .500 .473 .417

60 1 56.072 .750 • 554 .602

PROBABLE ERROR OF LINEAR FIT " .036

STANDARD DEVIATION CF STRESS = 2.6E+07 N/M t2 RELATIVE STAND. DEV. CF STRESS =11.6 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE SI* POLISHED METALLCGRAPH ICALLY THROUGH 600 GIRD SIC

YOUNG'S MODULUS - 2.1E*11 N/Mt2; 2.1E*04 KG/MMt2J 3.00E+07 PD/lNt2

PCISSCN'S RATIC « .30

STRESS CCMP0NENT=-4.1E*0P N/M!2i -4.1E*0l KG/MMt2; -5.9E>04 PD/IN12

THIS IS A COMPRESSIVE STRESS IN THE PLANE CF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH ' ( 1 .33784 )*(S IN PS n '2 ( 3. 40231E-2 )

ANGLE CF

LSE FIT INCLINATION 2-THETA S INt2 DEL 2TH

0 155.322 .000 .000 .034

0 1 55.302 .000 -.020 .034

15 1 55.503 .067 .1 81 .124

15 1 55.4P6 .067 .1 64 .124

30 155.738 .2 50 .416 .368

30 155.704 .2 50 .382 .368

45 155.961 .500 .639 .703

45 155.964 .500 .642 .703

60 156.378 .750 1 .056 1 .037

60 156.395 .7 50 I .073 . 1.037

PROBABLE ERROR CF LINEAR FIT - .0 34

STANDARD DEVIATION CF STRESS - 1.8E+07 N/M«2

RELATIVE STAND. DEV. CF STRESS « 4.3 PER CENT

B-1
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE SI* METALLCGRAPHICALLY POLISHED

YOUNG'S MODULUS - 2.1E>U N/M»2; 2.1E+04 KG/MM»2; 3.00E+07 PD/IN»2

PCISSON'S RATIO » .30

STRESS C0MP0NENT = -2 .'SE-'-OP N/MI2; -2.4E*01 KG/MMI2; -3.<iE>04 PD/lNf2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE:

DEL 2TH " ( .78451 )*(SIN PS I ) «2 < 1 .29358E-2 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155.575 .000 .000 .013

15 155.642 .067 .067 .065

30 155.800 .250 .225 .209

45 155.983 .500 .408 .405

60 156.169 .750 .594 .601

PROBABLE ERROR OF LINEAR FIT » .009

STANDARD DEVIATION OF STRESS « 6.1E+06 N/M»2

RELATIVE STAND. DEV. OF STRESS = 2.6 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE Sl> ETCHED 5X NITAL TO REMOVE .001 IN.

YOUNG'S MODULUS » 2.1E+11 N/M»2; 2.1E+04 KG/MM»2i 3.00E+07 PD/INt2

POISSON'S RATIO « .30

STRESS C0MP0NENT--7.7E+07 N/M!2i -7.9E+00 KG/MMI2; -l.lE+04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO, LSE STRAIGHT LINEt

DEL 2TH ( .258463 )*<SIN PS I ) »2 ( 3«11982E-2 > ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155.764 .000 .000 .031

15 155.823 .067 .059 • .049

30 155.880 .250 .116 .096

45 155.949 .500 .185 .160

60 155.965 .750 .201 .225

PROBABLE ERROR OF LINEAR FIT • .020

STANDARD DEVIATION OF STRESS 1 .4E-K)7 N/M»2

RELATIVE STAND. DEV. OF STRESS « 18.5 PER CENT

B-2
RESIDUAL STRESS MEASUREMENTS

STEEL BLCCK SURFACE Sl# ELECTRCPOLISHED TC REMOVED .002 IN.

YOUNG'S MODULUS = 2.1E + 1I N/Mtg; 2.1E+04 KG/MMt2; 3.0OE+07 PD/IN»2

POISSCN'S RATIO = .30

STRESS CCMPCNENT=-3 .5E+07 N/M»2; -3.5E*00 KG/MM!2; -5.0E+03 PD/1NI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TC LSE STRAIGHT LINEt

DEL 2TH = ( .1 16285 >*(S1N PSI)t2 * C 3.74e38E-2 ) ANGLE OF

. I NAT I ON 2-THETA S INt2 DEL 2TH LSE FIT

0 1 55 .767 .000 .000 .037

0 1 55.767 .000 .000 .037

15 1 55.81

9

.067 .052 .045

30 1 55.871 .2 50 .104 .067

30 1 55.866 .2 50 .099 .067

45 1 55.903 .500 .136 .096

45 1 55.889 .500 .122 .096

60 1 55.854 .750 .087 .125

60 1 55 .861 .750 .0 94 .125

PROBABLE ERROR OF LINEAR FIT = .026

STANDARD DEVIATION OF STRESS = 1 .3E+07 N/Mt2

RELATIVE STAND. DEV. OF STRESS = 38.6 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLCCK SURFACE S2/1 * MACHINED

YOUNG'S MODULUS = 2.1E*11 N/Mt2; 2.1E+04 KG/MM»2J 3 .OOE+07 PD/INt2

POISSCN'S RATIO = .30

STRESS C0MP0NENT=-3 .5E*08 N/MI2; -3.6E+01 KG/MMf2; -5.1E*04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH » ( 1 .17328 >*<SIN PS I ) »2 <-3.10448E-3 )

ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155e489 .000 .000 -.003

15 155.564 .067 .075 .075

30 155.783 .250 .294 .290

45 156.057 .500 .568 -584

60 156.375 .750 .886 .877

PROBABLE ERROR OF LINEAR FIT .00 7

STANDARD DEVIATION OF STRESS - 5.2E+06 N/Mt2

RELATIVE STAND. DEV. OF STRESS 1.5 PER CENT

B-3
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S2/2, MACHINED

YOUNG'S MODULUS « 2.1E*11 N/Mt2; 2.1E-»04 KG/MM»2; 3.00E*07 PD/IN»2

PCISSON'S RATIO » .30

STRESS C0MPCNENT = -1 .6E*08 N/MJ2; -1.6E+01 KG/MM!2; -2 .3E*04 PD/INJ2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH = ( .533885 )*(SIN PSI)»2 (-4.31723E-3 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155.654 .000 .000 -.004

15 155. 6PP .067 .034 .031

30 155.767 .850 .1 13 .129

45 155.929 .500 .275 .263

60 156.047 .750 .393 .396

PROBABLE ERROR OF LINEAR FIT « .00 8

STANDARD DEVIATION OF STRESS = 5.9E+06 N/MI2

RELATIVE STAND. DEV. OF STRESS » 3.7 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S2/2# METALLOGRAPHICALLY POLISHED

YOUNG'S MODULUS = 2.1E + 11 N/M»2; 2.1E+04 KG/MKt2; 3.00E+07 PD/IN»2

PCISSON'S RATIO = .30

STRESS CCMJ'0NENT = -3 .1E+0 8 N/Mf2; -3.2E+01 KG/MMf2; -4.5E+04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2«THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH ' ( 1 .02396 )*(SIN PSn»2 ( P.6955PE-3 > ANGLE OF

INCLINATION 2-THETA SINf2 DEL 2TH LSE FIT

0 155.477 .000 .000 .009

15 155.573 .067 .096 .077

30 155.735 .250 .258 .265

45 155.986 .500 .509 .521

60 156.262 .750 .785 .777

PROBABLE ERROR OF LINEAR FIT " .010

STANDARD DEVIATION OF STRESS = 7.3E+06 N/Mt2

RELATIVE STAND. DEV. OF STRESS 2.4 PER CENT

B-A
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S2/2* ETCHED 5X NITAL TC REMOVE .001 IN.

YOUNG'S MODULUS = 2.1E+11 N/Mts; 2.1E+04 KG/MMt2i 3.00E+07 PD/IN»2

POISSCN'S RATIO = .30

STRESS CCKPONENT= 8.0E+06 N/M!2i 8.1E-01 KG/MMf2; 1 .2E+03 PD/INI2

THIS IS A TENSILE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TC LSE STRAIGHT LINEt

DEL 2TH = (-2.68746E-2 )*(SIN PS I) '2 < 2.76229E-2 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155.890 .000 .000 .028

15 155.937 .067 .047 .026

30 155.926 .250 .036 .021

45 155.899 .500 .009 .014

60 155.894 .750 .004 .007

PROBABLE ERROR OF LINEAR FIT = .015

STANDARD DEVIATION OF STRESS = l.lE-»-07 N/M»S

RELATIVE STAND. DEV. OF STRESS =132.5 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S2/2* ELECTROPCLISHED TC REMOVED .002 IN.

YOUNG'S MODULUS = 2.1E + 11 N/M»2; 2.1E+04 KG/MMt2J 3.00E+07 PD/IN»2

POISSCN'S RATIO = .30

STRESS CCMP0NENT=-3 .1 E+06 N/M!2; -3.2E-01 KG/MMI2; -4.5E+02 PD/INt2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TC LSE STRAIGHT LINE!

DEL 2TH ( 1.04798E-2 >*(SIN PSI)t2 ( 4.04165E-2 ) ANGLE OF

INCLINATION 2-THETA SlNt2 DEL 2TH LSE FIT

0 1 55 .842 .000 .000 .040

0 1 55.843 .000 .001 .040

15 1 55.889 .067 .04 7 .041

15 155.886 .067 •044 .041

30 1 55.926 .2 50 .0 84 .043

30 1 55.91

9

.250 .077' .043

45 1 55.916 .500 .074 .046

45 155.925 .500 .0 83 .046

60 1 55.859 .750 .017 .048

60 1 55.852 .750 .010 .048

PRCBABLE ERROR OF LINEAR FIT .025

STANDARD DEVIATION OF STRESS 1 .2E*07 N/M»2

RELATIVE STAND . DEV. OF STRESS 396.0 PER CENT

B-5
RESIDUAL STHESS MEASUREMENTS

STEEL BLOCK SURFACE S3/2, METALLCGRAPHICALLY POLISHED

YOUNG'S MODULUS « 8.1E*ll N/M»2; 2.1E*04 KG/MMt2; 3.0OE*07 PD/IN»2

PCISSCN'S RATIO « .30

STRESS CCKP0NENT=-2 .6E*0e N/M!2; -2.6E+01 KG/MM!2J -3.PE+04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE!

DEL 2TH «= ( .P69P39 )*(SIN PS I) «2 ( 1.16137E-2 )

,1 NAT ION 2-THETA SINtg DEL 2TH LSE FIT

0 1 55.471 .000 .000 .012

IS 1 55.554 •067 .083 .069

30 1 55.695 .2 50 .224 .227

30 1 55.700 .2 50 .229 .227

45 1 55.910 .500 .439 .442

60 1 56.128 .7 50 .657 .656

PROBABLE ERROR OF LINEAR FIT - .006

STANDARD DEVIATION OF STRESS » 4.5E+06 N/M»2

RELATIVE STAND. DEV. OF STRESS •= 1 .7 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S3/2» ETCHED 5X NITAL

YOUNG'S MODULUS = 2.1E+11 N/M»2; 2.1E+04 KG/MMt2; 3.00E+07 PD/INt2

PCISSON'S RATIO « .30 i

STRESS C0MPCNENT=-2 .6E*08 N/MI2; -2.7E*0I KG/MMI2; -3.8E*04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE!

DEL 2TH «: ( .8752 )^<SIN PSI)t2 ( 3.93152E -2 ) ANGLE OF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 I 55.467 .000 .000 .039

I 5 155.569 .067 .102 .098

30 1 55.778 .2 50 .31 1 .258

45 155.945 .500 .478 .477

60 156.144 .750 .677 .696

PROBABLE ERROR OF LINEAR FIT .027

STANDARD DEVIATION OF STRESS 1 .9E*07 N/M»2

RELATIVE STAND. DEV. OF STRESS - 7.3 PER CENT

B-6
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE SA/lt MACHINED

YOUNG'S MODULUS = 2.1E+11 N/Mt2; 2.1E+04 KG/MMt2J 3.00E*07 PD/INt2

PCISSCN'S RATIO = .30

STRESS CCMPCNENT = -3 .eE*08 N/MI2J -3.8E*01 KG/KMI2; -5 .4E+04 PD/IN!2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEl

DEL 2TH = ( 1 .23P84 )*(SIN PSI ) t2 ( 6. 37494E-2 ) ANGLE OF

INCLINATION 2-THETA SINI2 DEL 2TH LSE FIT

0 1 55.398 .000 .000 .064

1 5 1 55.580 .067 .182 .147

30 1 55.798 .2 50 .400 .3 73

45 1 56.123 .500 .72 5 .683

60 I 56.351 .750 .953 .993

PROBABLE ERROR OF LINEAR FIT - .038

STANDARD DEVIATION OF STRESS = 2.7E*07 N/M»2

RELATIVE STAND. DEV. OF STRESS - 7.2 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S4/1 * METALLOGRAPHICALLY POLISHED

YOUNG'S MODULUS 2.1E*11 N/M»2J 2.1E+04 KG/MM»2; 3.00E+07 PD/IN»2

PCISSON'S RATIO » .30

STRESS C0MP0NENT--2 .9E+0 8 N/MI2; -2.9E*01 KG/MMI2; -4.2E*04 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE!

DEL 2TH » < .9541 74 >*(S1N PSI)»2 < 5. 37637E-2 ) ANGLE OF

IhKLINATION 2-THETA SIN»2 DEL 2TH LSE FIT

0 155 .440 .000 .000 .0 54

15 155 .592 .067 .152 .11 8

30 155 .774 .250 • 334 .292

45 155 .955 .500 .51 5 .531

60 156 .203 .750 .763 .769

PROBABLE ERROR OF LINEAR FIT - .0 30

STANDARD DEVIATION OF STRESS 2 .2E+07 N/Mt2

RELATIVE STAND. DEV. OF STRESS » 7.6 PER CENT

B-7
RESIDUAL STRESS MEASUREMENTS

STEEL BLCX:K SURFACE S4/1, ELECTRCPCLISHED TC REMOVED .001 IN.

YOUNG'S MODULUS = 2.1E*11 N/Mt2J 2.1E*04 KG/MM»2J 3.00E*07 PD/INt2

POISSCN'S RATIO = .30

STRESS COMPONENT" 2.8E*07 N/MI2j 2 .9E*00 KG/MM»2; 4.1E*03 PD/IN12

THIS IS A TENSILE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TC LSE STRAIGHT LINEt

DEL 2TH = (-9.47678E -2 )*(SIN PSI)«2 ( 4.97008E-2

ANGLE OF

INCLINATI ON 2-THETA SIN»2 DEL 2TH LSE FIT

0 155. 8M .000 .000 .0 50

15 155.863 .067 .049 .043

30 1 55.877 .2 50 .063 .026

45 1 55.876 .500 .062 .002

60 1 55.740 .750 - .074 -.021

PROBABLE ERROR OF LINEAR FIT « .039

STANDARD DEVIATION OF STRESS = 2.8E*07 N/M»2

RELATIVE STAND. DEV. OF STRESS « 98.7 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S4/1* ELECTROPOLISHED TO REMOVED .0018 IN.

YOUNG'S MODULUS « 2.1E*11 N/M«2; 2.1E+04 KG/MM»2; 3.00E+07 PD/IN»2

POISSON'S RATIO » .30

STRESS COMPONENT" 1 .4E+07 N/MI2; 1 .4E+00 KG/MMf2; 2.0E+03 PD/IN!2

THIS IS A TENSILE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH » (-4.75223E-2 )*(SIN PSI)«2 ( 1 .50938E-2 ) ANGLE OF

INCLINATI ON 2-THETA SIN»2 DEL 2TH LSE FIT

0 1 55.945 .000 .000 .015

0 1 55.946 .000 .001 .015

15 I 55.961 .067 .016 .012

15 155.962 .0 6 7 .017 .012

30 1 55.960 .250 .015 .003

30 155.957 .2 50 .012 .003

45 1 55.947 .500 .002 -.009

45 1 55.947 .500 .002 -.009

60 1 55.950 .750 .005 -.021

60 1 55.877 .750 -.068 -.021

PROBABLE ERROR OF LINEAR FIT .015

STANDARD DEVIATION OF STRESS 7.3E+06 N/Mt2

RELATIVE STAND . DEV. OF STRESS - 52.2 PER CENT

B-8
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S5/2* METALLCGRAPHIC ALLY POLISHED

YOUNG'S MODULUS = 2.1E*!! N/M»2i 2.1E+04 KG/MM»2; 3.00E+07 PD/IN»2

PCISSON'S RATIO = .30

STRESS C0MPCNENT = -2.1E*0 8 N/MI2i -2.1E+01 KG/MM!2i -3.0E+04 PD/lNf2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINE!

DEL 2TH = ( .687597 )*{SIN PS I ) t2 C 5.10967E-3 ) ANGLE OF

INCLINATION 2-THETA SINtg DEL 2TH LSE FIT

0 155.574 .000 .000 .005

15 155.641 .067 .067 .051

30 155.756 .250 . 1 P2 .177

45 155.885 .500 .311 .349

60 156.117 .750 .543 .521

PROBABLE ERROR OF LINEAR FIT » .018

STANDARD DEVIATION OF STRESS = 1 .3E+07 N/M»2

RELATIVE STAND. DEV. OF STRESS = 6.4 PER CENT

RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S5/2* ELECTR OP CL I SHED TO REMOVED .001 IN.

YOUNG'S MODULUS = 2.1E+11 N/Mt2; 2.1E*04 KG/MM»2; 3.00E+07 PD/INt2

PCISSON'S RATIO = .30

STRESS CCMP0NENT=-1 .3E*07 N/M!2; -1.3E+00 KG/MMI2; -l.9E*03 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE "CF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH » ( 4.29908E-2 )*CSIN PS I > »2 < .040327 ) ANGLE CF

INCLINATION 2-THETA SINt2 DEL 2TH LSE FIT

0 155.820 .000 .000 .040

15 155.876 .067 .056 .043

30 1 55 . 90 8 . 2 50 .0 8 8 .051

45 155.894 .500 .074 .062

60 155.871 .750 .051 .073

PROBABLE ERROR OF LINEAR FIT " .024

STANDARD DEVIATION CF STRESS 1.7E+07 N/M»2

RELATIVE STAND. DEV. CF STRESS -132.3 PER CENT

B-9
RESIDUAL STRESS MEASUREMENTS

STEEL BLOCK SURFACE S5/2> ELECTROPCLISHED TC REMOVED .0018 IN.

YOUNG'S MODULUS = 2.1E-»-ll N/Mt2; 2.1E+04 KG/MM»2; 3.00E+07 PD/INT2

POISSON'S RATIO = .30

STRESS CCMP0NENT=-5 .7E+07 N/M!2; -5.8E+00 KG/MM!2; -8.3E+03 PD/INI2

THIS IS A COMPRESSIVE STRESS IN THE PLANE OF THE SURFACE.

DELTA 2*THETA FITTED TO LSE STRAIGHT LINEt

DEL 2TH = ( .1921 53 )*(SIN PS I ) »2 ( 5.2680AE-2 ) ANGLE OF

INCLINATION 2-THETA

1 55 .793

1 55.798

1 55.859

1 55.900

1 55.931

155.930

1 55 .971

1 55.952

I 55.960

I 55 .965

SINt2

.000

.000

.067

.067

.250

.250

.500

.500

.750

.750

DEL 2TH LSE FIT

0

0

1 5

1 5

30

30

45

AS

60

60

.000

.005

.066

.107

.138

.137

.1 78

.1 59

.167

• 1 72

.053

.053

.066

.066

.101

.101

.149

.149

.1 97

.197

PROBABLE ERROR OF LINEAR FIT .026

STANDARD DEVIATION OF STRESS

RELATIVE STAND. DEV. OF STRESS

1 .3E-«'07 N/Kt2

22.8 PER CENT

USCOMMNBS-DC

B-10
NBS-lUA (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR Rl-l^ORT NO.

NBSIR 76-984

2. Gov't Acces.sion No.

4. TITLE AND SUBTITLF

IMPROVED ULTRASONIC STANDARD REFERENCE BLOCKS

3. Recipient's Accession No.

5. Publication Date November 1976

6. Performing Organization ( ode

7. AUTHOR(S) G. F. Sushlnsky, D. G. Eitzen, D. J. Chwlrut,

C. J. Bechtoldt. and A. W. Ruff

8. Performing Organ. Report No. NBSIR 76-984

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 2005443

11. Contract/Grant No. DO F33615-74-M6752

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Air Force Materials Laboratory, WPAFB, Ohio 45433

National Aeronautics and Space Administration

Cleveland, OEiio 44135

Army Materials & Mechanics Research Ctr. Watertown, Mass. 02172

13. Type of Report & Period

Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

A program to improve the quality, reproducibility and reliability of nondestructive testing through the development of an improved ASTM-type ultrasonic reference

standards system is described. Reference blocks of aluminum, steel, and titanium

alloys are considered. Equipment representing the state-of-the-art in laboratory and

field ultrasonic equipment was obtained and evaluated. RF and specral data on twentytwo sets of ultrasonic reference blocks were taken as part of a task to quantify the

variability in response from nominally identical blocks. Techniques for residual

stress, preferred orientation, and microstrue tural measurements were refined and

applied to reference blocks rejected by manufacturers during fabrication in order to

evaluate the effect of metallurgical condition on block response. The effects of

certain dimensional variables on block response were studied and new fabrication

techniques considered. A study of the effects of measurement system variables on block response was carried out. A calibration service for ASTM E127-type reference

blocks has been established and the development of a loaner service for calibration

blocks is underway.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Aluminum ultrasonic Standards; ASTM-tjrpe reference standards;

calibration; fabrication variables; immersion testing; Interim reference standard;

longitudinal waves; metallurgical variables; nondestructive evaluation; pulse echo;

steel ultrasonic standards; tttanixnn ultrasonic standards; ultrasonics.

18. AVAILABILITY Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

1 For Official Distribution. Do Not Release to NTIS

UNCL ASSIFIED

128

1

' Order From Sup. of Doc, U.S. Government Printing Office Washineton. D.C. 20402. SD Cat. No. C13

20. SECURITY CLASS

(THIS PAGE)

22. Price

[JiJ Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED $6.00

USCOMM-DC 29042-P74