December 2011 

NASA/TM-2011-217318 

NESC-RP-10-00680 

 

Space Transportation System (STS)-133/ 

External Tank (ET)-137 Intertank (IT) 

Stringer Cracking Issue and Repair Assessment: 

Proximate Cause Determination and Material 

Characterization Study 

Robert S. Piascik/NESC 

Langley Research Center, Hampton, Virginia 
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December 2011 

NASA/TM-2011-217318 

NESC-RP-10-00680 

 

Space Transportation System (STS)-133/ 

External Tank (ET)-137 Intertank (IT) 

Stringer Cracking Issue and Repair Assessment: 

Proximate Cause Determination and Material 

Characterization Study 

Robert S. Piascik/NESC 

Langley Research Center, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

The use of trademarks or names of manufacturers in the report is for accurate reporting and does not 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration. 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Space Transportation System (STS)-133/External 

Tank (ET)-137 Intertank (IT) Stringer Cracking 

Issue and Repair Assessment: Proximate Cause 

Determination and Material Characterization Study

September 29, 2011
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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2 of 152

NESC Request No.: 10-00680 (Materials)

Approval and Document Revision History 

NOTE: This document was approved at the September 29, 2011, NRB. This document was 

submitted to the NESC Director on November 17, 2011, for configuration control.

Approved: Original Signature on File 11/17/11

NESC Director Date

Version Description of Revision Office of Primary 

Responsibility

Effective Date

1.0 Initial Release Dr. Robert S. Piascik, 

NASA Technical Fellow 

for Materials, LaRC

9/29/11
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Material Characterization Study

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Table of Contents

1.0 Notification and Authorization.....................................................................................................5

2.0 Signature Page................................................................................................................................6

3.0 Team List........................................................................................................................................7

3.1 Acknowledgements..........................................................................................................................7

4.0 Executive Summary.......................................................................................................................8

5.0 Background ....................................................................................................................................9

5.0.1 External Tank Stringer Cracking ..............................................................................9

5.0.2 Stringer Material and Fabrication ...........................................................................11

5.0.3 Fracture Toughness Testing and Initial Microstructural Examinations..................13

5.0.4 Initial Assessment ...................................................................................................14

5.1 Investigation Objectives.....................................................................................................15

5.2 Materials Examined............................................................................................................16

5.3 Mechanical Property Characterization Tests......................................................................17

5.3.1 Tensile Tests ...........................................................................................................18

5.3.2 Shear and Combined Tensile/Shear Tests...............................................................20

5.3.3 3-Point Bend Tests..................................................................................................22

5.4 Fracture Toughness Tests...................................................................................................25

5.4.1 Thermal Aging Study..............................................................................................26

5.4.2 Thermal Exposure Study.........................................................................................28

5.5 Microstructure Characterization.........................................................................................29

5.5.1 Transmission Electron Microscopy (TEM) Analysis..............................................29

5.5.2 Electron Backscatter Diffraction EBSD Analysis...................................................31

6.0 Findings.........................................................................................................................................35

7.0 NESC Recommendation..............................................................................................................36

8.0 Alternate Viewpoints...................................................................................................................36

9.0 Other Deliverables.......................................................................................................................36

10.0 Lessons Learned...........................................................................................................................36

11.0 Definition of Terms......................................................................................................................36

12.0 Acronyms List ..............................................................................................................................37

13.0 References.....................................................................................................................................38

14.0 Appendices....................................................................................................................................38

List of Figures

Figure 5.0-1. Location of the ET IT Cracked Foam.................................................................................9

Figure 5.0-2. Panel 2, S7 Cracked Stringer (LO2 flange end) after IT Removal ....................................10

Figure 5.0-3. Cracked Stringers Locations Relative to the IT Circumference .......................................10

Figure 5.0-4. Lot-to-Lot and Within-Lot Variation in Yield Stress and Ultimate Stress for 2090 Al-Li 

Lots Aged to the T8 Condition and Tested in the Long-Transverse Orientation..............12
NASA Engineering and Safety Center 

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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Figure 5.0-5. Schematic of IT Stringer Forming Steps ..........................................................................13

(Note: “L” indicates the longitudinal or rolling direction)................................................13

Figure 5.0-6. Example of Grain Boundary Precipitation in Lot 620853 and a Control Lot...................14

Figure 5.0-7. Schematic of Crack Location and Nominal Plane of Propagation....................................15

Figure 5.3-1. Tensile Test Results for Three Loading Orientations of the L2 Material (Lot 400768)...19

Figure 5.3-2. Summary of Tensile Test Results for All Lots (Long-transverse Orientation).................20

Figure 5.3-3. Combined Tensile/Shear Data for the L1 Material (Lot 400751).....................................21

Figure 5.3-4. 3-point Bend Fixture.........................................................................................................23

Figure 5.3-5. Strain to Failure from 3-point Bend Tests ........................................................................23

Figure 5.3-6. Measured Displacement and Load from 3-point Bend Tests for Different Spans............24

Figure 5.4-1. Fracture Test Results from Suspect and Control Lot Materials Following Nominal 

Peak Aging........................................................................................................................25

Figure 5.4-2. Fracture Test Results from the Thermal Aging Study ......................................................27

Figure 5.4-3. Fracture Test Results for the Thermal Exposure Study ....................................................29

Figure 5.5-1. Example of a High Angle Grain Boundary ’ PFZ ..........................................................30

Figure 5.5-2. Schematic of GOS Calculation .........................................................................................32

Figure 5.5-3. Schematic Describing the Location of the EBSD Analysis for the Stringer Materials.....33

Figure 5.5-4. GOS Values for a Through-the-Thickness Strip of Control Coil Lot 400751 in the 

as-received (T3) and Peak-Aged Condition......................................................................34

Figure 5.5-5. GOS Values for a Through-the-Thickness Strips of Control Coil Lots 400768 and 

400766 in the Peak-Aged Condition.................................................................................34

Figure 5.5-6. GOS Values for a Through-the-Thickness Strip of Stringer Lot 620853 in the 

as-received Peak-Aged, Cold-Formed + Hot-Formed, and Cold-Formed Conditions .....35

List of Tables

Table 5.2-1. Description of Materials Examined ..................................................................................17

Table 5.4-1. Summary of Fracture Thermal Aging Study.....................................................................27

Table 5.4-2. Summary of Fracture Exposure Aging Study...................................................................28

Table 5.5-1. Summary of TEM Matrix T1 and ’ Precipitate Measurements.......................................31

Appendices

Appendix A. Tensile Test Results..........................................................................................................39

Appendix B. Shear Test Results.............................................................................................................58

Appendix C. 3-Point Bend Test Results.................................................................................................65

Appendix D. Fracture Test Results ........................................................................................................90

Appendix E. Fractographic Photographs.............................................................................................146
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NESC Request No.: 10-00680 (Materials)

1.0 Notification and Authorization 

The NASA Engineering and Safety Center (NESC) Director requested the NESC team to 

augment the Space Shuttle Program (SSP)-led team with appropriate technical subject matter 

expertise, facility and test equipment, and other resources to address the observed intertank (IT) 

foam crack in External Tank (ET)-137. This support ranged from inline support to independent 

analyses, testing, and inspections. 

As part of the multi-discipline investigation, Dr. Robert S. Piascik, the NASA Technical Fellow 

for Materials, requested a detailed metallurgical and mechanical property characterization of the 

aluminum-lithium (Al-Li) 2090-T83 material used in the IT stringer fabrication.

An out-of-board activity was approved on November 9, 2010. An assessment plan was waived 

for this activity due to the dynamic nature of the developing investigation. 

The primary stakeholders for this assessment are the SSP Manager, the NASA Chief Engineer, 

and the NASA Chief of Safety and Mission Assurance.
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Material Characterization Study

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2.0 Signature Page

Submitted by:

Original Signature on File – 12/7/11

Dr. Robert S. Piascik Date

The signatory declares the findings and observations compiled in the report are factually based 

from data extracted from Program/Project documents, contractor reports, and open literature, 

and/or generated from independently conducted tests, analysis, and inspections.
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Assessment: Proximate Cause Determination and 

Material Characterization Study

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3.0 Team List

Name Discipline Organization

Core Team

Robert Piascik NESC Lead LaRC

David Dawicke Fracture Mechanics AS&M, Inc.

William Johnston Experimental Mechanics Lockheed Martin

Laura Leybold MTSO Program Analyst LaRC

Greg Shanks Fracture Testing LaRC

Jim Baughman SEM Analysis Lockheed Martin

Harold “Clay” Claytor Materials Technician Lockheed Martin

Stewart Walker Tensile and Shear Testing Lockheed Martin

Scott Willard SEM Analysis Lockheed Martin

Roy Crooks Materials Analysis Black Laboratories, LLC

Administrative Support

Terri Derby Project Coordinator LaRC/ATK

Erin Moran Technical Writer LaRC/ATK

3.1 Acknowledgements

The Langley Research Center (LaRC) Metals Application Technology Branch (Engineering 

Directorate) provided outstanding support for this investigation by providing rapid turnaround 

time of machined specimen and components, accurate handling and labeling of specimens, and 

the resourcefulness of extracting the specimens from the stringer material. In particular, Johnnie 

West and George West provided exceptional support to this investigation.
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Material Characterization Study

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4.0 Executive Summary

Several cracks were detected in stringers located beneath the foam on the External Tank (ET) 

following the launch scrub of Space Transportation System (STS)-133 on November 5, 2010. 

The stringer material was aluminum-lithium (AL-Li) 2090-T83 fabricated from sheets that were 

nominally 0.064 inches thick. The mechanical properties of the stringer material were known to 

vary between different material lots, with the stringers from ET-137 (predominately lots 620853 

and 620854) having the highest yield and ultimate stresses. Subsequent testing determined that 

these same lots also had the lowest fracture toughness properties. 

The objective of this investigation was to develop a database of test results to provide validation 

for structural analysis models, independently confirm test results obtained from other 

investigators, and determine the proximate cause of the anomalous low fracture toughness 

observed in stringer lots 620853 and 620854. The investigation revealed that the proximate 

cause of the low fracture toughness was a microstructure evolution process, termed recovery,

which occurred prior to stringer processing. Recovery in the two affected lots resulted in 

material with higher yield and ultimate stresses and lower fracture toughness.
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Assessment: Proximate Cause Determination and 

Material Characterization Study

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5.0 Background

5.0.1 External Tank Stringer Cracking

Following the launch scrub of STS-133 on November 5, 2010, a foam crack was observed on the 

ET adjacent to the IT-to-liquid oxygen (LO2) tank flange (Figure 5.0-1). Subsequent imagery 

analysis determined the foam crack occurred during the ET propellant fill when the LO2 level 

was at this location. Non-destructive evaluation and foam removal revealed axial cracking in 

five Al-Li 2090-T83 stringers (Figure 5.0-2). Two cracked stringers, S6 and S7, were on 

Panel 2, and three cracked stringers, S6, S7, and S11, were on Panel 6 (Figure 5.0-3). The cracks 

were in the stringer “foot” near the radius transition. The crack lengths ranged from 

approximately 4 to 9 inches, with the longest crack allowing sufficient radial displacement 

during the cryogenic propellant fill to exceed the foam tensile strength.

Figure 5.0-1. Location of the ET IT Cracked Foam [ref. 1]

Foam Crack

Foam Crack
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Figure 5.0-2. Panel 2, S7 Cracked Stringer (LO2 flange end) after IT Removal

Figure 5.0-3. Cracked Stringers Locations Relative to the IT Circumference [ref. 2]

~5 inches

Location of

Cracked

stringers
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Stringer fractographic examination generated the following observations [ref. 3]:

 Crack growth was along the rolling direction (axial). 

 Multiple thumbnail cracks nucleated on the stringer bottom surface, away from the end of 

the stringer, and propagated through the thickness.

 No indications of pre-existing defects at the region of crack nucleation or along the crack 

path.

 The crack path relative to the fastener clamping and IT construction suggests a complex 

stress state consistent with the expected mixture of bending and shear stresses during 

cryogenic tanking.

5.0.2 Stringer Material and Fabrication

The 2090 Al-Li alloy used to manufacture the stringers was obtained in sheet (coil) T3 product 

form. Each coil was identified by a unique lot number. The material exhibited a nominal 

thickness of about 0.064 inches and a width of about 8.5 inches. Prior to incoming receipt lot 

acceptance, tensile coupons were extracted from each lot and aged using the nominal peak aging 

process (T8 condition of 25 hours at 325°F) and tensile tests were conducted to certify that the 

yield stress, ultimate stress, and elongation minimums could be achieved after peak aging. A 

plot of lot acceptance test data is shown in Figure 5.0-4. The plot shows the lot-to-lot and 

within-lot tensile property variation. Note that the yield and ultimate stress data for the lots used 

to fabricate most of the ET-137 stringers (lots 620853 and 620854) are greater than the measured 

values for the other lots. 
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Figure 5.0-4. Lot-to-Lot and Within-Lot Variation in Yield Stress and Ultimate Stress for 2090 Al-Li 

Lots Aged to the T8 Condition and Tested in the Long-Transverse Orientation [ref. 3]

Using the Al-Li 2090-T3 coil material, the stringers were manufactured in the 3-step process 

illustrated in Figure 5.0-5. The coil material is first cold-formed to obtain the stringer general 

shape and length of approximately 20 feet. Hot forming (i.e., exposure to temperatures less than 

325°F for less than 10 minutes) was performed to obtain the final stringer shape. This hot 

forming step included bending the stringer ends to conform to the IT upper LO2 and lower liquid 

hydrogen flanges. The stringers were then peak aged at 325°F for 25 hours to obtain the 

desired -T83 temper. The nominal stringer final thickness varied from 0.058 to 0.064 inches. 

The stringers (total of 108 stringers per IT) are riveted to 6 of the 8 panels that are assembled 

into the completed IT (2 of the panels are integrally machined). 

65

70

75

80

85

90

Lot Number

ET-137

Stringers

Stress

(ksi)

Ultimate Min & Max 

Yield Min & Max 
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Figure 5.0-5. Schematic of IT Stringer Forming Steps

(Note: “L” indicates the longitudinal or rolling direction)

5.0.3 Fracture Toughness Testing and Initial Microstructural Examinations

Initial fracture toughness testing of specimens extracted from the ET-137 cracked stringers 

showed that suspect lots 620853 and 620854 exhibited brittle behavior in the form of low 

toughness and little or no stable crack growth. In addition, microstructural examinations 

revealed that the amount of grain and subgrain boundary precipitation was abnormally high in 

the suspect lots when compared to that observed in the control lots, as shown in Figure 5.0-6. 

The materials shown in the micrographs of Figure 5.0-6 were in the -T83 temper following cold 

forming and hot forming. 

Excessive grain boundary precipitation suggested that off-nominal thermo-mechanical 

processing (high temperature and/or excessive time at temperature) resulted in poor fracture 

toughness without substantial influence on tensile properties. Subtle changes in aging 

temperature or time, temperature excursions during the hot forming process, and/or thermal 

excursions prior to delivery of the coil could account for the anomalous boundary precipitation.

Based on these observations, a test plan was created to understand the effect of process time and 

temperature on microstructure and fracture properties.

Coil - T3

(aging studies)

L

L

T3 + Cold Formed

(aging studies)

T3 + Cold Formed

+ Hot Formed

(aging studies)

T3 + Cold Formed

+ Hot Formed

+ Peak Aged (325 F)
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Material Characterization Study

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Figure 5.0-6. Example of Grain Boundary Precipitation in Lot 620853 and a Control Lot [ref. 3]

5.0.4 Initial Assessment

The failure analysis of the ET-137 cracked stringers indicated that the cracks initiated on the side 

of the stringer flange that mated with the IT skin, as illustrated in Figure 5.0-7. This region is 

subjected to a complex combination of tensile and bending loading due to the installation 

process, material processing, and the cryogenic thermal loading. Given the complex loading, 

material anisotropy must be considered. Alloy 2090 rolled products are known to have 

dramatically reduced mechanical properties in specific directions relative to the rolling direction, 

especially in thin sheet material. Short transverse and longitudinal (long transverse) properties 

are important for the initial stages of stringer crack propagation and later stages of through-thethickness cracking, respectively. The observations of the complex loading, crack path, material 

anisotropy, and the lack of publically available data for these variables led to the development of

unique test methods in an attempt to understand the complex failure mode. Furthermore, the 

limited cross-sectional size of the stringer and the localized hot forming area preclude the 

generation of American Society for Testing and Materials (ASTM) standard size test coupons in 

the required orientation. This required additional testing to validate sub-sized specimen data. 

Lot 620853 Control Lot

Grain Boundary

Precipitation

Clean Subgrain

Boundary

15 mm 15 mm
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Figure 5.0-7. Schematic of Crack Location and Nominal Plane of Propagation

The failure analysis revealed the suspect material lots 620853 and 620854 were likely linked to 

the ET-137 stringer cracking. Both suspect lots exhibited anomalous microstructure and low 

toughness properties. Therefore, test parameters (i.e., heat treatment time and temperatures) 

were thought to be important variables and needed to be replicated in the laboratory to develop 

the understanding of proximate cause (see Section 11.0) for the observed anomalous 

microstructure and low toughness properties.

5.1 Investigation Objectives

In concert with parallel materials and process (M&P) efforts that were being conducted at 

Marshall Space Flight Center (MSFC), Michoud Assembly Facility (MAF), and Johnson Space 

Center (JSC), the NESC investigation examined the mechanical and fracture properties

(e.g., tensile, shear, fracture toughness, and bend behavior) of the 2090-T83 material from the 

two suspect lots (620853 and 620854) used to manufacture the ET-137 stringers and several 

control lots (i.e., 400751, 400766, and 400768) that exhibited nominal tensile and fracture 

toughness properties. The primary objectives of the study were:

 Develop a tensile and fracture properties database.

o Perform mechanical property characterization tests to compare behavior of 

suspect and control material lots.

o Provide independent validation of tests conducted by the MSFC, MAF, and JSC 

from sub-sized specimens taken from stringers. 

Short

Transverse

Long

Transverse

Rolling

Direction

Crack

Bottom

Surface of

Stringer Foot

Rolling

Direction

Long

Transverse

Nominal Plane

of Crack Propagation
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 Conduct tests to replicate complex local loading to understand the influence of anisotropy 

effects.

o 3-point bend tests were conducted to understand through-the-thickness fracture to 

replicate stringer fracture mode.

o Pure shear and combined tensile/shear tests were conducted to characterize 

mechanical properties under stringer failure mode loading conditions.

 Characterize microstructures to determine proximate cause(s) of the low toughness of

stringers from suspect lots 620853 and 620854.

o Perform a thermal aging (precipitation strengthening) study to characterize the 

influence of elevated aging temperature on microstructure and fracture toughness.

o Conduct thermal exposure study to examine the effect of stringer process 

excursions on fracture toughness behavior.

o Conduct detailed microstructure characterization using transmission electron 

microscopy (TEM) and electron back-scatter diffraction methods (EBSD). 

5.2 Materials Examined

Material was provided in several product forms (i.e., sheet/coil, and several stages of stringer 

manufacture) from five different lots. Table 5.2-1 describes the material form, designations used 

to identify the material, and the types of tests that were conducted. The designation “mottled” 

(i.e., L4MCR and L5MCR) refers to the visible condition of the stringer surfaces, as shown in 

Table 5.2-1. This study did not address any differences in behavior due to the visible material 

surface condition.
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Table 5.2-1. Description of Materials Examined

LaRC 

Designation

Other 

Designations

Lot 

Number

Description Tests/Characterization

L1 400751*Four sheets in T3 condition

~ 4-ft. long by ~8.5-in. wide by 

0.063-in. thick

 Tensile

 Bend

 Fracture

 EBSD

L2 400768*Four sheets in T3 condition

~ 4-ft. long by ~8.5-in. wide by 

0.063-in. thick

 Tensile

 Bend

 Fracture

 EBSD

L3 400766* Coil in T3 condition

~16-ft. long by ~8.5-in. wide by 

0.065-in. thick

 Tensile

 Bend

 Fracture

 EBSD

L4CR J1

902D138

620854** 8-ft. stringer cold formed, but in 

T3 condition

 Bend

 Fracture

L4MCR G1

902D130

620854** 8-ft. stringer cold formed, but in 

T3 condition, labeled mottled

 Bend

 Fracture

L4HR K1 620854** 8-ft. stringer cold formed and 

hot formed, but in T3 condition

 Bend

 Fracture

L5CR L1

903D615

620853** 8-ft. stringer cold formed, but in 

T3 condition

 Bend

 Fracture

L5MCR I1

903D689

620853** 8-ft. stringer cold formed, but in 

T3 condition, labeled mottled

 Bend

 Fracture

L5HR H1 620853** 8-ft. stringer cold formed and 

hot formed, but in T3 condition

 Bend

 Fracture

Stringer-7 

Sister

620853** ~12-in. stringer  Bend

 Fracture

C-1D Control 1D 400766*~12-in. stringer  Bend

 Fracture

Note: *control lots and **suspect lots

5.3 Mechanical Property Characterization Tests

Tensile, shear, and 3-point bend tests were conducted to characterize the behavior under possible 

stringer local loading conditions that resulted in cracking. Tensile tests were only conducted on 

the sheet and coil material because the stringers were not large enough to accommodate the 

standard size tensile specimens. However, sub-sized tensile coupons were made from the 

suspect stringer material and tested by MSFC.
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5.3.1 Tensile Tests

Tensile tests were performed using 4-inch gage length, 0.25-inch-wide specimens according to 

ASTM E8/E8M [ref. 4] standards. The tests were conducted using a 20-kip servo-hydraulic 

controlled load frame with a 2-kip range card. The strain was determined from two 1-inch 

displacement gages placed on opposite specimen sides. The specimens were loaded to failure at 

a constant displacement rate of 0.01 inch/minute and data readings were collected every 

0.1 seconds.

Tests were conducted on material that was peak aged (i.e., 325°F for 24 hours), over aged 

(i.e., >325°F for 24 hours), and for different orientations (L – loaded parallel to the rolling 

direction, T – loaded perpendicular to the rolling direction, and 45 – loaded at 45 degrees to the 

rolling direction). A representative set of tests for the three different loading orientations is 

provided in Figure 5.3-1 for the L2 (lot 400768) sheet material. A complete summary of the 

tensile test results is provided in Appendix A. 

A summary of the measured yield and ultimate strengths for long-transverse orientation data for 

the control and suspect lots [ref. 3] is shown in Figure 5.3-2. The average yield and ultimate 

strengths for the suspect lot materials were about 2 ksi higher than the corresponding averages

for the control lot materials. Comparisons of the tensile test results indicate that the suspect 

material had higher yield and ultimate strengths than the control material (Observation 1).
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Figure 5.3-1. Tensile Test Results for Three Loading Orientations of the L2 Material (Lot 400768)
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Figure 5.3-2. Summary of Tensile Test Results for All Lots (Long-transverse Orientation)

5.3.2 Shear and Combined Tensile/Shear Tests

Shear tests were performed using single shear specimens, double shear specimens, and a 

specially designed combined tensile/shear fixture. Alloy 2090 material is anisotropic and 

exhibits reduced properties in the short transverse (through-the-thickness) direction. The stringer 

failure analysis showed that the local tensile stress in the short transverse direction and the local 

shear stress in the short transverse direction produced cracking, with the combined loading 

potentially exacerbating the weakness (reduced properties) in the short transverse direction. The 

tests described in this section were conducted to investigate the influence of combined loading 

on the weaker through-the-thickness properties. The details of the specimens, fixtures, and data 

are provided in Appendix B.

A representative set of shear, tensile, and combined tensile/shear results are shown in 

Figure 5.3-3 for the control lot 400751. The tensile test results (blue squares) represent the yield 

stress calculated from the 0.2 percent offset strain and the original cross sectional area. The 

maximum shear stress and maximum normal stress yield surfaces were calculated from the 

Stress

(ksi) 400768

400751

400766620853

(MSFC)

620854

(MSFC)

Lots

Suspect Lots

Yield

Ultimate

400766

(MSFC)

Average

82.0 ksi

76.2 ksi

Average

84.3 ksi

78.2 ksi
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tensile test results and assumed that the compressive yield was equal to the tensile yield. Both 

yield surfaces are used to represent the yield surface of brittle materials with the maximum yield 

surface being more conservative. These curves represent the theoretical principal stress 

(1 and 2) boundary between elastic and plastic behavior for an isotropic material under multiaxial loading. An exacerbation of the weakness in the short direction due to combined 

tensile/shear loading would be manifested by test results that fell on the inside of the surfaces. 

The shear tests only provided a measurement of the peak loads, so the shear test results (red 

symbols) and the combined tensile/shear test results (green symbols) are more representative of 

an ultimate stress and not a yield stress. The small difference between the yield stress (76.5 ksi) 

and the ultimate stress (82.0 ksi) observed in the tensile tests suggest that the shear yield would 

be less than 10 percent lower than the shear ultimate, and move the red and green symbols closer 

to the theoretical yield surface. This indicates that the combined tensile/shear loading of the 

2090 material may not adversely influence the stringer material yield behavior in the loading 

regime examined.

Figure 5.3-3. Combined Tensile/Shear Data for the L1 Material (Lot 400751)

2

(ksi)

1

(ksi)
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5.3.3 3-Point Bend Tests

Rectangular coupons (2 inches long by 0.75 inches wide) were machined from the coil and the 

stringer materials and were tested in 3-point bending. The 3-point bend tests were conducted to 

simulate the bending loading present in the stringers at the failure location. The tests provide 

data for computational model verification and to evaluate a screening test for stringer material 

with brittle behavior.

The specimens were oriented with the rolling direction perpendicular to the long side of the 

specimen. This bending orientation produces cracking in the same plane (short longitudinal) as 

the stringer cracking plane. The distance between the two fixed boundaries was defined as “L” 

and the displacement of the center mandrel was defined as “”, as shown in Figure 5.3-4. The 

tests were conducted by applying a constant displacement rate of 0.05 inches/minute until the 

specimen either failed suddenly into two pieces (defined as brittle behavior) or emitted an 

audible sound that indicated damage, producing an intact ligament and rapidly dropping the load, 

without complete failure (defined as less-brittle behavior). The applied displacement and load 

were measured for each test. Several tests had strain gages on the specimen tensile side opposite 

the mandrel. The strain to failure, or cracking, was noted for each test and was plotted as a 

function of the normalized displacement (t/L2) in Figure 5.3-5. The open square symbols 

represent the maximum strain observed in individual tests on suspect lot material and likewise, 

the solid circular symbols represent tests on control lot materials. The failure strains of the 

control and suspect lots overlap on the lower end of the control lot and the upper end of the 

suspect lot failure strains. The 3-point bend tests demonstrated that the suspect lot materials 

were more brittle and had lower strains to failure than the control lot materials 

(Observation 2).
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Figure 5.3-4. 3-point Bend Fixture

Figure 5.3-5. Strain to Failure from 3-point Bend Tests

0

0.002

0.004

0.006

0.008

0.01

0.012

0 5 10 15 20 25

 t/L2

Max % Strain

Strain Gage Fit

Control Lots

Suspect Lots

L

t


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The measured center mandrel displacement () was reported as a function of the applied load for 

model verification. Different span lengths (L) were tested, as shown in Figure 5.3-6. The failure 

load increased as the span length decreased, corresponding to a reduction in the outer surface 

bending stress for an equivalent center mandrel displacement. Likewise, the displacement at 

failure increased as the span increased. Additional details of the specimens, fixtures, and data 

are provided in Appendix C. The 3-point bend test database was provided to the NESC 

structures assessment team for use in the 3-D elastic-plastic models for stringer-line loading 

conditions (ref. 6) (Observation 3).

Figure 5.3-6. Measured Displacement and Load from 3-point Bend Tests for Different Spans

Load

(kips)

Displacement

(inch)
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5.4 Fracture Toughness Tests

Fracture toughness tests were conducted using 1.5-inch-wide compact tension specimens 

according to ASTM E1820 [ref. 5] standard. The tests were conducted to evaluate the influence 

of processing variables (e.g., processing temperature and time at temperature) on the fracture 

toughness behavior, and to provide a database to assist in the independent validation of the 

fracture toughness test data produced by the MSFC M&P group. The two stringer thermal 

processing steps that could potentially alter the material and produce the abundant boundary 

precipitation and low toughness observed in the two suspect lots are hot rolling and peak aging. 

This could only have occurred if an off-nominal high temperature was not detected by normal 

process controls. A thermal treatment test matrix was developed to envelop the probable 

anomalous temperature and processing times that could occur during stringer processing. For 

each of these thermal test conditions, fracture toughness testing was used to characterize the 

influence of anomalous temperature and process time conditions.

Based on MSFC fracture criteria, the stress intensity factor (K) at peak load (Pmax) was used to 

characterize the test specimen fracture behavior. Fracture tests were conducted on the control 

and suspect lot materials following nominal peak aging processing (325°F for 24 hours), as 

shown in Figure 5-4.1. The K at Pmax for the suspect lot materials was about 6 ksi in1/2 lower 

than the corresponding averages for the control lot materials. The fracture test results showed 

that the suspect lot materials were less tough than the control lot materials (Observation 4).

Figure 5.4-1. Fracture Test Results from Suspect and Control Lot Materials Following Nominal Peak 

Aging

K at Pmax

(ksi inch1/2) 400766 400751 400768 620863 620854

Suspect Lots

Average

25.0 ksi in1/2

Average

19.0 ksi in1/2
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Testing was conducted on a variety of specimens that had experienced different thermal 

exposures to examine the influence of both thermal aging temperature and brief, high 

temperature exposures on the fracture behavior for coil and stringer materials. The nominal peak 

aged condition (T83) was produced by exposing the alloy 2090-T3 stringer material to a 

temperature of 325°F for 24 hours in an air environment. (Note that the production stringer 

aging process aged at 325°F for 25 hours and started with the oven at room temperature.) The 

thermal aging study examined the influence of temperatures to 400°F on K at peak load and the 

fracture surface morphology. In addition, a thermal exposure study examined 10- and 20-minute 

exposures to temperatures to 500°F prior to the nominal aging process. These tests were 

performed to simulate temperature excursions during the hot forming process. Additional 

information on the test specimens, test conditions, and data are provided in Appendix D. 

Photographs of representative fracture surfaces are provided in Appendix E.

5.4.1 Thermal Aging Study

The thermal aging (precipitation strengthening) study was performed by aging the 2090-T3 

control material and suspect material at temperatures that ranged from the nominal 325 to 400°F, 

as summarized in Table 5.4-1. The results for the individual tests are provided in Appendix D. 

The goal of the tests was to reproduce the process conditions that produce low toughness during 

the thermal aging process. Multiple tests were conducted at each temperature and material 

combination and the K at Pmax was plotted for each aging temperature, as shown in Figure 5.4-2. 

The red symbols in this figure represent individual tests conducted on the two suspect lot stringer 

materials (“plus” symbols for lot 620853, and “x” symbols for lot 620854). The circle symbols 

represent individual tests conducted on the control lots.

The measured fracture index (i.e., K at Pmax) decreased with increasing temperatures for aging 

temperatures between 325 and 350°F. The micrographs in Figure 5.4-2 show representative 

crack surfaces for fracture specimens that were aged at different temperatures. Examinations of 

these micrographs reveal a general increase in grain boundary delamination with aging 

temperature (i.e., straight and parallel microstructural features along the crack length). For aging 

temperatures above 350°F (toughness minima), there is a dramatic increase in boundary 

delamination. The correlation of increasing toughness and boundary delamination with 

increasing thermal aging temperatures above 350°F suggests that the increase in toughness for 

aging temperatures greater than 350°F is the result of delamination toughening. The toughness 

increase is the result of the increased crack driving force required to propagate delamination 

cracking. The suspect lot materials exhibited lower fracture toughness values compared to 

the control lot materials at elevated aging temperatures (Observation 5). Above 350°F, the 

observed increase in fracture toughness is related to delamination fracture mechanism 

(Observation 6). 
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Table 5.4-1. Summary of Fracture Thermal Aging Study

Figure 5.4-2. Fracture Test Results from the Thermal Aging Study

Average 

(ksi inch1/2)

Std Dev. 

(ksi inch1/2) Delam.

Average 

(ksi inch1/2)

Std Dev. 

(ksi inch1/2) Delam.

Average 

(ksi inch1/2)

Std Dev. 

(ksi inch1/2) Delam.

325 25.2 2.2 N 26.7 2.1 N 24.3 0.9 N

333 21.0 0.8 N 22.3 0.1 N 22.7 1.5 N

340 21.4 0.9 N 20.1 0.7 N 20.3 1.8 N

350 19.1 0.4 N 19.7 0.7 N 17.6 0.3 N

375 18.7 1.0 Y 21.0 1.1 Y 18.1 0.6 Y

400 23.1 1.5 Y 25.6 0.3 Y

Lot 400751 

K at Pmax

Lot 400768 

K at Pmax

Lot 400766 

K at Pmax

24 Hour 

Aging 

Temperature 

(°F)
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5.4.2 Thermal Exposure Study

The thermal exposure study was performed by heating the 2090-T3 coil materials to 

temperatures above the nominal aging temperature (325°F) for a brief period (10 and 

20 minutes), as summarized in Table 5.4-2. The results for the individual tests are provided in 

Appendix D. The goal of the tests was to determine if short duration temperature anomalies 

during the hot forming process could influence the microstructure or material behavior. The 

specimens were aged for 24 hours at the nominal aging temperature after the brief thermal 

exposures. Multiple tests were conducted at each temperature and material combination, and 

K at Pmax was plotted for each exposure temperature, as shown in Figure 5.4-3. The control 

material did not show a reduction in toughness until the exposure temperature exceeded 375°F.

The toughness minima occurred at about 450°F, where delaminations were becoming visible on 

the fracture surfaces. Further increases in the exposure temperature resulted in a higher 

density of fracture surface delaminations and little measureable change in the toughness

index (Observation 7).

Table 5.4-2. Summary of Fracture Exposure Aging Study

Average 

(ksi inch1/2)

Std Dev. 

(ksi inch1/2) Delam.

Average 

(ksi inch1/2)

Std Dev. 

(ksi inch1/2) Delam.

325 - - 25.2 2.2 N 26.7 2.1 N

325 340 10 25.1 0.6 N 24.9 2.2 N

325 350 10 25.6 - N 24.4 1.1 N

325 375 10 25.6 - Y 23.6 - Y

325 400 10 20.9 0.5 Y 20.6 0.8 Y

325 425 10 20.3 0.7 Y 20.6 0.5 Y

325 450 10 18.7 - Y 20.1 - Y

325 475 10 19 - Y 16.6 - Y

325 500 10 17.5 - Y 16.7 - Y

325 340 20 24.6 1.1 N N

325 350 20 24.1 0.8 N 24.6 - N

325 400 20 22.3 - Y 19.5 2.8 Y

325 450 20 17.3 - Y Y

325 500 20 20 - Y 19.4 - Y

Lot 400751 

K at Pmax

Lot 400768 

K at Pmax 24 Hour 

Aging 

Temperature 

(°F)

Exposure 

Time (min)

Exposure 

Temperature 

(°F)
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Figure 5.4-3. Fracture Test Results for the Thermal Exposure Study

5.5 Microstructure Characterization

The objective of this effort was to characterize the microstructure of the suspect materials 

compared to the control materials that exhibit good material properties. Anomalous 

microstructure is linked to poor properties and is likely that proximate cause(s) can be 

hypothesized by thoroughly characterizing the anomalous microstructure. Two critical 

characterization techniques, TEM and EBSD, were used to identify anomalous microstructures. 

5.5.1 Transmission Electron Microscopy (TEM) Analysis

Alloy 2090 is a well-known precipitation strengthened alloy, thus important precipitate features 

can be linked to mechanical and fracture properties. The TEM analysis of the suspect and 

control material lots characterized the ’ (Al3Li), T1 (Al2CuLi) and T2 (Al6CuLi3) precipitate 

morphology. Evidence of classical and deleterious microstructure morphologies, such as grain 

boundary precipitation free zones (PFZs), can assist in determining the cause of the observed low 

fracture toughness exhibited by the two suspect lots. 

Lot 400751 Lot 400768 Lot 400766
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TEM analysis was performed on suspect (Stringer-7 Sister) and control (C-1D) stringer material. 

The TEM examinations of high angle grain boundaries, refer to Figure 5.5-1, revealed that 

PFZs were present in suspect lot material, but not in the control lot (Observation 8). 

Examinations revealed large quantities of grain boundary precipitates (likely T2 precipitate); the 

formation of large grain boundary precipitates consume nearby solute (Li) atoms preventing the 

formation of ’ precipitate, and resulting in the observed ’ PFZ. Classically, the presence of 

PFZs suggests reduced fracture toughness; the PFZ exhibits reduced mechanical properties 

compared to the matrix, resulting in crack-tip-process-zone void nucleation (strain localization), 

which results in reduced crack growth resistance (lower toughness).

Multiple dark and bright field TEM images were used to obtain an estimate of the size and 

number of matrix T1 and ’ precipitates, as summarized in Table 5.5-1. The TEM 

examinations revealed that the suspect material had fewer and larger matrix T1

precipitates compared to the control material (Observation 9). The sizes of the matrix ’ 

precipitates were about the same in the suspect and control stringer material, but more 

precipitate particles were present in the control stringer material (Observation 10). These 

are significant observations and will be discussed further relative to the EBSD analysis results 

discussed in the following section.

Figure 5.5-1. Example of a High Angle Grain Boundary ’ PFZ

0.000005 inch

’ PFZ

High Angle

Grain Boundary 

’
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Table 5.5-1. Summary of TEM Matrix T1 and ’ Precipitate Measurements

5.5.2 Electron Backscatter Diffraction EBSD Analysis

EBSD analysis characterizes the crystallographic orientation and thereby gives a qualitative 

measure of dislocation morphology. This information in combination with the TEM analysis of 

the precipitate characterizations can yield important understanding relative to the proximate 

cause of the low toughness material. EBSD was performed on the suspect lot 620853 and 

control lots 400766 and 400768. The grain orientation spread (GOS) is a quantification of EBSD 

data. Grains (high angle) and sub-grains (low angle) are regions of similarly oriented 

crystallographic material that are defined by boundaries with neighboring grains. Boundaries are 

detected by point-to-point crystallographic orientation changes greater than a defined value. A 

high-angle boundary may be defined by a point-to-point change of 15 degrees, while a low-angle 

boundary may be just a few degrees. The orientation measurements within a grain are averaged 

and the GOS, or average grain misorientation, is calculated, as shown in Figure 5.5-2. For this 

investigation, the boundary threshold was set at the default value of 5 degrees. Areas with high 

dislocation densities show high GOS values. Regions within these boundaries with a low 

average grain misorientation (blue and green colors) would suggest that these regions contain 

lower dislocation density and that these regions exhibit a higher degree of recovery. Recovery is 

an elevated temperature process that reduces the stored energy in deformed grains by the 

removal or rearrangement of dislocations. The EBSD analyses showed these regions to be 

recovered and not recrystallized because no evidence of grain nucleation and growth was 

observed. 

Material

Number of 

Micrographs

Number of 

Precipitates

Average 

Size (nm)

Std. 

Deviation 

Suspect 

(Lot 620843) 7 32 87 24

Control 

(Lot 400766) 5 80 61 29

Suspect 

(Lot 620843) 2 13 14 2

Control 

(Lot 400766) 2 22 14 3

T1 Precipitate Measurements

' Precipitate Measurements
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Figure 5.5-2. Schematic of GOS Calculation

Figure 5.5-3 shows all of the material conditions examined (coil, cold form, etc) and location 

(red X) where the EBSD samples were obtained. Note that the location of the EBSD samples 

was in a region away from where the material was cold worked. The examined locations were 

taken from regions where no bending (cold work) was conducted. The figure also defines the 

through-the-thickness EBSD analysis region relative to the rolling or longitudinal direction. The 

GOS data are presented in a crystallographic orientation (colored) map that indicates the average 

misorientation; blue corresponding to low misorientation measurement and red corresponding to 

a high misorientation measurement. 

Figure 5.5-4 summarizes the EBSD data from control material (lot 400751) in both the asreceived (T3) condition and after peak aging at 325°F for 24 hours. The EBSD crystallographic 

orientation maps reveal little difference in the as-received and peak aged materials. The EBSD 

results shown in Figure 5.5-5 for the control coil lots 400768 and 400766 in the peak-aged 

condition (325°F for 24 hours) also exhibit no difference in orientation or dislocation 

morphology. These EBSD data shows that stringer processing had no influence on the 

microstructure (no change in crystallographic misorientation) of the control lot material 

(Observation 11).

Figure 5.5-6 shows the results of EBSD analysis conducted on the suspect materials 

(lot 620853), including processed stringers (as-received), cold-formed stringers, and cold + hot 

1 2 3

N

Average Grain Orientation





N

i

i N 1

1

 

Average Grain Misorientation  



 

N

i

i N

GOS

1

1

 

Grain Boundary

Measurement Locations
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formed stringers. All the suspect materials showed a higher percentage material that exhibited

recovery; the interior of the sheet (middle 1/3) had fewer blue regions compared to the exterior 

regions (remaining 2/3). Conversely, a comparison of the suspect lot material EBSD results 

compared to the control lot (Figures 5.5-6 and 5.5-5, respectively) revealed a dramatic difference 

in misorientation or dislocation morphology. 

The EBSD data revealed that the suspect material exhibits evidence of grain recovery parallels 

the TEM observations 8, 9, and 10. Grain recovery (removal or redistribution of dislocations) 

reduces or changes the number of energetic sites for precipitation; removal or redistribution of 

dislocations could alter precipitate morphology (alter precipitate size, number, and location). 

Thus, the EBSD analysis revealed that the as-received suspect lot microstructure exhibits 

grain recovery (reduced dislocation density) and confirms the TEM observations relative to 

differences in precipitate morphology (Observation 12).

Figure 5.5-3. Schematic Describing the Location of the EBSD Analysis for the Stringer Materials

Coil - T3

L

L

X X X

A

A

T3

+

Cold

Formed

T3

+

Cold

Formed

+

Hot

Formed

T3

+

Cold

Formed

+

Hot

Formed

+

Peak

L Aged (325 F)

A A

Fracture Surface Plane

Sheet

Thickness

EBSD

Analysis
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Figure 5.5-4. GOS Values for a Through-the-Thickness Strip of Control Coil Lot 400751 in the 

as-received (T3) and Peak Aged Condition

Figure 5.5-5. GOS Values for a Through-the-Thickness Strips of Control Coil Lots 400768 and 400766 

in the Peak-Aged Condition

Lot 400751 (T3 Condition)

13% (Blue Region)

Lot 400751 (Aged at 325 F for 24 Hours)

14% (Blue Region)

0.02 inch Surface Surface Surface

Lot 400768 (Aged at 325 F for 24 Hours)

11% (Blue Region)

Lot 400766 (Aged at 325 F for 24 Hours)

14% (Blue Region)

0.02 inch Surface Surface Surface
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Material Characterization Study

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Figure 5.5-6. GOS Values for a Through-the-Thickness Strip of Stringer Lot 620853 in the as-received 

Peak-Aged, Cold-Formed + Hot-Formed, and Cold-Formed Conditions

6.0 Findings

F-1. The proximate cause (see Section 11.0) leading to Alloy 2090 ET stringer lot-to-lot 

variability in mechanical and fracture properties (O-1, O-2, and O-4) is linked to a 

metallurgical process termed grain recovery (O-8, O-9, O-10, and O-12). 

 The EBSD microstructural characterization of the as-received suspect material 

showed that grain recovery had occurred prior to stringer processing (O-11). 

 Grain recovery caused the two suspect lots to age differently than the control lots for 

the specified (325°F for 25 hours) process parameters. This produced a 

microstructure in the suspect lots that resulted in low fracture toughness. 

 Fracture-test-aging studies showed that nominal and possible off-nominal stringer 

processing would not cause the low fracture toughness, brittle behavior, and fracture 

morphology exhibited by the suspect lot material (O-5, O-6, and O-7).

F-2. The 3-point bend tests generated a stringer damage mode understanding and a database 

for validating the structural analysis models (O-3).

Lot 620853 (as received, peak aged stringer)

26% (Blue Region)

Lot 620853 – Cold Formed/Hot Formed (T3 Condition)

28% (Blue Region)

Lot 620853 – Cold Formed (T3 Condition)

27% (Blue Region)

0.02 inch Surface Surface Surface Surface Surface
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7.0 NESC Recommendation

R-1. Alloy 2090 T8 sheet should not be used for “hat” configured stringer applications that are 

attached by fasteners. 

 These stringers can develop complex, concentrated through-the-thickness bending 

and shear stresses near the fasteners.

 Alloy 2090 through-the-thickness properties are marginal (i.e., low ductility) and 

material processing variations (within specification) can alter microstructure/

properties and unknowingly exacerbate cracking under bending and shear stress 

stringer environments. 

8.0 Alternate Viewpoints

There were no alternate viewpoints during the course of this assessment.

9.0 Other Deliverables

No unique hardware, software, or data packages, outside those contained in this report, were 

disseminated to other parties outside this assessment.

10.0 Lessons Learned

No applicable lessons learned were identified for entry into the NASA Lessons Learned 

Information System.

11.0 Definition of Terms

Corrective Actions

Changes to design processes, work instructions, workmanship practices, training, inspections, 

tests, procedures, specifications, drawings, tools, equipment, facilities, resources, or material that 

result in preventing, minimizing, or limiting the potential for recurrence of a problem. 

Finding

A conclusion based on facts established during the assessment/inspection by the investigating 

authority. 

Lessons Learned

Knowledge or understanding gained by experience. The experience may be positive, as in a 

successful test or mission, or negative, as in a mishap or failure. A lesson must be significant in 
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that it has real or assumed impact on operations; valid in that it is factually and technically 

correct; and applicable in that it identifies a specific design, process, or decision that reduces or 

limits the potential for failures and mishaps, or reinforces a positive result. 

Observation

A significant factor established during this assessment that supports and influences the 

conclusions reached in the statement of Findings and Recommendations. 

Problem

The subject of the independent technical assessment/inspection.

Proximate Cause 

The event(s) that occurred, including any condition(s) that existed immediately before the 

undesired outcome, directly resulted in its occurrence and, if eliminated or modified, would have 

prevented the undesired outcome. Also known as the direct cause(s).

Recommendation

An action identified by the assessment/inspection team to correct a root cause or deficiency 

identified during the investigation. The recommendations may be used by the responsible 

C/P/P/O in the preparation of a corrective action plan. 

Root Cause

Along a chain of events leading to a mishap or close call, the first causal action or failure to act 

that could have been controlled systemically either by policy/practice/procedure or individual 

adherence to policy/practice/procedure.

12.0 Acronyms List

Al-Li aluminum-lithium

AS&M, Inc. Analytical Services & Materials, Inc.

ASTM American Society for Testing and Materials

ATK Alliant Techsystems Inc.

EBSD electron backscatter diffraction 

ET external tank 

GOS grain orientation spread 

IT intertank

JSC Johnson Space Center

ksi kilopounds per square inch
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LaRC Langley Research Center

LLC Limited Liability Corporation

LO2 liquid oxygen

M&P materials and process

MAF Michoud Assembly Facility

MSFC Marshall Space Flight Center

MTSO Management and Technical Support Office

NESC NASA Engineering and Safety Center

NRB NESC Review Board

PFZ precipitation free zone

SEM scanning electron microscope

SSP Space Shuttle Program

STS Space Transportation System

TEM transmission electron microscopy

13.0 References

1. Gomez, R. J., III, “Estimated Airloads for IPR 133V-072 Crack Location,” Space Shuttle 

Systems ICB, November 16, 2010.

2. “SR4851 STS-133/ET-137 Intertank Stringer Crack Joint SERB/SICB,” November 16, 2010.

3. Jerman, G., “ET-137 Stringer Fractography Update,” NASA MSFC EM31 Failure Analysis 

& Metallurgy Branch, December 9, 2010.

4. “Annual Book of ASTM Standards,” Standard E8/E8M, Volume 03.01, 2010.

5. “Annual Book of ASTM Standards,” Standard E1820, Volume 03.01, 2010.

6. Burkholder, J. “Effect of Tensile Specimen Geometry on Test Results for Al-Li 2090-T83 

ET Stringer Material,” MSFC Materials and Processes Laboratory Flash Report, 

MPFR-11-015, February 24, 2011.

14.0 Appendices

A. Tensile Test Results

B. Shear Test Results

C. 3-Point Bend Test Results

D. Fracture Test Results

E. Fractographic Photographs
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Appendix A. Tensile Test Results

Tensile tests were conducted on 4-inch long, 0.25-inch-wide dogbone specimens, as shown in 

Figure A-1. The tests were performed on a 20-kip load frame with a 2-kip range card. The 

strain was determined from 1-inch displacement gages placed on opposite sides of the specimen. 

The specimens were loaded to failure at a constant displacement rate of 0.01 in/min and data 

readings were taken every 0.1 seconds. The elastic modulus (E) was calculated by calculating 

the slope of a linear least–squares-fit to the initial elastic portion of the calculated stress (S) and 

measured strain (e). The yield stress (Sys) was determined by calculating the stress at the point 

where the plastic component of the strain (ep = e – S/E) was 0.002. The ultimate stress (Sult) was 

calculated from the maximum load observed in the test and the initial specimen cross sectional 

area. A summary of the tensile test results is provided in Tables A-1, A-2, and A-3 for control 

lots 400766, 400751, and 400768, respectively. Preliminary tensile tests were conducted on 

specimens machined from a sheet of 2090-T85 stock material (lot P3) that was not related to the 

stringer material, as summarized in Table A-4. The tensile data for each test was reduced to 

41 pointes (evenly spaced in time) and presented in Table A-5.

Figure A-1. Tensile Specimen Drawing
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Table A-1. Tensile Test Summary for Control Coil Lot 400766

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L3C1-T-01 400766 T 12133 76.4 82.3 0.113

L3C1-T-03 400766 T 11995 76.2 82.1 0.110

Average 400766 T 12064 76.3 82.2 0.112

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L3C1-T-10 400766 T 12287 77.6 83.5 0.095

L3C1-T-11 400766 T 12196 77.9 83.3 0.105

L3C1-T-12 400766 T 11911 77.4 83.2 0.099

Average 400766 T 12131 77.7 83.3 0.100

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L3C1-T-04 400766 T 12080 75.6 80.6 0.101

L3C1-T-05 400766 T 12128 76.0 80.9 0.101

L3C1-T-06 400766 T 12326 75.9 80.9 0.101

Average 400766 T 12178 75.8 80.8 0.101

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L3C1-T-07 400766 T 12304 71.8 78.1 0.088

L3C1-T-08 400766 T 12242 72.1 78.5 0.086

L3C1-T-09 400766 T 12026 70.9 77.4 0.082

Average 400766 T 12191 71.6 78.0 0.086

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L3C1-T-13 400766 T 11351 78.7 83.4 0.079

L3C1-T-14 400766 T 11443 78.3 83.0 0.084

L3C1-T-15 400766 T 11443 78.1 82.8 0.096

L3C1-T-16 400766 T 11371 77.9 82.5 0.089

Average 400766 T 11402 78.3 82.9 0.087

Aged at 375°F for 24 hours

Aged at 340°F for 24 hours

Aged at 325°F for 24 hours

Exposed to 400°F for 10 minutes and Aged at 325°F for 24 hours

Aged at 350°F for 24 hours
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Table A-2. Tensile Test Summary for Control Coil Lot 400751

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L1P1-T1-325 400751 T 11240 76.3 82.1 0.101

L1P1-T2-325 400751 T 11208 76.4 82.1 0.109

L1P1-T3-325 400751 T 11412 76.5 82.2 0.105

L1P1-T4-325 400751 T 11437 76.5 82.1 0.099

Average 400751 T 11425 76.5 82.2 0.102

L1P1-L1-325 400751 L 10892 75.7 83.4 0.080

L1P1-L2-325 400751 L 10994 76.4 83.5 0.079

L1P1-L3-325 400751 L 11412 76.5 82.2 0.105

L1P1-L4-325 400751 L 11125 76.5 83.5 0.063

Average 400751 L 11269 76.5 82.8 0.084

L1P1-45-1-325 400751 45 10792 63.4 69.2 0.115

L1P1-45-2-325 400751 45 10892 63.6 69.4 0.121

L1P1-45-3-325 400751 45 10865 63.8 69.6 0.134

L1P1-45-4-325 400751 45 10863 63.4 69.2 0.127

Average 400751 45 10864 63.6 69.4 0.131

E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L1P2-T1-350 400751 T 11279 76.4 81.1 0.104

L1P2-T2-350 400751 T 11119 76.4 81.1 0.099

L1P2-T3-350 400751 T 11105 76.4 81.1 0.105

L1P2-T3-350 400751 T 11114 76.3 81.0 0.101

Average 400751 T 11154 76.4 81.1 0.102

Aged at 325°F for 24 hours

Aged at 350°F for 24 hours

Specimen Lot Orientation
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Table A-3. Tensile Test Summary for Control Coil Lot 400768

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

L2P1-T1-325 400768 T 11165 75.5 81.8 0.076

L2P1-T2-325 400768 T 11182 76.0 81.8 0.109

L2P1-T3-325 400768 T 11313 76.0 81.8 0.103

L2P1-T4-325 400768 T 11257 75.9 81.7 0.105

Average 400768 T 11229 75.8 81.8 0.098

L2P1-L1-325 400768 L 11257 75.2 80.0 0.023

L2P1-L2-325 400768 L 11559 75.2 79.8 0.024

L2P1-L3-325 400768 L 11152 75.4 82.8 0.070

L2P1-L4-325 400768 L 11152 75.8 83.1 0.084

Average 400768 L 11152 75.6 82.9 0.077

L2P1-45-1-325 400768 45 10840 63.5 69.0 0.112

L2P1-45-2-325 400768 45 10742 63.4 69.4 0.131

L2P1-45-3-325 400768 45 10735 63.3 69.3 0.134

L2P1-45-4-325 400768 45 10691 63.5 69.3 0.129

Average 400768 45 10713 63.4 69.3 0.131

Aged at 325°F for 24 hours
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Table A-4. Tensile Test Summary for Control Coil Lot 400766

Specimen Lot Orientation E Sys Sult Max

(ksi) (ksi) (ksi) Strain

P3-T-01 P3 T 11002 68.3 79.7 0.073

P3-T-02 P3 T 11077 68.2 79.5 0.077

P3-T-03 P3 T 10971 68.3 79.5 0.072

P3-T-04 P3 T 11092 68.2 79.4 0.072

Average P3 T 11036 68.3 79.5 0.074

P3-L-01 P3 L 11172 76.38 84.08104 0.034

P3-L-02 P3 L 11237 76.13 84.12141 0.035

P3-L-03 P3 L 11230 76.06 84.26082 0.035

P3-L-04 P3 L 11169 75.7 83.62265 0.036

Average P3 L 11202 76.1 84.0 0.035

P3-45-01 P3 45 10816 59.88 72.63121 0.085

P3-45-02 P3 45 10836 59.33 72.32395 0.082

P3-45-03 P3 45 10821 59.36 72.57665 0.09

P3-45-04 P3 45 10897 59.59 72.80638 0.0914

Average P3 45 10843 59.5 72.6 0.087

P3 2090-T85
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Table A-5. Tensile Test Results by Specimen Number

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.0003 3.45289 0.000213 2.402423 0.001197 13.37328 0.001497 16.31242

0.000657 7.286021 0.000579 6.689174 0.002163 24.19853 0.002449 26.90852

0.000996 11.0577 0.00106 12.34216 0.003202 35.69167 0.00364 40.19238

0.001513 16.85348 0.001555 17.96828 0.004191 46.68679 0.004784 52.90692

0.001852 20.60596 0.001875 21.67937 0.005162 57.1144 0.005947 64.72684

0.002296 25.65279 0.002246 25.97764 0.006164 66.76216 0.007316 73.04184

0.002722 30.43844 0.002667 30.70956 0.00741 73.02412 0.009152 76.23694

0.00312 34.87458 0.003056 35.28415 0.008985 75.6455 0.01113 77.80931

0.003537 39.58341 0.003445 39.67835 0.010656 77.12413 0.013226 78.64197

0.003962 44.18087 0.003867 44.33353 0.012432 77.96575 0.015465 79.19192

0.004361 48.50562 0.004283 48.96567 0.014263 78.49466 0.017676 79.57533

0.004764 52.85342 0.004672 53.27545 0.016131 78.89231 0.01986 79.92776

0.005176 57.27035 0.005066 57.5008 0.018013 79.22818 0.022039 80.23371

0.005579 61.23407 0.005455 61.4268 0.019876 79.53317 0.024187 80.57065

0.005995 65.08641 0.005872 65.35281 0.021744 79.83044 0.026334 80.84949

0.006439 68.42791 0.006307 68.69548 0.02358 80.09297 0.028476 81.10898

0.006906 71.07807 0.006769 71.31665 0.02542 80.35935 0.030624 81.34522

0.007469 73.01 0.007309 73.14341 0.027238 80.57941 0.032771 81.56984

0.008078 74.30436 0.007941 74.40219 0.029078 80.83421 0.034927 81.78285

0.008728 75.27608 0.008591 75.33092 0.030905 81.01952 0.037083 81.95326

0.009388 76.04424 0.009278 76.0409 0.032755 81.20869 0.039263 82.12753

0.010061 76.66646 0.009978 76.61273 0.034586 81.41331 0.041442 82.29407

0.010756 77.16192 0.010693 77.07325 0.036431 81.56387 0.043644 82.43349

0.011443 77.56905 0.011416 77.41481 0.038285 81.73374 0.045837 82.53418

0.012162 77.88015 0.012158 77.71799 0.040144 81.86114 0.048071 82.64649

0.012881 78.14517 0.012904 77.9521 0.042003 82.00399 0.050305 82.75106

0.013613 78.36025 0.013673 78.15933 0.043875 82.13139 0.052562 82.84788

0.01435 78.56766 0.014433 78.309 0.045757 82.24335 0.054833 82.90597

0.015087 78.73665 0.015198 78.49705 0.047652 82.336 0.057113 82.96794

0.015847 78.88261 0.015976 78.63137 0.049525 82.39391 0.059439 83.01829

0.016594 79.0324 0.016754 78.75418 0.051438 82.51359 0.061737 83.02991

0.017349 79.16298 0.017523 78.89234 0.053347 82.5522 0.064086 83.05702

0.018118 79.28973 0.018302 79.01899 0.055284 82.61011 0.066462 83.06476

0.018869 79.41648 0.019075 79.14947 0.05723 82.68732 0.068842 83.05702

0.019615 79.54707 0.019854 79.26076 0.059194 82.71821 0.071232 83.05314

0.020357 79.65077 0.020614 79.3759 0.061153 82.70662 0.073668 83.03765

0.021112 79.76215 0.021387 79.48719 0.063126 82.77226 0.076122 82.9873

0.021854 79.87738 0.022143 79.57162 0.065118 82.78384 0.078598 82.93696

0.022587 79.98876 0.022907 79.7021 0.067137 82.7877 0.081135 82.85176

0.023328 79.99644 0.023681 79.73664 0.06917 82.79156 0.083703 82.71233

L2P1-L1-325 L2P1-L2-325 L2P1-L3-325 L2P1-L4-325

400768 400768 400768 400768
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Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001122 11.98942 0.001305 14.38347 0.001415 15.90034 0.000765 8.277678

0.002486 26.86702 0.002303 25.38462 0.00261 29.58284 0.001836 20.23645

0.003516 38.23207 0.003379 37.27828 0.003978 45.05416 0.002774 30.62856

0.004679 50.84203 0.00451 49.52434 0.005306 59.62533 0.003759 41.57991

0.005846 62.5365 0.005627 61.11922 0.006794 71.60325 0.004674 51.55833

0.007133 71.34278 0.006835 70.87546 0.008873 76.62502 0.005595 61.2303

0.008781 75.48354 0.008392 75.65208 0.011496 77.60179 0.006597 69.80293

0.010631 77.42559 0.010232 77.66691 0.014142 78.1802 0.00781 74.72893

0.012604 78.54026 0.012178 78.73179 0.016788 78.62453 0.009321 76.96976

0.014623 79.16463 0.014206 79.34466 0.019416 79.02673 0.010892 78.26064

0.01671 79.63961 0.016275 79.76985 0.022044 79.40212 0.012526 78.98077

0.018816 80.03032 0.018377 80.13374 0.024649 79.73537 0.014206 79.55534

0.020918 80.35974 0.02046 80.46317 0.027259 80.04947 0.015877 79.89242

0.023015 80.67767 0.022525 80.76961 0.029873 80.3291 0.017612 80.1912

0.025079 80.95347 0.02458 81.05689 0.032482 80.58574 0.019347 80.45167

0.027158 81.24075 0.026618 81.3097 0.035119 80.80408 0.021064 80.75811

0.029227 81.48591 0.02866 81.55485 0.037752 81.03008 0.022813 81.01093

0.031301 81.71957 0.030697 81.78468 0.040393 81.21777 0.024512 81.20245

0.03338 81.92641 0.032748 81.99919 0.04304 81.39397 0.026224 81.43994

0.035463 82.13326 0.034808 82.19072 0.045713 81.54336 0.027945 81.65445

0.037546 82.31329 0.036859 82.37841 0.048401 81.68126 0.029658 81.86512

0.039638 82.47417 0.038938 82.54695 0.05112 81.8115 0.031351 82.03367

0.04173 82.62356 0.040993 82.68102 0.053858 81.91109 0.03305 82.19455

0.043841 82.7538 0.043085 82.81891 0.056605 81.99153 0.034753 82.35543

0.045974 82.8802 0.045191 82.93383 0.059375 82.07197 0.036474 82.48949

0.048117 82.98746 0.047288 83.02193 0.062176 82.11411 0.0382 82.65803

0.050264 83.07173 0.049412 83.11769 0.064997 82.16007 0.039908 82.74614

0.052448 83.15217 0.05156 83.20579 0.067849 82.18305 0.041634 82.87254

0.054622 83.22878 0.053702 83.27091 0.070729 82.19455 0.04341 82.95298

0.056834 83.26325 0.055854 83.30922 0.073631 82.2137 0.045132 83.09088

0.059059 83.30539 0.058029 83.382 0.07657 82.19072 0.046858 83.1943

0.061288 83.33986 0.060226 83.42413 0.079555 82.14858 0.048625 83.22495

0.063545 83.34369 0.062428 83.44711 0.082559 82.11411 0.05036 83.29773

0.065825 83.3705 0.064644 83.47393 0.085589 82.05282 0.0521 83.38966

0.068128 83.35901 0.066887 83.4701 0.088652 81.97621 0.053853 83.38966

0.070449 83.35518 0.06914 83.47393 0.091752 81.88045 0.055598 83.43945

0.072807 83.33986 0.071406 83.45478 0.094879 81.74638 0.057342 83.45861

0.075188 83.29389 0.073686 83.43179 0.098033 81.6238 0.059082 83.47776

0.077596 83.21729 0.075984 83.38966 0.101238 81.42079 0.060817 83.47393

0.080054 83.13301 0.078283 83.32454 0.10452 80.89984 0.06252 83.4203

400751 400751

L1P1-L1-325 L1P1-L2-325 L1P1-L3-325 L1P1-L4-325

400751 400751
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

46 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001459 16.38681 0.00152 17.03034 0.00152 17.03034 0.001525 16.96522

0.002659 29.97354 0.002784 31.27591 0.002784 31.27591 0.002637 29.73605

0.004014 45.05416 0.004157 46.50975 0.004157 46.50975 0.003887 44.04292

0.005305 59.19248 0.005444 60.57529 0.005444 60.57529 0.005123 57.71392

0.00672 70.84099 0.006959 72.05142 0.006959 72.05142 0.006437 69.59225

0.008684 76.18451 0.009038 76.50628 0.009038 76.50628 0.008268 76.02746

0.011234 77.26088 0.01161 77.41793 0.01161 77.41793 0.010608 77.32217

0.013811 77.85078 0.014225 78.01932 0.014225 78.01932 0.013062 77.92355

0.016384 78.31809 0.016834 78.46748 0.016834 78.46748 0.015543 78.37938

0.018962 78.72796 0.019453 78.88118 0.019453 78.88118 0.017997 78.80074

0.021512 79.10717 0.022058 79.24124 0.022058 79.24124 0.020469 79.14548

0.024062 79.44043 0.024681 79.57832 0.024681 79.57832 0.022937 79.47107

0.026607 79.76219 0.027268 79.90009 0.027268 79.90009 0.025395 79.78134

0.029158 80.0533 0.029868 80.1912 0.029868 80.1912 0.027849 80.05713

0.031703 80.32144 0.032464 80.45934 0.032464 80.45934 0.030308 80.31378

0.034248 80.55893 0.035078 80.70449 0.035078 80.70449 0.032784 80.56659

0.036803 80.78493 0.037715 80.91899 0.037715 80.91899 0.035252 80.78876

0.039376 80.99177 0.040339 81.10286 0.040339 81.10286 0.037743 80.9956

0.04194 81.17564 0.042976 81.29055 0.042976 81.29055 0.040238 81.16415

0.044517 81.34418 0.045631 81.44377 0.045631 81.44377 0.042728 81.30204

0.047118 81.50123 0.048323 81.58933 0.048323 81.58933 0.045251 81.46292

0.049746 81.61614 0.05101 81.70424 0.05101 81.70424 0.047787 81.60082

0.052369 81.73872 0.053716 81.80767 0.053716 81.80767 0.050351 81.7119

0.055024 81.82299 0.056458 81.89194 0.056458 81.89194 0.052906 81.8115

0.057689 81.9379 0.059219 81.97238 0.059219 81.97238 0.055497 81.8996

0.060381 81.97238 0.061994 82.01451 0.061994 82.01451 0.058102 81.96089

0.063077 82.02983 0.0648 82.05665 0.0648 82.05665 0.060725 82.01834

0.065806 82.07963 0.067638 82.08729 0.067638 82.08729 0.063358 82.05282

0.068562 82.09112 0.070514 82.09878 0.070514 82.09878 0.066031 82.08346

0.07135 82.11411 0.073393 82.0758 0.073393 82.0758 0.068714 82.08729

0.074161 82.11411 0.076328 82.05282 0.076328 82.05282 0.071434 82.0758

0.077009 82.09878 0.079308 81.99536 0.079308 81.99536 0.074199 82.01451

0.079884 82.04516 0.082334 81.88428 0.082334 81.88428 0.076996 81.92641

0.082828 81.95706 0.085406 81.70424 0.085406 81.70424 0.079848 81.77319

0.085781 81.82682 0.088561 81.45526 0.088561 81.45526 0.082751 81.5357

0.088811 81.64296 0.094503 80.66618 0.094503 80.66618 0.085731 81.15648

0.091874 81.37099 0.097818 80.015 0.097818 80.015 0.088785 80.65086

0.095038 80.98794 0.101169 79.20294 0.101169 79.20294 0.091935 79.98436

0.09822 80.467 0.104594 78.15338 0.104594 78.15338 0.095121 79.13782

0.101479 79.74304 0.108169 76.5216 0.108169 76.5216 0.098381 78.01932

L1P1-T1-325 L1P1-T2-325 L1P1-T3-325 L1P1-T4-325

400751 400751 400751 400751
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

47 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.000824 8.908427 0.001628 18.12561 0.001563 17.60982 0.001563 17.24578

0.002051 22.50509 0.002905 32.5545 0.002712 30.75038 0.002753 30.62258

0.003031 33.4946 0.00432 48.47764 0.003999 45.25806 0.004109 45.78089

0.004065 44.99858 0.00568 62.94545 0.005276 59.30486 0.005381 59.6418

0.005073 55.95328 0.007328 73.38966 0.006659 70.77235 0.006823 71.14415

0.006094 65.91772 0.009754 76.4988 0.008655 75.98908 0.008888 76.03942

0.007371 72.88432 0.01246 77.31208 0.011241 77.04249 0.011562 77.05023

0.009092 75.6346 0.015193 77.87242 0.013856 77.63503 0.014236 77.63503

0.01112 76.42371 0.01799 78.33159 0.016447 78.10365 0.016877 78.0959

0.013167 76.91496 0.020714 78.7285 0.019015 78.47544 0.019496 78.49093

0.0152 77.31726 0.023439 79.09818 0.021574 78.84723 0.022119 78.83949

0.017223 77.677 0.026153 79.4445 0.02412 79.18417 0.024715 79.1803

0.019247 77.99419 0.028868 79.73635 0.026647 79.48625 0.027306 79.50949

0.021261 78.27657 0.031579 80.01263 0.029174 79.77284 0.029907 79.76897

0.023285 78.528 0.034298 80.28891 0.031724 80.03232 0.032503 80.02458

0.025295 78.7949 0.037031 80.50682 0.034261 80.26857 0.035098 80.2647

0.0273 79.02699 0.03976 80.71306 0.036769 80.48932 0.037717 80.48932

0.029296 79.24748 0.042516 80.9193 0.039324 80.68296 0.04034 80.67134

0.031297 79.46023 0.045267 81.07106 0.041837 80.88048 0.042982 80.83013

0.03332 79.66138 0.048042 81.22671 0.044415 81.01603 0.045628 81.0199

0.035325 79.83931 0.050834 81.37458 0.046869 81.17094 0.048293 81.13609

0.037358 80.00178 0.05365 81.46408 0.04962 81.27938 0.050989 81.25614

0.039382 80.16424 0.05647 81.55747 0.05218 81.41493 0.053704 81.35296

0.04141 80.30349 0.059318 81.63529 0.054743 81.50013 0.056442 81.44979

0.043438 80.41567 0.062184 81.69366 0.05739 81.57759 0.059203 81.52724

0.045475 80.55879 0.065059 81.72869 0.060494 81.69765 0.061972 81.58146

0.04754 80.65937 0.067961 81.78705 0.06319 81.67828 0.06477 81.62794

0.0496 80.77154 0.070896 81.8104 0.066056 81.72088 0.067613 81.66666

0.051679 80.88372 0.07384 81.79873 0.068853 81.75574 0.070474 81.66666

0.053762 80.94948 0.076811 81.81429 0.071806 81.74025 0.073358 81.65505

0.055859 81.01524 0.079805 81.79095 0.074668 81.73638 0.076275 81.64343

0.057955 81.081 0.082809 81.73647 0.077575 81.71314 0.079228 81.6047

0.06008 81.13902 0.085871 81.70534 0.0805 81.65505 0.082222 81.54661

0.062213 81.18544 0.088957 81.62751 0.08344 81.58534 0.08523 81.45753

0.064365 81.21638 0.092075 81.51466 0.086434 81.43817 0.088256 81.33747

0.066526 81.25893 0.095243 81.38625 0.089501 81.23678 0.091355 81.1477

0.068696 81.27441 0.098439 81.16056 0.092628 80.91921 0.094505 80.84562

0.070884 81.27828 0.101717 80.81034 0.095824 80.44285 0.097696 80.44285

0.073105 81.28214 0.1051 80.26945 0.099074 79.78059 0.100942 79.85805

0.075334 81.27828 0.108739 78.20707 0.102357 78.63423 0.104279 78.9518

400768 400768

L2P1-T1-325 L2P1-T2-325 L2P1-T3-325 L2P1-T4-325

400768 400768
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

48 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001557 16.52295 0.001667 18.14726 0.0017 18.4756 0.001678 18.13753

0.002866 30.64361 0.003091 33.71026 0.003242 35.10403 0.003138 34.08005

0.004262 45.60564 0.004574 49.34601 0.004872 52.0942 0.004622 49.72812

0.00575 58.5042 0.006259 61.33698 0.006896 62.91557 0.006416 61.57507

0.008035 63.47632 0.008891 64.12416 0.009954 64.65499 0.009255 64.02247

0.010763 64.58039 0.011711 65.04301 0.013058 65.52855 0.012217 64.92877

0.013497 65.2809 0.014573 65.70534 0.016208 66.15967 0.01522 65.56739

0.016257 65.84435 0.017439 66.20305 0.019385 66.66764 0.018224 66.08747

0.019018 66.28598 0.020341 66.62802 0.022562 67.07941 0.021241 66.49282

0.021778 66.68573 0.023267 66.99556 0.025744 67.4296 0.024258 66.8561

0.024557 66.99411 0.026183 67.30184 0.028944 67.74131 0.027302 67.1735

0.027355 67.28726 0.029113 67.58516 0.032172 68.01839 0.030337 67.46413

0.030166 67.54614 0.032052 67.83018 0.035404 68.26853 0.033396 67.6974

0.032995 67.77457 0.035001 68.07521 0.038668 68.47633 0.036454 67.91537

0.035824 67.98396 0.037972 68.26281 0.041937 68.6649 0.03953 68.10275

0.038654 68.18193 0.04092 68.44658 0.045206 68.83807 0.042621 68.2863

0.04151 68.34945 0.043914 68.60355 0.048516 68.99585 0.04572 68.44691

0.044363 68.50935 0.046913 68.73755 0.051849 69.119 0.048843 68.58458

0.047224 68.63117 0.04993 68.87154 0.055173 69.24984 0.051974 68.69165

0.050127 68.74539 0.05297 68.97874 0.058556 69.33835 0.055151 68.81402

0.053052 68.8558 0.05601 69.0936 0.061935 69.42686 0.058347 68.91727

0.055968 68.9662 0.059059 69.174 0.065391 69.48074 0.061565 68.98228

0.058917 69.04996 0.062131 69.23525 0.068848 69.55001 0.064798 69.05111

0.061897 69.10326 0.065249 69.30034 0.072359 69.59618 0.068076 69.09318

0.064887 69.16417 0.06838 69.33863 0.075894 69.61543 0.07139 69.13524

0.067931 69.18321 0.071544 69.38457 0.079479 69.61158 0.074741 69.1926

0.070976 69.20224 0.074703 69.39605 0.083118 69.61927 0.078143 69.17348

0.074094 69.16417 0.077907 69.39988 0.086799 69.58464 0.081581 69.15054

0.077243 69.11468 0.081181 69.36925 0.090503 69.52692 0.08507 69.11995

0.080434 69.00427 0.084477 69.31948 0.094243 69.43456 0.088609 69.0167

0.083685 68.86722 0.087842 69.2008 0.098039 69.31526 0.092203 68.86756

0.086981 68.62356 0.091257 69.05914 0.101861 69.13054 0.095856 68.64576

0.090337 68.31899 0.094764 68.84474 0.10573 68.86116 0.099541 68.3016

0.093734 67.91163 0.098312 68.5576 0.109635 68.52251 0.103264 67.88095

0.097145 67.39005 0.101906 68.18241 0.113577 68.07996 0.107022 67.32646

0.10062 66.72761 0.105555 67.66555 0.117528 67.50272 0.110818 66.63048

0.104122 65.89385 0.10925 67.04916 0.121529 66.77924 0.114677 65.728

0.107688 64.81262 0.112976 66.24517 0.125567 65.86335 0.1186 64.55402

0.111287 63.38875 0.116804 65.03152 0.129651 64.64729 0.122616 62.91349

0.114991 61.46615 0.120901 62.42429 0.133817 62.92326 0.126892 60.56934

400751 400751 400751 400751

L1P1-45-1-325 L1P1-45-2-325 L1P1-45-3-325 L1P1-45-4-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

49 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001643 17.78017 0.001715 18.46735 0.001818 19.47151 0.001854 19.80358

0.002806 30.4841 0.003327 35.71585 0.00331 35.641 0.003324 35.73993

0.004226 45.74703 0.004957 52.48372 0.00494 52.21307 0.004889 51.73037

0.005681 58.72811 0.006994 62.74977 0.007064 62.70756 0.006862 62.61345

0.007842 63.48923 0.009956 64.29929 0.010214 64.24825 0.009792 64.29015

0.01047 64.56371 0.012982 65.13749 0.013345 65.10762 0.012773 65.13622

0.013089 65.25092 0.016022 65.75653 0.016523 65.73474 0.015795 65.74277

0.015726 65.80145 0.019071 66.26022 0.019705 66.23798 0.01883 66.25273

0.018372 66.24947 0.022152 66.67548 0.022891 66.65605 0.021897 66.65839

0.021055 66.64813 0.025302 67.04075 0.026077 67.03155 0.024951 67.01768

0.023729 66.94427 0.02842 67.36757 0.029291 67.34511 0.028037 67.31902

0.026402 67.2632 0.031556 67.63287 0.032505 67.60834 0.031127 67.60104

0.029094 67.50619 0.034697 67.88279 0.035737 67.87157 0.034222 67.85216

0.031791 67.75298 0.037847 68.10965 0.038988 68.08448 0.037349 68.05306

0.034506 67.95801 0.041005 68.3019 0.042234 68.27416 0.040485 68.24623

0.037202 68.14405 0.04416 68.46338 0.045503 68.45223 0.043621 68.42394

0.039931 68.30731 0.047333 68.63256 0.04879 68.61482 0.046771 68.59006

0.042646 68.46677 0.050533 68.75945 0.0521 68.75418 0.049939 68.72528

0.04537 68.59966 0.053737 68.89786 0.055428 68.87418 0.053116 68.84891

0.048126 68.70976 0.056979 68.99014 0.058789 68.98644 0.056316 68.95322

0.050868 68.80848 0.060257 69.0978 0.062176 69.06386 0.059548 69.04594

0.053615 68.8996 0.063544 69.17855 0.065573 69.12967 0.062785 69.11934

0.056385 68.96794 0.066872 69.24776 0.069025 69.21096 0.066059 69.20434

0.059164 69.0135 0.070228 69.29005 0.0725 69.25742 0.069369 69.2507

0.061966 69.03628 0.073607 69.33234 0.07603 69.27677 0.072711 69.27774

0.064786 69.0211 0.077022 69.35157 0.079564 69.28452 0.07608 69.31638

0.067643 68.96414 0.080492 69.36695 0.083158 69.28064 0.079491 69.3241

0.070541 68.88441 0.083981 69.3285 0.086803 69.2458 0.082943 69.29706

0.073567 68.74773 0.087547 69.26314 0.090479 69.18 0.086441 69.25843

0.076694 68.5541 0.091173 69.14779 0.094192 69.06386 0.090002 69.16184

0.079931 68.29212 0.094873 68.98245 0.097941 68.91289 0.093592 69.02662

0.083213 67.93902 0.098631 68.73638 0.101741 68.71934 0.097245 68.82187

0.086537 67.53657 0.102422 68.39033 0.10555 68.43288 0.100949 68.50893

0.089906 67.01641 0.106291 67.94816 0.109405 68.06126 0.104666 68.11101

0.093317 66.37097 0.110191 67.36372 0.113301 67.58511 0.108439 67.60877

0.096787 65.55846 0.114115 66.64472 0.117225 66.95026 0.112234 66.96359

0.100313 64.52575 0.118084 65.7027 0.121176 66.16056 0.116075 66.13683

0.103929 63.18929 0.122136 64.47616 0.125195 65.09214 0.119967 65.05509

0.107656 61.38963 0.126206 62.79207 0.129325 63.63662 0.123927 63.6102

0.111493 59.02046 0.130422 60.46586 0.133638 61.43784 0.128024 61.64375

L2P1-45-3-325 L2P1-45-4-325

400768 400768 400768 400768

L2P1-45-1-325 L2P1-45-2-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

50 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001252 14.12091 0.001191 13.28098 0.001361 14.90305 0.00127 14.17485

0.002625 29.6019 0.002551 28.3998 0.002689 29.94481 0.002598 28.98929

0.003967 44.6976 0.003879 43.15644 0.004071 45.24472 0.003889 43.299

0.005281 58.88402 0.005183 57.18488 0.005404 59.49277 0.005171 57.05774

0.006682 70.95903 0.006516 69.24834 0.006805 71.13241 0.006485 69.06725

0.008618 76.31843 0.00831 75.76361 0.008787 76.34155 0.008252 75.6827

0.011058 77.31248 0.010618 77.11213 0.011305 77.28166 0.010633 77.06204

0.013622 77.84418 0.01309 77.6708 0.013901 77.83262 0.013128 77.61301

0.016168 78.34506 0.015576 78.14086 0.016469 78.32194 0.0156 78.08692

0.018686 78.75347 0.018034 78.57238 0.019024 78.73035 0.018054 78.52615

0.021208 79.13876 0.020488 78.95382 0.021574 79.11564 0.020508 78.89603

0.023722 79.49708 0.02291 79.29288 0.024124 79.45085 0.022962 79.23123

0.026258 79.7899 0.025346 79.5857 0.026669 79.7244 0.025416 79.52405

0.028803 80.02878 0.027786 79.84384 0.029251 79.9864 0.027874 79.7899

0.03134 80.24069 0.030231 80.07887 0.031834 80.21757 0.030347 79.99796

0.033904 80.42948 0.032689 80.28307 0.034425 80.39866 0.032828 80.20602

0.036486 80.61057 0.035166 80.4526 0.037039 80.56048 0.035323 80.3794

0.039095 80.73001 0.037656 80.59901 0.039662 80.68763 0.03785 80.53351

0.041714 80.83789 0.040152 80.72616 0.042313 80.81092 0.040377 80.64525

0.044333 80.93422 0.042679 80.82633 0.044968 80.89183 0.042932 80.74542

0.047011 80.99586 0.045201 80.89183 0.04766 80.94963 0.0455 80.81478

0.049698 81.05366 0.047747 80.96119 0.050375 81.00357 0.048092 80.89183

0.052409 81.09989 0.05032 81.01513 0.053113 81.0421 0.05071 80.92651

0.055142 81.09604 0.052911 81.03824 0.055832 81.05366 0.053352 80.96504

0.057902 81.1076 0.055521 81.0498 0.058625 81.06522 0.056026 80.9766

0.060691 81.09989 0.058153 81.05366 0.061432 81.05366 0.058704 80.98045

0.063497 81.06907 0.060804 81.03824 0.064275 81.03439 0.061433 80.9766

0.066335 81.02669 0.0635 81.02669 0.067136 80.99201 0.064184 80.94192

0.069215 80.9843 0.066215 80.9843 0.070039 80.92651 0.066968 80.88028

0.072113 80.9111 0.068967 80.91495 0.072973 80.85716 0.069788 80.81478

0.075052 80.81863 0.071764 80.83019 0.075944 80.73001 0.072654 80.68763

0.078047 80.68378 0.074598 80.69534 0.078961 80.58745 0.075556 80.52966

0.081068 80.5104 0.077491 80.53351 0.082043 80.39481 0.078495 80.30619

0.084163 80.2484 0.08044 80.27922 0.085169 80.07887 0.081503 80.00181

0.087322 79.89393 0.083461 79.92861 0.088338 79.68202 0.084539 79.5934

0.090559 79.40461 0.08651 79.47396 0.091579 79.15802 0.087638 79.07326

0.093814 78.76888 0.089633 78.87676 0.094857 78.46065 0.090783 78.399

0.097133 77.9983 0.092796 78.16783 0.098185 77.63613 0.093951 77.55521

0.100471 77.04663 0.09601 77.26625 0.101518 76.64593 0.097184 76.57658

0.103886 75.4207 0.099251 76.13734 0.104952 75.29741 0.100439 75.31667

400751 400751 400751 400751

L1P2-T1-350 L1P2-T2-350 L1P2-T3-350 L1P2-T4-350
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

51 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0

0.001069 13.02482 0.001372 16.50498 0.001372 16.50498

0.00242 29.27643 0.002631 31.42251 0.002631 31.42251

0.003802 45.43693 0.003954 46.71221 0.003954 46.71221

0.005171 60.66356 0.005296 61.5234 0.005296 61.5234

0.006641 72.21165 0.006811 72.70775 0.006811 72.70775

0.008902 76.80887 0.009077 76.70297 0.009077 76.70297

0.011732 77.71237 0.011829 77.57265 0.011829 77.57265

0.014579 78.30458 0.014594 78.13092 0.014594 78.13092

0.017418 78.7867 0.017345 78.57526 0.017345 78.57526

0.020238 79.1815 0.020175 79.16391 0.020175 79.16391

0.023044 79.56492 0.023018 79.38038 0.023018 79.38038

0.025842 79.89519 0.025737 79.71838 0.025737 79.71838

0.028662 80.24445 0.028443 80.03359 0.028443 80.03359

0.031459 80.52916 0.031167 80.31462 0.031167 80.31462

0.034284 80.7873 0.033882 80.58426 0.033882 80.58426

0.037095 81.03026 0.03662 80.82352 0.03662 80.82352

0.03992 81.20868 0.039366 81.01721 0.039366 81.01721

0.042772 81.38331 0.042113 81.1919 0.042113 81.1919

0.045633 81.5959 0.044769 81.40458 0.044769 81.40458

0.048513 81.70979 0.047561 81.51851 0.047561 81.51851

0.051374 81.81228 0.050372 81.65523 0.050372 81.65523

0.054291 81.92617 0.053193 81.76916 0.053193 81.76916

0.057253 82.03246 0.056017 81.8679 0.056017 81.8679

0.060206 82.1008 0.058902 81.93626 0.058902 81.93626

0.063209 82.14635 0.061777 81.98943 0.061777 81.98943

0.066235 82.1919 0.064675 82.0426 0.064675 82.0426

0.06927 82.1995 0.0676 82.08437 0.0676 82.08437

0.072347 82.22987 0.07059 82.09197 0.07059 82.09197

0.075456 82.20709 0.073584 82.09576 0.073584 82.09576

0.078596 82.15394 0.076596 82.05779 0.076596 82.05779

0.081787 82.15394 0.079659 82.01601 0.079659 82.01601

0.085015 82.08941 0.082763 81.96284 0.082763 81.96284

0.088261 81.97932 0.085899 81.84132 0.085899 81.84132

0.091589 81.78951 0.089081 81.67421 0.089081 81.67421

0.094945 81.47442 0.092327 81.42736 0.092327 81.42736

0.098365 81.12517 0.095642 81.05518 0.095642 81.05518

0.101849 80.52157 0.098997 80.5197 0.098997 80.5197

0.105429 79.70159 0.10244 79.83991 0.10244 79.83991

0.109023 78.69179 0.105929 78.97022 0.105929 78.97022

0.112717 77.32515 0.109491 77.80432 0.109491 77.80432

L3C1-T-01 L3C1-T-03 L3C1-T-04

400766 400766 400766
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

52 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001363 16.6086 0.001237 15.3894 0.000966 11.88174 0.001133 13.9185

0.00253 30.63127 0.002372 29.18248 0.002069 25.54175 0.002172 26.55613

0.003771 45.09953 0.003586 43.54947 0.003132 38.14543 0.003234 39.18236

0.004989 58.7147 0.004794 57.04608 0.004217 50.50973 0.004255 50.82798

0.006325 70.42946 0.006053 68.85894 0.005306 61.41874 0.005359 61.78946

0.008161 75.85267 0.007775 75.36969 0.006629 69.34497 0.006672 69.54308

0.010588 76.97616 0.010137 76.8444 0.008488 72.39615 0.008417 72.65593

0.01311 77.57409 0.012673 77.44872 0.010617 73.45247 0.010504 73.75815

0.015647 78.06919 0.015168 77.95423 0.012773 74.21241 0.012583 74.52591

0.018123 78.53381 0.017645 78.41412 0.01493 74.86597 0.014657 75.17965

0.020619 78.91847 0.020136 78.80561 0.017063 75.42453 0.016722 75.72316

0.023114 79.26123 0.022603 79.14768 0.019206 75.89569 0.018809 76.20967

0.025609 79.53924 0.025085 79.44034 0.021371 76.31366 0.020892 76.63155

0.028108 79.81726 0.027571 79.69879 0.023532 76.65564 0.023007 76.97743

0.03064 80.01911 0.030089 79.94204 0.02573 76.95202 0.025132 77.25868

0.033167 80.21714 0.032607 80.14348 0.027941 77.199 0.027288 77.55134

0.035736 80.38852 0.035152 80.30312 0.030166 77.40038 0.029463 77.72998

0.038304 80.53705 0.037707 80.43234 0.032405 77.56757 0.031637 77.90482

0.040895 80.62846 0.040293 80.56157 0.03468 77.71576 0.03384 78.05685

0.043496 80.7389 0.042889 80.64899 0.036964 77.82975 0.036042 78.17848

0.046115 80.81888 0.045494 80.706 0.039267 77.92474 0.03828 78.26969

0.04877 80.84935 0.048131 80.76681 0.041579 78.00834 0.040519 78.34951

0.051425 80.89124 0.0508 80.82383 0.04391 78.06153 0.04279 78.40652

0.054126 80.92171 0.053483 80.85043 0.046272 78.09573 0.045079 78.46734

0.056823 80.9179 0.056203 80.84663 0.048657 78.10713 0.047396 78.49774

0.059556 80.9179 0.05894 80.83523 0.051052 78.11473 0.049717 78.50534

0.062321 80.89505 0.06171 80.82003 0.053487 78.11473 0.052074 78.50914

0.065105 80.89505 0.064494 80.77061 0.055946 78.08813 0.054441 78.49774

0.067907 80.83411 0.067314 80.7212 0.058422 78.03874 0.056845 78.48634

0.070745 80.77318 0.070152 80.64139 0.06094 77.95894 0.059271 78.44833

0.073616 80.71224 0.073046 80.55017 0.063481 77.87155 0.061721 78.36851

0.076495 80.60941 0.075981 80.41714 0.066063 77.73856 0.064211 78.3001

0.079421 80.48374 0.078947 80.2195 0.068696 77.53717 0.066716 78.18228

0.082374 80.36567 0.081955 79.93064 0.071365 77.27499 0.069279 78.02644

0.085373 80.17144 0.085013 79.56576 0.074103 76.91782 0.071875 77.8022

0.088417 79.88581 0.088108 79.07166 0.076863 76.47705 0.074512 77.51714

0.091494 79.49354 0.091244 78.42933 0.079656 75.93749 0.077163 77.13706

0.094643 78.9794 0.094435 77.66157 0.082485 75.27254 0.079869 76.66196

0.09783 78.33958 0.097654 76.68476 0.085347 74.50119 0.082616 76.08424

0.101071 77.40652 0.100932 75.48371 0.088213 73.52846 0.08539 75.38109

L3C1-T-05 L3C1-T-06 L3C1-T-07 L3C1-T-08

400766 400766 400766 400766
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

53 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001107 13.31426 0.001147 14.11418 0.001316 16.55208 0.001124 13.41275

0.002078 25.00778 0.002259 27.77368 0.002447 30.23453 0.002296 27.39091

0.003144 37.58362 0.003321 40.40635 0.003647 44.38334 0.003514 41.51137

0.004179 49.20519 0.004448 53.51264 0.004878 58.35163 0.004754 55.4783

0.005232 59.68316 0.005606 65.79293 0.00621 70.72149 0.005995 67.89127

0.006477 67.67323 0.006989 74.62898 0.008014 77.27312 0.007597 75.80712

0.008167 71.1722 0.00898 78.2172 0.010454 78.943 0.009832 78.40953

0.010149 72.40289 0.011402 79.17962 0.013087 79.60117 0.012391 79.16966

0.012237 73.20948 0.013856 79.74797 0.015719 80.07505 0.014932 79.70138

0.014265 73.89488 0.016282 80.19508 0.018333 80.485 0.017454 80.13574

0.01632 74.47804 0.018713 80.58535 0.020961 80.84982 0.019981 80.51768

0.018339 74.99683 0.021126 80.93773 0.02358 81.17326 0.022495 80.84345

0.020372 75.42852 0.023525 81.25222 0.026194 81.4779 0.02499 81.15424

0.022405 75.79205 0.025929 81.55156 0.028817 81.73741 0.027508 81.43508

0.024465 76.09499 0.028337 81.80921 0.031441 81.99692 0.030012 81.6897

0.02653 76.35249 0.03074 82.04413 0.034069 82.20753 0.032526 81.92561

0.028622 76.57591 0.033162 82.2639 0.03671 82.3843 0.035048 82.13904

0.030723 76.7501 0.035598 82.44956 0.039366 82.55354 0.037571 82.31129

0.032839 76.90535 0.038033 82.65038 0.042039 82.71526 0.040126 82.49477

0.034963 77.02653 0.040492 82.79057 0.044718 82.85442 0.042676 82.62582

0.037096 77.14013 0.042959 82.93077 0.047432 82.95597 0.045235 82.75314

0.039248 77.2083 0.045432 83.0596 0.050175 83.06503 0.04784 82.86922

0.041427 77.28403 0.047927 83.1619 0.052922 83.12145 0.050449 82.96283

0.043588 77.32947 0.050454 83.25284 0.055705 83.20043 0.053082 83.04895

0.045777 77.35598 0.052981 83.32483 0.058507 83.2418 0.055719 83.09388

0.048006 77.38249 0.055545 83.38545 0.061327 83.25684 0.058402 83.1538

0.050231 77.37113 0.058127 83.4385 0.064189 83.27565 0.061098 83.1875

0.052456 77.34462 0.060732 83.46881 0.067064 83.26437 0.063822 83.19873

0.054722 77.32947 0.063369 83.48397 0.069985 83.26813 0.06656 83.20996

0.056993 77.2651 0.066029 83.48397 0.072956 83.19291 0.06933 83.19499

0.059282 77.18558 0.068712 83.46881 0.075945 83.11017 0.072145 83.1538

0.061622 77.08333 0.071431 83.42713 0.078985 82.97853 0.074988 83.10137

0.064007 76.90157 0.074183 83.36272 0.082062 82.76792 0.077877 83.02274

0.066443 76.67436 0.07698 83.21116 0.085202 82.44823 0.080794 82.89543

0.068942 76.36763 0.079805 83.02549 0.088389 82.027 0.083751 82.7082

0.071534 75.97002 0.082698 82.75268 0.091594 81.53808 0.086764 82.43486

0.074157 75.47396 0.085596 82.4003 0.094876 80.84982 0.089836 82.08662

0.076817 74.8908 0.088549 81.93804 0.098186 80.03368 0.092949 81.61856

0.079541 74.18646 0.091543 81.36589 0.101524 79.05959 0.096108 81.03816

0.082306 73.23598 0.094551 80.57777 0.104935 77.75077 0.09929 80.2331

L3C1-T-09 L3C1-T-10 L3C1-T-11 L3C1-T-12

400766 400766 400766 400766
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

54 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.001223 13.88508 0.001249 14.30493 0.00146 16.47154 0.001477 16.87529

0.002129 24.16286 0.002279 26.12453 0.002536 28.81856 0.002498 28.41237

0.003228 36.76179 0.003405 38.97241 0.003827 43.51811 0.003675 41.83753

0.00429 48.63013 0.00449 51.31943 0.005031 56.96551 0.00486 54.97455

0.005357 60.43378 0.005603 63.37048 0.006253 69.10384 0.006019 66.89455

0.00641 70.55174 0.006748 72.85651 0.007805 76.71922 0.007406 75.34926

0.007746 77.03576 0.008336 77.84996 0.009998 78.67714 0.009315 78.15486

0.009573 79.02206 0.010401 78.95034 0.012415 79.23112 0.011554 78.78422

0.01162 79.58142 0.012635 79.4512 0.014837 79.64471 0.013847 79.20885

0.013694 79.95432 0.014869 79.83064 0.017277 80.01277 0.01615 79.57662

0.015777 80.31582 0.017103 80.15696 0.01969 80.35427 0.018458 79.91405

0.017837 80.60501 0.019315 80.47569 0.022084 80.64264 0.020756 80.20598

0.019892 80.88279 0.021508 80.75268 0.024493 80.9462 0.02305 80.49033

0.021934 81.15676 0.023691 81.02209 0.026905 81.19663 0.025334 80.75193

0.023967 81.38888 0.025871 81.27252 0.029318 81.42809 0.027619 81.00216

0.026009 81.63621 0.028059 81.50777 0.031717 81.6254 0.029908 81.19931

0.028064 81.8493 0.030243 81.70129 0.034157 81.84168 0.032215 81.40405

0.030102 82.02814 0.032427 81.90618 0.036597 82.00104 0.034518 81.57845

0.032153 82.22221 0.034638 82.06555 0.039042 82.14903 0.03683 81.74148

0.034208 82.37061 0.03684 82.22112 0.041501 82.27045 0.03916 81.88934

0.036264 82.52282 0.039051 82.36531 0.043973 82.39566 0.041481 81.9955

0.038338 82.66741 0.041276 82.46396 0.04644 82.49811 0.043816 82.11303

0.040375 82.78157 0.043474 82.44878 0.048954 82.60056 0.04616 82.21539

0.042495 82.88811 0.045658 82.70301 0.051467 82.64609 0.048536 82.28364

0.044546 82.99846 0.04791 82.74475 0.054017 82.7068 0.050913 82.36705

0.04662 83.06696 0.050181 82.83581 0.056581 82.72578 0.053307 82.40496

0.048456 83.13165 0.052447 82.87376 0.059159 82.75993 0.055706 82.43908

0.050456 83.21155 0.054759 82.93447 0.061764 82.76752 0.058123 82.46562

0.052938 83.2458 0.057071 82.98759 0.064378 82.78269 0.060568 82.49216

0.055149 83.26102 0.059401 83.00277 0.067033 82.74475 0.063022 82.49216

0.057379 83.31049 0.061736 83.01795 0.069721 82.72957 0.065494 82.48458

0.059585 83.31429 0.064094 82.99897 0.072435 82.69163 0.067985 82.45804

0.061842 83.34093 0.066475 82.99897 0.075178 82.61574 0.070503 82.46183

0.064118 83.3219 0.068869 82.97621 0.077948 82.52467 0.073039 82.40496

0.066375 83.30668 0.071291 82.95344 0.080777 82.36531 0.075607 82.35188

0.06865 83.28385 0.073736 82.90032 0.083629 82.17938 0.078185 82.29122

0.070967 83.242 0.076194 82.82823 0.086545 81.92136 0.08079 82.19265

0.073288 83.15828 0.078694 82.72578 0.089521 81.54571 0.083445 82.07511

0.075664 83.05554 0.081244 82.58538 0.092525 81.05624 0.086142 81.89692

0.078068 82.85006 0.083817 82.38428 0.095597 80.35806 0.088925 81.28272

L3C1-T-13 L3C1-T-14 L3C1-T-15 L3C1-T-16

400766 400766 400766 400766
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

55 of 152

NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.00146 16.0435 0.00138 15.3042 0.00135 14.8243 0.00146 16.1736

0.00273 30.0345 0.0026 28.8411 0.00266 29.2519 0.00253 28.1262

0.00405 44.4429 0.00385 42.5737 0.00394 43.202 0.00371 41.1319

0.00537 57.9903 0.00511 56.053 0.0052 56.5557 0.00491 54.149

0.00709 65.8729 0.00672 64.8953 0.00684 65.1619 0.00628 63.4256

0.00921 69.462 0.0087 68.9768 0.00887 69.0786 0.0081 68.1157

0.01165 70.8565 0.01098 70.4505 0.01125 70.5231 0.01027 69.9227

0.01406 71.8132 0.01331 71.4666 0.01366 71.5189 0.0125 70.9499

0.01645 72.6568 0.01562 72.2984 0.01602 72.3728 0.01471 71.7124

0.01883 73.3497 0.01794 73.018 0.01835 73.0821 0.0169 72.5123

0.02124 73.9817 0.02025 73.6455 0.0207 73.7073 0.01911 73.1454

0.02362 74.5441 0.02256 74.2183 0.02304 74.2747 0.0213 73.7352

0.02601 75.0311 0.02486 74.7076 0.02539 74.79 0.02349 74.233

0.0284 75.495 0.02719 75.1681 0.02772 75.2474 0.02568 74.7222

0.03078 75.9038 0.02951 75.5826 0.03006 75.6729 0.02788 75.1566

0.03316 76.2893 0.03183 75.9654 0.03239 76.0782 0.03007 75.5451

0.03555 76.6285 0.03417 76.3252 0.03474 76.4371 0.03228 75.9019

0.03794 76.988 0.03652 76.6533 0.0371 76.7758 0.03446 76.25

0.04034 77.2721 0.03887 76.9613 0.03947 77.0798 0.03668 76.5665

0.04273 77.5446 0.04123 77.2319 0.04185 77.3374 0.03891 76.8629

0.04514 77.823 0.04357 77.5053 0.04423 77.6095 0.04113 77.1334

0.04755 78.0404 0.04593 77.7471 0.04661 77.8527 0.04335 77.378

0.04999 78.2578 0.0483 77.9515 0.04902 78.0988 0.04559 77.6225

0.05243 78.4724 0.0507 78.1587 0.05145 78.3159 0.04784 77.8556

0.05488 78.655 0.0531 78.3487 0.05389 78.4896 0.05012 78.0426

0.05734 78.8057 0.0555 78.507 0.05634 78.6546 0.0524 78.221

0.05984 78.9739 0.05793 78.6682 0.05878 78.8138 0.05469 78.3994

0.06233 79.1015 0.06036 78.8121 0.06126 78.973 0.057 78.5577

0.06486 79.229 0.06281 78.9445 0.06375 79.1033 0.05933 78.6929

0.0674 79.3421 0.06529 79.0568 0.06626 79.2046 0.06165 78.831

0.06995 79.4435 0.06778 79.1604 0.06881 79.3117 0.06402 78.9375

0.07254 79.5276 0.0703 79.2352 0.07138 79.3754 0.0664 79.0497

0.07515 79.5914 0.07283 79.3216 0.07399 79.4564 0.0688 79.1447

0.07781 79.6494 0.07537 79.3791 0.07664 79.5027 0.07122 79.2454

0.08048 79.6813 0.07797 79.4309 0.07934 79.5114 0.07365 79.3

0.08321 79.69 0.0806 79.4741 0.08209 79.4796 0.07615 79.3605

0.08598 79.661 0.08324 79.4943 0.08494 79.3898 0.07865 79.3835

0.08882 79.5943 0.08593 79.4971 0.08785 79.2364 0.08122 79.3892

0.09174 79.4406 0.08869 79.4741 0.09086 79.0048 0.08383 79.3576

0.09471 79.2029 0.09149 79.4252 0.09391 78.669 0.08651 79.3029

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P3 P3 P3 P3
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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (cont.)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.00056 6.26145 0.0005 5.6875 0.00052 5.79412 0.00049 5.37243

0.00154 17.1952 0.00124 13.7775 0.0012 13.5599 0.00133 14.8844

0.00187 20.9013 0.00171 19.1997 0.0017 19.118 0.00176 19.7325

0.00241 26.8138 0.0023 25.8995 0.00229 25.6029 0.00228 25.3642

0.00298 33.3405 0.00289 32.5272 0.00286 32.085 0.00286 31.9091

0.00355 39.7174 0.00348 38.9617 0.00343 38.4951 0.00344 38.4712

0.00414 46.1749 0.00403 45.3068 0.004 44.7324 0.00401 44.7222

0.00471 52.4133 0.0046 51.5481 0.00455 50.8633 0.00457 50.8897

0.00524 58.2623 0.00517 57.6941 0.00511 56.9338 0.00513 56.9333

0.0058 64.1402 0.00572 63.6816 0.00564 62.6876 0.00568 62.8992

0.00636 69.5046 0.00627 68.9451 0.00619 67.9751 0.00626 68.2601

0.00706 72.9714 0.007 72.6397 0.00686 71.9501 0.00694 71.9819

0.00792 74.8807 0.00788 74.6182 0.00769 74.0859 0.00782 74.056

0.00882 76.3458 0.00879 76.1439 0.00858 75.6315 0.00871 75.5914

0.00971 77.5917 0.00971 77.4273 0.00947 76.9124 0.00962 76.8906

0.01063 78.5723 0.01062 78.431 0.01038 77.9774 0.01056 77.9276

0.01155 79.3395 0.01159 79.2097 0.01132 78.7776 0.01154 78.7313

0.01252 79.9279 0.0126 79.801 0.01229 79.3993 0.01254 79.3305

0.01351 80.3692 0.01361 80.2538 0.01329 79.8857 0.01358 79.8

0.01453 80.747 0.01466 80.6547 0.01431 80.2714 0.01461 80.2062

0.01554 81.0585 0.01569 80.9748 0.01534 80.6139 0.01567 80.5288

0.01657 81.3555 0.01673 81.2748 0.01636 80.9248 0.0167 80.8342

0.01759 81.6151 0.01778 81.5603 0.01738 81.181 0.01772 81.1222

0.01863 81.843 0.01883 81.791 0.01841 81.44 0.01876 81.3729

0.01965 82.0795 0.01983 81.6786 0.01944 81.6818 0.01979 81.6091

0.02067 82.2813 0.02058 81.9352 0.02046 81.8977 0.02083 81.8338

0.02169 82.4919 0.0216 82.3419 0.02148 82.1193 0.02187 82.0585

0.0222 82.3563 0.02284 82.3852 0.0225 82.3208 0.02276 81.9692

0.02268 82.4717 0.02409 82.5438 0.02352 82.5108 0.0234 82.1996

0.02361 82.6534 0.02543 82.463 0.02455 82.7036 0.0244 82.4243

0.02494 82.5409 0.02675 82.5553 0.02556 82.8619 0.02559 82.456

0.0262 82.8524 0.0281 82.3967 0.02658 83.0462 0.02683 82.6259

0.02756 82.6361 0.02938 82.7774 0.02759 83.2045 0.02809 82.721

0.02889 82.6707 0.03039 82.5323 0.0286 83.3887 0.02937 82.842

0.03019 82.8841 0.03074 82.6649 0.02961 83.5384 0.03072 82.77

0.03154 82.9043 0.03106 83.1581 0.03063 83.6823 0.03209 82.6317

0.03286 82.7486 0.03159 83.7407 0.03164 83.8319 0.03338 82.8938

0.03331 82.9764 0.03263 83.5734 0.03265 83.9528 0.03474 82.8938

0.03372 83.6225 0.03384 83.6628 0.03366 84.0968 0.03538 82.7037

0.03409 83.9801 0.03508 83.9599 0.03467 84.2263 0.03567 83.2366

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Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table A-5. Tensile Test Results by Specimen Number (concluded)

Strain Stress Strain Stress Strain Stress Strain Stress

(in/in) (ksi) (in/in) (ksi) (in/in) (ksi) (in/in) (ksi)

0 0 0 0 0 0 0 0

0.00163 17.6316 0.00165 17.9187 0.00174 18.9152 0.00166 18.0451

0.003 32.4748 0.00304 32.9142 0.00324 35.088 0.00304 33.2502

0.00451 48.1767 0.00461 49.0296 0.00492 51.1632 0.00455 48.8142

0.00637 57.9344 0.00678 58.4513 0.00725 59.1117 0.00654 58.3249

0.00895 60.9496 0.00959 61.0644 0.01025 61.5268 0.00926 61.1334

0.01161 62.7587 0.01249 62.819 0.01329 63.2756 0.01201 62.9224

0.01429 64.1514 0.01543 64.1715 0.01637 64.5907 0.01481 64.3294

0.01701 65.2455 0.01841 65.2139 0.01953 65.6159 0.01768 65.4178

0.01977 66.1271 0.0214 66.084 0.02271 66.4745 0.02059 66.2879

0.02253 66.8708 0.02443 66.8363 0.02589 67.2183 0.0235 67.0373

0.02531 67.5399 0.02745 67.4997 0.02907 67.8615 0.02642 67.6921

0.02811 68.1199 0.03049 68.0826 0.03227 68.4502 0.02937 68.2721

0.03092 68.6454 0.03354 68.6139 0.03549 68.9642 0.0323 68.789

0.03374 69.1193 0.03659 69.0819 0.03872 69.4294 0.03528 69.26

0.0366 69.5442 0.03965 69.5098 0.04197 69.8515 0.03824 69.6821

0.03945 69.9377 0.04273 69.8975 0.04523 70.2334 0.04122 70.0726

0.04231 70.2794 0.04581 70.2564 0.0485 70.5924 0.04421 70.4258

0.04519 70.6039 0.04891 70.5723 0.05181 70.8882 0.04722 70.7417

0.04811 70.891 0.05203 70.8652 0.05513 71.1523 0.05026 71.0289

0.05103 71.1667 0.05517 71.1236 0.05849 71.4165 0.0533 71.2787

0.054 71.3878 0.05831 71.3677 0.06186 71.6434 0.05638 71.5228

0.05699 71.6118 0.06146 71.5544 0.06528 71.8329 0.05946 71.7295

0.05999 71.8128 0.06463 71.7525 0.06872 72.0081 0.06259 71.9191

0.06303 71.9908 0.06783 71.9133 0.07219 72.1488 0.06572 72.0914

0.0661 72.1402 0.07103 72.0569 0.07572 72.2866 0.06888 72.2493

0.0692 72.2723 0.07425 72.1689 0.07927 72.3871 0.07206 72.367

0.07231 72.3756 0.07746 72.2464 0.08287 72.479 0.07529 72.4905

0.07548 72.4761 0.08071 72.3038 0.08654 72.5364 0.07855 72.5939

0.07871 72.5594 0.08391 72.301 0.09025 72.5623 0.08183 72.6657

0.08197 72.5996 0.08711 72.2407 0.09406 72.5422 0.08517 72.7174

0.08529 72.6197 0.09033 72.1086 0.09791 72.479 0.08852 72.7662

0.08868 72.5853 0.09357 71.9133 0.10186 72.3584 0.09194 72.7891

0.09212 72.5221 0.09686 71.6434 0.10585 72.1488 0.0954 72.7719

0.09561 72.3929 0.10023 71.2471 0.10989 71.8329 0.09891 72.7116

0.09914 72.1746 0.10367 70.7704 0.11399 71.428 0.1025 72.6025

0.10272 71.8645 0.10719 70.1904 0.11812 70.8968 0.10614 72.4273

0.10635 71.4625 0.11078 69.5098 0.12229 70.2449 0.10984 72.1488

0.10999 70.9398 0.11448 68.6627 0.12648 69.438 0.11359 71.7697

0.11368 70.2593 0.11829 67.5887 0.13072 68.4301 0.11734 71.2844

0.11764 67.7495 0.12223 66.1443 0.13501 67.112 0.12115 70.6096

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Material Characterization Study

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Appendix B. Shear Test Results

Shear tests were performed using four types of specimens: single shear, thin double shear, wide 

double shear, and tension/shear. The single shear specimens, shown in Figure B-1, were in 

accordance with the ASTM standard B831-05. The specimens were loaded in tension, creating a 

shear stress between the two notches. The specimens were machined with the loading orientated 

in the L (Longitudinal) and T (Long Transverse) direction, resulting in shear along the LS and 

TS planes, respectively, as shown in Figure B-2. A displacement rate of 0.05 inches/minute was 

applied and the peak load recorded. The ultimate shear stress was calculated from the peak load 

and the area between the notches. The test configuration was not possible to generate a shear 

yield stress. The results from the longitudinal shear tests are provided in Table B-1.

Figure B-1. Schematic of the Single Shear Specimen 
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Figure B-2. Testing Orientations for all of the Shear Specimens
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Table B-1. Results from the Single Shear Tests

The thin double shear and wide double shear tests were conducted using a test fixture that was 

designed based upon the concepts presented in the ASTM standard D769 for thick, round 

specimens. The test fixture allowed shear testing with loading in the S (Short Transverse) 

direction on sheet material. The thickness of the coil and stringer materials precluded the use of 

the specimen sizes required by the ASTM D769 standard. The fixture, an exploded view is 

shown in Figure B-3, held the small specimens in tool steel shearing blocks and a precise plunger 

was pressed into a slot in the stainless steel block, shearing the specimen. The fixture 

accommodated different size specimens and a schematic of the wide double shear is shown in 

Figure B-4. The thin double shear specimens were identical to the wide double shear specimens, 

but at a width of 0.06 inches rather than 0.25 inches and allowed loading in the L or T directions. 

The orientations of the double shear tests are shown in Figure B-5. The results from the wide 

and think double shear tests are provided in Table B-2.

Shear Shear Width Thickness Load Stress Axial Load

Direction Plane (inch) (inch) (lbs.) (ksi) (% Sys)

L2P1-L-01 400768 Longitudinal Shear L LS 0.1851 0.0633 478.4 40.8 0

L2P1-L-02 400768 Longitudinal Shear L LS 0.1850 0.0631 481.2 41.2 0

L2P1-L-03 400768 Longitudinal Shear L LS 0.1847 0.0632 476.0 40.8 0

L1P1-L-01 400751 Longitudinal Shear L LS 0.1851 0.0641 485.0 40.9 0

L1P1-L-02 400751 Longitudinal Shear L LS 0.1850 0.0642 485.2 40.9 0

L1P1-L-03 400751 Longitudinal Shear L LS 0.1848 0.0641 486.0 41.0 0

L2P1-T-01 400768 Longitudinal Shear T TS 0.1850 0.0633 543.4 46.4 0

L2P1-T-02 400768 Longitudinal Shear T TS 0.1852 0.0632 545.6 46.6 0

L2P1-T-03 400768 Longitudinal Shear T TS 0.1850 0.0632 537.6 46.0 0

L1P1-T-01 400751 Longitudinal Shear T TS 0.1854 0.0643 547.6 45.9 0

L1P1-T-02 400751 Longitudinal Shear T TS 0.1845 0.0644 550.2 46.3 0

L1P1-T-03 400751 Longitudinal Shear T TS 0.1850 0.0645 544.6 45.7 0

325oF for 24 hours

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Figure B-3. Exploded View of the Fixture used for the Double Shear and Combined 

Tensile/Shear Tests

Tensile/Shear Specimen

Plunger

Steel Block
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Figure B-4. Schematic of the Wide Double Shear Specimen
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Table B-2. Results from the Wide and Thin Double Shear Tests

The combined tension/shear tests were conducted using the same fixture (Figure B-3) as was 

used for the wide and thin double shear tests. The tensile/shear specimens were similar to the 

double shear specimens shown in Figure B-4, except that the length was 8.5 inches to allow the 

ends to extend outside of the stainless steel block. The ends of the specimen were loaded using a 

servo-hydraulic load frame to obtain the constant axial load and the shear plunger was loaded 

using a hand-operated hydraulic ram. A load cell that was inline with the hydraulic ram was 

used to obtain the peak shear load. The specimen orientation and loading directions were the 

same as shown in Figure B-2. The results from the wide and think double shear tests are 

provided in Table B-3.

Shear Shear Width Thickness Load Stress Axial Load

Direction Plane (inch) (inch) (lbs.) (ksi) (% Sys)

L1P1-TL-Thin-01 400751 Thin Double Shear L LS 0.0640 0.0615 368.8 46.8 0

L1P1-TL-Thin-02 400751 Thin Double Shear L LS 0.0635 0.0615 358.0 45.8 0

L1P1-TL-Thin-03 400751 Thin Double Shear L LS 0.0635 0.0610 366.8 47.3 0

L1P1-TS-Thin-01 400751 Thin Double Shear S LS 0.0610 0.0635 313.2 40.4 0

L1P1-TS-Thin-02 400751 Thin Double Shear S LS 0.0610 0.0635 328.4 42.4 0

L1P1-TS-Thin-03 400751 Thin Double Shear S LS 0.0610 0.0635 310.4 40.1 0

L1P1-TS-Wide-01 400751 Wide Double Shear S LS 0.2480 0.0635 1256.4 39.9 0

L1P1-TS-Wide-02 400751 Wide Double Shear S LS 0.2480 0.0634 1263.6 40.2 0

L1P1-TS-Wide-03 400751 Wide Double Shear S LS 0.2480 0.0635 1248.0 39.6 0

L1P1-LS-Wide-01 400751 Wide Double Shear S TS 0.2480 0.0645 1369.2 42.8 0

L1P1-LS-Wide-02 400751 Wide Double Shear S TS 0.2480 0.0645 1380.8 43.2 0

L1P1-LS-Wide-03 400751 Wide Double Shear S TS 0.2480 0.0650 1377.2 42.7 0

L2P1-LS-Wide-01 400768 Wide Double Shear S TS 0.2480 0.0640 1358.8 42.8 0

L2P1-LS-Wide-02 400768 Wide Double Shear S TS 0.2480 0.0640 1361.2 42.9 0

L2P1-LS-Wide-03 400768 Wide Double Shear S TS 0.2480 0.0645 1344.8 42.0 0

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Material Characterization Study

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Table B-3. Results from the Wide and Thin Double Shear Tests

Shear Shear Width Thickness Load Stress Axial Load

Direction Plane (inch) (inch) (lbs.) (ksi) (% Sys)

TC-Wide-L1P1-T-01 400751 Tension/Shear 50% Sys S LS 0.2490 0.0635 1253.0 39.6 50

TC-Wide-L1P1-T-02 400751 Tension/Shear 50% Sys S LS 0.2480 0.0635 1222.5 38.8 50

TC-Wide-L1P1-T-03 400751 Tension/Shear 50% Sys S LS 0.2480 0.0635 1247.0 39.6 50

TC-Wide-L1P1-T-04 400751 Tension/Shear 75% Sys S LS 0.248 0.0635 1049.0 33.3 75

TC-Wide-L1P1-T-05 400751 Tension/Shear 75% Sys S LS 0.248 0.0635 1117.0 35.5 75

TC-Wide-L1P1-T-06 400751 Tension/Shear 75% Sys S LS 0.248 0.0635 1084.0 34.4 75

TC-Wide-L1P1-T-07 400751 Tension/Shear 90% Sys S LS 0.248 0.0635 989.5 31.4 90

TC-Wide-L1P1-T-08 400751 Tension/Shear 90% Sys S LS 0.248 0.0635 936.5 29.7 90

TC-Wide-L1P1-T-09 400751 Tension/Shear 90% Sys S LS 0.248 0.064 831.0 26.2 90

TC-Wide-L1P1-T-10 400751 Tension/Shear 100% Sys S LS 0.248 0.0635 638.0 20.3 100

TC-Wide-L1P1-T-11 400751 Tension/Shear 100% Sys S LS 0.248 0.0635 686.0 21.8 100

TC-Wide-L1P1-T-12 400751 Tension/Shear 100% Sys S LS 0.248 0.0635 766.5 24.3 100

TC-Wide-L2P1-T-01 400768 Tension/Shear 50% Sys S LS 0.2490 0.0630 1281.0 40.8 50

TC-Wide-L2P1-T-02 400768 Tension/Shear 50% Sys S LS 0.2485 0.063 1275.0 40.7 50

TC-Wide-L2P1-T-03 400768 Tension/Shear 50% Sys S LS 0.2485 0.063 1234.0 39.4 50

TC-Wide-L2P1-T-04 400768 Tension/Shear 75% Sys S LS 0.2485 0.063 1032.5 33.0 75

TC-Wide-L2P1-T-05 400768 Tension/Shear 75% Sys S LS 0.2485 0.063 1124.0 35.9 75

TC-Wide-L2P1-T-06 400768 Tension/Shear 75% Sys S LS 0.2485 0.063 1056.0 33.7 75

TC-Wide-L2P1-T-07 400768 Tension/Shear 90% Sys S LS 0.248 0.063 935.5 29.9 90

TC-Wide-L2P1-T-08 400768 Tension/Shear 90% Sys S LS 0.2485 0.063 957.0 30.6 90

TC-Wide-L2P1-T-09 400768 Tension/Shear 90% Sys S LS 0.248 0.063 935.5 29.9 90

TC-Wide-L2P1-T-10 400768 Tension/Shear 100% Sys S LS 0.2485 0.063 727.0 23.2 100

TC-Wide-L2P1-T-11 400768 Tension/Shear 100% Sys S LS 0.2485 0.063 744.0 23.8 100

TC-Wide-L2P1-T-12 400768 Tension/Shear 100% Sys S LS 0.2485 0.063 724.5 23.1 100

TC-Wide-L1P1-L-02 400751 Tension/Shear 50% Sys S TS 0.2475 0.0640 1259.0 39.7 50

TC-Wide-L1P1-L-03 400751 Tension/Shear 50% Sys S TS 0.247 0.064 1246.5 39.4 50

TC-Wide-L1P1-L-04 400751 Tension/Shear 50% Sys S TS 0.2475 0.064 1258.5 39.7 50

TC-Wide-L1P1-L-05 400751 Tension/Shear 75% Sys S TS 0.2475 0.064 1011.5 31.9 75

TC-Wide-L1P1-L-06 400751 Tension/Shear 75% Sys S TS 0.2475 0.064 1091.0 34.4 75

TC-Wide-L1P1-L-07 400751 Tension/Shear 75% Sys S TS 0.247 0.064 1040.5 32.9 75

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Appendix C. 3-Point Bend Test Results

The 3-point bend tests were conducted on small rectangular coupons that were approximately 

2 inches long and 0.75 inches wide (W). The thickness of the specimens (t) ranged between 

0.05 inches to 0.065 inches depending on the material being tested. The test fixture had two 

fixed rollers (diameter Df) separated by a distance or span (L) and a center mandrel (diameter 

Dm) that loaded the specimen, as shown in Figure C-1. The displacement () of the center 

mandrel was increased at a rate of 0.06 inches/minute and the data recorded at a rate of 

10 readings per second.

Figure C-1. 3-point Bend Test Fixture and Nomenclature

Strain gages were placed on the tensile side of several test specimens, directly below the center 

mandrel. These tests considered different specimen thicknesses, different spans, and different 

lots of the 2090 material. The measured axial strain was plotted as a function of the normalized 

displacement (t/L2) for spans of L = 0.8, 1.0, and 1.6 inches, as shown in Figure C-2. The 

normalized displacement vs. strain behavior provided a good correlation of the different 

thicknesses (0.05 inch < t < 0.065 inch), but did not correlate the different span lengths. 

Polynomial curve fits were calculated for the data for each span length to allow estimates of the 

strain for tests conducted without strain gages. The parameters to the curve fits are provided in 

Table C-1.

L

t



Df

Df

Dm
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Figure C-2. Strain and Normalized Displacement Data from 3-point Bend Tests and Polynomial 

Curve Fits

Table C-1. Polynomial Curve Fits to the Normalized Displacement vs. Axial Strain Data

a0 a1 a2 a3 a4

L = 0.8 0 0.2202 3784.6 -365547 18726597

L = 1.0 0 0.1809 3835.8 -297336 13512671

L = 1.6 0 1.0121 4745.8 -450453 23946859

4

4 2

3

3 2

2

0 1 2 2 2













 











 











 











 

L

t

a

L

t

a

L

t

a

L

t

e a a

   
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

67 of 152

NESC Request No.: 10-00680 (Materials)

A summary of the 3-point bend test on the coil and stringer materials is provided in Table C-2.

The summary contains the specimen number, material thickness, maximum load, maximum 

normalized displacement, the strain at failure, and an indication of the failure (brittle or less 

brittle). The initial conditions (specimen width and thickness, and span length), normalized 

displacement, measured load, and the strains (estimated or measured) for each of the 3-point 

bend tests are provided in Table C-3.

Table C-2. Summary of 3-point Bend Test Results by Specimen Number

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

S7-04 0.058 258.1 0.00645 1 10.4 Brittle

S7-05 0.06 270.1 0.00567 1 8.3 Brittle

S7-01 0.06 271.5 0.00561 1 8.5 Brittle

S7-06 0.058 247.6 0.0051 1 7.0 Brittle

S7-02 0.059 265.0 0.00496 1 7.1 Brittle

S7-03 0.059 264.9 0.00432 1 5.3 Brittle

S7-08 0.058 246.5 0.00483 1 6.4 Brittle

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

C10-01 0.052 198.3 0.00831 1 16.0 LB

C10-02 0.052 198.6 0.00808 1 14.2 LB

C10-03 0.052 198.3 0.00819 1 14.7 LB

C10-04 0.051 187.0 0.00671 1 11.1 LB

C10-05 0.051 188.1 0.00667 1 11.0 LB

C10-06 0.052 99.4 0.00743 1.8 15.1 LB

C10-07 0.052 257.5 0.00846 0.8 15.2 LB

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

L1P1-01-325 0.064 158.4 0.00807 1.8 18.8 LB

L1P1-02-325 0.063 309.2 0.00757 1 13.7 LB

L1P1-03-325 0.063 309.9 0.00792 1 15.1 LB

L1P1-04-325 0.064 177.9 0.00818 1.6 18.7 LB

L1P1-05-325 0.064 400.8 0.00814 0.8 13.4 LB

L1P1-06-325 0.063 311.9 0.00873 1 17.8 LB

L1P1-07-325 0.063 307.9 0.00701 1 12.0 LB

L1P1-08-325 0.063 304.5 0.00723 1 12.6 LB

L1P1-09-325 0.063 309.4 0.00724 1 12.7 LB

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

L2P1-01-325 0.062 287.5 0.00707 1 12.2 LB

L2P1-02-325 0.062 291.0 0.00681 1 11.4 LB

L2P1-07-325 0.062 297.2 0.00824 1 15.8 LB

L2P1-08-325 0.062 294.7 0.00711 1 12.3 LB

Coil Aged at 325F for 24 Hours (Lot 400768)

Stringer-7 Sister (Lot 620853)

Control-1D (Lot 400766)

Coil Aged at 325F for 24 Hours (Lot 400751)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

68 of 152

NESC Request No.: 10-00680 (Materials)

Table C-2. Summary of 3-point Bend Test Results by Specimen Number (concluded)

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

L5CR-01-325 0.058 243.4 0.00665 1 11.0 LB

L5CR-29-325 0.057 232.5 0.007 1 12.0 LB

L5CR-22-325 0.057 238.5 0.00699 1 11.9 Brittle

L5CR-27-325 0.057 234.6 0.00664 1 11.0 Brittle

L5CR-02-325 0.057 240.8 0.00654 1 10.7 Brittle

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

L5MCR-01-325 0.057 240.3 0.00601 1 9.3 LB

L5MCR-03-325 0.0575 237.5 0.0056 1 8.2 LB

L5MCR-13-325 0.057 240.4 0.00688 1 11.6 LB

L5MCR-17-325 0.057 245.9 0.00672 1 11.2 LB

L5MCR-04-325 0.057 240.3 0.00675 1 11.3 Brittle

L5MCR-28-325 0.056 222.6 0.00686 1 11.6 Brittle

L5MCR-20-325 0.058 242.2 0.00701 1 12.0 Brittle

Specimen Thickness Max Load d t/L^2 Span % Strain Failure

L5HR-01-325 0.062 277.3 0.00596 1 9.1 Brittle

L5HR-02-325 0.06 255.1 0.00626 1 9.9 Brittle

L5HR-03-325 0.06 261.0 0.00626 1 9.9 Brittle

L5HR-04-325 0.06 258.8 0.00656 1 10.7 Brittle

L5HR-17-325 0.059 256.7 0.00655 1 10.7 Brittle

L5HR-19-325 0.06 260.3 0.00607 1 9.4 Brittle

L5HR-09-325 0.0575 316.3 0.00789 0.8 13.0 Brittle

L5HR-14-325 0.059 328.7 0.00651 0.8 9.5 Brittle

L5HR-13-325 0.059 325.7 0.00695 0.8 10.5 Brittle

L5HR-12-325 0.059 334.0 0.00688 0.8 10.4 Brittle

L5HR-11-325 0.059 319.3 0.00704 0.8 10.8 Brittle

L5HR-16-325 0.059 331.4 0.00655 0.8 9.5 Brittle

L5HR-15-325 0.057 319.1 0.00672 0.8 10.0 Brittle

L5HR-20-325 0.059 148.5 0.00637 1.6 12.2 Brittle

L5HR-21-325 0.057 141.2 0.00623 1.6 11.8 Brittle

L5HR-18-325 0.06 151.6 0.00643 1.6 12.4 Brittle

L5HR-23-325 0.059 148.0 0.00642 1.6 12.4 Brittle

Cold Formed Aged at 325F for 24 Hours (Lot 620853)

Cold/Hot Formed Aged at 325F for 24 Hours (Lot 620853)

Cold Formed Aged at 325F for 24 Hours (Lot 620853)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

69 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number

L 1 inch L 1 inch L 1 inch

W 0.746 inch W 0.748 inch W 0.748 inch

t 0.057 inch t 0.06 inch t 0.058 inch

Load dt/L2 Est. Strain Load dt/L2 Est. Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

22.6 0.00026 0.0003 19.3 0.00023 0.0002 23.1 0.00027 0.0016

49.6 0.00051 0.0011 45.3 0.00045 0.0008 55.1 0.00054 0.0031

76.9 0.00077 0.0023 72.3 0.00068 0.0018 88.5 0.00082 0.0047

104.3 0.00103 0.0040 99.5 0.00091 0.0031 90.6 0.00084 0.0048

130.2 0.00129 0.0060 126.8 0.00114 0.0048 90.7 0.00084 0.0048

151.0 0.00155 0.0085 151.5 0.00137 0.0067 90.6 0.00084 0.0048

166.3 0.00181 0.0113 171.3 0.00160 0.0089 90.6 0.00084 0.0048

177.5 0.00207 0.0144 186.0 0.00182 0.0114 90.6 0.00084 0.0048

186.0 0.00233 0.0179 197.3 0.00205 0.0142 90.7 0.00084 0.0048

193.1 0.00259 0.0216 205.7 0.00228 0.0172 90.6 0.00084 0.0048

199.0 0.00285 0.0256 212.2 0.00251 0.0205 90.7 0.00084 0.0048

203.6 0.00310 0.0299 217.6 0.00274 0.0239 108.5 0.00098 0.0056

207.4 0.00336 0.0344 222.6 0.00297 0.0276 140.2 0.00126 0.0075

210.4 0.00362 0.0392 230.1 0.00319 0.0313 166.2 0.00153 0.0099

213.1 0.00388 0.0442 231.2 0.00342 0.0354 185.3 0.00180 0.0127

215.2 0.00414 0.0494 233.5 0.00365 0.0396 199.1 0.00208 0.0159

217.4 0.00440 0.0548 236.0 0.00387 0.0440 209.2 0.00235 0.0195

219.1 0.00466 0.0604 238.4 0.00410 0.0486 216.8 0.00262 0.0235

220.9 0.00492 0.0662 240.4 0.00433 0.0533 223.2 0.00290 0.0278

222.3 0.00518 0.0723 242.3 0.00456 0.0582 227.9 0.00317 0.0324

223.5 0.00544 0.0784 244.0 0.00479 0.0632 231.5 0.00344 0.0372

224.5 0.00570 0.0848 245.5 0.00502 0.0685 234.8 0.00371 0.0422

225.6 0.00596 0.0913 247.0 0.00524 0.0738 237.8 0.00399 0.0474

226.3 0.00621 0.0980 248.5 0.00547 0.0793 240.2 0.00426 0.0528

227.1 0.00647 0.1050 249.7 0.00570 0.0849 242.4 0.00454 0.0583

227.6 0.00673 0.1121 250.9 0.00593 0.0906 243.9 0.00481 0.0640

228.1 0.00699 0.1194 252.0 0.00616 0.0966 245.3 0.00508 0.0697

228.4 0.00725 0.1270 252.8 0.00639 0.1027 246.7 0.00536 0.0756

228.7 0.00751 0.1348 253.6 0.00662 0.1089 248.0 0.00563 0.0817

228.7 0.00777 0.1427 254.1 0.00685 0.1153 249.3 0.00590 0.0881

228.5 0.00803 0.1509 254.7 0.00707 0.1218 250.5 0.00618 0.0945

228.4 0.00829 0.1594 254.9 0.00730 0.1285 251.3 0.00645 0.1011

227.8 0.00855 0.1682 255.2 0.00916 0.1902 251.7 0.00672 0.1080

227.3 0.00880 0.1772 253.8 0.00939 0.1989 252.1 0.00700 0.1151

226.4 0.00906 0.1866 252.5 0.00962 0.2078 252.1 0.00727

225.6 0.00932 0.1962 251.2 0.00985 0.2170 251.9 0.00754

225.2 0.00958 0.2063 251.6 0.00782

224.4 0.00984 0.2166 251.3 0.00809

P3-BD-01 P3-BD-02 P3-BD-03
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

70 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1.4 inch L 0.8 inch L 1.2 inch

W 0.745 inch W 0.748 inch W 0.746 inch

t 0.059 inch t 0.06 inch t 0.06 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

14.2 0.00020 0.00128 30.0 0.00031 0.0018 24.0508 0.00027 0.00167

30.7 0.00041 0.00244 72.1 0.00063 0.0035 51.9473 0.00054 0.00321

47.4 0.00061 0.00363 115.6 0.00094 0.0052 80.21 0.00082 0.00479

64.0 0.00082 0.00483 159.6 0.00126 0.0071 107.862 0.00109 0.00647

80.4 0.00102 0.00608 197.8 0.00158 0.0097 131.486 0.00136 0.00867

95.8 0.00123 0.00751 225.7 0.00189 0.0130 149.066 0.00164 0.01146

108.9 0.00144 0.00921 245.1 0.00221 0.0167 162.068 0.00191 0.01481

119.4 0.00164 0.0112 258.8 0.00252 0.0209 171.652 0.00218 0.0186

127.5 0.00185 0.01349 268.8 0.00284 0.0254 178.733 0.00245 0.02277

134.0 0.00205 0.01601 276.3 0.00316 0.0301 184.288 0.00273 0.02719

139.0 0.00226 0.01875 282.0 0.00347 0.0352 188.5 0.003 0.03188

142.8 0.00246 0.02171 286.9 0.00379 0.0403 191.796 0.00327 0.03676

146.2 0.00267 0.02485 291.3 0.00411 0.0456 194.787 0.00355 0.04178

149.0 0.00287 0.0282 295.3 0.00442 0.0511 197.046 0.00382 0.04696

151.6 0.00308 0.0317 299.4 0.00474 0.0566 198.999 0.00409 0.05225

153.5 0.00328 0.03532 302.8 0.00506 0.0622 200.952 0.00437 0.0577

155.3 0.00349 0.03904 305.7 0.00537 0.0679 202.356 0.00464 0.06329

157.0 0.00369 0.04288 308.2 0.00569 0.0738 203.455 0.00491 0.06901

158.6 0.00390 0.04681 310.1 0.00601 0.0799 204.004 0.00518

160.1 0.00410 0.05087 311.9 0.00632 0.0860 204.92 0.00546

161.3 0.00431 0.05505 313.6 0.00664 0.0922 205.958 0.00573

162.2 0.00451 0.05928 315.0 0.00696 0.0985 206.629 0.006

163.2 0.00472 0.0636 316.1 0.00727 0.1049 207.118 0.00627

163.9 0.00492 0.06798 317.2 0.00759 0.1114 207.484 0.00655

164.0 0.00513 0.07243 318.2 0.00791 0.1181 207.606 0.00682

164.6 0.00533 0.07691 318.9 0.00822 0.1249 207.911 0.00709

164.9 0.00554 0.08148 319.6 0.00854 0.1318 207.789 0.00737

165.3 0.00574 0.08616 319.7 0.00885 0.1390 207.362 0.00764

165.2 0.00595 0.09101 320.2 0.00917 0.1492 206.69 0.00791

165.4 0.00615 0.09591 320.4 0.00949 205.714 0.00819

165.1 0.00636 0.101 320.5 0.00980 204.859 0.00846

164.8 0.00657 0.10622 320.2 0.01012 204.31 0.00873

164.4 0.00677 0.11154 319.7 0.01044 203.455 0.009

163.8 0.00698 0.11691 318.9 0.01075 202.539 0.00928

162.9 0.00718 0.1224 318.3 0.01107 201.38 0.00955

162.1 0.00739 0.12822 317.8 0.01139 200.342 0.00982

161.4 0.00759 0.13493 317.4 0.01170 198.816 0.0101

161.0 0.00780 316.3 0.01202 194.97 0.01037

P3-BD-04 P3-BD-05 P3-BD-06
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

71 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch L 1 inch

W 0.747 inch W 0.745 inch W 0.746 inch W 0.746 inch

t 0.06 inch t 0.059 inch t 0.059 inch t 0.058 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0 0 0 0

9.0 0.00014 0.00039 13.2 0.00013 0.00046 11.6 0.00010 0.00005 5.4 0.00009 0.00005

21.5 0.00029 0.00094 23.6 0.00026 0.00096 17.4 0.00016 0.00013 11.3 0.00018 0.00016

35.6 0.00044 0.00160 35.0 0.00039 0.00152 17.3 0.00016 0.00013 18.4 0.00028 0.00034

51.5 0.00059 0.00236 47.6 0.00052 0.00218 22.2 0.00021 0.00021 26.7 0.00037 0.00058

68.2 0.00074 0.00315 61.5 0.00066 0.00291 31.9 0.00031 0.00042 36.0 0.00046 0.00088

86.1 0.00089 0.00401 76.6 0.00079 0.00368 42.4 0.00041 0.00070 45.7 0.00056 0.00124

104.0 0.00104 0.00489 92.1 0.00092 0.00447 53.4 0.00051 0.00105 55.5 0.00065 0.00166

122.1 0.00118 0.00580 107.3 0.00105 0.00528 64.6 0.00061 0.00146 65.7 0.00075 0.00215

139.9 0.00133 0.00672 122.7 0.00118 0.00607 76.1 0.00071 0.00195 76.2 0.00084 0.00267

157.4 0.00148 0.00767 138.3 0.00132 0.00690 87.9 0.00080 0.00248 86.5 0.00093 0.00326

174.0 0.00163 0.00872 153.7 0.00145 0.00777 99.8 0.00090 0.00309 96.9 0.00102 0.00390

188.9 0.00178 0.00995 168.4 0.00158 0.00872 111.3 0.00100 0.00377 156.0 0.00157 0.00867

201.5 0.00193 0.01141 181.9 0.00171 0.00984 123.3 0.00110 0.00449 165.7 0.00166 0.00967

212.1 0.00207 0.01307 194.0 0.00184 0.01111 135.2 0.00120 0.00526 174.5 0.00176 0.01070

220.5 0.00222 0.01496 204.4 0.00198 0.01256 147.1 0.00130 0.00610 182.3 0.00185 0.01170

227.6 0.00237 0.01701 213.0 0.00211 0.01418 158.8 0.00140 0.00699 189.4 0.00194 0.01280

233.3 0.00252 0.01919 220.5 0.00224 0.01594 170.0 0.00150 0.00794 195.6 0.00204 0.01400

238.2 0.00267 0.02152 226.6 0.00237 0.01785 181.6 0.00161 0.00907 202.7 0.00217 0.01570

242.6 0.00282 0.02397 231.8 0.00251 0.01986 191.5 0.00171 0.01010 208.3 0.00227 0.01700

246.6 0.00296 0.02654 236.3 0.00264 0.02199 200.1 0.00181 0.01120 212.1 0.00236 0.01830

249.8 0.00312 0.02923 240.1 0.00277 0.02423 207.7 0.00190 0.01240 215.7 0.00245 0.01960

252.7 0.00326 0.03199 243.4 0.00290 0.02656 217.1 0.00205 0.01420 219.0 0.00254 0.02100

254.9 0.00341 0.03485 246.4 0.00304 0.02898 222.4 0.00215 0.01550 221.9 0.00264 0.02240

256.9 0.00356 0.03777 248.8 0.00317 0.03147 227.0 0.00225 0.01680 226.0 0.00283 0.02530

258.9 0.00371 0.04078 251.1 0.00330 0.03403 232.2 0.00242 0.01920 230.6 0.00292 0.02680

260.8 0.00385 0.04386 252.9 0.00343 0.03667 238.4 0.00252 0.02060 232.0 0.00301 0.02840

262.1 0.00400 0.04699 254.7 0.00356 0.03938 241.2 0.00262 0.02210 233.4 0.00311 0.02990

263.6 0.00415 0.05020 256.3 0.00369 0.04214 243.8 0.00272 0.02360 234.8 0.00320 0.03150

264.9 0.00430 0.05345 257.7 0.00383 0.04498 249.8 0.00292 0.02690 236.1 0.00329 0.03320

265.8 0.00445 0.05676 259.0 0.00396 0.04793 251.8 0.00302 0.02850 237.3 0.00339 0.03480

266.9 0.00460 0.06015 260.1 0.00409 0.05089 253.0 0.00312 0.03020 238.6 0.00348 0.03650

267.7 0.00475 0.06359 261.1 0.00422 0.05393 254.2 0.00322 0.03190 242.9 0.00372 0.04110

268.6 0.00490 0.06708 262.3 0.00436 0.05702 255.5 0.00332 0.03370 246.2 0.00427 0.05200

269.2 0.00504 0.07063 263.1 0.00449 0.06013 256.6 0.00342 0.03540 248.9 0.00436 0.05390

269.9 0.00519 0.07424 263.9 0.00462 0.06333 257.8 0.00352 0.03720 252.0 0.00505 0.06930

270.5 0.00534 0.07790 264.7 0.00475 0.06660 258.8 0.00361 0.03900 254.9 0.00553 0.08060

270.9 0.00549 0.08162 265.1 0.00488 0.07019 263.8 0.00391 0.04480 256.5 0.00595 0.09110

271.4 0.00564 0.08543 265.0 0.00502 264.7 0.00401 0.04670 257.8 0.00639 0.10300

S7-01 S7-02 S7-03 S7-04
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

72 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.747 inch W 0.746 inch W 0.746 inch

t 0.06 inch t 0.058 inch t 0.058 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

5.4 0.00017 0.00015 6.3 0.00010 0.00006 6.8 0.00009 0.00005

5.3 0.00018 0.00015 13.1 0.00021 0.00021 14.1 0.00019 0.00017

7.7 0.00021 0.00020 21.2 0.00032 0.00044 22.7 0.00029 0.00036

19.3 0.00036 0.00056 30.8 0.00043 0.00075 32.1 0.00038 0.00060

32.9 0.00052 0.00108 41.6 0.00054 0.00115 41.9 0.00047 0.00092

47.3 0.00067 0.00177 52.7 0.00065 0.00164 52.1 0.00057 0.00129

64.7 0.00083 0.00261 64.5 0.00075 0.00219 62.0 0.00066 0.00173

82.5 0.00098 0.00360 76.3 0.00086 0.00282 72.2 0.00076 0.00222

101.0 0.00113 0.00473 88.2 0.00097 0.00353 82.6 0.00086 0.00281

119.6 0.00129 0.00602 100.9 0.00109 0.00439 93.3 0.00096 0.00342

138.4 0.00144 0.00743 113.2 0.00120 0.00524 103.9 0.00105 0.00409

156.8 0.00160 0.00896 125.3 0.00131 0.00618 114.6 0.00114 0.00480

174.0 0.00175 0.01062 136.9 0.00142 0.00717 125.3 0.00125 0.00566

189.8 0.00191 0.01241 148.5 0.00153 0.00822 135.9 0.00134 0.00650

203.2 0.00206 0.01432 161.0 0.00165 0.00954 146.2 0.00144 0.00737

214.1 0.00221 0.01631 171.0 0.00176 0.01070 156.1 0.00153 0.00831

223.0 0.00237 0.01845 181.7 0.00190 0.01230 167.5 0.00166 0.00956

230.1 0.00253 0.02068 189.6 0.00201 0.01360 176.2 0.00175 0.01060

235.9 0.00268 0.02301 196.3 0.00211 0.01500 183.7 0.00185 0.01170

240.8 0.00283 0.02542 204.8 0.00229 0.01730 190.6 0.00194 0.01280

245.0 0.00299 0.02794 210.0 0.00240 0.01890 196.5 0.00204 0.01400

248.6 0.00314 0.03054 213.8 0.00251 0.02050 203.6 0.00220 0.01610

251.6 0.00330 0.03325 217.4 0.00262 0.02210 209.4 0.00229 0.01740

254.1 0.00345 0.03600 223.4 0.00283 0.02530 212.9 0.00239 0.01870

256.3 0.00361 0.03889 226.7 0.00294 0.02710 216.0 0.00248 0.02010

258.3 0.00376 0.04182 232.5 0.00329 0.03300 219.9 0.00271 0.02350

259.9 0.00392 0.04484 235.1 0.00339 0.03500 225.7 0.00280 0.02500

261.5 0.00407 0.04792 235.7 0.00351 0.03700 227.3 0.00290 0.02650

263.0 0.00422 0.05109 236.6 0.00361 0.03900 229.9 0.00317 0.03090

264.1 0.00438 0.05434 237.4 0.00372 0.04100 234.3 0.00326 0.03260

265.2 0.00453 0.05766 238.3 0.00383 0.04320 235.1 0.00335 0.03430

266.4 0.00469 0.06102 242.1 0.00415 0.04950 235.8 0.00345 0.03600

267.5 0.00484 0.06444 246.7 0.00462 0.05960 236.5 0.00354 0.03770

268.4 0.00500 0.06798 247.8 0.00473 0.06190 237.5 0.00364 0.03950

269.0 0.00515 0.07151 247.2 0.00484 0.06440 238.3 0.00374 0.04130

269.7 0.00530 0.07520 247.3 0.00495 0.06680 240.3 0.00403 0.04720

269.7 0.00546 0.07895 247.5 0.00505 0.06930 244.4 0.00438 0.05440

270.1 0.00561 0.08269 247.8 0.00516 0.07190 247.5 0.00476 0.06260

S7-05 S7-06 S7-08
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

73 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch L 1 inch

W 0.746 inch W 0.752 inch W 0.752 inch W 0.747 inch

t 0.052 inch t 0.052 inch t 0.052 inch t 0.051 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0 0 0 0

8.2 0.00017 0.00013 9.4 0.00021 0.00054 9.6 0.00021 0.00058 9.0 0.00015 0.00011

20.6 0.00033 0.00048 23.8 0.00042 0.00141 24.3 0.00043 0.00151 20.1 0.00030 0.00040

35.0 0.00050 0.00102 39.7 0.00063 0.00243 40.8 0.00064 0.00269 32.4 0.00046 0.00086

49.9 0.00067 0.00176 57.1 0.00085 0.00357 58.5 0.00086 0.00393 52.2 0.00071 0.00195

65.1 0.00084 0.00269 75.3 0.00106 0.00477 77.0 0.00107 0.00522 56.5 0.00076 0.00223

80.6 0.00101 0.00379 94.1 0.00127 0.00605 96.2 0.00129 0.00654 69.0 0.00092 0.00316

95.8 0.00118 0.00507 112.5 0.00148 0.00740 114.8 0.00150 0.00801 81.4 0.00107 0.00422

110.4 0.00135 0.00650 129.4 0.00169 0.00900 131.5 0.00172 0.00979 93.8 0.00122 0.00543

124.2 0.00151 0.00811 143.3 0.00190 0.01100 145.2 0.00193 0.01200 123.1 0.00163 0.00925

136.2 0.00168 0.00987 154.4 0.00212 0.01330 155.9 0.00215 0.01460 132.4 0.00178 0.01090

146.3 0.00185 0.01180 162.9 0.00233 0.01600 164.1 0.00237 0.01750 140.0 0.00197 0.01320

154.6 0.00202 0.01380 169.4 0.00254 0.01900 170.0 0.00258 0.02080 148.1 0.00213 0.01510

161.3 0.00219 0.01590 174.5 0.00275 0.02240 174.8 0.00280 0.02440 156.3 0.00237 0.01840

167.0 0.00236 0.01830 181.3 0.00318 0.02960 178.5 0.00301 0.02820 161.2 0.00263 0.02220

171.5 0.00252 0.02070 183.9 0.00339 0.03350 181.4 0.00323 0.03210 164.6 0.00278 0.02460

175.3 0.00269 0.02320 186.3 0.00360 0.03750 184.0 0.00344 0.03630 166.3 0.00293 0.02700

178.4 0.00286 0.02590 188.1 0.00381 0.04150 186.4 0.00366 0.04060 168.1 0.00309 0.02960

181.1 0.00303 0.02870 190.0 0.00403 0.04570 190.4 0.00409 0.04960 172.8 0.00340 0.03510

183.4 0.00320 0.03150 191.8 0.00424 0.04990 192.2 0.00431 0.05430 173.7 0.00355 0.03780

185.4 0.00337 0.03450 193.1 0.00445 0.05430 193.3 0.00452 0.05910 174.2 0.00370 0.04070

187.1 0.00354 0.03760 194.1 0.00466 0.05870 194.2 0.00474 0.06400 175.2 0.00386 0.04370

188.5 0.00371 0.04080 195.0 0.00487 0.06330 194.9 0.00495 0.06890 176.0 0.00401 0.04670

189.9 0.00387 0.04400 195.6 0.00509 0.06790 195.8 0.00517 0.07400 177.0 0.00416 0.04990

191.3 0.00404 0.04740 196.1 0.00530 0.07270 196.4 0.00538 0.07920 177.9 0.00432 0.05300

192.5 0.00421 0.05080 196.6 0.00551 0.07750 196.9 0.00560 0.08450 178.7 0.00447 0.05630

193.4 0.00438 0.05430 197.0 0.00572 0.08240 197.4 0.00582 0.08990 179.3 0.00462 0.05960

194.3 0.00455 0.05800 197.6 0.00593 0.08740 197.8 0.00603 0.09540 180.0 0.00478 0.06300

195.0 0.00472 0.06170 198.4 0.00615 0.09250 198.1 0.00625 0.10100 180.6 0.00493 0.06650

195.5 0.00488 0.06540 198.6 0.00636 0.09770 198.1 0.00646 0.10685 181.1 0.00508 0.07000

195.9 0.00505 0.06930 198.4 0.00657 0.10300 198.3 0.00668 0.11278 181.5 0.00524 0.07360

196.4 0.00522 0.07330 198.4 0.00678 0.10847 198.3 0.00689 0.11891 182.0 0.00539 0.07720

196.9 0.00539 0.07730 198.3 0.00700 0.11409 198.1 0.00711 0.12525 182.7 0.00554 0.08100

197.0 0.00556 0.08140 197.8 0.00721 0.11990 197.9 0.00732 0.13183 182.9 0.00570 0.08480

197.5 0.00573 0.08560 197.6 0.00742 0.12588 197.4 0.00754 0.13868 185.1 0.00624 0.09870

197.7 0.00590 0.08980 197.2 0.00763 0.13250 197.4 0.00775 0.14583 187.0 0.00639 0.10300

197.9 0.00607 0.09410 197.0 0.00784 197.0 0.00797 0.15350 186.1 0.00655 0.10700

196.7 0.00811 0.15400 196.6 0.00806 196.3 0.00819 0.16163 185.9 0.00670 0.11100

C10-01 C10-02 C10-03 C10-04
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

74 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1.8 inch L 0.8 inch

W 0.749 inch W 0.75 inch W 0.75 inch

t 0.051 inch t 0.052 inch t 0.052 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

7.9 0.00017 0.00014 11.1 0.00025 0.00125 14.2 0.00022 0.00059

20.5 0.00035 0.00052 23.3 0.00050 0.00284 32.9 0.00044 0.00153

34.7 0.00052 0.00111 35.8 0.00074 0.00449 56.9 0.00066 0.00287

49.1 0.00070 0.00189 48.7 0.00099 0.00613 82.2 0.00088 0.00422

63.5 0.00087 0.00290 60.9 0.00124 0.00793 108.0 0.00111 0.00559

78.3 0.00105 0.00408 72.0 0.00149 0.01017 133.6 0.00133 0.00699

93.0 0.00122 0.00545 80.6 0.00174 0.01305 157.6 0.00155 0.00858

107.5 0.00140 0.00701 86.7 0.00198 0.01663 177.9 0.00177 0.01052

120.4 0.00158 0.00873 90.7 0.00223 0.02074 194.1 0.00200 0.01281

131.6 0.00175 0.01060 93.7 0.00248 0.02529 206.0 0.00222 0.01544

148.3 0.00210 0.01490 95.8 0.00273 0.03015 214.9 0.00244 0.01840

154.7 0.00228 0.01720 97.2 0.00298 0.03525 221.5 0.00266 0.02161

159.9 0.00245 0.01960 98.2 0.00323 0.04053 226.6 0.00289 0.02507

164.0 0.00263 0.02220 98.6 0.00347 0.04590 231.0 0.00311 0.02870

167.4 0.00280 0.02490 99.0 0.00372 0.05136 234.9 0.00333 0.03251

170.1 0.00298 0.02780 99.1 0.00397 0.05693 238.4 0.00355 0.03646

172.4 0.00315 0.03070 99.4 0.00422 0.06259 241.0 0.00378 0.04052

174.5 0.00333 0.03380 99.1 0.00447 0.06838 243.6 0.00400 0.04468

176.1 0.00351 0.03700 98.8 0.00472 0.07425 245.5 0.00422 0.04896

177.6 0.00368 0.04030 98.5 0.00496 0.08019 247.3 0.00445 0.05334

179.0 0.00386 0.04370 98.0 0.00521 0.08619 249.0 0.00467 0.05783

180.1 0.00403 0.04710 97.3 0.00546 0.09229 250.4 0.00489 0.06243

181.4 0.00421 0.05080 96.6 0.00571 0.09849 251.7 0.00511 0.06708

182.3 0.00438 0.05440 96.1 0.00596 0.10476 252.7 0.00534 0.07181

183.1 0.00456 0.05820 95.3 0.00620 0.11113 253.9 0.00556 0.07662

183.9 0.00473 0.06210 94.2 0.00645 0.11762 254.5 0.00578 0.08147

184.7 0.00491 0.06600 93.4 0.00670 0.12426 255.3 0.00601 0.08641

185.4 0.00508 0.07000 91.6 0.00695 0.13100 255.8 0.00623 0.09146

185.9 0.00526 0.07420 89.4 0.00720 0.13776 256.3 0.00645 0.09664

186.4 0.00544 0.07840 85.8 0.00745 0.14437 256.7 0.00667 0.10191

186.8 0.00561 0.08270 79.5 0.00763 0.14997 257.1 0.00689 0.10732

187.0 0.00579 0.08700 75.1 0.15086 257.2 0.00712 0.11284

187.3 0.00596 0.09150 73.2 0.15124 257.4 0.00734 0.11855

187.6 0.00614 0.09610 72.5 0.15151 257.5 0.00756 0.12440

187.8 0.00631 0.10100 71.9 0.15169 257.4 0.00778 0.13040

187.8 0.00649 0.10500 71.4 0.15183 257.1 0.00823 0.14306

187.9 0.00667 0.11000 71.2 0.15195 255.1 0.00845 0.15145

C10-05 C10-06 C10-07
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

75 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.75 inch W 0.748 inch W 0.746 inch

t 0.064 inch t 0.063 inch t 0.063 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

15.4 0.00021 0.00119 41.7 0.00041 0.00064 18.2 0.00021 0.00071

32.1 0.00043 0.00260 65.6 0.00061 0.00161 43.2 0.00042 0.00181

49.6 0.00064 0.00403 91.6 0.00080 0.00265 69.3 0.00062 0.00293

66.2 0.00085 0.00546 117.7 0.00100 0.00379 98.0 0.00083 0.00420

82.6 0.00106 0.00692 144.1 0.00119 0.00494 127.2 0.00104 0.00547

98.8 0.00128 0.00860 169.8 0.00138 0.00613 155.8 0.00125 0.00678

113.2 0.00149 0.01073 193.6 0.00157 0.00739 182.9 0.00146 0.00825

124.3 0.00170 0.01339 214.1 0.00177 0.00888 206.9 0.00167 0.01008

132.6 0.00192 0.01650 230.7 0.00196 0.01067 226.5 0.00188 0.01228

139.0 0.00213 0.01995 243.4 0.00216 0.01281 241.4 0.00208 0.01486

143.7 0.00234 0.02372 253.5 0.00235 0.01524 252.8 0.00229 0.01774

147.2 0.00256 0.02772 261.4 0.00254 0.01789 261.4 0.00250 0.02084

149.8 0.00277 0.03193 267.7 0.00274 0.02075 268.3 0.00271 0.02411

152.2 0.00298 0.03639 272.7 0.00293 0.02378 273.9 0.00292 0.02758

153.7 0.00320 0.04106 277.2 0.00312 0.02693 278.6 0.00313 0.03119

155.0 0.00341 0.04593 281.2 0.00332 0.03026 282.5 0.00333 0.03497

156.5 0.00362 0.05096 284.6 0.00351 0.03374 285.9 0.00354 0.03892

157.5 0.00383 0.05616 287.4 0.00371 0.03736 288.7 0.00375 0.04298

157.9 0.00405 0.06146 289.9 0.00390 0.04113 291.1 0.00396 0.04722

158.3 0.00426 0.06688 291.8 0.00409 0.04500 293.3 0.00417 0.05155

158.3 0.00447 0.07242 293.9 0.00429 0.04901 295.3 0.00438 0.05603

158.2 0.00469 0.07805 295.7 0.00448 0.05310 297.1 0.00459 0.06060

158.0 0.00490 0.08384 297.3 0.00468 0.05729 298.7 0.00479 0.06530

157.9 0.00511 0.08975 298.9 0.00487 0.06159 300.2 0.00500 0.07007

157.3 0.00533 0.09581 300.3 0.00506 0.06597 301.7 0.00521 0.07498

156.9 0.00554 0.10200 301.8 0.00526 0.07049 302.6 0.00542 0.08000

156.8 0.00575 0.10836 302.8 0.00545 0.07511 304.1 0.00563 0.08512

156.0 0.00597 0.11490 303.8 0.00564 0.07986 304.8 0.00583 0.09037

155.4 0.00618 0.12162 304.7 0.00584 0.08465 305.6 0.00605 0.09568

154.7 0.00639 0.12850 305.8 0.00603 0.08954 306.4 0.00625 0.10110

153.7 0.00661 0.13558 306.6 0.00623 0.09454 307.1 0.00646 0.10663

153.2 0.00682 0.14289 307.3 0.00642 0.09962 307.6 0.00667 0.11228

152.2 0.00703 0.15047 307.8 0.00661 0.10480 308.0 0.00688 0.11806

151.2 0.00724 0.15832 308.4 0.00681 0.11013 308.6 0.00709 0.12399

150.1 0.00746 0.16649 309.0 0.00700 0.11562 309.0 0.00730 0.13007

148.7 0.00767 0.17502 309.4 0.00719 309.4 0.00750 0.13628

147.6 0.00788 0.18396 308.9 0.00739 309.6 0.00771 0.14266

146.0 0.00810 309.8 0.00792 0.14925

L1P1-01-325 L1P1-02-325 L1P1-03-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

76 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1.6 inch L 0.8 inch L 1 inch

W 0.745 inch W 0.745 inch W 0.748 inch

t 0.064 inch t 0.064 inch t 0.063 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

17.6 0.00023 0.00129 13.6 0.00021 0.00032 20.7 0.00023 0.00083

37.2 0.00045 0.00273 43.5 0.00042 0.00122 48.8 0.00046 0.00204

56.9 0.00068 0.00419 77.9 0.00064 0.00228 77.7 0.00069 0.00331

77.0 0.00091 0.00570 114.0 0.00085 0.00343 108.7 0.00092 0.00466

96.5 0.00113 0.00726 151.0 0.00106 0.00464 140.8 0.00115 0.00607

115.1 0.00136 0.00911 188.0 0.00128 0.00589 171.8 0.00138 0.00759

130.6 0.00159 0.01150 224.1 0.00149 0.00722 200.3 0.00160 0.00941

142.6 0.00182 0.01443 256.4 0.00170 0.00878 223.4 0.00183 0.01169

151.5 0.00204 0.01784 283.7 0.00192 0.01070 240.9 0.00206 0.01445

157.9 0.00227 0.02162 305.5 0.00213 0.01298 253.8 0.00229 0.01755

162.6 0.00250 0.02567 321.8 0.00234 0.01558 263.4 0.00252 0.02096

165.9 0.00272 0.02994 334.5 0.00256 0.01842 271.0 0.00275 0.02459

168.7 0.00295 0.03443 344.4 0.00277 0.02144 276.8 0.00298 0.02843

170.7 0.00318 0.03912 352.6 0.00299 0.02462 281.6 0.00321 0.03248

172.8 0.00341 0.04403 358.7 0.00320 0.02791 285.7 0.00344 0.03673

174.2 0.00363 0.04912 364.0 0.00341 0.03132 289.2 0.00367 0.04114

175.5 0.00386 0.05438 368.5 0.00363 0.03486 292.3 0.00390 0.04574

176.2 0.00409 0.05977 372.2 0.00384 0.03852 294.8 0.00413 0.05050

176.7 0.00431 0.06528 375.4 0.00405 0.04233 297.2 0.00436 0.05541

177.1 0.00454 0.07095 378.1 0.00427 0.04625 299.3 0.00459 0.06045

177.5 0.00477 0.07671 380.7 0.00448 0.05028 301.2 0.00482 0.06563

177.7 0.00500 0.08261 383.0 0.00470 0.05443 302.8 0.00505 0.07093

177.8 0.00522 0.08865 385.1 0.00491 0.05864 304.4 0.00528 0.07638

177.1 0.00545 0.09482 387.4 0.00512 0.06300 305.8 0.00551 0.08197

176.7 0.00568 0.10118 389.3 0.00534 0.06745 307.3 0.00574 0.08771

176.1 0.00590 0.10771 390.8 0.00556 0.07195 308.4 0.00597 0.09361

175.3 0.00613 0.11441 392.1 0.00576 0.07651 309.3 0.00620 0.09961

174.6 0.00636 0.12131 393.4 0.00598 0.08118 309.7 0.00643 0.10574

174.0 0.00659 0.12841 394.6 0.00619 0.08592 310.3 0.00665 0.11197

173.4 0.00681 0.13573 396.0 0.00641 0.09078 310.8 0.00689 0.11837

172.4 0.00704 0.14338 396.7 0.00662 0.09569 311.1 0.00711 0.12495

171.3 0.00727 0.15138 397.6 0.00683 0.10073 311.5 0.00734 0.13170

170.2 0.00749 0.15979 398.4 0.00705 0.10588 311.8 0.00757 0.13865

169.0 0.00772 0.16860 399.4 0.00726 0.11113 311.7 0.00780 0.14581

168.2 0.00795 0.17776 399.9 0.00748 0.11649 311.8 0.00803 0.15324

166.7 0.00818 0.18730 400.7 0.00769 0.12198 311.7 0.00826 0.16095

165.5 0.00840 400.9 0.00791 0.12760 311.5 0.00849 0.16896

163.7 0.00863 399.8 0.00812 0.13342 311.1 0.00872 0.17727

L1P1-04-325 L1P1-05-325 L1P1-06-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

77 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.751 inch W 0.746 inch W 0.746 inch

t 0.063 inch t 0.063 inch t 0.063 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

46.7 0.00040 0.00066 18.1 0.00018 0.00016 15.4 0.00019 0.00061

101.2 0.00080 0.00247 41.4 0.00038 0.00059 40.1 0.00037 0.00159

155.2 0.00120 0.00529 66.0 0.00057 0.00128 65.7 0.00056 0.00262

199.9 0.00158 0.00879 91.2 0.00075 0.00220 91.8 0.00075 0.00373

199.2 0.00158 0.00878 117.0 0.00094 0.00334 117.6 0.00094 0.00487

199.2 0.00158 0.00877 142.3 0.00113 0.00472 143.8 0.00113 0.00606

198.9 0.00158 0.00876 167.1 0.00132 0.00630 169.3 0.00132 0.00728

197.7 0.00158 0.00877 190.2 0.00151 0.00810 192.9 0.00151 0.00871

221.3 0.00181 0.01128 209.9 0.00170 0.01005 213.0 0.00170 0.01042

245.4 0.00221 0.01628 225.4 0.00189 0.01222 228.9 0.00189 0.01248

245.9 0.00231 0.01758 237.4 0.00208 0.01456 241.2 0.00208 0.01484

244.7 0.00231 0.01760 246.7 0.00227 0.01703 251.1 0.00227 0.01744

244.1 0.00231 0.01758 254.0 0.00246 0.01972 258.6 0.00246 0.02022

243.7 0.00231 0.01760 260.0 0.00265 0.02252 264.5 0.00265 0.02318

257.5 0.00249 0.02009 264.9 0.00284 0.02549 269.6 0.00284 0.02627

267.5 0.00289 0.02629 269.5 0.00303 0.02859 274.0 0.00303 0.02948

276.0 0.00329 0.03311 273.7 0.00322 0.03183 278.4 0.00322 0.03284

281.9 0.00369 0.04048 277.0 0.00341 0.03519 282.3 0.00341 0.03636

286.4 0.00410 0.04846 279.6 0.00360 0.03868 285.0 0.00360 0.03997

290.1 0.00450 0.05688 282.0 0.00379 0.04229 287.6 0.00379 0.04370

293.6 0.00490 0.06576 284.1 0.00398 0.04605 289.8 0.00397 0.04756

285.4 0.00495 0.06700 286.0 0.00416 0.04986 291.8 0.00416 0.05150

282.9 0.00495 0.06700 288.0 0.00436 0.05386 293.7 0.00435 0.05557

280.9 0.00495 0.06700 289.8 0.00454 0.05786 295.3 0.00454 0.05972

266.8 0.00495 0.06703 291.4 0.00473 0.06204 297.0 0.00473 0.06395

298.7 0.00528 0.07454 292.9 0.00492 0.06630 298.4 0.00492 0.06827

292.5 0.00550 0.07991 294.2 0.00511 0.07069 299.9 0.00511 0.07269

289.1 0.00550 0.07995 295.6 0.00530 0.07515 301.2 0.00530 0.07720

287.4 0.00550 0.07993 296.8 0.00549 0.07967 302.2 0.00549 0.08181

286.0 0.00550 0.07998 298.1 0.00568 0.08438 303.4 0.00568 0.08649

300.9 0.00576 0.08631 299.2 0.00587 0.08915 304.4 0.00587 0.09127

303.0 0.00616 0.09659 300.3 0.00606 0.09404 305.4 0.00606 0.09611

303.7 0.00656 0.10739 301.1 0.00625 0.09897 306.4 0.00625 0.10104

293.8 0.00657 0.10763 302.0 0.00644 0.10401 307.3 0.00644 0.10607

291.4 0.00657 0.10760 302.7 0.00663 0.10929 308.1 0.00663 0.11118

289.8 0.00657 0.10760 303.4 0.00682 0.11451 308.6 0.00682 0.11642

278.1 0.00659 0.10805 303.9 0.00701 0.11985 309.0 0.00701 0.12174

307.9 0.00699 0.11940 304.5 0.00720 0.12537 309.6 0.00720 0.12722

L1P1-07-325 L1P1-08-325 L1P1-09-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

78 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch L 1 inch

W 0.752 inch W 0.745 inch W 0.747 inch W 0.746 inch

t 0.062 inch t 0.062 inch t 0.062 inch t 0.062 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0 0 0 0

15.9 0.00035 0.00051 14.2 0.00034 0.00048 19.9 0.00022 0.00021 15.6 0.00013 0.00009

38.6 0.00072 0.00202 35.5 0.00069 0.00186 47.6 0.00043 0.00076 32.9 0.00027 0.00032

62.9 0.00110 0.00443 59.0 0.00104 0.00402 76.2 0.00065 0.00165 50.3 0.00041 0.00068

87.6 0.00147 0.00770 82.7 0.00139 0.00690 105.1 0.00087 0.00285 68.0 0.00054 0.00118

112.3 0.00184 0.01170 106.6 0.00174 0.01050 134.4 0.00109 0.00435 85.6 0.00068 0.00179

136.7 0.00222 0.01630 130.4 0.00209 0.01470 163.1 0.00130 0.00611 103.7 0.00082 0.00254

160.7 0.00259 0.02160 153.8 0.00245 0.01960 190.0 0.00152 0.00816 121.8 0.00095 0.00340

182.9 0.00296 0.02750 176.0 0.00280 0.02490 211.8 0.00174 0.01040 139.5 0.00109 0.00439

202.1 0.00333 0.03390 196.0 0.00315 0.03070 228.4 0.00195 0.01300 157.0 0.00123 0.00550

217.5 0.00371 0.04080 212.6 0.00350 0.03700 241.0 0.00217 0.01570 174.2 0.00136 0.00668

229.5 0.00408 0.04810 225.9 0.00385 0.04360 250.1 0.00239 0.01870 189.8 0.00150 0.00798

238.9 0.00445 0.05600 236.2 0.00421 0.05070 257.4 0.00261 0.02190 203.5 0.00164 0.00940

246.1 0.00483 0.06410 244.5 0.00456 0.05820 263.4 0.00283 0.02530 217.0 0.00180 0.01110

252.4 0.00519 0.07260 251.3 0.00491 0.06600 268.6 0.00304 0.02880 226.2 0.00194 0.01280

257.6 0.00557 0.08160 256.6 0.00527 0.07430 273.2 0.00326 0.03260 233.8 0.00207 0.01450

262.1 0.00594 0.09100 261.6 0.00561 0.08270 276.2 0.00348 0.03650 240.2 0.00221 0.01630

265.6 0.00632 0.10100 265.8 0.00597 0.09160 278.8 0.00370 0.04060 245.6 0.00235 0.01810

268.6 0.00669 0.11100 269.0 0.00632 0.10100 281.2 0.00391 0.04480 250.1 0.00248 0.02010

271.2 0.00706 0.12100 271.8 0.00667 0.11000 283.3 0.00413 0.04920 254.1 0.00262 0.02210

273.5 0.00743 0.13200 274.3 0.00703 0.12000 285.3 0.00435 0.05370 257.7 0.00276 0.02420

275.4 0.00781 0.14400 276.5 0.00738 0.13100 286.9 0.00457 0.05840 257.6 0.00282 0.02520

277.0 0.00818 0.15600 278.5 0.00773 0.14200 288.5 0.00478 0.06320 262.2 0.00296 0.02750

278.7 0.00855 0.16800 280.1 0.00808 0.15300 290.1 0.00500 0.06810 268.1 0.00323 0.03210

280.1 0.00892 0.18100 281.6 0.00843 0.16400 291.4 0.00522 0.07320 270.2 0.00337 0.03450

281.3 0.00930 0.19500 282.9 0.00879 0.17700 292.5 0.00544 0.07840 271.4 0.00351 0.03700

282.3 0.00967 0.21000 284.2 0.00914 0.18900 293.3 0.00565 0.08370 272.7 0.00364 0.03960

283.2 0.01000 0.22500 285.2 0.00949 0.20200 294.2 0.00587 0.08920 274.1 0.00378 0.04220

284.0 0.01040 0.24100 286.3 0.00984 0.21700 294.7 0.00609 0.09480 275.2 0.00392 0.04490

284.6 0.01080 0.25800 287.0 0.01020 0.23100 295.4 0.00631 0.10100 276.3 0.00405 0.04760

285.3 0.01120 0.27600 287.9 0.01050 0.24700 295.8 0.00653 0.10600 277.6 0.00419 0.05040

285.7 0.01150 0.29500 288.5 0.01090 0.26300 296.3 0.00674 0.11200 278.6 0.00433 0.05330

286.2 0.01190 0.31600 289.2 0.01120 0.28100 296.7 0.00696 0.11900 279.6 0.00447 0.05620

286.5 0.01230 0.33700 289.4 0.01160 0.29900 296.9 0.00718 0.12500 280.6 0.00460 0.05920

286.8 0.01270 0.36100 289.9 0.01200 0.31800 297.0 0.00740 0.13100 281.4 0.00474 0.06210

287.1 0.01300 0.38500 290.3 0.01230 0.33900 297.0 0.00761 0.13800 285.4 0.00506 0.06950

287.4 0.01340 0.41100 290.6 0.01270 0.36100 296.9 0.00783 0.14500 289.2 0.00555 0.08110

287.5 0.01380 0.44000 290.9 0.01300 0.38400 296.9 0.00805 0.15200 293.4 0.00625 0.09890

286.5 0.01410 0.47000 291.0 0.01340 0.40900 296.7 0.00826 0.15900 294.8 0.00700 0.12000

L2P1-01-325 L2P1-02-325 L2P1-07-325 L2P1-08-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

79 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.743 inch W 0.745 inch W 0.745 inch

t 0.058 inch t 0.057 inch t 0.057 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

9.0 0.00017 0.00014 9.1 0.00017 0.00013 8.5 0.00018 0.00016

20.8 0.00034 0.00050 22.3 0.00034 0.00049 23.0 0.00036 0.00055

34.4 0.00052 0.00109 38.6 0.00051 0.00105 40.6 0.00055 0.00119

51.4 0.00069 0.00187 56.8 0.00068 0.00181 59.7 0.00073 0.00205

70.3 0.00087 0.00287 75.8 0.00085 0.00275 79.8 0.00091 0.00313

89.4 0.00104 0.00402 94.9 0.00102 0.00390 99.4 0.00109 0.00442

108.8 0.00121 0.00537 113.4 0.00120 0.00522 119.0 0.00128 0.00589

127.5 0.00139 0.00692 131.9 0.00137 0.00670 138.1 0.00146 0.00756

145.8 0.00156 0.00861 149.2 0.00154 0.00834 155.8 0.00164 0.00942

162.4 0.00174 0.01048 164.9 0.00171 0.01015 171.2 0.00183 0.01145

176.7 0.00191 0.01248 177.8 0.00188 0.01210 183.2 0.00201 0.01363

188.0 0.00209 0.01464 188.4 0.00205 0.01420 193.0 0.00219 0.01597

197.0 0.00226 0.01694 196.6 0.00222 0.01643 200.7 0.00237 0.01850

204.2 0.00244 0.01939 203.3 0.00239 0.01877 207.0 0.00256 0.02113

210.1 0.00261 0.02196 209.1 0.00257 0.02128 212.4 0.00274 0.02391

215.2 0.00279 0.02467 213.8 0.00274 0.02388 216.1 0.00292 0.02683

219.3 0.00296 0.02745 217.6 0.00291 0.02662 219.3 0.00310 0.02986

222.7 0.00313 0.03038 220.7 0.00308 0.02949 222.1 0.00329 0.03305

225.5 0.00331 0.03342 223.2 0.00325 0.03245 224.3 0.00347 0.03636

227.8 0.00348 0.03659 225.4 0.00342 0.03549 226.3 0.00365 0.03973

229.9 0.00366 0.03981 227.3 0.00359 0.03864 227.7 0.00384 0.04326

231.7 0.00383 0.04316 229.0 0.00377 0.04195 229.2 0.00402 0.04685

233.1 0.00401 0.04666 230.5 0.00394 0.04528 230.4 0.00420 0.05063

234.5 0.00418 0.05016 231.7 0.00411 0.04872 231.5 0.00438 0.05444

235.7 0.00435 0.05382 232.7 0.00428 0.05226 232.6 0.00457 0.05838

236.8 0.00453 0.05756 233.9 0.00445 0.05590 233.3 0.00475 0.06233

237.8 0.00470 0.06138 234.7 0.00462 0.05965 234.2 0.00493 0.06652

238.7 0.00488 0.06527 235.6 0.00479 0.06340 234.9 0.00511 0.07073

239.6 0.00505 0.06928 236.4 0.00496 0.06726 235.4 0.00530 0.07502

240.3 0.00522 0.07330 237.0 0.00514 0.07124 235.9 0.00548 0.07944

240.9 0.00540 0.07750 237.7 0.00531 0.07531 236.5 0.00566 0.08391

241.2 0.00557 0.08175 238.1 0.00548 0.07940 236.8 0.00585 0.08854

241.8 0.00575 0.08608 238.7 0.00565 0.08361 237.2 0.00603 0.09323

242.3 0.00592 0.09049 239.3 0.00582 0.08796 237.4 0.00621 0.09796

242.7 0.00610 0.09497 239.6 0.00599 0.09229 237.6 0.00639 0.10282

243.1 0.00627 0.09957 240.0 0.00617 0.09677 238.1 0.00658 0.10783

243.2 0.00645 0.10425 240.2 0.00634 0.10126 238.2 0.00676 0.11287

243.4 0.00662 0.10903 240.7 0.00651 0.10590 238.5 0.00694 0.11803

L5CR-01-325 L5CR-02-325 L5CR-22-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

80 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch

W 0.745 inch W 0.745 inch

t 0.057 inch t 0.057 inch

Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0

8.1 0.00017 0.00014 2.6 0.00018 0.00015

18.9 0.00034 0.00050 7.9 0.00036 0.00056

31.0 0.00052 0.00107 16.7 0.00055 0.00119

46.7 0.00069 0.00187 27.0 0.00073 0.00205

64.3 0.00086 0.00283 38.9 0.00091 0.00313

82.5 0.00104 0.00400 52.5 0.00109 0.00442

100.8 0.00121 0.00534 68.7 0.00128 0.00590

118.8 0.00138 0.00685 86.8 0.00146 0.00756

136.3 0.00156 0.00853 105.3 0.00164 0.00941

152.3 0.00173 0.01037 123.6 0.00182 0.01143

166.6 0.00190 0.01236 140.9 0.00201 0.01364

178.2 0.00208 0.01451 156.9 0.00219 0.01597

187.4 0.00225 0.01678 170.6 0.00237 0.01847

195.0 0.00242 0.01921 181.5 0.00256 0.02113

201.2 0.00259 0.02171 190.1 0.00274 0.02391

206.6 0.00277 0.02439 197.5 0.00292 0.02682

210.4 0.00294 0.02717 203.4 0.00310 0.02989

213.8 0.00312 0.03010 208.0 0.00329 0.03305

216.6 0.00329 0.03308 211.7 0.00347 0.03635

219.0 0.00346 0.03620 214.7 0.00365 0.03977

221.0 0.00363 0.03941 217.3 0.00383 0.04325

222.6 0.00381 0.04276 219.5 0.00402 0.04689

224.0 0.00398 0.04619 221.3 0.00420 0.05059

225.6 0.00415 0.04964 223.0 0.00438 0.05440

226.7 0.00433 0.05328 224.4 0.00457 0.05834

227.9 0.00450 0.05697 225.6 0.00475 0.06241

228.8 0.00467 0.06074 226.8 0.00493 0.06648

229.6 0.00485 0.06465 227.6 0.00511 0.07069

230.4 0.00502 0.06860 228.5 0.00530 0.07502

231.2 0.00519 0.07261 229.3 0.00548 0.07940

231.8 0.00537 0.07675 229.8 0.00566 0.08393

232.5 0.00554 0.08091 230.6 0.00585 0.08851

232.9 0.00571 0.08523 230.9 0.00603 0.09319

233.4 0.00589 0.08962 231.5 0.00621 0.09793

233.7 0.00606 0.09402 231.7 0.00639 0.10282

234.2 0.00623 0.09858 232.0 0.00657 0.10773

234.5 0.00641 0.10320 232.1 0.00676 0.11287

234.6 0.00658 0.10790 232.3 0.00694 0.11800

L5CR-27-325 L5CR-29-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

81 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.745 inch W 0.745 inch W 0.745 inch

t 0.058 inch t 0.058 inch t 0.057 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

8.7 0.00016 0.00013 7.9 0.00016 0.00013 8.5 0.00014 0.00010

19.7 0.00032 0.00044 18.6 0.00033 0.00046 18.3 0.00029 0.00037

32.6 0.00048 0.00094 31.5 0.00049 0.00097 30.6 0.00044 0.00078

48.9 0.00064 0.00161 48.0 0.00066 0.00168 44.6 0.00058 0.00134

66.0 0.00080 0.00246 65.8 0.00082 0.00257 60.6 0.00073 0.00206

83.5 0.00096 0.00348 83.9 0.00099 0.00363 76.4 0.00088 0.00290

100.9 0.00112 0.00464 102.2 0.00115 0.00484 92.8 0.00102 0.00389

118.2 0.00128 0.00596 120.5 0.00131 0.00622 108.8 0.00117 0.00499

135.3 0.00145 0.00744 138.0 0.00148 0.00775 124.8 0.00131 0.00623

151.6 0.00161 0.00906 154.6 0.00165 0.00946 140.4 0.00146 0.00759

166.0 0.00177 0.01077 169.3 0.00181 0.01125 154.6 0.00161 0.00907

178.5 0.00193 0.01265 181.5 0.00197 0.01321 167.9 0.00176 0.01066

188.6 0.00209 0.01464 191.3 0.00214 0.01528 178.5 0.00190 0.01235

196.7 0.00225 0.01676 199.2 0.00230 0.01750 187.9 0.00205 0.01415

203.1 0.00241 0.01900 205.5 0.00247 0.01984 194.8 0.00220 0.01606

208.6 0.00257 0.02136 210.8 0.00263 0.02225 201.1 0.00234 0.01803

213.2 0.00273 0.02381 215.5 0.00280 0.02483 205.7 0.00249 0.02013

217.0 0.00289 0.02638 219.1 0.00296 0.02750 210.5 0.00263 0.02232

220.2 0.00305 0.02903 222.0 0.00312 0.03021 214.0 0.00278 0.02460

222.9 0.00321 0.03177 224.6 0.00329 0.03313 217.2 0.00293 0.02694

225.2 0.00337 0.03462 226.9 0.00345 0.03605 219.8 0.00307 0.02937

227.3 0.00354 0.03758 228.9 0.00362 0.03911 222.6 0.00322 0.03188

229.1 0.00370 0.04060 230.7 0.00378 0.04227 224.3 0.00337 0.03450

230.6 0.00386 0.04370 232.4 0.00395 0.04550 226.3 0.00352 0.03718

232.2 0.00402 0.04688 233.6 0.00411 0.04883 227.8 0.00366 0.03993

233.4 0.00418 0.05018 234.8 0.00428 0.05221 229.1 0.00381 0.04274

234.5 0.00434 0.05352 236.0 0.00444 0.05570 230.2 0.00395 0.04561

235.6 0.00450 0.05693 236.8 0.00461 0.05928 231.5 0.00410 0.04859

236.4 0.00466 0.06044 237.7 0.00477 0.06290 232.6 0.00425 0.05158

237.3 0.00482 0.06405 238.4 0.00494 0.06662 233.7 0.00439 0.05468

237.8 0.00498 0.06769 239.2 0.00510 0.07043 234.2 0.00454 0.05781

238.4 0.00514 0.07141 239.8 0.00527 0.07428 235.3 0.00469 0.06101

238.9 0.00530 0.07521 240.1 0.00543 0.07823 235.7 0.00483 0.06428

239.3 0.00546 0.07906 240.8 0.00559 0.08225 236.4 0.00498 0.06758

239.7 0.00563 0.08301 241.0 0.00576 0.08639 236.6 0.00513 0.07102

240.1 0.00579 0.08708 241.5 0.00593 0.09056 237.2 0.00527 0.07444

240.1 0.00595 0.09108 242.0 0.00609 0.09481 237.3 0.00542 0.07796

240.3 0.00611 0.09527 242.5 0.00625 0.09908 237.5 0.00557 0.08154

L5MCR-01-325 L5MCR-02-325 L5MCR-03-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

82 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.745 inch W 0.746 inch W 0.745 inch

t 0.057 inch t 0.056 inch t 0.057 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0 0 0 0

9.4 0.00017 0.00014 9.0 0.00018 0.00015 7.6 0.00017 0.00014

23.6 0.00035 0.00052 21.7 0.00036 0.00054 19.3 0.00035 0.00052

40.0 0.00053 0.00112 38.2 0.00053 0.00115 33.3 0.00053 0.00112

59.5 0.00070 0.00193 55.7 0.00072 0.00199 51.2 0.00071 0.00194

78.8 0.00088 0.00295 73.6 0.00089 0.00302 70.6 0.00088 0.00293

98.5 0.00106 0.00415 91.4 0.00107 0.00426 91.0 0.00106 0.00415

117.9 0.00124 0.00555 109.0 0.00125 0.00570 110.9 0.00124 0.00556

136.9 0.00141 0.00713 126.5 0.00143 0.00733 130.7 0.00141 0.00712

154.7 0.00159 0.00888 142.7 0.00161 0.00909 149.6 0.00159 0.00888

169.9 0.00177 0.01079 157.1 0.00179 0.01107 166.3 0.00177 0.01078

182.4 0.00195 0.01288 168.7 0.00197 0.01319 180.9 0.00194 0.01285

192.0 0.00212 0.01506 177.9 0.00215 0.01547 192.0 0.00212 0.01508

199.6 0.00230 0.01744 185.4 0.00233 0.01789 200.9 0.00230 0.01743

205.7 0.00248 0.01995 191.7 0.00251 0.02045 207.9 0.00247 0.01994

211.1 0.00265 0.02261 196.6 0.00269 0.02315 214.0 0.00265 0.02257

215.2 0.00283 0.02535 200.3 0.00287 0.02601 219.3 0.00283 0.02538

218.5 0.00301 0.02823 203.5 0.00305 0.02893 223.0 0.00301 0.02824

221.4 0.00318 0.03123 205.8 0.00323 0.03205 226.6 0.00318 0.03123

223.8 0.00336 0.03436 208.1 0.00341 0.03522 228.9 0.00336 0.03438

226.1 0.00354 0.03760 209.9 0.00359 0.03853 231.3 0.00354 0.03758

227.9 0.00372 0.04096 211.7 0.00377 0.04196 233.4 0.00371 0.04091

229.6 0.00389 0.04437 213.0 0.00395 0.04546 234.8 0.00389 0.04436

231.0 0.00407 0.04792 214.3 0.00413 0.04906 236.4 0.00407 0.04792

232.1 0.00425 0.05157 215.5 0.00431 0.05282 237.6 0.00424 0.05153

233.4 0.00442 0.05527 216.5 0.00449 0.05663 238.7 0.00442 0.05529

234.3 0.00460 0.05912 217.4 0.00467 0.06054 240.0 0.00460 0.05910

235.3 0.00478 0.06304 218.0 0.00484 0.06452 240.6 0.00478 0.06303

236.0 0.00495 0.06704 218.8 0.00502 0.06864 241.6 0.00495 0.06704

236.7 0.00513 0.07110 219.3 0.00520 0.07282 242.5 0.00513 0.07110

237.3 0.00531 0.07529 220.0 0.00538 0.07713 242.7 0.00531 0.07527

237.8 0.00549 0.07957 220.5 0.00556 0.08146 243.6 0.00549 0.07959

238.4 0.00566 0.08393 220.8 0.00574 0.08595 243.9 0.00566 0.08395

238.7 0.00584 0.08840 221.3 0.00592 0.09045 244.4 0.00584 0.08836

239.3 0.00602 0.09290 221.6 0.00610 0.09510 244.8 0.00602 0.09287

239.7 0.00619 0.09752 222.4 0.00628 0.09982 245.0 0.00620 0.09755

240.0 0.00637 0.10219 222.6 0.00646 0.10464 245.5 0.00637 0.10224

240.2 0.00655 0.10702 222.6 0.00664 0.10955 245.6 0.00655 0.10704

240.3 0.00673 0.11192 222.6 0.00682 0.11458

L5MCR-04-325 L5MCR-13-325 L5MCR-17-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

83 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch

W 0.745 inch W 0.746 inch

t 0.058 inch t 0.057 inch

Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in)

0 0 0 0 0 0

9.0 0.00018 0.00015 8.4 0.00018 0.00015

21.3 0.00036 0.00055 22.2 0.00036 0.00055

36.4 0.00055 0.00120 38.1 0.00054 0.00117

55.6 0.00073 0.00207 57.3 0.00072 0.00201

75.7 0.00092 0.00317 77.2 0.00090 0.00306

96.0 0.00110 0.00445 97.2 0.00108 0.00432

115.9 0.00128 0.00596 116.8 0.00126 0.00577

135.5 0.00147 0.00767 136.0 0.00144 0.00741

153.8 0.00165 0.00951 153.9 0.00162 0.00923

169.9 0.00183 0.01155 169.6 0.00181 0.01123

182.8 0.00202 0.01377 182.1 0.00199 0.01337

193.2 0.00220 0.01614 191.9 0.00217 0.01567

201.2 0.00239 0.01866 199.7 0.00235 0.01813

207.7 0.00257 0.02135 206.2 0.00253 0.02074

213.2 0.00276 0.02419 211.6 0.00271 0.02348

217.5 0.00294 0.02712 215.9 0.00289 0.02633

221.0 0.00312 0.03020 219.3 0.00307 0.02931

223.9 0.00331 0.03342 222.1 0.00325 0.03246

226.3 0.00349 0.03677 224.3 0.00343 0.03568

228.5 0.00368 0.04021 226.4 0.00362 0.03905

230.3 0.00386 0.04375 228.2 0.00379 0.04245

231.8 0.00404 0.04740 229.7 0.00398 0.04603

233.4 0.00423 0.05120 231.1 0.00416 0.04970

234.6 0.00441 0.05507 232.3 0.00434 0.05346

235.8 0.00460 0.05905 233.4 0.00452 0.05732

236.8 0.00478 0.06308 234.2 0.00470 0.06126

237.5 0.00496 0.06724 235.3 0.00488 0.06534

238.6 0.00515 0.07151 236.1 0.00506 0.06948

239.3 0.00533 0.07586 236.7 0.00524 0.07370

239.7 0.00552 0.08031 237.3 0.00542 0.07805

240.4 0.00570 0.08484 237.9 0.00560 0.08244

240.8 0.00588 0.08950 238.4 0.00578 0.08698

241.1 0.00607 0.09425 238.7 0.00597 0.09157

241.5 0.00625 0.09901 239.2 0.00615 0.09629

241.7 0.00644 0.10396 239.5 0.00633 0.10105

241.9 0.00662 0.10898 239.8 0.00651 0.10593

242.0 0.00680 0.11411 240.1 0.00669 0.11088

242.1 0.00699 0.11931 240.4 0.00687 0.11593

L5MCR-20-325 L5MCR-28-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

84 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 1 inch L 1 inch

W 0.745 inch W 0.746 inch W 0.746 inch

t 0.062 inch t 0.06 inch t 0.06 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

9.3 0.0002 0.0001 8.4 0.0002 0.0001 9.0 0.0002 0.0001

22.3 0.0003 0.0004 21.7 0.0003 0.0004 21.0 0.0003 0.0005

38.0 0.0005 0.0009 36.6 0.0005 0.0009 36.7 0.0005 0.0010

56.7 0.0006 0.0015 53.8 0.0007 0.0015 55.0 0.0007 0.0017

76.3 0.0008 0.0023 72.2 0.0008 0.0024 73.7 0.0008 0.0026

95.9 0.0009 0.0033 91.0 0.0010 0.0033 92.5 0.0010 0.0036

115.5 0.0011 0.0044 109.9 0.0011 0.0044 111.2 0.0011 0.0048

134.8 0.0013 0.0057 128.4 0.0013 0.0057 129.8 0.0013 0.0062

153.7 0.0014 0.0071 146.2 0.0015 0.0071 148.0 0.0015 0.0077

171.7 0.0016 0.0087 163.4 0.0016 0.0087 165.2 0.0016 0.0094

188.1 0.0017 0.0103 178.4 0.0018 0.0103 180.6 0.0018 0.0112

202.2 0.0019 0.0121 190.8 0.0020 0.0121 193.2 0.0020 0.0132

214.0 0.0020 0.0141 200.8 0.0021 0.0141 203.5 0.0021 0.0152

223.5 0.0022 0.0161 208.5 0.0023 0.0161 211.6 0.0023 0.0175

230.8 0.0024 0.0182 215.1 0.0025 0.0183 218.3 0.0025 0.0197

237.0 0.0025 0.0205 220.3 0.0026 0.0205 223.7 0.0026 0.0222

242.1 0.0027 0.0229 224.9 0.0028 0.0229 228.5 0.0028 0.0247

246.8 0.0028 0.0253 229.0 0.0030 0.0254 232.9 0.0030 0.0274

251.0 0.0030 0.0279 232.3 0.0031 0.0279 236.2 0.0031 0.0301

254.5 0.0031 0.0305 235.1 0.0033 0.0306 239.3 0.0033 0.0330

257.2 0.0033 0.0333 237.5 0.0034 0.0333 241.6 0.0034 0.0359

259.7 0.0035 0.0361 239.8 0.0036 0.0361 243.9 0.0036 0.0390

262.0 0.0036 0.0390 241.7 0.0038 0.0391 245.8 0.0038 0.0421

264.0 0.0038 0.0421 243.3 0.0039 0.0421 247.8 0.0039 0.0453

265.8 0.0039 0.0452 244.8 0.0041 0.0452 249.3 0.0041 0.0486

267.4 0.0041 0.0483 246.4 0.0043 0.0483 250.6 0.0043 0.0520

268.9 0.0042 0.0515 247.4 0.0044 0.0516 251.9 0.0044 0.0555

270.2 0.0044 0.0548 248.4 0.0046 0.0549 253.1 0.0046 0.0591

271.6 0.0046 0.0582 249.6 0.0048 0.0583 254.2 0.0048 0.0627

272.9 0.0047 0.0617 250.5 0.0049 0.0617 255.2 0.0049 0.0664

273.6 0.0049 0.0652 251.3 0.0051 0.0652 256.1 0.0051 0.0702

274.4 0.0050 0.0688 252.1 0.0053 0.0688 257.0 0.0053 0.0741

275.2 0.0052 0.0724 252.7 0.0054 0.0725 257.8 0.0054 0.0780

275.9 0.0053 0.0762 253.5 0.0056 0.0763 258.7 0.0056 0.0820

276.3 0.0055 0.0800 254.1 0.0058 0.0800 259.2 0.0057 0.0861

276.8 0.0057 0.0839 254.7 0.0059 0.0840 259.9 0.0059 0.0902

277.3 0.0058 0.0878 255.0 0.0061 0.0879 260.4 0.0061 0.0945

277.1 0.0060 0.0918 255.0 0.0062 0.0919 261.0 0.0062 0.0988

L5HR-01-325 L5HR-02-325 L5HR-03-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

85 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1 inch L 0.8 inch L 0.8 inch

W 0.744 inch W 0.748 inch W 0.747 inch

t 0.06 inch t 0.0575 inch t 0.059 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

8.4 0.0002 0.0001 8.9 0.0002 0.0002 8.9 0.0002 0.0002

19.9 0.0003 0.0005 26.4 0.0004 0.0007 21.9 0.0004 0.0006

34.1 0.0005 0.0011 47.4 0.0006 0.0015 39.6 0.0005 0.0012

51.4 0.0007 0.0019 72.3 0.0008 0.0026 62.6 0.0007 0.0020

70.9 0.0009 0.0028 100.0 0.0010 0.0039 87.2 0.0009 0.0031

90.6 0.0010 0.0040 127.8 0.0012 0.0054 112.3 0.0011 0.0044

110.3 0.0012 0.0053 156.1 0.0014 0.0072 137.7 0.0013 0.0058

129.7 0.0014 0.0068 183.1 0.0017 0.0092 162.7 0.0015 0.0074

148.4 0.0016 0.0085 208.2 0.0019 0.0114 186.9 0.0017 0.0092

165.9 0.0017 0.0103 228.9 0.0021 0.0138 209.2 0.0018 0.0112

181.2 0.0019 0.0123 245.0 0.0023 0.0163 228.4 0.0020 0.0133

193.7 0.0021 0.0144 257.2 0.0025 0.0190 244.2 0.0022 0.0155

203.6 0.0022 0.0167 266.5 0.0027 0.0218 256.3 0.0024 0.0178

211.1 0.0024 0.0190 273.9 0.0029 0.0249 265.8 0.0026 0.0203

217.7 0.0026 0.0216 279.5 0.0031 0.0280 273.5 0.0028 0.0229

222.9 0.0028 0.0242 284.0 0.0033 0.0312 279.4 0.0029 0.0256

227.6 0.0029 0.0270 288.0 0.0035 0.0345 284.2 0.0031 0.0284

231.4 0.0031 0.0299 291.1 0.0037 0.0380 288.3 0.0033 0.0313

234.6 0.0033 0.0328 294.2 0.0039 0.0416 291.8 0.0035 0.0343

237.2 0.0034 0.0359 297.0 0.0041 0.0453 294.8 0.0037 0.0374

239.7 0.0036 0.0391 299.8 0.0043 0.0491 297.4 0.0039 0.0406

241.8 0.0038 0.0424 301.9 0.0046 0.0530 300.0 0.0041 0.0438

243.7 0.0040 0.0458 303.9 0.0048 0.0570 302.5 0.0042 0.0472

245.4 0.0041 0.0493 305.5 0.0050 0.0611 304.5 0.0044 0.0506

247.1 0.0043 0.0528 306.9 0.0052 0.0653 306.4 0.0046 0.0541

248.5 0.0045 0.0565 308.4 0.0054 0.0696 308.0 0.0048 0.0577

249.8 0.0047 0.0603 309.6 0.0056 0.0738 309.5 0.0050 0.0613

251.1 0.0048 0.0641 310.8 0.0058 0.0784 310.8 0.0052 0.0650

252.1 0.0050 0.0680 312.0 0.0060 0.0829 312.2 0.0053 0.0688

252.9 0.0052 0.0720 312.9 0.0062 0.0876 313.3 0.0055 0.0728

253.8 0.0053 0.0761 313.6 0.0064 0.0924 314.2 0.0057 0.0767

254.8 0.0055 0.0803 314.2 0.0066 0.0974 315.3 0.0059 0.0807

255.6 0.0057 0.0845 314.9 0.0068 0.1024 316.1 0.0061 0.0849

256.3 0.0059 0.0888 315.2 0.0070 0.1075 316.7 0.0063 0.0891

257.0 0.0060 0.0933 315.8 0.0072 0.1128 317.4 0.0065 0.0933

257.6 0.0062 0.0978 315.9 0.0074 0.1182 318.2 0.0066 0.0979

258.2 0.0064 0.1023 316.3 0.0077 0.1239 318.6 0.0068 0.1023

258.8 0.0065 0.1071 316.2 0.0079 0.1297 319.2 0.0070 0.1069

L5HR-04-325 L5HR-09-325 L5HR-11-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

86 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 0.8 inch L 0.8 inch L 0.8 inch

W 0.747 inch W 0.746 inch W 0.746 inch

t 0.059 inch t 0.059 inch t 0.059 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

9.9 0.0002 0.0001 10.1 0.0002 0.0002 10.4 0.0002 0.0001

25.7 0.0003 0.0005 23.9 0.0004 0.0006 25.4 0.0003 0.0005

45.5 0.0005 0.0011 44.3 0.0005 0.0012 45.2 0.0005 0.0010

69.3 0.0007 0.0019 68.6 0.0007 0.0020 68.4 0.0007 0.0017

94.5 0.0009 0.0029 93.8 0.0009 0.0030 92.5 0.0008 0.0026

120.7 0.0011 0.0041 119.3 0.0011 0.0043 116.6 0.0010 0.0037

147.3 0.0012 0.0055 144.7 0.0013 0.0057 140.9 0.0012 0.0049

173.1 0.0014 0.0070 169.2 0.0014 0.0072 165.2 0.0013 0.0064

198.1 0.0016 0.0087 193.5 0.0016 0.0090 188.8 0.0015 0.0079

221.0 0.0018 0.0105 215.9 0.0018 0.0108 211.3 0.0017 0.0095

241.1 0.0020 0.0124 235.1 0.0020 0.0129 230.9 0.0019 0.0113

257.0 0.0021 0.0146 250.6 0.0022 0.0150 247.3 0.0020 0.0133

269.0 0.0023 0.0168 262.7 0.0024 0.0173 260.3 0.0022 0.0153

278.7 0.0025 0.0191 272.1 0.0025 0.0198 270.6 0.0024 0.0174

286.4 0.0027 0.0215 279.8 0.0027 0.0223 278.9 0.0025 0.0196

292.3 0.0028 0.0241 285.9 0.0029 0.0249 285.6 0.0027 0.0221

297.5 0.0030 0.0268 290.7 0.0031 0.0277 291.0 0.0029 0.0244

301.7 0.0032 0.0296 294.9 0.0033 0.0304 295.4 0.0030 0.0270

304.8 0.0034 0.0324 298.4 0.0034 0.0334 299.3 0.0032 0.0296

307.9 0.0036 0.0353 301.4 0.0036 0.0364 302.5 0.0034 0.0323

310.6 0.0037 0.0383 304.1 0.0038 0.0395 305.1 0.0035 0.0351

313.0 0.0039 0.0414 306.7 0.0040 0.0427 307.7 0.0037 0.0379

315.3 0.0041 0.0447 309.0 0.0042 0.0460 310.0 0.0039 0.0408

317.8 0.0043 0.0479 311.3 0.0044 0.0492 312.2 0.0041 0.0439

319.9 0.0045 0.0512 313.1 0.0045 0.0527 314.4 0.0042 0.0469

321.7 0.0046 0.0546 314.6 0.0047 0.0562 316.3 0.0044 0.0501

323.4 0.0048 0.0580 316.0 0.0049 0.0597 317.8 0.0046 0.0533

324.7 0.0050 0.0616 317.4 0.0051 0.0634 319.3 0.0047 0.0565

326.0 0.0052 0.0652 318.7 0.0053 0.0671 320.7 0.0049 0.0598

327.5 0.0054 0.0689 319.8 0.0054 0.0708 321.9 0.0051 0.0632

328.6 0.0055 0.0726 320.9 0.0056 0.0747 323.0 0.0052 0.0667

329.5 0.0057 0.0765 321.8 0.0058 0.0786 324.1 0.0054 0.0702

330.3 0.0059 0.0803 322.7 0.0060 0.0827 325.2 0.0056 0.0737

331.2 0.0061 0.0843 323.5 0.0062 0.0868 326.0 0.0058 0.0774

332.1 0.0062 0.0883 324.2 0.0064 0.0909 327.1 0.0059 0.0811

332.6 0.0064 0.0925 324.9 0.0065 0.0952 327.9 0.0061 0.0848

333.3 0.0066 0.0968 325.4 0.0067 0.0996 328.5 0.0063 0.0887

333.9 0.0068 0.1010 325.7 0.0069 0.1040 327.7 0.0064 0.0927

L5HR-12-325 L5HR-13-325 L5HR-14-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

87 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 0.8 inch L 0.8 inch L 1 inch

W 0.747 inch W 0.747 inch W 0.745 inch

t 0.059 inch t 0.059 inch t 0.059 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

9.5 0.0002 0.0002 10.6 0.0002 0.0001 10.1 0.0002 0.0001

21.6 0.0004 0.0005 25.6 0.0003 0.0005 24.8 0.0003 0.0005

38.0 0.0005 0.0012 45.1 0.0005 0.0011 43.2 0.0005 0.0011

58.8 0.0007 0.0020 68.3 0.0007 0.0018 63.1 0.0007 0.0018

82.8 0.0009 0.0030 92.6 0.0009 0.0028 83.4 0.0009 0.0028

107.4 0.0011 0.0043 117.6 0.0010 0.0039 103.4 0.0010 0.0039

132.6 0.0013 0.0057 142.7 0.0012 0.0052 123.6 0.0012 0.0052

157.2 0.0014 0.0072 167.5 0.0014 0.0066 143.3 0.0014 0.0067

181.4 0.0016 0.0090 191.6 0.0015 0.0082 162.2 0.0015 0.0084

203.8 0.0018 0.0109 214.4 0.0017 0.0099 178.9 0.0017 0.0102

223.6 0.0020 0.0129 234.4 0.0019 0.0117 193.0 0.0019 0.0121

240.1 0.0022 0.0151 250.9 0.0021 0.0137 204.0 0.0021 0.0142

253.5 0.0024 0.0173 263.9 0.0022 0.0159 212.7 0.0022 0.0164

263.8 0.0025 0.0197 274.3 0.0024 0.0180 219.4 0.0024 0.0188

272.1 0.0027 0.0223 282.7 0.0026 0.0204 225.1 0.0026 0.0213

278.7 0.0029 0.0249 289.1 0.0028 0.0228 230.1 0.0027 0.0240

284.0 0.0031 0.0276 294.7 0.0029 0.0253 234.2 0.0029 0.0267

288.3 0.0033 0.0304 299.1 0.0031 0.0279 237.3 0.0031 0.0295

292.1 0.0034 0.0334 303.0 0.0033 0.0306 240.1 0.0033 0.0325

295.0 0.0036 0.0364 306.1 0.0034 0.0334 242.4 0.0034 0.0355

297.9 0.0038 0.0395 308.6 0.0036 0.0362 244.2 0.0036 0.0387

300.4 0.0040 0.0427 311.3 0.0038 0.0392 245.9 0.0038 0.0420

302.8 0.0042 0.0459 313.6 0.0040 0.0422 247.3 0.0039 0.0453

305.1 0.0044 0.0493 315.9 0.0041 0.0453 248.7 0.0041 0.0488

306.9 0.0045 0.0527 318.1 0.0043 0.0484 249.8 0.0043 0.0523

308.4 0.0047 0.0562 320.2 0.0045 0.0516 250.9 0.0045 0.0559

309.9 0.0049 0.0598 321.6 0.0046 0.0548 252.0 0.0046 0.0597

311.1 0.0051 0.0634 323.0 0.0048 0.0582 252.7 0.0048 0.0635

312.4 0.0053 0.0671 324.4 0.0050 0.0617 253.5 0.0050 0.0673

313.5 0.0054 0.0709 325.4 0.0052 0.0652 253.9 0.0051 0.0714

314.7 0.0056 0.0748 326.6 0.0053 0.0687 254.5 0.0053 0.0754

315.5 0.0058 0.0786 327.6 0.0055 0.0724 255.2 0.0055 0.0796

316.3 0.0060 0.0827 328.5 0.0057 0.0761 255.6 0.0057 0.0837

317.1 0.0062 0.0867 329.4 0.0059 0.0798 256.0 0.0058 0.0880

317.7 0.0064 0.0910 330.1 0.0060 0.0836 256.2 0.0060 0.0924

318.5 0.0065 0.0952 330.7 0.0062 0.0875 256.4 0.0062 0.0968

319.2 0.0067 0.0996 331.4 0.0064 0.0915 256.6 0.0063 0.1014

318.5 0.0069 0.1040 256.7 0.0065 0.1060

L5HR-15-325 L5HR-16-325 L5HR-17-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

88 of 152

NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (cont.)

L 1.6 inch L 1 inch L 1.6 inch

W 0.746 inch W 0.745 inch W 0.746 inch

t 0.06 inch t 0.06 inch t 0.059 inch

Load dt/L2 Strain Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in) (Lbs.) (in/in)

9.5 0.0002 0.0003 9.1 0.0002 0.0001 9.2 0.0002 0.0003

20.5 0.0003 0.0009 21.5 0.0003 0.0004 20.2 0.0003 0.0008

32.8 0.0005 0.0017 37.9 0.0005 0.0009 32.0 0.0005 0.0016

45.4 0.0007 0.0027 56.2 0.0006 0.0016 44.3 0.0007 0.0027

58.0 0.0008 0.0040 75.3 0.0008 0.0024 56.6 0.0008 0.0039

70.2 0.0010 0.0054 94.4 0.0009 0.0034 68.7 0.0010 0.0053

82.8 0.0012 0.0071 113.2 0.0011 0.0045 81.1 0.0012 0.0070

95.0 0.0014 0.0090 131.9 0.0013 0.0058 92.7 0.0013 0.0088

106.1 0.0015 0.0110 150.0 0.0014 0.0072 103.7 0.0015 0.0108

115.7 0.0017 0.0133 167.3 0.0016 0.0088 113.1 0.0017 0.0130

123.4 0.0019 0.0157 182.7 0.0017 0.0105 120.7 0.0018 0.0154

129.3 0.0020 0.0182 195.6 0.0019 0.0123 126.8 0.0020 0.0178

134.4 0.0022 0.0209 206.0 0.0021 0.0142 131.5 0.0022 0.0205

138.1 0.0024 0.0237 214.4 0.0022 0.0163 135.3 0.0023 0.0233

141.1 0.0025 0.0267 221.1 0.0024 0.0184 138.0 0.0025 0.0262

143.5 0.0027 0.0298 226.8 0.0025 0.0207 140.2 0.0027 0.0292

145.4 0.0029 0.0330 231.8 0.0027 0.0232 142.0 0.0028 0.0324

146.8 0.0030 0.0364 236.1 0.0028 0.0256 143.5 0.0030 0.0356

148.0 0.0032 0.0398 239.3 0.0030 0.0282 144.9 0.0032 0.0390

148.9 0.0034 0.0434 242.2 0.0032 0.0309 145.9 0.0033 0.0425

149.8 0.0035 0.0470 244.4 0.0033 0.0336 146.6 0.0035 0.0461

150.4 0.0037 0.0508 246.6 0.0035 0.0365 147.1 0.0037 0.0498

150.8 0.0039 0.0547 248.3 0.0036 0.0395 147.7 0.0038 0.0536

151.1 0.0041 0.0586 249.9 0.0038 0.0425 148.1 0.0040 0.0575

151.4 0.0042 0.0627 251.3 0.0040 0.0456 148.3 0.0042 0.0615

151.5 0.0044 0.0668 252.7 0.0041 0.0488 148.4 0.0043 0.0655

151.4 0.0046 0.0711 253.6 0.0043 0.0521 148.4 0.0045 0.0697

151.3 0.0047 0.0754 254.7 0.0044 0.0554 148.3 0.0047 0.0739

151.3 0.0049 0.0798 255.6 0.0046 0.0588 148.3 0.0048 0.0782

151.1 0.0051 0.0843 256.4 0.0047 0.0623 148.0 0.0050 0.0826

150.8 0.0052 0.0889 257.2 0.0049 0.0659 148.0 0.0052 0.0872

150.5 0.0054 0.0936 257.8 0.0051 0.0695 147.7 0.0053 0.0918

150.4 0.0056 0.0984 258.6 0.0052 0.0732 147.4 0.0055 0.0964

150.1 0.0057 0.1032 259.1 0.0054 0.0770 146.9 0.0057 0.1012

149.7 0.0059 0.1082 259.6 0.0055 0.0808 146.4 0.0058 0.1061

149.1 0.0061 0.1133 259.9 0.0057 0.0847 145.9 0.0060 0.1111

148.5 0.0063 0.1184 260.3 0.0059 0.0887 145.5 0.0062 0.1161

147.8 0.0064 0.1238 260.0 0.0060 0.0928 145.0 0.0063 0.1213

L5HR-18-325 L5HR-19-325 L5HR-20-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Version:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table C-3. 3-point Bend Test Results by Specimen Number (concluded)

L 1.6 inch L 1.6 inch

W 0.747 inch W 0.745 inch

t 0.057 inch t 0.059 inch

Load dt/L2 Strain Load dt/L2 Strain

(Lbs.) (in/in) (Lbs.) (in/in)

8.4 0.0002 0.0003 8.9 0.0002 0.0003

18.4 0.0003 0.0008 19.2 0.0003 0.0009

30.0 0.0005 0.0016 31.4 0.0005 0.0017

41.6 0.0007 0.0026 43.4 0.0007 0.0027

53.0 0.0008 0.0038 55.6 0.0008 0.0040

64.8 0.0010 0.0052 67.6 0.0010 0.0054

76.2 0.0011 0.0067 79.4 0.0012 0.0071

87.5 0.0013 0.0085 91.5 0.0013 0.0090

97.9 0.0015 0.0104 102.0 0.0015 0.0110

106.7 0.0016 0.0125 111.3 0.0017 0.0132

114.3 0.0018 0.0148 118.8 0.0019 0.0156

120.0 0.0020 0.0172 124.8 0.0020 0.0181

124.6 0.0021 0.0198 129.3 0.0022 0.0208

128.1 0.0023 0.0225 133.0 0.0024 0.0236

131.0 0.0025 0.0253 135.6 0.0025 0.0266

133.2 0.0026 0.0282 138.1 0.0027 0.0297

135.0 0.0028 0.0312 139.8 0.0029 0.0329

136.6 0.0029 0.0344 141.4 0.0030 0.0362

137.4 0.0031 0.0377 142.7 0.0032 0.0396

138.4 0.0033 0.0411 143.8 0.0034 0.0432

139.3 0.0034 0.0446 144.5 0.0035 0.0468

139.8 0.0036 0.0481 145.5 0.0037 0.0506

140.6 0.0038 0.0518 146.0 0.0039 0.0544

140.8 0.0039 0.0556 146.6 0.0040 0.0583

141.0 0.0041 0.0594 147.2 0.0042 0.0624

141.0 0.0043 0.0633 147.8 0.0044 0.0665

141.2 0.0044 0.0674 147.6 0.0046 0.0707

141.2 0.0046 0.0715 147.8 0.0047 0.0750

141.3 0.0047 0.0757 147.8 0.0049 0.0794

141.0 0.0049 0.0799 147.8 0.0051 0.0839

140.9 0.0051 0.0843 147.8 0.0052 0.0885

140.3 0.0052 0.0887 147.8 0.0054 0.0931

140.0 0.0054 0.0932 147.7 0.0056 0.0979

139.3 0.0056 0.0979 147.4 0.0057 0.1027

138.9 0.0057 0.1026 147.1 0.0059 0.1077

138.7 0.0059 0.1074 146.6 0.0061 0.1127

138.3 0.0061 0.1123 146.1 0.0062 0.1179

137.7 0.0062 0.1173 145.3 0.0064 0.1231

L5HR-21-325 L5HR-23-325
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Appendix D. Fracture Test Results

The fracture test results are presented in Tables D-1 to D-8 for the different material lots in terms 

of the test conditions and the stress intensity factor calculated at the peak load of the test. The 

measured crack mouth opening displacement and load for each fracture test is provided in 

Figures D-1 to D-191.

Table D-1. Thermal Aging Fracture Test Results for Lot 400751

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

o

F)

K at Pmax 

(ksi inch1/2)

L1P1-07-325 400751 - - 325 28.0

L1P1-13-325 400751 - - 325 28.6

L1P2-03-325 400751 - - 325 26.0

L1P1-04T-325 400751 325 24.9

L1P1-05T-325 400751 325 23.3

L1P1-06T-325 400751 325 25.0

L1P1-07T-325 400751 - - 325 23.0

L1P1-08T-325 400751 - - 325 22.1

L1P1-09T-325 400751 - - 325 25.7

L1P3-15-333 400751 - - 333 20.4

L1P3-16-333 400751 - - 333 21.6

L1P3-12-340 400751 - - 340 22.4

L1P3-13-340 400751 - - 340 21.1

L1P3-14-340 400751 - - 340 20.7

L1P1-02-350 400751 - - 350 19.6

L1P1-08-350 400751 - - 350 18.9

L1P2-06-350 400751 - - 350 18.7

L1P2-10-350 400751 - - 350 19.2

L1P1-04-375 400751 - - 375 18.0

L1P1-09-375 400751 - - 375 19.4

L1P1-03-400 400751 - - 400 24.0

L1P1-10-400 400751 - - 400 20.9

L1P1-19-400 400751 - - 400 24.3

L1P1-20-400 400751 - - 400 23.2
NASA Engineering and Safety Center 

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Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-2. Thermal Aging Fracture Test Results for Lot 400768

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

o

F)

K at Pmax 

(ksi inch1/2)

L2P1-07-325 400768 - - 325 28.6

L2P1-13-325 400768 - - 325 29.4

L2P1-07T-325 400768 - - 325 25.0

L2P1-08T-325 400768 - - 325 25.4

L2P1-09T-325 400768 - - 325 25.0

L2P3-15-333 400768 - - 333 22.3

L2P3-16-333 400768 - - 333 22.3

L2P3-12-340 400768 - - 340 19.5

L2P3-13-340 400768 - - 340 20.1

L2P3-14-340 400768 - - 340 20.9

L2P1-03-350 400768 - - 350 20.3

L2P1-08-350 400768 - - 350 20.3

L2P2-03-350 400768 - - 350 19.6

L2P2-10-350 400768 - - 350 18.8

L2P1-03-375 400768 - - 375 21.8

L2P1-09-375 400768 - - 375 20.2

L2P1-04-400 400768 - - 400 25.4

L2P1-10-400 400768 - - 400 25.9
NASA Engineering and Safety Center 

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Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-3. Thermal Aging Fracture Test Results for Lot 400766

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

oF)

K at Pmax 

(ksi inch1/2)

L3C1-01-325 400766 - - 325 25.4

L3C1-12-325 400766 - - 325 23.7

L3C1-23-325 400766 - - 325 24.5

L3C1-51-325 400766 - - 325 24.1

L3C1-52-325 400766 - - 325 24.2

L3C1-53-325 400766 - - 325 24.3

L3C1-60-325 400766 - - 325 24.5

L3C1-61-325 400766 - - 325 25.1

L3C1-67-325 400766 - - 325 23.1

L3C1-59-325 400766 - - 325 25.6

L3C1-68-325 400766 - - 325 22.6

L3C1-75-325 400766 - - 325 24.9

L3C1-76-325 400766 - - 325 23.7

L3C1-37-333 400766 - - 333 21.8

L3C1-32-333 400766 - - 333 19.1

L3C1-44-333 400766 - - 333 23.1

L3C1-46-333 400766 - - 333 24.0

L3C1-48-333 400766 - - 333 23.6

L3C1-50-333 400766 - - 333 23.6

L3C1-43-333 400766 - - 333 22.4

L3C1-45-333 400766 - - 333 22.6

L3C1-47-333 400766 - - 333 24.3

L3C1-49-333 400766 - - 333 22.3

L3C1-26-340 400766 - - 340 18.9

L3C1-30-340 400766 - - 340 18.4

L3C1-31-340 400766 - - 340 19.6

L3C1-29-340 400766 - - 340 18.2

L3C1-27-340 400766 - - 340 17.9

L3C1-28-340 400766 - - 340 17.1

L3C1-34-340 400766 - - 340 21.9

L3C1-35-340 400766 - - 340 21.4

L3C1-40-340 400766 - - 340 21.8

L3C1-33-340 400766 - - 340 21.6

L3C1-36-340 400766 - - 340 22.6

L3C1-41-340 400766 - - 340 21.0

L3C1-42-340 400766 - - 340 21.0

L3C1-38-340 400766 - - 340 20.6

L3C1-39-340 400766 - - 340 22.0

L3C1-02-350 400766 - - 350 17.4

L3C1-13-350 400766 - - 350 17.9

L3C1-24-350 400766 - - 350 17.5

L3C1-03-375 400766 - - 375 18.3

L3C1-14-375 400766 - - 375 17.4

L3C1-25-375 400766 - - 375 18.5
NASA Engineering and Safety Center 

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-4. Thermal Aging Fracture Test Results for Lot 620853

K at Pmax

(ksi inch1/2)

S7-01 Stringer7-Sister 620853 17.8

S170-35-01 Stringer-170-35 620853 18.3

S170-35-02 Stringer-170-36 620853 20.1

L5HR-01-325 Cold/Hot Formed (325F for 24 Hrs.) H1 620853 16.3

L5HR-02-325 Cold/Hot Formed (325F for 24 Hrs.) H1 620853 15.3

L5HR-03-325 Cold/Hot Formed (325F for 24 Hrs.) H1 620853 16.8

L5HR-04-325 Cold/Hot Formed (325F for 24 Hrs.) H1 620853 17.2

L5CR-01-325 Cold Formed (325F for 24 Hrs.) L1 620853 19.6

L5CR-02-325 Cold Formed (325F for 24 Hrs.) L1 620853 17.8

L5CR-03-325 Cold Formed (325F for 24 Hrs.) L1 620853 19.6

L5CR-04-325 Cold Formed (325F for 24 Hrs.) L1 620853 19.7

L5MCR-01-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.3

L5MCR-02-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.8

L5MCR-03-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 15.2

L5MCR-04-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 17.1

L5MCR-08-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.9

L5MCR-09-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 20.0

L5MCR-10-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.1

L5MCR-11-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.2

L5MCR-12-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.1

L5MCR-13-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 17.3

L5MCR-14-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 18.0

L5MCR-15-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 17.0

L5MCR-16-325 Mottled Cold Formed (325F for 24 Hrs.) I1 620853 19.1

L4HR-01-325 Cold/Hot Formed (325F for 24 Hrs.) K1 620854 21.3

L4HR-02-325 Cold/Hot Formed (325F for 24 Hrs.) K1 620854 17.7

L4HR-03-325 Cold/Hot Formed (325F for 24 Hrs.) K1 620854 21.2

L4HR-04-325 Cold/Hot Formed (325F for 24 Hrs.) K1 620854 20.3

L4CR-01-325 Cold Formed (325F for 24 Hrs.) J1 620854 21.6

L4CR-02-325 Cold Formed (325F for 24 Hrs.) J1 620854 21.4

L4CR-03-325 Cold Formed (325F for 24 Hrs.) J1 620854 20.9

L4CR-04-325 Cold Formed (325F for 24 Hrs.) J1 620854 21.4

L4MCR-01-325 Mottled Cold Formed (325F for 24 Hrs.) G1 620854 21.2

L4MCR-02-325 Mottled Cold Formed (325F for 24 Hrs.) G1 620854 22.8

L4MCR-03-325 Mottled Cold Formed (325F for 24 Hrs.) G1 620854 21.5

L4MCR-04-325 Mottled Cold Formed (325F for 24 Hrs.) G1 620854 21.6

LaRC ID Description

MSFC 

Designation Lot
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-5. Thermal Aging Fracture Test Results for Lot 620853

K at Pmax

(ksi inch1/2)

L5HR-05-340 Cold/Hot Formed (340F for 24 Hrs.) H1 620853 13.9

L5HR-06-340 Cold/Hot Formed (340F for 24 Hrs.) H1 620853 12.4

L5HR-07-340 Cold/Hot Formed (340F for 24 Hrs.) H1 620853 13.6

L5CR-05-340 Cold Formed (340F for 24 Hrs.) L1 620853 14.0

L5CR-06-340 Cold Formed (340F for 24 Hrs.) L1 620853 14.7

L5CR-07-340 Cold Formed (340F for 24 Hrs.) L1 620853 13.9

L5MCR-05-340 Mottled Cold Formed (340F for 24 Hrs.) I1 620853 13.7

L5MCR-06-340 Mottled Cold Formed (340F for 24 Hrs.) I1 620853 14.8

L5MCR-07-340 Mottled Cold Formed (340F for 24 Hrs.) I1 620853 14.1

L4HR-05-340 Cold/Hot Formed (340F for 24 Hrs.) K1 620854 16.9

L4HR-06-340 Cold/Hot Formed (340F for 24 Hrs.) K1 620854 17.9

L4HR-07-340 Cold/Hot Formed (340F for 24 Hrs.) K1 620854 18.1

L4CR-05-340 Cold Formed (340F for 24 Hrs.) L1 620853 16.7

L4CR-06-340 Cold Formed (340F for 24 Hrs.) L1 620853 16.5

L4CR-07-340 Cold Formed (340F for 24 Hrs.) L1 620853 16.4

L4MCR-05-340 Mottled Cold Formed (340F for 24 Hrs.) G1 620854 16.7

L4MCR-06-340 Mottled Cold Formed (340F for 24 Hrs.) G1 620854 17.1

L4MCR-07-340 Mottled Cold Formed (340F for 24 Hrs.) G1 620854 17.9

LaRC ID Description

MSFC 

Designation Lot
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials)

Table D-6. Thermal Exposure Fracture Test Results for Lot 400751

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

o

F)

K at Pmax 

(ksi inch1/2)

L1P2-14-340-325 400751 340 10 325 25.6

L1P2-16-340-325 400751 340 10 325 24.7

L1P1-05-350-325 400751 350 10 325 25.6

L1P1-06-375-325 400751 375 10 325 25.6

L1P2-01-400-325 400751 400 10 325 21.3

L1P2-05-400-325 400751 400 10 325 20.6

L1P2-02-425-325 400751 425 10 325 19.8

L1P2-06-425-325 400751 425 10 325 20.8

L1P2-03-450-325 400751 450 10 325 18.7

L1P2-11-475-325 400751 475 10 325 19.0

L1P2-13-500-325 400751 500 10 325 17.5

L1P2-07-340B-325 400751 340 20 325 23.1

L1P2-10-340B-325 400751 340 20 325 25.5

L1P2-15-340B-325 400751 340 20 325 24.8

L1P2-16-340B-325 400751 340 20 325 25.2

L1P2-08-350B-325 400751 350 20 325 24.7

L1P2-12-350B-325 400751 350 20 325 23.5

L1P2-09-400B-325 400751 400 20 325 22.3

L1P2-04-450B-325 400751 450 20 325 17.3

L1P2-15-500B-325 400751 500 20 325 20.0
NASA Engineering and Safety Center 

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Document #:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-7. Thermal Exposure Fracture Test Results for Lot 400768

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

o

F)

K at Pmax 

(ksi inch1/2)

L2P2-03-340-325 400768 340 10 325 23.3

L2P2-04-340-325 400768 340 10 325 26.5

L2P1-05-350-325 400768 350 10 325 25.2

L2P1-06-375-325 400768 375 10 325 23.6

L2P2-01-400-325 400768 400 10 325 21.2

L2P2-05-400-325 400768 400 10 325 20.1

L2P2-02-425-325 400768 425 10 325 21.0

L2P2-06-425-325 400768 425 10 325 20.3

L2P2-10-450-325 400768 450 10 325 20.1

L2P2-09-475-325 400768 475 10 325 16.6

L2P2-08-500-325 400768 500 10 325 16.7

L2P2-13-350B-325 400768 350 20 325 24.6

L2P2-12-400B-325 400768 400 20 325 17.5

L2P2-10-400B-325 400768 400 20 325 21.4

L2P2-07-500B-325 400768 500 20 325 19.4
NASA Engineering and Safety Center 

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Document #:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Table D-8. Thermal Exposure Fracture Test Results for Lot 400766

ID Lot

Elevated 

Temp (oF)

Hold 

Time 

(min)

24 Hour 

Aging 

Temp 

(

o

F)

K at Pmax 

(ksi inch1/2)

L3C1-04-400/325 400766 400 10 325 24.9

L3C1-15-400/325 400766 400 10 325 23.8

L3C1-05-425/325 400766 425 10 325 20.8

L3C1-16-425/325 400766 425 10 325 18.6

L3C1-06-450/325 400766 450 10 325 16.8

L3C1-17-450/325 400766 450 10 325 17.8

L3C1-07-475/325 400766 475 10 325 17.0

L3C1-18-475/325 400766 475 10 325 17.0

L3C1-19-500/325 400766 500 10 325 18.7

L3C1-08-500/325 400766 500 10 325 16.8

L3C1-09-400/400/325 400766 400 20 325 20.9

L3C1-20-400/400/325 400766 400 20 325 20.3

L3C1-10-450/450/325 400766 450 20 325 16.3

L3C1-21-450/450/325 400766 450 20 325 15.7

L3C1-11-500/500/325 400766 500 20 325 17.5

L3C1-22-500/500/325 400766 500 20 325 18.4
NASA Engineering and Safety Center 

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Document #:

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Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-1 CMOD vs. Load for fracture test 

L1P1-07-325 (Lot 400751 aged at 

325 F for 24 hours)

Figure D-2 CMOD vs. Load for fracture test 

L1P1-13-325 (Lot 400751 aged at 

325 F for 24 hours)

Figure D-3 CMOD vs. Load for fracture test 

L1P2-03-325 (Lot 400751 aged at 

325 F for 24 hours)

Figure D-4 CMOD vs. Load for fracture test 

L1P1-04T-325 (Lot 400751 aged 

at 325 F for 24 hours)
NASA Engineering and Safety Center 

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-5 CMOD vs. Load for fracture test 

L1P1-05T-325 (Lot 400751 aged 

at 325 F for 24 hours)

Figure D-6 CMOD vs. Load for fracture test 

L1P1-06T-325 (Lot 400751 aged 

at 325 F for 24 hours)

Figure D-7 CMOD vs. Load for fracture test 

L1P2-07T-325 (Lot 400751 aged 

at 325 F for 24 hours)

Figure D-8 CMOD vs. Load for fracture test 

L1P1-08T-325 (Lot 400751 aged 

at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-9 CMOD vs. Load for fracture test 

L1P1-09T-325 (Lot 400751 aged 

at 325 F for 24 hours)

Figure D-10 CMOD vs. Load for fracture 

test L1P3-15-333 (Lot 400751 

aged at 333 F for 24 hours)

Figure D-11 CMOD vs. Load for fracture 

test L1P3-16-333 (Lot 400751 

aged at 333 F for 24 hours)

Figure D-12 CMOD vs. Load for fracture 

test L1P3-12-340 (Lot 400751 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-13 CMOD vs. Load for fracture 

test L1P3-13-340 (Lot 400751 

aged at 340 F for 24 hours)

Figure D-14 CMOD vs. Load for fracture 

test L1P3-14-340 (Lot 400751 

aged at 340 F for 24 hours)

Figure D-15 CMOD vs. Load for fracture 

test L1P1-02-350 (Lot 400751 

aged at 350 F for 24 hours)

Figure D-16 CMOD vs. Load for fracture 

test L1P1-08-350 (Lot 400751 

aged at 350 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-17 CMOD vs. Load for fracture 

test L1P2-06-350 (Lot 400751 

aged at 350 F for 24 hours)

Figure D-18 CMOD vs. Load for fracture 

test L1P2-10-350 (Lot 400751 

aged at 350 F for 24 hours)

Figure D-19 CMOD vs. Load for fracture 

test L1P1-04-3750 (Lot 400751 

aged at 375 F for 24 hours)

Figure D-20 CMOD vs. Load for fracture 

test L1P1-09-375 (Lot 400751 

aged at 375 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-21 CMOD vs. Load for fracture 

test L1P1-03-400 (Lot 400751 

aged at 400 F for 24 hours)

Figure D-22 CMOD vs. Load for fracture 

test L1P1-10-400 (Lot 400751 

aged at 400 F for 24 hours)

Figure D-23 CMOD vs. Load for fracture 

test L1P1-19-400 (Lot 400751 

aged at 400 F for 24 hours)

Figure D-24 CMOD vs. Load for fracture 

test L1P1-20-400 (Lot 400751 

aged at 400 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-25 CMOD vs. Load for fracture 

test L2P1-07-325 (Lot 400768 

aged at 325 F for 24 hours)

Figure D-26 CMOD vs. Load for fracture 

test L2P1-13-325 (Lot 400768 

aged at 325 F for 24 hours)

Figure D-27 CMOD vs. Load for fracture 

test L2P1-07T-325 (Lot 400768 

aged at 325 F for 24 hours)

Figure D-28 CMOD vs. Load for fracture 

test L2P1-08T-325 (Lot 400768 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-29 CMOD vs. Load for fracture 

test L2P1-09T-325 (Lot 400768 

aged at 325 F for 24 hours)

Figure D-30 CMOD vs. Load for fracture 

test L2P3-15-333 (Lot 400768 

aged at 333 F for 24 hours)

Figure D-31 CMOD vs. Load for fracture 

test L2P3-16-333 (Lot 400768 

aged at 333 F for 24 hours)

Figure D-32 CMOD vs. Load for fracture 

test L2P3-12-340 (Lot 400768 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-33 CMOD vs. Load for fracture 

test L2P3-13-340 (Lot 400768 

aged at 340 F for 24 hours)

Figure D-34 CMOD vs. Load for fracture 

test L2P3-14-340 (Lot 400768 

aged at 340 F for 24 hours)

Figure D-35 CMOD vs. Load for fracture 

test L2P1-03-350 (Lot 400768 

aged at 350 F for 24 hours)

Figure D-36 CMOD vs. Load for fracture 

test L2P1-08-350 (Lot 400768 

aged at 350 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-37 CMOD vs. Load for fracture 

test L2P2-03-350 (Lot 400768 

aged at 350 F for 24 hours)

Figure D-38 CMOD vs. Load for fracture 

test L2P2-10-350 (Lot 400768 

aged at 350 F for 24 hours)

Figure D-39 CMOD vs. Load for fracture 

test L2P1-03-375 (Lot 400768 

aged at 375 F for 24 hours)

Figure D-40 CMOD vs. Load for fracture 

test L2P1-09-375 (Lot 400768 

aged at 375 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-41 CMOD vs. Load for fracture 

test L2P1-04-400 (Lot 400768 

aged at 400 F for 24 hours)

Figure D-42 CMOD vs. Load for fracture 

test L2P1-10-400 (Lot 400768 

aged at 400 F for 24 hours)

Figure D-43 CMOD vs. Load for fracture 

test L3C1-01-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-44 CMOD vs. Load for fracture 

test L3C1-12-325 (Lot 400766 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-45 CMOD vs. Load for fracture 

test L3C1-23-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-46 CMOD vs. Load for fracture 

test L3C1-51-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-47 CMOD vs. Load for fracture 

test L3C1-52-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-48 CMOD vs. Load for fracture 

test L3C1-53-325 (Lot 400766 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-49 CMOD vs. Load for fracture 

test L3C1-60-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-50 CMOD vs. Load for fracture 

test L3C1-61-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-51 CMOD vs. Load for fracture 

test L3C1-67-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-52 CMOD vs. Load for fracture 

test L3C1-59-325 (Lot 400766 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-53 CMOD vs. Load for fracture 

test L3C1-68-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-54 CMOD vs. Load for fracture 

test L3C1-75-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-55 CMOD vs. Load for fracture 

test L3C1-76-325 (Lot 400766 

aged at 325 F for 24 hours)

Figure D-56 CMOD vs. Load for fracture 

test L3C1-37-333 (Lot 400766 

aged at 333 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-57 CMOD vs. Load for fracture 

test L3C1-32-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-58 CMOD vs. Load for fracture 

test L3C1-44-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-59 CMOD vs. Load for fracture 

test L3C1-46-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-60 CMOD vs. Load for fracture 

test L3C1-48-333 (Lot 400766 

aged at 333 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-61 CMOD vs. Load for fracture 

test L3C1-50-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-62 CMOD vs. Load for fracture 

test L3C1-43-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-63 CMOD vs. Load for fracture 

test L3C1-45-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-64 CMOD vs. Load for fracture 

test L3C1-47-333 (Lot 400766 

aged at 333 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-65 CMOD vs. Load for fracture 

test L3C1-49-333 (Lot 400766 

aged at 333 F for 24 hours)

Figure D-66 CMOD vs. Load for fracture 

test L3C1-26-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-67 CMOD vs. Load for fracture 

test L3C1-30-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-68 CMOD vs. Load for fracture 

test L3C1-31-340 (Lot 400766 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-69 CMOD vs. Load for fracture 

test L3C1-49-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-70 CMOD vs. Load for fracture 

test L3C1-27-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-71 CMOD vs. Load for fracture 

test L3C1-28-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-72 CMOD vs. Load for fracture 

test L3C1-34-340 (Lot 400766 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-73 CMOD vs. Load for fracture 

test L3C1-35-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-74 CMOD vs. Load for fracture 

test L3C1-40-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-75 CMOD vs. Load for fracture 

test L3C1-33-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-76 CMOD vs. Load for fracture 

test L3C1-36-340 (Lot 400766 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

117 of 152

NESC Request No.: 10-00680 (Materials) Figure D-77 CMOD vs. Load for fracture 

test L3C1-41-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-78 CMOD vs. Load for fracture 

test L3C1-42-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-79 CMOD vs. Load for fracture 

test L3C1-38-340 (Lot 400766 

aged at 340 F for 24 hours)

Figure D-80 CMOD vs. Load for fracture 

test L3C1-39-340 (Lot 400766 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

118 of 152

NESC Request No.: 10-00680 (Materials) Figure D-81 CMOD vs. Load for fracture 

test L3C1-02-350 (Lot 400766 

aged at 350 F for 24 hours)

Figure D-82 CMOD vs. Load for fracture 

test L3C1-13-350 (Lot 400766 

aged at 350 F for 24 hours)

Figure D-83 CMOD vs. Load for fracture 

test L3C1-24-350 (Lot 400766 

aged at 350 F for 24 hours)

Figure D-84 CMOD vs. Load for fracture 

test L3C1-03-375 (Lot 400766 

aged at 375 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

119 of 152

NESC Request No.: 10-00680 (Materials) Figure D-85 CMOD vs. Load for fracture 

test L3C1-14-375 (Lot 400766 

aged at 375 F for 24 hours)

Figure D-86 CMOD vs. Load for fracture 

test L3C1-25-375 (Lot 400766 

aged at 375 F for 24 hours)

Figure D-87 CMOD vs. Load for fracture 

test S7-01 (Lot 620853 as 

received)

Figure D-88 CMOD vs. Load for fracture 

test S170-35-01 (Lot 620853 as 

received)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-89 CMOD vs. Load for fracture 

test S170-35-02 (Lot 620853 as 

received)

Figure D-90 CMOD vs. Load for fracture 

test L5HR-01-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-91 CMOD vs. Load for fracture 

test L5HR-02-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-92 CMOD vs. Load for fracture 

test L5HR-03-325 (Lot 620853 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

121 of 152

NESC Request No.: 10-00680 (Materials) Figure D-93 CMOD vs. Load for fracture 

test L5HR-04-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-94 CMOD vs. Load for fracture 

test L5CR-01-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-95 CMOD vs. Load for fracture 

test L5CR-02-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-96 CMOD vs. Load for fracture 

test L5CR-03-325 (Lot 620853 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-97 CMOD vs. Load for fracture 

test L5CR-04-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-98 CMOD vs. Load for fracture 

test L5MCR-01-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-99 CMOD vs. Load for fracture 

test L5MCR-02-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-100 CMOD vs. Load for fracture 

test L5MCR-03-325 (Lot 620853 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

123 of 152

NESC Request No.: 10-00680 (Materials) Figure D-101 CMOD vs. Load for fracture 

test L5MCR-04-325 (Lot 

620853 aged at 325 F for 24 

hours)

Figure D-102 CMOD vs. Load for fracture 

test L5MCR-08-325 (Lot 

620853 aged at 325 F for 24 

hours)

Figure D-103 CMOD vs. Load for fracture 

test L5MCR-09-325 (Lot 

620853 aged at 325 F for 24 

hours)

Figure D-104 CMOD vs. Load for fracture 

test L5MCR-10-325 (Lot 620853 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-105 CMOD vs. Load for fracture 

test L5MCR-11-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-106 CMOD vs. Load for fracture 

test L5MCR-12-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-107 CMOD vs. Load for fracture 

test L5MCR-13-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-108 CMOD vs. Load for fracture 

test L5MCR-14-325 (Lot 620853 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

125 of 152

NESC Request No.: 10-00680 (Materials) Figure D-109 CMOD vs. Load for fracture 

test L5MCR-15-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-110 CMOD vs. Load for fracture 

test L5MCR-16-325 (Lot 620853 

aged at 325 F for 24 hours)

Figure D-111 CMOD vs. Load for fracture 

test L4HR-01-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-112 CMOD vs. Load for fracture 

test L4HR-02-325 (Lot 620854 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

126 of 152

NESC Request No.: 10-00680 (Materials) Figure D-113 CMOD vs. Load for fracture 

test L4HR-03-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-114 CMOD vs. Load for fracture 

test L4HR-04-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-115 CMOD vs. Load for fracture 

test L4CR-01-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-116 CMOD vs. Load for fracture 

test L4CR-02-325 (Lot 620854 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

127 of 152

NESC Request No.: 10-00680 (Materials) Figure D-117 CMOD vs. Load for fracture 

test L4CR-03-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-118 CMOD vs. Load for fracture 

test L4CR-04-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-119 CMOD vs. Load for fracture 

test L4MCR-01-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-120 CMOD vs. Load for fracture 

test L4MCR-02-325 (Lot 620854 

aged at 325 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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128 of 152

NESC Request No.: 10-00680 (Materials) Figure D-121 CMOD vs. Load for fracture 

test L4MCR-03-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-122 CMOD vs. Load for fracture 

test L4CR-04-325 (Lot 620854 

aged at 325 F for 24 hours)

Figure D-123 CMOD vs. Load for fracture 

test L5HR-05-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-124 CMOD vs. Load for fracture 

test L5HR-06-340 (Lot 620853 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

129 of 152

NESC Request No.: 10-00680 (Materials) Figure D-125 CMOD vs. Load for fracture 

test L5HR-07-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-126 CMOD vs. Load for fracture 

test L5CR-05-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-127 CMOD vs. Load for fracture 

test L5CR-06-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-128 CMOD vs. Load for fracture 

test L4CR-07-340 (Lot 620853 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

130 of 152

NESC Request No.: 10-00680 (Materials) Figure D-129 CMOD vs. Load for fracture 

test L5MCR-05-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-130 CMOD vs. Load for fracture 

test L5MCR-06-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-131 CMOD vs. Load for fracture 

test L5MCR-07-340 (Lot 620853 

aged at 340 F for 24 hours)

Figure D-132 CMOD vs. Load for fracture 

test L4HR-05-340 (Lot 620854 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

131 of 152

NESC Request No.: 10-00680 (Materials) Figure D-133 CMOD vs. Load for fracture 

test L4HR-06-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-134 CMOD vs. Load for fracture 

test L4HR-07-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-135 CMOD vs. Load for fracture 

test L4CR-05-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-136 CMOD vs. Load for fracture 

test L4CR-06-340 (Lot 620854 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

132 of 152

NESC Request No.: 10-00680 (Materials) Figure D-137 CMOD vs. Load for fracture 

test L4CR-07-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-138 CMOD vs. Load for fracture 

test L4MCR-05-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-139 CMOD vs. Load for fracture 

test L4MCR-06-340 (Lot 620854 

aged at 340 F for 24 hours)

Figure D-140 CMOD vs. Load for fracture 

test L4MCR-07-340 (Lot 620854 

aged at 340 F for 24 hours)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-141 CMOD vs. Load for fracture 

test L1P2-14-340-325 (Lot 

400751 exposed to 340 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-142 CMOD vs. Load for fracture 

test L1P2-16-340-325 (Lot 

400751 exposed to 340 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-143 CMOD vs. Load for fracture 

test L1P1-15-350-325 (Lot 

400751 exposed to 350 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-144 CMOD vs. Load for fracture 

test L1P1-06-375-325 (Lot 

400751 exposed to 375 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-145 CMOD vs. Load for fracture 

test L1P2-01-400-325 (Lot 

400751 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-146 CMOD vs. Load for fracture 

test L1P2-05-400-325 (Lot 

400751 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-147 CMOD vs. Load for fracture 

test L1P2-02-425-325 (Lot 

400751 exposed to 425 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-148 CMOD vs. Load for fracture 

test L1P1-06-425-325 (Lot 

400751 exposed to 425 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-149 CMOD vs. Load for fracture 

test L1P2-03-450-325 (Lot 

400751 exposed to 450 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-150 CMOD vs. Load for fracture 

test L1P2-11-475-325 (Lot 

400751 exposed to 475 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-151 CMOD vs. Load for fracture 

test L1P2-13-500-325 (Lot 

400751 exposed to 500 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-152 CMOD vs. Load for fracture 

test L1P2-07-340B-325 (Lot 

400751 exposed to 340 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-153 CMOD vs. Load for fracture 

test L1P2-10-340-325 (Lot 

400751 exposed to 340 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-154 CMOD vs. Load for fracture 

test L1P2-15-340-325 (Lot 

400751 exposed to 340 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-155 CMOD vs. Load for fracture 

test L1P2-16-340-325 (Lot 

400751 exposed to 340 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-156 CMOD vs. Load for fracture 

test L1P2-08-350B-325 (Lot 

400751 exposed to 350 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-157 CMOD vs. Load for fracture 

test L1P2-12-350-325 (Lot 

400751 exposed to 350 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-158 CMOD vs. Load for fracture 

test L1P2-09-400-325 (Lot 

400751 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-159 CMOD vs. Load for fracture 

test L1P2-04-400-325 (Lot 

400751 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-160 CMOD vs. Load for fracture 

test L1P2-15-500B-325 (Lot 

400751 exposed to 500 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-161 CMOD vs. Load for fracture 

test L2P2-03-340-325 (Lot 

400768 exposed to 340 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-162 CMOD vs. Load for fracture 

test L2P2-04-340-325 (Lot 

400768 exposed to 340 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-163 CMOD vs. Load for fracture 

test L2P2-05-350-325 (Lot 

400768 exposed to 350 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-164 CMOD vs. Load for fracture 

test L2P1-06-375-325 (Lot 

400768 exposed to 375 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials) Figure D-165 CMOD vs. Load for fracture 

test L2P2-01-400-325 (Lot 

400768 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-166 CMOD vs. Load for fracture 

test L2P2-05-400-325 (Lot 

400768 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-167 CMOD vs. Load for fracture 

test L2P2-02-425-325 (Lot 

400768 exposed to 425 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-168 CMOD vs. Load for fracture 

test L2P2-06-425-325 (Lot 

400768 exposed to 425 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-169 CMOD vs. Load for fracture 

test L2P2-10-450-325 (Lot 

400768 exposed to 450 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-170 CMOD vs. Load for fracture 

test L2P2-09-475-325 (Lot 

400768 exposed to 475 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-171 CMOD vs. Load for fracture 

test L2P2-08-500-325 (Lot 

400768 exposed to 500 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-172 CMOD vs. Load for fracture 

test L2P2-13-350B-325 (Lot 

400768 exposed to 350 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

141 of 152

NESC Request No.: 10-00680 (Materials) Figure D-173 CMOD vs. Load for fracture 

test L2P2-12-400B-325 (Lot 

400768 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-174 CMOD vs. Load for fracture 

test L2P2-10-400B-325 (Lot 

400768 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-175 CMOD vs. Load for fracture 

test L2P2-07-500-325 (Lot 

400768 exposed to 500 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-176 CMOD vs. Load for fracture 

test L3C1-04-400-325 (Lot 

400766 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials) Figure D-177 CMOD vs. Load for fracture 

test L3C1-15-400-325 (Lot 

400766 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-178 CMOD vs. Load for fracture 

test L3C1-05-425-325 (Lot 

400766 exposed to 400 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-179 CMOD vs. Load for fracture 

test L3C1-16-425-325 (Lot 

400766 exposed to 425 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-180 CMOD vs. Load for fracture 

test L3C1-06-450-325 (Lot 

400766 exposed to 450 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

143 of 152

NESC Request No.: 10-00680 (Materials) Figure D-181 CMOD vs. Load for fracture 

test L3C1-17-450-325 (Lot 

400766 exposed to 450 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-182 CMOD vs. Load for fracture 

test L3C1-07-475-325 (Lot 

400766 exposed to 475 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-183 CMOD vs. Load for fracture 

test L3C1-18-475-325 (Lot 

400766 exposed to 475 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-184 CMOD vs. Load for fracture 

test L3C1-19-500-325 (Lot 

400766 exposed to 500 F for 10 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

144 of 152

NESC Request No.: 10-00680 (Materials) Figure D-185 CMOD vs. Load for fracture 

test L3C1-08-500-325 (Lot 

400766 exposed to 500 F for 10 

min. & aged at 325 F for 24 hrs.)

Figure D-186 CMOD vs. Load for fracture 

test L3C1-09-400B-325 (Lot 

400766 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-187 CMOD vs. Load for fracture 

test L3C1-20-400B-325 (Lot 

400766 exposed to 400 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-188 CMOD vs. Load for fracture 

test L3C1-10-450B-325 (Lot 

400766 exposed to 450 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

145 of 152

NESC Request No.: 10-00680 (Materials) Figure D-189 CMOD vs. Load for fracture 

test L3C1-21-450B-325 (Lot 

400766 exposed to 450 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-190 CMOD vs. Load for fracture 

test L3C1-11-500B-325 (Lot 

400766 exposed to 500 F for 20 

min. & aged at 325 F for 24 hrs.)

Figure D-191 CMOD vs. Load for fracture 

test L3C1-22-500B-325 (Lot 

400766 exposed to 500 F for 20 

min. & aged at 325 F for 24 hrs.)
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

146 of 152

NESC Request No.: 10-00680 (Materials)

Appendix E. Fractographic Photographs

Examinations of the fracture surfaces from the tests were performed using a scanning electron 

microscope (SEM). Low magnification examinations (~50x) were performed to characterize the 

surface texture and identify delaminations. Higher magnification examinations (up to 5,000x) 

were performed to identify features that indicate ductile or brittle behavior. Two sets of 

photographs are presented to illustrated differences in the material lots and thermal aging 

temperatures. The first set of photographs (Figures E-1 to E-5) contains low magnification 

images of the fracture surface of compact tension fracture specimens (see Appendix D) made 

from the control material (lot 400766) and aged at temperatures from 325°F to 375°F for 

24 hours. The second set of photographs (Figures E-6 to E-12) contains high magnification 

images of the fracture surface for each lot of material tested, all aged at 325°F for 24 hours.

Figure E-1. Fracture Surface from Specimen L3C1-23-325 (lot 400766) that was Aged at 325°F for 

24 hours

Fatigue Precrack Region Fracture Region

0.05 inch
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Version:

1.0

Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Figure E-2. Fracture Surface from Specimen L3C1-50-333 (lot 400766) that was Aged at 333°F for

24 hours

Figure E-3. Fracture Surface from Specimen L3C1-27-340 (lot 400766) that was Aged at 340°F for 

24 hours

Fatigue Precrack Region Fracture Region

0.05 inch

Fatigue Precrack Region Fracture Region

0.05 inch
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Figure E-4. Fracture Surface from Specimen L3C1-24-350 (lot 400766) that was Aged at 350°F for 

24 hours

Figure E-5. Fracture Surface from Specimen L3C1-14-375 (lot 400766) that was Aged at 375°F for 

24 hours

Fatigue Precrack Region Fracture Region

0.05 inch

Delaminations

Fatigue Precrack Region Fracture Region

0.05 inch

Delaminations
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

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Version:

1.0

Title:

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Assessment: Proximate Cause Determination and 

Material Characterization Study

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NESC Request No.: 10-00680 (Materials)

Figure E-6. Fracture Surface from Specimen S7-07 (lot 620853) from as-received Stringer-7 Sister

Figure E-7. Fracture Surface from Specimen L1P1-05-325 (lot 400751) that was Aged at 325°F for

24 hours

0.0005 inch

0.0005 inch
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

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150 of 152

NESC Request No.: 10-00680 (Materials)

Figure E-8. Fracture Surface from Specimen L2P1-09-325 (lot 400768) that was Aged at 325°F for

24 hours

Figure E-9. Fracture Surface from Specimen L3C1-12-325 (lot 400766) that was Aged at 325°F for 

24 hours

0.0005 inch 0.0005 inch
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

151 of 152

NESC Request No.: 10-00680 (Materials)

Figure E-10. Fracture Surface from Specimen L5CR-02-325 (lot 620853) that was Aged at 325°F for 

24 hours

Figure E-11. Fracture Surface from Specimen L5HR-04-325 (lot 620853) that was Aged at 325°F for 

24 hours

0.0005 inch 0.0005 inch
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00680

Version:

1.0

Title:

STS-133/ET-137 IT Stringer Cracking Issue and Repair 

Assessment: Proximate Cause Determination and 

Material Characterization Study

Page #:

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NESC Request No.: 10-00680 (Materials)

Figure E-12. Fracture Surface from Specimen L5MCR-04-325 (lot 620853) that was Aged at 325°F for 

24 hours

0.0005 inch
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Space Transportation System (STS)-133/External Tank (ET)-137 Intertank 

(IT) Stringer Cracking Issue and Repair Assessment: Proximate Cause 

Determination and Material Characterization Study

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Piascik, Robert S.

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-20106 NESC-RP-10-00680

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 16 Space Transportation and Safety

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

Several cracks were detected in stringers located beneath the foam on the External Tank (ET) following the launch scrub of Space 

Transportation System (STS)-133 on November 5, 2010. The stringer material was aluminum-lithium (AL-Li) 2090-T83 fabricated from 

sheets that were nominally 0.064 inches thick. The mechanical properties of the stringer material were known to vary between different 

material lots, with the stringers from ET-137 (predominately lots 620853 and 620854) having the highest yield and ultimate stresses. 

Subsequent testing determined that these same lots also had the lowest fracture toughness properties. The NASA Engineering and Safety 

Center (NESC) supported the Space Shuttle Program (SSP)-led investigation. The objective of this investigation was to develop a database 

of test results to provide validation for structural analysis models, independently confirm test results obtained from other investigators, and 

determine the proximate cause of the anomalous low fracture toughness observed in stringer lots 620853 and 620854. This document 

contains the outcome of the investigation. 

15. SUBJECT TERMS

Space Transportation System; intertank; NASA Engineering and Safety Center; External Tank; thermal protection system; 

transmission electron microscopy

18. NUMBER

 OF 

 PAGES

157

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

November 2010 - September 2011

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

869021.05.07.04.12

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/TM-2011-217318

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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE (DD-MM-YYYY)

01- 12 - 2011