August 2015 

NASA/TP−2015-218785

Buckling Test Results from the 8-Foot-Diameter 

Orthogrid-Stiffened Cylinder Test Article TA01 

Test Dates: 19‒21 November 2008 

Mark W. Hilburger 

Langley Research Center, Hampton, Virginia 

W. Allen Waters, Jr. 

Analytical Mechanics Associates, Inc., Hampton, Virginia 

Waddy T. Haynie 

Langley Research Center, Hampton, Virginia 
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August 2015 

NASA/TP−2015-218785

Buckling Test Results from the 8-Foot-Diameter 

Orthogrid-Stiffened Cylinder Test Article TA01 

Test Dates: 19‒21 November 2008 

Mark W. Hilburger 

Langley Research Center, Hampton, Virginia 

W. Allen Waters, Jr. 

Analytical Mechanics Associates, Inc., Hampton, Virginia 

Waddy T. Haynie 

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. 
iii 

Preface 

The Shell Buckling Knockdown Factor (SBKF) Project was established in the spring of 2007 by 

the NASA Engineering and Safety Center with the goal of developing improved (i.e., lessconservative, more robust), analysis-based shell buckling design factors (a.k.a. knockdown 

factors) for modern launch-vehicle structures. Preliminary design studies indicated that 

implementation of these new knockdown factors could help mitigate some of NASA’s future 

launch vehicle development and performance risks by improving baseline designs, providing 

high-fidelity estimates of structural performance, reducing reliance on testing, and enabling 

increased payload capability. To this end, the SBKF project has been engaged in several 

technical work areas to support the development, validation, and implementation of the new 

design factors, including subscale and full-scale structural testing. The primary objectives of the 

test program are to: 

1. Provide validation data for high-fidelity structural analysis models and new design

knockdown factors.

2. Verify the performance and behavioral characteristics of a variety of buckling-critical

structural designs subjected to relevant loading conditions.

3. Determine the effects of common structural details such as weld lands and joints on the

buckling response.

4. Understand the effects of scale-up from subscale to full-scale on the buckling response.

To meet these objectives, tests on nine different subscale 8-foot-diameter, integrally stiffened 

aluminum-alloy barrels were planned in order to obtain the majority of the required validation 

data along with two full-scale, 27.5-foot-diameter, aluminum-lithium, integrally stiffened test 

articles to determine structural scaling trends. Data from these tests and the corresponding pretest 

analysis predictions and data archival information will be summarized in a series of NASA 

technical publications. The pretest predictions presented in these test reports were used to 

determine the testing and instrumentation requirements and are included for reference. Detailed 

test and analysis correlation will be presented in a separate series of NASA technical 

publications in which refined modeling and analysis results will be discussed thoroughly. 
iv 

Table of Contents 

1.0 Introduction ............................................................................................................................1 

2.0 Test Description ......................................................................................................................2

2.1 Test Objectives........................................................................................................ 2 

2.2 Test Article Design ................................................................................................. 2 

2.3 Test Article Fabrication .......................................................................................... 8 

2.4 Test Facility ............................................................................................................ 9 

2.5 Testing................................................................................................................... 11 

2.5.1 Test Article Installation and Alignment Verification ........................................... 11 

2.5.2 Instrumentation ..................................................................................................... 12 

2.5.3 Low-Speed Digital Image Correlation .................................................................. 17 

2.5.4 High-speed Digital Image Correlation .................................................................. 18 

2.5.5 Load Sequences .................................................................................................... 19

3.0 Analysis Description .............................................................................................................19 

4.0 Results and Discussion .........................................................................................................21

4.1 Initial Geometric Imperfection Data ..................................................................... 21 

4.2 Buckling Response of TA01 ................................................................................. 22

4.2.1 Load versus Displacement Response .................................................................... 22 

4.2.2 Full-Field Displacement Contours ........................................................................ 27 

4.2.3 Load versus Axial Strain Response ...................................................................... 37 

4.2.4 Axial Strain Distribution ....................................................................................... 42

5.0 Concluding Remarks ............................................................................................................47 

6.0 References ............................................................................................................................49

Appendix A Archival Information .............................................................................................50

List of Figures 

Figure 2.1. Al-Li orthogrid-stiffened cylinder test article, TA01 (post-test). ........................... 3

Figure 2.2. Orthogrid geometry definition. ............................................................................... 4

Figure 2.3. Space shuttle ET and TA01 weld land designs shown in the flat condition for 

machining. ............................................................................................................... 5

Figure 2.4. Typical weld land region in TA01. ......................................................................... 5

Figure 2.5. LaRC Drawing 1167189. ........................................................................................ 6

Figure 2.6. Measured geometric imperfection for TA01 from photogrametry/white-light 

geometry scanning system. ..................................................................................... 9

Figure 2.7. Coordinate system and displacement definitions. 0° circumferential location 

corresponds to the center of Panel A and the dashed lines indicate the location 

of longitudinal weld lands. ...................................................................................... 9

Figure 2.8. Eight-foot-diameter shell buckling test facility at MSFC: a) test article 

assembly, b) hydraulic actuator, c) loading rod, d) load cell, e) attachment ring, 

f) transition section, g) load strut, and h) loading spider. ..................................... 10

Figure 2.9. Test article orientation and panel, weld land, and load line locations. ................. 11
v 

Figure 2.10. Typical IML strain gage pattern for one of the TA01 panel segments. ................ 13

Figure 2.11. Schematic view showing locations of EDIs (view from outer surface) and 

EDI location table. ................................................................................................ 15

Figure 2.12. Schematic view showing locations and orientations of EDIs, top view. .............. 16

Figure 2.13. Location of load lines 18 and low-speed and high-speed DIC systems. ............ 17

Figure 2.14. High-speed camera FOVs. .................................................................................... 18

Figure 2.15. Using 2D DIC technique to qualitatively assess the radial deformations of 

TA01. .................................................................................................................... 19

Figure 3.1. Finite-element model of test assembly. ................................................................ 20

Figure 4.1. Geometric imperfection for TA01 from DIC measurement. ................................ 22

Figure 4.2. Measured and predicted load versus end-shortening response of TA01 

subjected to axial compression. ............................................................................ 23

Figure 4.3. Measured and predicted load versus radial displacement response of TA01 at 

the center of each panel. ........................................................................................ 24

Figure 4.4. Measured and predicted load versus radial displacement response of TA01 at 

the center of each longitudinal weld land. ............................................................ 24

Figure 4.5. Measured and predicted load versus radial displacement response of TA01 at 

the center of panel A (D246CR) and at the center of weld land AB (D243BR). . 25

Figure 4.6. TA01 after global buckling. .................................................................................. 26

Figure 4.7. DIC noise signature for u and w displacement measurements. ............................ 29

Figure 4.8. Predicted and measured axial displacement (u) contours at 159.9 Kips 

(22.0% Pcr). ........................................................................................................... 29

Figure 4.9. Predicted and measured radial displacement (w) contours at 159.9 Kips 

(22.0% Pcr). ........................................................................................................... 30

Figure 4.10. Predicted and measured radial displacement (w) contours at 319.8 Kips 

(44.0% Pcr). ........................................................................................................... 30

Figure 4.11. Predicted and measured axial displacement (u) contours incipient to buckling. .. 31

Figure 4.12. Predicted and measured radial displacement (w) contours incipient to buckling. 31

Figure 4.13. Predicted and measured initial postbuckling radial displacement (w) contours. .. 32

Figure 4.14. Predicted and measured deep postbuckling radial displacement (w) contours. .... 32

Figure 4.15. v-displacement contours from 2D high-speed DIC indicating the initiation and 

propagation of buckling deformations in TA01. ................................................... 34

Figure 4.16. Measured radial displacements at selected locations on panel A of TA01 

during the collapse response. ................................................................................ 36

Figure 4.17. Test/analysis correlation of back-to-back axial strains, skin, and adjacent axial 

stiffener near center of panel A. ............................................................................ 38

Figure 4.18. Test/analysis correlation of back-to-back axial strains, skin, and adjacent axial 

stiffener near center of panel B. ............................................................................ 38

Figure 4.19. Test/analysis correlation of back-to-back axial strains, skin, and adjacent axial 

stiffener near center of panel C. ............................................................................ 39
vi 

Figure 4.20. Test/analysis correlation of back-to-back axial strains, centers of weld land 

AB, and adjacent axial stiffener. ........................................................................... 39

Figure 4.21. Test/analysis correlation of back-to-back axial strains, centers of weld land 

BC, and adjacent axial stiffener. ........................................................................... 40

Figure 4.22. Test/analysis correlation of back-to-back axial strains, centers of weld land 

CA, and adjacent axial stiffener. ........................................................................... 40

Figure 4.23. Test/analysis correlation of back-to-back axial strains, skin, and adjacent axial 

stiffener near the predicted buckling initiation site in Panel A. ............................ 41

Figure 4.24. Test/analysis correlation of back-to-back axial strains in a skin pocket near 

the buckling initiation sight in Panel C. ................................................................ 41

Figure 4.25. Predicted and measured axial membrane strain distribution around 

circumference, 159.9 Kips (22.0% Pcr). ............................................................... 43

Figure 4.26. Predicted and measured axial membrane strain distribution around 

circumference, 319.8 Kips (44.0% Pcr). ............................................................... 44

Figure 4.27. Predicted and measured axial membrane strain distribution around 

circumference, 581.4 Kips (79.9% Pcr). ............................................................... 45

Figure 4.28. Predicted and measured axial membrane strain distribution around 

circumference, predicted buckling strains and measured data at 619.8 Kips 

(85.3% Pcr), measured buckling strains at 689.2 Kips (94.8% Pcr). ..................... 46

List of Tables 

Table A1. Electronic Displacement Indicator (EDI) Locations ............................................. 54

Table A2. Strain Gage Locations and Orientations for TA01 ............................................... 55

Table A3. Data Files to Generate X-Y Plots of Axial Membrane Strain Distribution Around 

the Test Article Circumference (see Figures 4.27–4.30) ...................................... 60

Table A.4. Files Used to Generate Color Contour Plots (Tecplot Format) ............................ 61
vii 

Nomenclature 

Symbols 

D263AA measured displacement: subscript corresponds to specific LVDT 

channel 

imp measured geometric imperfection 

L cylinder length 

Mcr predicted linear bifurcation buckling load of a cylinder subjected to a 

bending moment 

P axial load 

Pcr predicted linear bifurcation buckling load of a compression-loaded 

cylinder 

R cylinder OML radius 

ru, rv, rw rotations about the x, , z axis

u, v, w axial, circumferential, and radial displacements 

x, , z axial, circumferential, and radial coordinate of a cylindrical 

coordinate system 

 microstrain or 1.0e-6 strain 

Orthogrid design 

variables See Figure 2.2 

br circumferential stiffener (ring) spacing 

bs axial stiffener (stringer) spacing 

h stiffener height measured from the IML 

H stiffener height measured from the OML (H = h + t) 

t shell wall skin thickness 

teff effective shell wall thicknesses value 

tr circumferential stiffener (ring) thickness 

ts axial stiffener (stringer) thickness 

Acronyms 

2D Two Dimensional 

3D Three Dimensional 

Al-Li Aluminum Lithium Alloy 

CSS Central Storage System 

DAS Data Acquisition System 

DIC Digital Image Correlation 

EDI Electronic Displacement Indicator 

ET External Tank 

EU Engineering Units 

FOV Field(s) of View 

IML Inner Mold Line (inner surface of structure) 
viii 

IRIG Inter-range Instrumentation Group 

LaRC Langley Research Center 

LCS Load Control System 

LPS Load Point Scans 

LTA Load Test Annex 

LVDT Linear Voltage Displacement Transducer (type of EDI) 

MSFC Marshall Space Flight Center 

NESC NASA Engineering and Safety Center 

NSCKN NASA Safety Center Knowledge Now 

OML Outer Mold Line (outer surface of structure) 

SBKF Shell Buckling Knockdown Factor 

SLTMAS Structural Loads Test Measurement Acquisition System 

STAGS STructural Analysis of General Shells 

TA01 Cylinder Test Article SBKF-P2-CYL-TA01 

 
Abstract 

Results from the testing of cylinder test article SBKF-P2-CYLTA01 (referred to herein as TA01) are presented. The testing was 

conducted at the Marshall Space Flight Center (MSFC), November 

19‒21, 2008, in support of the Shell Buckling Knockdown Factor 

(SBKF) Project.i

 The test was used to verify the performance of a 

newly constructed buckling test facility at MSFC and to verify the 

test article design and analysis approach used by the SBKF project 

researchers. TA01 is an 8-foot-diameter (96-inches), 78.0-inchlong, aluminum-lithium (Al-Li), orthogrid-stiffened cylindrical 

shell similar to those used in current state-of-the-art launchvehicle structures and was designed to exhibit global buckling 

when subjected to compression loads. Five different load 

sequences were applied to TA01 during testing and included four 

sub-critical load sequences, i.e., loading conditions that did not 

cause buckling or material failure, and one final load sequence to 

buckling and collapse. The sub-critical load sequences consisted of 

either uniform axial compression loading or combined axial 

compression and bending and the final load sequence subjected 

TA01 to uniform axial compression. Traditional displacement 

transducers and strain gages were used to monitor the test article 

response at nearly 300 locations and an advanced digital image 

correlation system was used to obtain low-speed and high-speed 

full-field displacement measurements of the outer surface of the 

test article. Overall, the test facility and test article performed as 

designed. In particular, the test facility successfully applied all 

desired load combinations to the test article and was able to test 

safely into the postbuckling range of loading, and the test article 

failed by global buckling. In addition, the test results correlated 

well with initial pretest predictions. 

1.0 Introduction 

Results from the testing of cylinder test article SBKF-P2-CYL-TA01 (referred to herein as 

TA01) are presented. TA01 was the first in a series of nine subscale 8-foot-diameter, integrally 

stiffened cylindrical shells to be tested in the Shell Buckling Knockdown Factor project (SBKF) 

test program. The test was conducted at the Marshall Space Flight Center (MSFC), November 

19‒21, 2008. TA01 is an 8-foot-diameter (96-inches), 78.0-inch-long, aluminum-lithium (Al-Li), 

orthogrid-stiffened cylindrical shell similar to those used in current state-of-the-art launchvehicle structures and was designed to exhibit global buckling when subjected to compression 

loads. The primary objectives of this test were to verify the performance of the test facility, the 

test procedures, and the test article design and analysis approach. 

First, descriptions of the test article design, fabrication, and test are given in Section 2, and 

modeling and analysis methods used in support of the test article design and testing activities are 

described briefly in Section 3. Then, selected test results are presented and compared to pretest 

i NASA Engineering and Safety Center (NESC) Assessment #: 07-010-E
2 

predictions in Section 4, and concluding remarks are presented in Section 5. Finally, a complete 

listing of all test and analysis data, data files and drawings is provided in Appendix A. The 

listing includes archival directory names, file names, and file format descriptions. All references 

used to support the test are also provided and include test article design drawings, test article 

fabrication and test plans and procedures, and pretest analysis results. 

2.0 Test Description 

Cylinder test article TA01 was designed by SBKF project researchers at NASA Langley 

Research Center (LaRC) and was fabricated by the MSFC Metal Joining and Processing Branch 

(EM32). The testing of TA01 occurred on November 19‒21, 2008 at MSFC in Building 4619 

Load Test Annex (LTA) under the direction of the Structural Strength Test Group (ET30). A 

special-purpose test apparatus was designed and fabricated for this test effort. The test apparatus 

was designed to apply up to 1.5 million pounds of force in axial compression and bending and 

10 psi internal pressure. A multi-channel load control system was used to apply the test loads and 

included load control and displacement control options. Traditional strain and displacement data 

were obtained from 294 locations on the test article and full-field displacement data were 

obtained on the test article outer mold line (OML) by using low-speed and high-speed digital 

image correlation systems. This section gives a brief overview of the test objectives, test article, 

instrumentation, test facility, and test load cases. Additional details on the testing of TA01 can be 

found in the test plan and test procedure (Refs. 1 and 2). 

2.1 Test Objectives 

Testing of TA01 was designed to provide data necessary to verify the test apparatus performance 

and the test article design approach with the following objectives: 

1. Verify the operation and performance of the test system. Specifically, verify the adequacy 

of the test procedures, verify instrumentation, and low-speed and high-speed digital 

image correlation (DIC) systems and measurements, and assess test article/test fixture 

designs. 

2. Obtain test data necessary to verify the test article design and analysis approach through 

detailed test and analysis correlation. 

2.2 Test Article Design 

TA01 is an 8-foot-diameter (96-inches), 78.0-inch-long, orthogrid-stiffened cylindrical shell and 

is constructed from three 2195 Al-Li integrally stiffened curved-panel segments (120 arc 

segments) that were friction-stir welded together to form a complete cylinder. The test article 

included similar design features and had similar response characteristics as those found in 

current state-of-the-art launch-vehicle tank structures in an effort to maximize the applicability of 

the test data to the design of modern launch vehicles. A post-test photo of TA01 is shown in 

Fig. 2.1. The internal grid pattern shown in the photo, comprised of the internal axial and 

circumferential stiffeners, is referred to herein as an orthogrid pattern. 
3 

Figure 2.1. Al-Li orthogrid-stiffened cylinder test article, TA01 (post-test). 

One of the primary objectives of the test was to verify the performance of the test system and 

thus, specific requirements on the test article response and test data were defined. In particular, 

the test article was designed to exhibit global buckling at a load level between 50% and 70% of 

the maximum loading capacity of the apparatus. In addition, it was required that the test article 

exhibit an unstable collapse response characterized by a sudden reduction in axial load and 

release of energy, which is common in the buckling and collapse of thin-walled cylinders, so the 

safe control of testing into the postbuckling range of loading could be demonstrated. 

The test article was designed using a two-step process (Ref. 3). First, the acreage stiffener pattern 

was designed using closed-form solutions, assuming a uniform construction throughout the 

cylinder, i.e., the effects of the axial weld lands were excluded. Several design constraints were 

applied during the design process to ensure that the test article would fail due to global buckling 

only and would exhibit significant margins on all other critical failure modes, such as skin pocket 

buckling (buckling of the skin between stiffener elements), stiffener buckling, and material 

yielding, to minimize the potential for failure mode interaction. The design variables included 

the skin thickness t, stiffener height h, axial and circumferential stiffener thickness ts and tr, and 

axial and circumferential stiffener spacing bs and br (see Fig. 2.2 for orthogrid schematic). The 
4 

resulting acreage design includes a skin thickness of 0.100 inches, axial and circumferential 

stiffener spacing of 4.0 inches, axial and circumferential stiffener thickness of 0.100 inches, and 

a stiffener height, H, of 0.400 inches as measured from the OML. The design corresponds to an 

R/teff = 230.9, where teff is an effective shell wall thicknesses value defined in Fig. 2.2. A11 and 

A22 are axial and circumferential membrane stiffnesses and D11 and D22 are axial and 

circumferential bending stiffnesses as defined in Ref. 4. 

t = 0.100-inch H = 0.4000-inch br = 4.000-inch tr = 0.100-inch 

bs = 4.000-inch ts = 0.100-inch h = 0.300-inch 

L/D: Barrel length to diameter ratio = 0.816 4

2211

144 2211

AA

DD

teff  R/teff: Radius to effective wall thickness ratio = 230.9 

Figure 2.2. Orthogrid geometry definition. 

Next, the three axial weld lands were introduced into the test article design and the shell response 

was analyzed using a geometrically nonlinear finite-element analysis. One of the design 

objectives was to include scaled versions of the weld land design used on the 27.5-foot-diameter 

space shuttle external tank (ET) (see Fig. 2.3-a). Scaling of the ET weld land geometry 

corresponded to a test article weld land thickness and half-width equal to 0.093 inches and 

1.164 inches, respectively. However, the weld thickness was limited to a minimum of 

0.25 inches, and weld land width was limited to a minimum of 2.5 inches due to restrictions on 

the welding process and fixtures that existed at the time of manufacturing. 

Results from a detailed finite-element analysis of the preliminary test article design with three 

axial weld lands indicated that the test article was susceptible to local buckling along the weld 

lands due to the reduced bending stiffness in these locations (Ref. 3). Thus, additional 

reinforcement was added to the test article adjacent to the weld lands in order to minimize local 

buckling along the weld lands. Specifically, an additional axial stiffener was added on both sides 

of the weld land and the thickness of several of the stiffeners was increased as shown in 

Fig. 2.3-b and in Fig. 2.4. Finite element analysis results of this reinforced design indicated that 

these additional stiffeners eliminated the initiation of buckling in the weld land region and that 

the test article would exhibit similar behavioral characteristics as a uniform cylinder (Ref. 3). 

The final design drawing LaRC Drawing 1167189 is shown in Fig. 2.5 (Ref. 5). 
5 

Acreage Transition Weld land 

Weld center line 

3.0 in. 2.0 in. 

0.32 in. 

a) Typical space shuttle ET weld land design cross-section (not to scale). 

0.25 in. 

1.25 in. 

1.0 in. 

Additional axial 

stiffener 

b) TA01 weld land design cross-section (not to scale). 

Figure 2.3. Space shuttle ET and TA01 weld land designs shown in the flat condition for 

machining. 

Figure 2.4. Typical weld land region in TA01.
6 

a) Inner mold line (IML) orthogrid stiffener pattern for a TA01 panel segmen

Figure 2.5. LaRC Drawing 1167189. 
7 

b) TA01 panel segment details. 

Figure 2.5. Concluded. 
8 

2.3 Test Article Fabrication 

Three curved panel segments were used to construct the barrel and were fabricated in a threestep process. First, the rectangular (orthogrid) stiffener pattern was machined into 2195-T3 Al-Li 

flat-plate material to form the pockets and weld land details. Then, the flat orthogrid panels were 

bump-formed (while in the –T3 temper) into curved panel segments with an OML radius of 

48 inches using a brake press. Finally, the panels were heat treated and aged to a ‒T83 temper. 

Once machined, formed, and heat treated, the three orthogrid panels, referred to as Panels A, B, 

and C, were friction-stir welded together along the axial weld lands to form a cylinder with an 

96.0-inch (8-foot) OML diameter and 78.0-inch length (dimensions are nominal). The three weld 

lands joining the three panels were 0.250 inches thick, and 1.25 inches wide on either side of the 

weld seam, resulting in a total weld-land width of 2.5 inches. Each weld was subjected to a series 

of visual and ultrasonic quality inspections (see Ref. 6). No defects or anomalies were identified 

in TA01. 

The ends of the test article were machined flat and parallel to tolerances specified in the 

manufacturing and assembly drawing 1238206 (Ref. 7) in order to ensure uniform load 

introduction into the test article. Geometry inspection after machining indicated the top and 

bottom ends of the test article were flat to within 0.039 inches and 0.040 inches, respectively, 

and parallel to each other to within 0.064 inches. 

Once machining and inspection were complete, the test article was potted in attachment rings 

with a low-melting-temperature alloy (Ref. 8). Concentricity and bolt-hole alignment 

specifications between the top and bottom attachment rings were defined so as to minimize any 

loads that would result from the misalignment of the test assembly. Shims were used to position 

the test article in the attachment rings and adjust concentricity. Ring alignment and concentricity 

were verified using a plumb bob. 

Once potted, the geometry of the test article OML was measured using a GOM ATOS 

photogrammetry/white-light geometry measurement systemii with a measurement accuracy of 

±0.001 inch. The deviation of the measured geometry from a best-fit cylinder was calculated and 

defined as the initial geometric imperfection (imp) and is shown in Fig. 2.6. The coordinate 

system used in the geometry measurement is shown in Fig. 2.7. The three longitudinal weld 

lands are located at ‒60°, 60° and 180° and the 0° circumferential location is aligned with the 

center of Panel A. The OML geometry data indicate that the test article is circular to within 

±0.10 inches. The weld lands do not appear to have a strong influence on or correlation with the 

imperfection pattern. The top and bottom attachment ring loading surfaces of the test article 

assembly were measured using a Leica AT901 laser tracker systemiii to verify the tolerances on 

flatness and parallelism. The top and bottom attachment ring loading surfaces were flat to within 

0.014 inches and 0.009 inches, respectively, and were parallel to each other to within 

0.004 inches. The orthogrid design, barrel assembly, and attachment ring design are presented in 

Drawings 1167189 (Ref. 5), 1238206 (Ref. 7) and 1238205 (Ref. 8), respectively, and in 

Section 2.1 of the test plan (Ref. 1). 

 

ii http://www.gom.com/metrology-systems/3d-scanner.html

iii http://www.leica-geosystems.us/en/Leica-Absolute-Tracker-AT901_69047.htm
9 

Figure 2.6. Measured geometric imperfection for TA01 from photogrammetry/white-light 

geometry scanning system. 

Top

Bottom

x = 0.0

x = 34.375

x = -34.375

x, u

z, w, imp

 = 0

Figure 2.7. Coordinate system and displacement definitions. 0° circumferential location 

corresponds to the center of Panel A and the dashed lines indicate the location of longitudinal 

weld lands. 

2.4 Test Facility 

The test facility is comprised of the test assembly (test article, test fixtures), load control system, 

and data acquisition system (DAS). The test assembly is shown in Fig. 2.8 and engineering 

drawings are found in Drawing 90M12370 (Ref. 9). The test assembly is a self-reacting load 

system composed of an upper and lower load “spider”, 16 load struts, upper and lower loadintroduction cylinders (referred to in Ref. 9 and Fig. 2.8 as transition sections), the test article 

assembly, and eight load lines. Each load line consists of a hydraulic cylinder, a 4-inch-diameter 

loading rod, a load cell, and attachment hardware. Each load line attaches to the upper and lower 

loading spiders. The load lines can be controlled independently in load control or stroke 

(position) control to apply uniform compression or combined compression and bending with a 

maximum load capability of 1.5 million pounds of axial compression force and 80,000 pounds of 

axial tension force. The test fixtures were designed and analyzed to ensure uniform load 

introduction into the test article when subjected to uniform compression up to the maximum load 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.12

0.1

0.08

0.06

0.04

0.02

0

-0.02

-0.04

-0.06

-0.08

imp, in.

Panel C Panel B Panel A
10 

capability of the apparatus. It should be noted that the load lines are in tension when the test 

article is subjected to compression loads. Additional information on the loading structure is also 

documented in Drawing 90M12375 (Ref. 10). A top-view schematic of the test assembly is 

presented in Fig. 2.9 and indicates the test article orientation and load line locations (indicated by 

the filled circle symbols in the figure) with respect to the panel and weld locations. In addition, 

the three panel sections that comprise the barrel test article are labeled as Panels A, B, and C. 

Figure 2.8. Eight-foot-diameter shell buckling test facility at MSFC: a) test article assembly, 

b) hydraulic actuator, c) loading rod, d) load cell, e) attachment ring, f) transition section, 

g) load strut, and h) loading spider. 
11 

No. 4

No. 5

240o

Panel C Centerline

Panel C

No. 6 No. 7

180o

Weld Seam, Panels B, C

-60o/300o

Weld Seam, Panels A, C

Panel A

120o

Panel B Centerline

Panel B

No. 8

No. 3

0o

 Panel A

Centerline No. 2

Weld Seam, Panels A, B

60o

No. 1

TOP VIEW OF TEST ARTICLE

Load Line

Figure 2.9. Test article orientation and panel, weld land, and load line locations. 

The DAS was a custom-built Structural Loads Test Measurement Acquisition System 

(SLTMAS) developed by MSFC/ET30 that can record up to 4792 analog inputs and 192 digital 

inputs. The DAS uses National Instruments SCXI-1520 signal conditioners for the strain gages, 

load cells, and linear voltage displacement transducers (LVDTs). 

The load control system (LCS) was an MTS FlexTest® 60 multi-channel system. It was 

programmed to use a combination of load control and displacement control during the testing. 

More specifically, during sub-critical load sequences, the LCS applied loads to TA01 in load 

control to ensure uniform loading. However, during the final load sequence to failure, the LCS 

was programmed to apply loads in load control up to 60% of the expected buckling load. Then, 

the LCS was transitioned to displacement (stroke) control so that the test could proceed safely 

through any unstable buckling events and into the postbuckling range of loading. In all load 

cases, the LCS was programmed such that the load rate never exceeded 10,000 lbf per minute. 

Specific load control requirements are defined in the test plan and test procedure. 

2.5 Testing 

2.5.1 Test Article Installation and Alignment Verification 

Once the test article was installed into the test fixture and the load lines were mounted between 

the upper and lower loading spiders, relative alignment between the test article and the load lines 

was measured using an inclinometer. However, the inclinometer measurements were relatively 

low precision (±0.1°) and the data appeared to be inconsistent with observed alignments via 

plumb bob. Subsequent tests on similar 8-foot-diameter cylinders included higher precision 

measurements using a laser-tracker-based position measurement system with ±0.001° accuracy. 
12 

These measurements indicated that the load lines were typically parallel to the axis of the test 

article to within 0.050° corresponding to a maximum misalignment of 0.18 inches from top to 

bottom. 

2.5.2 Instrumentation 

TA01 was instrumented with 270 strain gages and a typical pattern is shown for Panel A in 

Fig. 2.10 (Ref. 11). Strain gage locations and naming convention are summarized in Table A1 in 

Appendix A. Twenty-four Electronic Displacement Indicators (EDIs), also referred to as LVDTs, 

were placed at various locations on the specimen to measure axial, radial, and tangential 

displacements. Schematic views of the EDI measurement locations and orientations are shown in 

Figs. 2.11 and 2.12. In particular, axial displacements measurement locations are indicated by 

open circle symbols and radial and tangential measurements are indicated by arrows in Figure 

2.12. EDI locations and naming convention are summarized in Table A2 in Appendix A. 

The axial end-shortening of TA01 was measured at four locations around the circumference of 

the test article and correspond to the relative displacement measurements between the upper and 

lower test article attachment rings at the 0°, 90°, 180°, and 270° locations around the 

circumference of the test article. End-shortening displacements at the four circumferential 

locations are defined as follows: 

 0°: D263AA = D239AA – D259AA

 90°: D264AA = D240AA – D260AA

180°: D265AA = D241AA – D261AA

270°: D266AA = D242AA – D262AA

where D239AA, D240AA, D241AA, D242AA and D259AA, D260AA, D261AA, D262AA correspond to EDI 

measurements on the top and bottom attachment rings, respectively, and D263AA, D264AA, D265AA, 

D266AA correspond to the derived end-shortening displacements. Similarly, transverse shear 

displacement and twisting of the cylinder were determined from the relative radial and tangential 

displacements measured at the top and bottom attachment rings. 

 
13 

Figure 2.10. Typical IML strain gage pattern for one of the TA01 panel segmen
14 

Figure 2.10. Concluded. 
15 

300o -60o 60o 180o 90o 0o 270o

Top Attachment Ring

Bottom Attachment Ring

Panel C Panel B

D240AA

D260AA

D241AA

D261AA

D242AA

D262AA

D248CR D244BR D247CR D243BR

D249DR

D252FR

D253FR

D256FR

D255FR

D245BR

Panel A

D246CR

D250ER

D239AA, D251FR,

D257GH

D254FR, D258GH,

D259AA

Circumferential

Location (degrees)

Key to EDI Nomenclature: DXXXYZ

XXX - EDI Identificaton No.

 Y - Location Code A-G From Test Plan

 Z - Orientation: A - Axial

 R - Radial

 H - Tangential

Solid veritcal line between panels corresponds to a weld land.

" " indicates EDI measurement location. 

Y – EDI Location Code 

A axial displacement measurements at four places on the top and bottom attachment rings 

B radial displacment measurements at the mid-length of each weld land 

C radial displacment measurements at the center of each panel 

D radial displacement measurement of weld land AB (weld land between panel A and panel 

B) 5 inches up from the bottom attachement ring 

E radial displacement measurement at mid-arc-width of panel A (0 degree circumferential 

location) and 5 inches up from the bottom attachment ring 

F radial displacement measurements at three points on both the bottom and top attachment 

rings, located at the mid-arc-width of each panel 

G tangential displacement measurements on both the bottom and top 

attachement rings, located at the 0 degree circumferential location 

Figure 2.11. Schematic view showing locations of EDIs (view from outer surface) and 

EDI location table. 
16 

240o Panel C

180o

Panel A

120o Panel B

0o

60o

Axial Measurement

Weld Seam, Panels A, B

Weld Seam, Panels B, C

Weld Seam, Panels A, C

-60o/300o

a) Axial, radial and tangential displacement measurement locations on the top and bottom 

attachment rings. 

240o Panel C

180o

Panel A

120o Panel B

0o

60o

Weld Seam, Panels A, B

Weld Seam, Panels B, C

Weld Seam, Panels A, C

-60o/300o

b) Radial displacement measurement locations at the test article mid-length. 

Figure 2.12. Schematic view showing locations and orientations of EDIs, top view. 
17 

2.5.3 Low-Speed Digital Image Correlation 

DIC was used to obtain full-field three-dimensional (3D) displacement data on 

approximately 85% of the test article OML surface. Schematics of the DIC coordinate 

system and fields of view (FOV) are presented in Figs. 2.7 and 2.13, respectively. 

Complete coverage of the TA01 OML could not be achieved due to four of the eight load 

lines obstructing the views of the DIC system cameras, specifically, load lines 2, 4, 6, and 

8 as illustrated in Fig 2.13. Note: the camera locations and FOV indicated in Fig. 2.13 are 

notional and are not to scale. 

No. 4

240o

180o

-60o/300o

120o No. 8

No. 3

0o

No. 2

60o

No. 1

Top View

Camera

Set No. 4

No. 5

No. 6 No. 7

Camera

Set No. 5

High-Speed Camera (typ.)

load line (typ.)

Test Article 01

Camera

Set No. 2

Camera

Set No. 1

Low-Speed Camera (typ.)

High-Speed

 3D

Camera (typ.)

Figure 2.13. Location of load lines 18 and low-speed and high-speed DIC systems. 

The DIC system was also used to measure a pretest OML surface geometry for 

correlation with previous white-light geometry measurements (described in Section 2.3) 

in order to verify that no significant changes in geometry had occurred between 

manufacturing and test integration. DIC data (images) were acquired every 5 seconds 

throughout each load sequence using the 2007 Correlated Solutions Vic-Snap softwareiv.

iv	www.correlatedsolutions.com 
18

The DIC requirements and setup information are presented in more detail in Section 3.0 

of Ref. 1. 

Displacement data were post-processed by using the 2007 Correlated Solutions VIC3DTM softwarev

 and converted into cylindrical coordinates (coordinate system defined in 

Fig. 2.7). In addition, the VIC-3DTM session files, all calibration information, and all 

acquired images have been archived to enable further detailed processing at a later date. 

See Appendix A for archival information. 

2.5.4 High-speed Digital Image Correlation 

Four single-camera, two-dimensional (2D) high-speed DIC systems were co-located with 

the four low-speed 3D DIC systems around the circumference of the test article as shown 

in Fig. 2.13. Notional FOV of the high-speed DIC systems are shown in Fig 2.13. The 

high-speed DIC systems used Vision Research Phantom 7.1 digital cameras with a 

resolution of 400 × 400 pixels and recorded images at 10000 fps. The cameras were 

synchronized using an inter-range instrumentation group (IRIG) option and used a 

manual post-trigger to capture images of the buckling event. The FOV of each high-speed 

camera is indicated in Fig. 2.14 with a shaded rectangle superposed on the low-speed 

DIC FOV images for reference. Unfortunately, the high-speed camera FOVs were not 

properly verified before testing and only limited regions of the test article OML were 

imaged. However, the high-speed images would still be useful in observing the initiation 

and propagation of buckling in the TA. 

Figure 2.14. High-speed camera FOVs. 

The images captured from each of the high-speed cameras were post-processed by using 

the 2007 Correlated Solutions VIC-2DTM software to calculate u and v displacements in 

the plane of each FOV. The u and v displacements are used to qualitatively observe the 

radial deformations w of the test article OML, as illustrated in Fig. 2.15, by calculating 

. 

 

v

 www.correlatedsolutions.com 

u

v

u

v

u

v

u

v
19 

Figure 2.15. Using 2D DIC technique to qualitatively assess the 

radial deformations of TA01. 

In addition, data from one high-speed 3D DIC system were also obtained and are 

presented herein. The 3D DIC system was positioned between load lines 1 and 2 with a 

FOV from approximately 15° to 70°, as shown in Fig. 2.13. 

2.5.5 Load Sequences 

TA01 was subjected to five loading sequences: four subcritical load sequences (i.e., load 

levels that do not induce test article buckling/failure) and one final loading sequence to 

buckling and collapse. These load cases include three uniform axial compression load 

cases and two combined axial compression and bending load cases as follows: 

Load Sequence 1: Uniform axial compression to 0.2 Pcr

Load Sequence 2: Combined axial compression and bending to 0.1 Pcr + 0.1 Mcr

Load Sequence 3: Uniform axial compression to 0.4 Pcr

Load Sequence 4: Combined axial compression and bending to 0.2 Pcr + 0.2 Mcr

Load Sequence 5: Uniform axial compression to failure. 

Pcr and Mcr correspond to the predicted linear bifurcation buckling loads for a 

geometrically perfect, uniform cylinder (i.e., uniform geometry and does not include the 

weld lands) subjected to uniform compression and uniform bending. Pcr = 726,800 lb and 

Mcr = 36.35e6 inch-lb. The load sequences are defined in more detail in the TA01 test 

plan (Ref. 1) and test procedure (Ref. 2).vi

3.0 Analysis Description 

Pretest predictions of the buckling response of TA01 were used to determine testing and 

instrumentation requirements and are presented in this test report for reference. These 

pretest predictions include many simplifying assumptions and should be viewed as 

preliminary in nature. Final post-test predictions will be presented in a separate series of 

NASA technical publications in which refined modeling and analysis approaches and 

results will be discussed in detail. 

Pretest predictions of the buckling response of TA01 were obtained using the STAGS 

(STructural Analysis of General Shells) nonlinear shell-analysis code (Ref 12). STAGS is 

a finite-element code developed for the static and dynamic analysis of general shells, and 

vi TA01 was subjected to combined axial compression and bending during some of the sub-critical load 

sequences. However, the test to failure, in which the test article was subjected to axial compression only, 

was the primary load sequence used to verify the performance of the test system. TA02 would be tested at a 

later date and would be subjected to combined axial compression and bending until buckling and collapse 

in order to verify the performance of the system under combined loading conditions.
20 

includes the effects of geometric nonlinearities in the analysis. The finite-element model 

included representations of the entire test assembly including the steel load introduction 

structure, load lines, test article attachment rings, and the test article (see Fig. 3.1). A 

combination of beam and shell elements was used to generate the model. The standard 

410 quadrilateral shell element from the STAGS element library was used in the model 

and is a four-noded flat facet-type element that is based on the Kirchoff-Love shell 

hypothesis and the nonlinear Lagrangian strain tensor. The element nodes include three 

translational degrees of freedom and three rotational degrees of freedom. Large element 

rotations are accounted for by using a corotational algorithm. The STAGS 210 beam 

element was also used and is based on the Timoshenko beam theory. 

Figure 3.1. Finite-element model of test assembly. 

The model was constructed such that the load-introduction fixtures, attachment rings, and 

TA were separate entities and joined at each interface with multi-point constraints. The 

load introduction structure was included in the analysis to ensure that the boundary 

stiffness and kinematics were modeled accurately. The TA01 model included the three 
21 

longitudinal weld land details, and beam elements were used to represent the stiffeners. 

The nominal as-designed TA dimensions were used to define the model. The asmeasured initial TA geometry (Fig. 2.6) was then used to modify the geometrically 

perfect nominal geometry of the test article mesh to accurately represent the as-built 

geometrically imperfect TA. Specifically, a user-written subroutine was used to read in 

the measured geometry of the TA OML and adjust or perturb the OML geometry of the 

finite-element mesh at each nodal location. 

The load was introduced into the structure by applying eight point loads at the ends of 

beams representing the load lines in the test configuration and the bottom-loading spider 

was held fixed at its base. The connections between each of the components of the test 

assembly were assumed to be perfect, that is, the bolted connections were assumed to be 

uniform rigid attachments with no relative movement between each component. It should 

be noted that the pretest analyses reported in Ref. 13 assumed all eight point loads were 

equal, achieving uniform compression. However, since that time, the analyses have been 

updated to include the actual measured load line load values, which produced a small 

amount of nonuniformity of loading. The results from these updated analyses are 

presented along with the test data but do not show any significant variation from the 

original pretest analysis results. 

Al-Li 2195-T8M4 plate material properties from MSFC-HDBK-3513 (Ref. 14) were 

used in the analysis and included an elastic modulus of 11.0e6 psi, a Poisson ratio of 

0.33, density of 0.098 lbm/in3

, and a yield stress of 66.0e3 psi. Material data obtained 

from Ref. 14 indicate that the material exhibits slight differences in the longitudinal and 

transverse stiffness properties but this was not considered during the preliminary test 

article design and pretest analysis. Standard A36 steel properties were used for all the test 

fixture components. Detailed modeling information and results are presented in Refs. 3 

and 13. 

4.0 Results and Discussion 

Results from the testing of TA01 are presented in this section. First, geometric 

imperfection data obtained from the DIC system are presented and compared to the 

photogrammetry/white-light geometry measurement in Section 4.1. Then, selected results 

from load sequence 5 (LS5) test to failure are presented and compared to pretest 

predictions in Section 4.2. The test results include, load versus end-shortening, and load 

versus radial displacement response curves. Then, low-speed and high-speed DIC 

displacement contours are presented for selected prebuckling, buckling and postbuckling 

load levels. Finally, load versus axial strain response curves are presented along with 

plots of the axial strain distribution around the circumference of the test article for 

selected prebuckling load levels and incipient buckling. 

4.1 Initial Geometric Imperfection Data 

The initial OML geometry of TA01 was measured prior to its installation into the test 

facility by using a photogrammetry/white-light metrology technique as described in 

Section 2.3. The measurement accuracy was ±0.001 inches. The deviation of the 

measured data from a best-fit cylinder was calculated and defined as the initial geometric 

imperfection (imp) and is shown in Fig. 2.6. The three longitudinal weld lands are located 

at ‒60°, 60°, and 180°. The measured data indicate that TA01 was, for the most part, 
22 

circular to within ±0.10 inches with some additional deviations near the lower boundary. 

The weld lands do not appear to have a strong influence on or correlation with the 

imperfection pattern. 

DIC geometry measurements were taken after TA01 was installed in the test facility, 

immediately prior to testing and are shown in Fig. 4.1. The DIC measurements were 

obtained to determine if any additional geometric distortions developed in TA01 during 

handling and installation into the test fixtures as compared to the geometry measurements 

shown in Fig. 2.6. The accuracy of the measurement was approximately ±0.020 inches 

and thus only gross geometric distortions could be observed. For the most part, the DIC 

pretest geometry measurement shares similar characteristics as the high-resolution whitelight/photogrammetry measurement including the circumferential periodic variation in 

the geometry and no significant differences were observed. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.090

0.070

0.050

0.030

0.010

-0.010

-0.030

-0.050

imp, in.

Figure 4.1. Geometric imperfection for TA01 from DIC measurement. 

4.2 Buckling Response of TA01 

Selected test results are presented to illustrate the overall buckling response of TA01 

subjected to uniform axial compression. In addition, pretest analysis results are presented 

and compared to the test results. 

4.2.1 Load versus Displacement Response 

Predicted and measured load versus end-shortening response curves for TA01 are shown 

in Fig. 4.2 and are indicated by the solid and dashed curves, respectively. TA01 exhibits a 

linear prebuckling response up to a maximum load of 689 Kips (1 Kip = 1000 lb force) 

during the test. The maximum load is followed by the buckling and collapse of TA01 and 

is characterized by a sudden reduction in the axial load of approximately 61% to a 

postbuckling load of 270 Kips. In addition, the measured load versus end-shortening 

response curve indicates a significant increase in the end-shortening displacement during 

the buckling response from 0.12 to 0.20 inches. This increase in end-shortening is 

associated with the release of elastic strain energy in the test fixtures coupled with the 

reduced stiffness of the test article during the buckling response and in the postbuckling 

range of loading. Note that the oscillation of the predicted axial load in the initial 

postbuckling range is attributed to the structural damping parameters used in the finite 

element simulation. 
23 

End Shortening, in.

Total Axial Load, Kips

0.00 0.05 0.10 0.15 0.20 0.25 0.30

0

100

200

300

400

500

600

700

Analysis

Test

Figure 4.2. Measured and predicted load versus end-shortening response of TA01 

subjected to axial compression. 

Overall, the character of the load versus end-shortening response is predicted well, 

including the prebuckling and postbuckling axial stiffness; however, the predicted 

maximum load of 620 Kips is approximately 10% lower than the measured maximum 

load of 689 Kips. 

Predicted and measured prebuckling load versus radial displacement response curves are 

presented in Figs. 4.3 and 4.4 and include displacements measured at the cylinder midlength at the center of each panel segment and at the center of each weld land, 

respectively. Positive displacements correspond to outward radial displacements. The 

buckling and postbuckling data are omitted from these figures so that the smallmagnitude prebuckling displacements could be seen more clearly. The results indicate 

that both the weld lands and the panel centers move radially outward during the 

prebuckling response. As the loading approaches the buckling point (maximum load), the 

measured radial displacements in panel C and at weld land BC increase at a higher rate 

than at the other measurement locations and are associated with the onset of buckling in 

panel C. The predicted results indicate similar response trends overall; however, the 

displacements exhibit rapid growth in panel A and correspond to the initiation of 

buckling in panel A. In addition, the predicted radial displacements are in all cases larger 

than the corresponding measured displacements. 

It is noted that, the measured displacement response at weld land AB indicates a sudden 

increase in the radial displacements between a load level of 415 Kips and 435 Kips. After 

435 Kips, the slope of the displacement response curve reverts back to its previous value. 

However, measured data from other nearby strain gages (e.g., see data in Section 4.2.3) 

and digital image correlation data do not indicate any type of local change in behavior. In 

addition, previous testing with these particular LVDT instruments indicated similar 

anomalies. After review of these measurement anomalies, it was determined that the 

LVDT interface connection with the test article could become partially detached. Thus, 
24 

based on these previous observations, it is very likely that this measurement anomaly is 

due to a faulty LVDT interface connection. 

Radial Displacement, in.

Total Axial Load, Kips

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

0

100

200

300

400

500

600

700

Panel A

Panel B

Panel C

Test

Analysis

Panel C Panel A Panel B

Figure 4.3. Measured and predicted load versus radial displacement response of TA01 at 

the center of each panel. 

Radial Displacement, in.

Total Axial Load, Kips

0.000 0.008 0.016 0.024 0.032 0.040

0

100

200

300

400

500

600

700

Weld Land AB

Weld Land BC

Weld Land CA

Test

Analysis

Panel C Panel A Panel B

Figure 4.4. Measured and predicted load versus radial displacement response of TA01 at 

the center of each longitudinal weld land. 
25 

Typical predicted and measured prebuckling, buckling, and postbuckling radial 

displacement response curves for the center of panel A and at the center of weld land AB 

are shown in Fig. 4.5 to illustrate the typical displacement response characteristics during 

the buckling event and postbuckling range of loading. Predicted and measured buckling, 

initial postbuckling, and deep post buckling (end of test) points are indicated on the 

curves with filled and open square, circle, and triangle symbols, respectively. The results 

indicate a sudden reversal in the displacements from radially outward at buckling (square 

symbols) to radially inward at initial postbuckling (circle symbols), and correspond to the 

buckling of the test article wall. Upon further loading into the postbuckling range, the 

predicted displacements increase with maximum inward displacements of 2.0 inches 

occurring at the AB weld land and are accompanied by a significant change in the fullfield displacement pattern (shown in Section 4.2.2). In contrast, the corresponding 

measured postbuckling displacements indicate little to no change in displacements. The 

difference in the postbuckling full-field displacement response will be presented in 

Section 4.2.2. A photo of the buckled test article is shown in Fig. 4.6. 

Radial Displacement, in.

Total Axial Load, Kips

-3.00 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50

0

100

200

300

400

500

600

700

Weld Land AB

Panel A

Test

Analysis

Panel C Panel B Panel A

Figure 4.5. Measured and predicted load versus radial displacement response of TA01 at 

the center of panel A (D246CR) and at the center of weld land AB (D243BR). 

Overall, the predicted load versus radial displacement response characteristics are similar 

to the measured results. However, the predicted prebuckling radial displacements are, in 

many cases, larger than the corresponding measured displacements. 
26 

Figure 4.6. TA01 after global buckling. 
27 

4.2.2 Full-Field Displacement Contours 

Predicted and measured full-field prebuckling, buckling, and postbuckling displacement 

contours are presented in this section. First, selected axial and radial full-field 

prebuckling, buckling, and postbuckling displacement contours obtained from low-speed 

DIC systems are presented and compared to initial pretest predictions. Dashed vertical 

lines are shown in the contour plots at 60°, 180°, and 300° and correspond to weld lands 

AB, BC, and CA, respectively. Then, high-speed DIC contours obtained during the 

collapse response of the test article are presented. Finally, measured radial displacement 

versus time response curves are presented that illustrate the transient deformation 

response and structural damping characteristics of the test article. 

Low-Speed Digital Image Correlation Displacement Measurements 

Estimates of the low-speed DIC measurement error for the axial, u, and radial, w, 

displacement measurements are presented in Figs. 4.7-a and 4.7-b, respectively, and are 

estimated from a DIC measurement noise of ±0.006 inches in the axial u displacements 

and ±0.015 inches in the radial w displacements. These levels of noise are typical for this 

type of DIC system, set-up parameters, and calibration method used. Note that data are 

missing in four locations around the circumference of the test article due to load lines 

obstructing the FOV. 

Selected axial u and radial w displacement contours are presented in Figs. 4.8 through 

4.14 and include predicted and measured results from three prebuckling load levels and 

two postbuckling load levels. Prebuckling u and w displacements at 159.9 Kips 

(approximately 22% Pcr) are shown in Figs. 4.8 and 4.9, respectively. The predicted 

u displacements indicate a relatively uniform distribution with slightly lower 

displacements near the weld lands. Overall, the corresponding measured displacements 

show a similar uniform distribution, however, slight discontinuities in the data exist 

between adjacent DIC systems due to a camera synchronization error. In addition, some 

localized variation is observed and is attributed to the inherent measurement noise (see 

Fig. 4.7-a). The predicted w displacements, Fig. 4.9-a, indicate the development of a 

periodic distribution of inward and outward radial deformations that are somewhat 

symmetric within each panel segment. In addition, a pronounced inward ellipse-shaped 

dimple appears at the mid-length of panel A at the 18° circumferential location. The 

corresponding measured displacements in Fig. 4.9-b are within the measurement noise 

for the magnitude of these displacements and thus no correlation can be made. 

Predicted radial displacement contours at 319.8 Kips (approximately 44% Pcr) are shown 

in Fig. 4.10-a and indicate further growth of the ellipse-shaped inward dimple in panel A 

with a maximum amplitude of 0.006 inches. The corresponding measured displacement 

contours in Fig. 4.10-b still remain within the noise of the DIC measurement. The u

displacement pattern at this load level is similar to those shown in Fig. 4.8. 

As the applied axial load increases up to the buckling load of the test article, the predicted 

and measured axial displacement continues to exhibit a relatively uniform distribution 

around the circumference with slight variations near the weld land (see Fig 4.11). The 

predicted and measured radial displacement contours indicate significant localization of 

the deformations near the location of buckling initiation. In particular, the predicted radial 

displacements in Fig. 4.12a show a marked increase in the amplitude of the inward 
28 

dimple to 0.070 inch. The analysis results predict the initiation of buckling to occur at 

this single dimple in panel A. The measured results indicate the formation of a second 

ellipse-shaped inward dimple at the mid-length of panel C at the 260° circumferential 

location where initiation of buckling was observed during the test (high-speed DIC 

contours will be presented herein that confirm this result). The amplitude of this dimple is 

approximately 0.05 inch. 

The difference in the location of buckling initiation is not unexpected based on the fact 

that the buckling response of compression loaded cylinders can be extremely sensitive to 

a multitude of variables including initial geometric imperfections, variations in loading 

and boundary conditions, and variations in material properties and as-built versus asdesigned dimensions. More importantly, the results do indicate good agreement in the 

overall character of the prebuckling displacement response. 

Initial postbuckling and deep postbuckling radial displacement contours are shown in 

Figs. 4.13 and 4.14, respectively. The results indicate large-magnitude inward buckles 

have developed throughout the test article during the collapse response with maximum 

postbuckling displacements on the order of ‒1.4 to ‒1.6 inches near the weld lands. The 

predicted initial postbuckling displacements exhibit a uniform periodic distribution of 

buckles as compared to a nonuniform distribution of buckles observed in the measured 

results. This difference in behavior is attributed to the use of linear elastic material 

properties in the finite-element model that cannot account for the material yielding that 

occurred in the test article. More specifically, the predicted transient buckling response 

(results not presented herein) exhibited a short-wavelength displacement pattern similar 

to the one observed in Fig. 4.13-b during the initial stages of the transient collapse 

response but as the transient collapse continued, these small buckles were predicted to 

coalesce into larger buckles as shown in Fig. 4.13-a. In contrast, the test article 

experienced material yielding in regions that exhibit large magnitude bending strains 

associated with the short-wavelength buckles during the early stages of collapse, which 

appears to have prohibited the movement and coalescence of these buckles. 

As loading continues into the deep postbuckling range of loading, the predicted radial 

displacement response exhibits a coalescence of some of the smaller buckles into larger 

buckles and a significant increase in the magnitude of the inward displacements as shown 

in Fig. 4.14-a. In contrast, the measured displacement pattern remains unchanged from 

the initial postbuckling pattern shown in Fig. 4.13-b with only a slight increase in the 

amplitude of the inward displacements. Post-test inspection of the test article indicated 

permanent deformations associated with material yielding in the areas of large bending 

strains. 
29 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.006

0.004

0.002

0.000

-0.002

-0.004

-0.006

Panel C Panel B Panel A u, in.

a) Axial displacement u measurement noise. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.015

0.010

0.005

0.000

-0.005

-0.010

-0.015

-0.020

Panel C Panel B Panel A w, in.

b) Radial displacement w measurement noise.

Figure 4.7. DIC noise signature for u and w displacement measurements. 

a) Finite-element prediction. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 -0.005

-0.010

-0.015

-0.020

-0.025

-0.030

-0.035

-0.040

-0.045

Panel C Panel B Panel A u, in.

b) DIC. 

Figure 4.8. Predicted and measured axial displacement (u) contours at 159.9 Kips 

(22.0% Pcr). 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 -0.005

-0.010

-0.015

-0.020

-0.025

-0.030

-0.035

-0.040

-0.045

u, in. Panel C Panel B Panel A 
30 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.010

0.008

0.006

0.004

0.002

0.000

-0.002

w, in.

Panel C Panel B Panel A 

a) Finite-element prediction. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.010

0.008

0.006

0.004

0.002

0.000

-0.002

w, in.

Panel C Panel B Panel A

b) DIC. 

Figure 4.9. Predicted and measured radial displacement (w) contours at 159.9 Kips 

(22.0% Pcr). 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.020

0.016

0.012

0.008

0.004

0.000

-0.004

-0.008

w, in. Panel C Panel B Panel A

a) Finite-element prediction. 

b) DIC. 

Figure 4.10. Predicted and measured radial displacement (w) contours at 319.8 Kips 

(44.0% Pcr). 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.020

0.016

0.012

0.008

0.004

0.000

-0.004

-0.008

w, in. Panel C Panel B Panel A
31 

a) Finite-element prediction at buckling load of 619.8 Kips (85.3% Pcr). 

b) DIC at buckling load of 689.2 Kips (94.8% Pcr). 

Figure 4.11. Predicted and measured axial displacement (u) contours incipient to 

buckling. 

a) Finite-element prediction at buckling load of 619.8 Kips (85.3% Pcr). 

b) DIC at buckling load of 689.2 Kips (94.8% Pcr). 

Figure 4.12. Predicted and measured radial displacement (w) contours incipient to 

buckling. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

-0.02

-0.04

-0.06

-0.08

-0.10

-0.12

u, in.

Panel C Panel B Panel A

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

-0.02

-0.04

-0.06

-0.08

-0.10

-0.12

u, in.

Panel C Panel B Panel A

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.05

0.04

0.03

0.02

0.01

0.00

-0.01

-0.02

-0.03

-0.04

Panel C Panel B Panel A w, in.

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.05

0.04

0.03

0.02

0.01

0.00

-0.01

-0.02

-0.03

-0.04

Panel C Panel B Panel A w, in.
32 

a) Finite-element prediction at initial postbuckling load of 241.4 Kips (33.2% Pcr). 

b) DIC at initial postbuckling load of 265.5 Kips (36.5% Pcr). 

Figure 4.13. Predicted and measured initial postbuckling radial displacement (w) 

contours. 

a) Finite-element prediction at deep postbuckling load of 207.2 Kips (28.5% Pcr). 

b) DIC at deep postbuckling load of 251.5 Kips (34.6% Pcr). 

Figure 4.14. Predicted and measured deep postbuckling radial displacement (w) contours. 

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.6

0.3

0.0

-0.3

-0.6

-0.9

-1.2

-1.5

w, in.

Panel C Panel B Panel A

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

0.6

0.3

0.0

-0.3

-0.6

-0.9

-1.2

-1.5

w, in. Panel C Panel B Panel A

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

-2.5

w, in. Panel C Panel B Panel A

Circumferential Coordinate, degrees

Axial Coordinate, in.

300 240 180 120 60 0 -60

-30

-20

-10

0

10

20

30 0.6

0.3

0.0

-0.3

-0.6

-0.9

-1.2

-1.5

-1.8

w, in. Panel C Panel B Panel A
33 

High-Speed Digital Image Correlation Displacement Measurements 

Selected high-speed DIC displacement contours are presented to illustrate the initiation of 

buckling and unstable transient collapse response of the test article. First, u-v-based 

displacement magnitudes are shown from four 2D high-speed DIC systems. The u and v

components of the displacement are used to give a qualitative indication of where the 

buckling deformations develop and how they propagate over time as described in Section 

2.5.4. Then, data from one high-speed 3D DIC system are presented. The 3D DIC system 

was positioned between load lines 1 and 2 with a FOV from approximately 15° to 70° 

around the circumference of the test article, as shown in Fig. 2.13. 

The displacement contours are presented in Fig. 4.15 with contours superposed on DIC 

reference images of the test article. Blue/purple contours correspond to maximum 

amplitude radial displacements and the red/orange contours correspond to minimum 

amplitude radial deformations. Incipient buckling contours are shown for t = 0.0 sec and 

shows a single ellipse-shaped buckle at the 260° circumferential location in Fig. 4.15-a 

and corresponds to the initial dimple shown in Fig. 4.12-b from the low-speed DIC.vii The 

other high-frequency variations in the displacement contours are associated with the 

inherent measurement noise. At time t = 0.0009 sec, the single ellipse-shaped buckle 

begins to grow in size and amplitude. After 0.0049 seconds have elapsed, additional 

buckles have formed in panel C. The formation and propagation of additional buckles 

into panels A and B continues throughout the global collapse event (e.g., 

Figs. 4.15-c‒4.15-e) until a stable postbuckling configuration is obtained as shown in 

Fig. 4.15-f. The postbuckling contours shown in Fig 4.15-f correlate well with the 

corresponding low-speed DIC contours presented in Fig. 4.13-b. 

Radial displacement data were obtained from one high-speed 3D DIC system and were 

used to characterize displacement versus time response for six locations on panel A as 

shown in Fig. 4.16-a. Points A and D are located on the AB weld land (60° 

circumferential location) and points C and F are at the 22.2° circumferential location. The 

corresponding radial-displacement versus time response curves are shown in Fig. 4.16-b. 

Buckling initiated in panel C, as described previously, and rapidly propagated around the 

circumference of the test article. From this camera view, the buckling first appears at the 

right side of the FOV (e.g., points C and F) and propagates to the left of the image 

towards the AB weld land (e.g., points A and D). This can be seen in the displacementtime history curves in which displacements first appear at measurement points C and F 

followed by B and E, and finally at A and D. The displacement pattern and magnitudes 

correlate well with the low-speed contour data and indicate maximum radial 

displacements on the order of 1.75 inches at the AB weld land. The propagation speed of 

the buckling deformations can be estimated based on the phase difference between the 

various measurement points. Specifically, the data indicate that it took approximately 

0.001 seconds for the buckling deformations to propagate from point C to point A, a 

distance of approximately 31.8 inches, corresponding to a propagation speed of 

31,800 in/sec. 

 

vii Note: t = 0.0 sec. is an arbitrary time reference used to determine elapsed time throughout the transient 

collapse response. 
34 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

a) Incipient buckling t = 0.0 sec. 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

b) Initial buckling t = 0.0009 sec. 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

c) Buckling t = 0.0049 sec. 

Figure 4.15. Displacement contours from 2D high-speed DIC indicating the initiation and 

propagation of buckling deformations in TA01. 
35 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

d) Buckling t = 0.0121 sec. 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

e) Buckling t = 0.0191 sec. 

Circumferential Coordinate, degrees 

300 240 180 120 60 0 -60

f) Postbuckling t = 0.0360 sec. 

Figure 4.15. Concluded. 
36 

a) Radial displacement contour plot from 3D DIC and measurement points. 

w, in. 

Time, seconds 

b) Radial displacement versus time response. 

Figure 4.16. Measured radial displacements at selected locations on panel A of TA01 

during the collapse response. 
37 

4.2.3 Load versus Axial Strain Response 

Predicted and measured load versus axial prebuckling strain response curves are 

presented in Figs. 4.17 through 4.24. The buckling and postbuckling strains have been 

omitted from the figures for clarity. In addition, schematics of strain gage locations are 

provided in each figure. 

Back-to-back strain gage results from skin pockets and axial stiffeners near the centers of 

panels A, B, and C, are shown in Figs. 4.17, 4.18, and 4.19, respectively. Each figure 

contains analysis and test results from the center of a skin pocket near the center of each 

panel, corresponding to the green and blue lines, and results from an axial stiffener 

adjacent to each of these skin pockets, corresponding to the red and black lines in the 

figures. The results indicate that the strain response is, for the most part, linear up to 

buckling with average strains that range from 1550 micro-strain ( to 2010  A 

slight amount of bending is observed in panels A and C as indicated by the divergent load 

versus strain response curves, and this behavior is predicted accurately in the preliminary 

analysis. However, the predicted results show a rapid increase in bending strain in panel 

A at the maximum load, corresponding to the initiation of buckling near the center of the 

panel as seen in the predicted displacement contours presented in Fig 4.12-a. 

Back-to-back strain gage results from weld lands AB, BC, and CA and from axial 

stiffeners adjacent to the weld lands, are shown in Figs. 4.20, 4.21 and 4.22, respectively. 

Each figure contains analysis and test results from the center of each weld land, 

corresponding to the red and black lines, and results from longitudinal stiffeners adjacent 

to each of the weld lands, corresponding to the green and blue lines in the figures. The 

results indicate similar strain behavior as was seen in the skin pockets and stiffeners 

presented in Figs. 4.17–4.19 previously. In particular, the strain response curves are 

linear up to the buckling point and range from 1520  to 1910 

Two additional load versus axial strain plots are shown in Figs. 4.23 and 4.24 in order to 

investigate further the initiation of buckling in the test article. More specifically, the 

preliminary analysis results predicted buckling to initiate near the mid-length of panel A 

as shown in Fig. 4.12-a, however, the low-speed and high-speed DIC contours indicate 

that buckling initiated in panel C as shown in Figs. 4.12-b and 4.15-b. Thus, strain gage 

data close to these two regions of interest are presented next. Predicted results from panel 

A near the predicted buckling initiation sight are presented in Fig. 4.23 and show strain 

reversal in several of the skin and stiffener gages which is consistent with the onset of 

buckling in that panel. In contrast, the measured strains exhibit only slight change in the 

rate of divergence in this region prior to the maximum load. Similar results are presented 

for skin pocket strains near the mid-length of panel C in Fig. 4.24. The measured results 

exhibit a strain reversal in the outer-surface skin pocket gage and the measured bending 

strains are slightly larger than the corresponding predicted strains. 

For the most part, the predicted strain results correlate well with the measured results and 

indicate that the load introduction into the test article is predicted accurately. However, 

predicted stiffener strain near weld land AB (gage 080IRA) is approximately 20‒25% 

greater than the corresponding measurement. Several factors may contribute to this 

difference and include simplifying assumptions used to model the stiffeners as well as the 

sensitivity of strain measurements in the presence of local bending gradients. Recall that 
38 

in the preliminary analyses the stiffeners were modeled with beam elements and thus 

accurate strain predictions can be difficult to obtain when local bending and twisting of 

the stiffener is present. In addition, variations in strain gage position and strain gradients 

along the stiffener could result in significant differences in strain measurements. Detailed 

model refinement and sensitivity studies with improved stiffener models shall be 

conducted in the future to better understand this behavior and modeling sensitivities. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Stiffener (030ORA)

IML Stiffener (085IRA)

OML Skin (029 OSA)

IML Skin (084ISA)

Analysis

Test

Figure 4.17. Test/analysis correlation of back-to-back axial strains, skin, and adjacent 

axial stiffener near center of panel A. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Stiffener (127ORA)

IML Stiffener (159IRA)

OML Skin (126OSA)

IML Skin (158ISA)

Analysis

Test

Figure 4.18. Test/analysis correlation of back-to-back axial strains, skin, and adjacent 

Panel A center line

Panel

mid-length

Panel B center line

Panel

mid-length
39 

axial stiffener near center of panel B. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000 -2400

0

100

200

300

400

500

600

700

OML Stiffener (191ORA)

IML Stiffener (223IRA)

OML Skin (190OSA)

IML Skin (222ISA)

Analysis

Test

Figure 4.19. Test/analysis correlation of back-to-back axial strains, skin, and adjacent 

axial stiffener near center of panel C. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Weld Land (024ORA)

IML Weld Land (079IWA)

OML Stiffener (025ORA)

IML Stiffener (080IRA)

Analysis

Test

Figure 4.20. Test/analysis correlation of back-to-back axial strains, centers of weld land 

AB, and adjacent axial stiffener. 

Panel C center line

Panel

mid-length

Panel

mid-length

Weld land 

AB center 

line
40 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Weld Land (122OWA)

IML Weld Land (154IWA)

OML Stiffener (123ORA)

IML Stiffener (155IRA)

Analysis

Test

Figure 4.21. Test/analysis correlation of back-to-back axial strains, centers of weld land 

BC, and adjacent axial stiffener. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Weld Land (186OWA)

IML Weld Land (218IWA)

OML Stiffener (187ORA)

IML Stiffener (219IRA)

Analysis

Test

Figure 4.22. Test/analysis correlation of back-to-back axial strains, centers of weld land 

CA, and adjacent axial stiffener. 

Panel

mid-length

Weld land BC 

center line

Panel

mid-length

Weld land CA 

center line
41 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000 -2400

0

100

200

300

400

500

600

700

OML Stiffener (028ORA)

IML Stiffener (083IRA)

OML Skin (027OSA)

IML Skin (082ISA)

Analysis

Test

Figure 4.23. Test/analysis correlation of back-to-back axial strains, skin, and adjacent 

axial stiffener near the predicted buckling initiation site in Panel A. 

Axial Strain, 

Total Axial Load, Kips

0 -400 -800 -1200 -1600 -2000

0

100

200

300

400

500

600

700

OML Skin (189OSA)

IML Skin (221ISA)

Analysis

Test

Figure 4.24. Test/analysis correlation of back-to-back axial strains in a skin pocket near 

the buckling initiation sight in Panel C. 

331o

Panel

mid-length

211o

Panel

mid-length
42 

4.2.4 Axial Strain Distribution 

Selected plots of the predicted and measured axial membrane strain distribution around 

the circumference of the test article are presented for selected prebuckling load levels and 

incipient buckling in Figs. 4.25 through 4.28. Each plot includes data from five different 

axial stations along the length of the test article including +32.84, +18.0, +2.0, ‒18.0, and 

‒32.84 inches. The predicted membrane strains are displayed as a solid line and the 

measured membrane strains from individual strain gages are plotted with open circle 

symbols. The measured membrane strains are obtained by taking the average of the backto-back strain gage pairs. The dashed vertical lines at 60°, 180°, and 300° mark the weld 

land locations. The primary objective of this strain data comparison is to assess the load 

distribution in the test article and to verify test predictions. 

Strain data at load levels of 159.9 Kips (22% Pcr), 319.8 Kips (44.0% Pcr), 581.4 Kips 

(79.9% Pcr), and incipient buckling are presented in Figs. 4.25 through 4.28. At a load 

level of 159.9 Kips, the measured strains near the ends of the test article, ±32.84 inches, 

are uniform across the panel width with an average value of 260  and with small 

periodic variations of ±10  associated with the alternating skin and stiffener 

construction. The strains increase in magnitude near the weld lands by approximately 

28% to 325 . Toward the mid-length of the test article, the strain distribution changes 

significantly. In particular, the stiffened acreage exhibits larger magnitude strains of 

425  as compared to average weld land strains of 390 . As loading increases up to 

79.9% Pcr (581.4 Kips), the strain distributions and correlation trends remain similar to 

those at 22% Pcr (see Figs. 4.26 and 4.27). 

Finally, strain distributions at the predicted and the measured buckling load are presented 

in Fig. 4.28. The predicted strains at 619.8 Kips (predicted buckling load) are displayed 

as a solid line and the corresponding measured strains are plotted with open circle 

symbols. In addition, the measured buckling strains at 689.2 Kips (measured buckling 

load) are presented and displayed as filled square symbols. The strain distributions, for 

the most part, continue to follow the trends observed at lower prebuckling load levels. 

In general, the overall character of the axial strain distribution is predicted accurately, and 

indicates a periodic distribution associated with the periodic displacement response (see 

Fig. 4.9-a). However, the predicted incipient buckling axial strains in the weld lands near 

the ends of test article are between 7% greater (weld land CA) and 18% greater (weld 

land AB) than the corresponding measured strains (e.g., Figs. 4.28-a and 4.28-e), and 

may suggest a slight difference between the predicted and as-tested load introduction into 

the test article in that region. 
43 

Circumferential Coordinate, degrees

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -360

-340

-320

-300

-280

-260

-240

(e)

x = -32.84-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -430

-420

-410

-400

-390

-380

(c)

x = +2.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -360

-340

-320

-300

-280

-260

-240 Analysis

Test

(a)

x = +32.84-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -420

-410

-400

-390

-380

(d)

x = -18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -430

-420

-410

-400

-390

-380

(b)

x = +18.00-in.

Figure 4.25. Predicted and measured axial membrane strain distribution around 

circumference, 159.9 Kips (22.0% Pcr). 
44 

Circumferential Coordinate, degrees

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -700

-650

-600

-550

-500

-450

(e)

x = -32.84-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -860

-840

-820

-800

-780

-760

(c)

x = +2.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -860

-840

-820

-800

-780

-760

(d)

x = -18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -860

-840

-820

-800

-780

-760

(b)

x = +18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -750

-700

-650

-600

-550

-500

-450

Analysis

Test

(a)

x = +32.84-in.

Figure 4.26. Predicted and measured axial membrane strain distribution around 

circumference, 319.8 Kips (44.0% Pcr). 
45 

Circumferential Coordinate, degrees

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1300

-1200

-1100

-1000

-900

-800

(e)

x = -32.84-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1600

-1500

-1400

-1300

(c)

x = +2.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1600

-1500

-1400

-1300

(d)

x = -18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1600

-1500

-1400

-1300

(b)

x = +18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1300

-1200

-1100

-1000

-900

-800

Analysis

Test

(a)

x = +32.84-in.

Figure 4.27. Predicted and measured axial membrane strain distribution around 

circumference, 581.4 Kips (79.9% Pcr). 
46 

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1900

-1800

-1700

-1600

-1500

-1400

(c)

x = +2.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1400

-1300

-1200

-1100

-1000

-900 Analysis

Test, 619.8 Kips

Test, 689.2 Kips

(a)

x = +32.84-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1800

-1700

-1600

-1500

-1400

(d)

x = -18.00-in.

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1900

-1800

-1700

-1600

-1500

-1400

(b)

x = +18.00-in.

Circumferential Coordinate, degrees

Axial Membrane Strain, 

300 240 180 120 60 0 -60 -1400

-1300

-1200

-1100

-1000

-900

(e)

x = -32.84-in.

Figure 4.28. Predicted and measured axial membrane strain distribution around 

circumference, predicted buckling strains and measured data at 619.8 Kips (85.3% Pcr), 

measured buckling strains at 689.2 Kips (94.8% Pcr). 
47 

5.0 Concluding Remarks 

Results from testing of the 8-foot-diameter Al-Li orthogrid-stiffened cylinder test article 

TA01 were presented. TA01 was the first in a series of nine subscale, integrally stiffened 

barrel tests defined in the SBKF test program. The test was conducted on November 

19‒21, 2008, at MSFC. The primary objectives of this test were to verify the performance 

of a new purpose-built test facility, and verify the adequacy of the test procedures, and 

test article design and analysis approach through detailed test and analysis correlation. To 

this end, selected results from the testing of TA01 were presented herein. First, 

descriptions of the test article design, fabrication, and test were presented and pretest 

analysis predictions were briefly described. Then, selected test results were presented and 

compared to pretest predictions. 

Test Objectives and Success Criteria 

All test objectives were successfully achieved and, for the most part, the test was 

executed as defined by the test plan and test procedure. Specifically, the test system and 

instrumentation operated as desired and the test article was tested to buckling and into the 

postbuckling range of loading. In addition, all test data necessary to verify the test article 

design and analysis approach were obtained; however, two minor discrepancies were 

identified in the data after testing. First, load line alignment verification measurements 

were made using a low-fidelity inclinometer, which did not have the accuracy necessary 

to verify the vertical alignment of the load lines to the specified tolerances. However, 

plum bob measurements and displacement and strain data obtained during the testing of 

TA01 indicated that the compression and bending loads were applied as desired and that 

no alignment-induced loads were present. Second, the high-speed DIC FOVs were not 

properly verified before the test and did not provide the full-field coverage as defined in 

the test plan. Fortunately, the high-speed DIC data that were obtained, and presented 

herein, were sufficient to characterize the initiation and propagation of the buckling 

response as required. 

Test Results and Pretest Predictions 

During testing, TA01 was subjected to uniform axial compression until buckling failure 

occurred. TA01 exhibited a linear prebuckling load-end-shortening response and 

achieved a maximum load of 689.2 Kips prior to buckling. Low-speed and high-speed 

digital image correlation displacement data indicated that buckling initiated as a single 

ellipse-shaped dimple in the cylinder wall and led to the sudden global collapse of the test 

article. The buckling and collapse of TA01 resulted in a significant reduction in axial 

load carrying capability and axial stiffness, and an initial postbuckling load level of 

270 Kips. In addition, the test article exhibited material yielding due to the development 

of large-magnitude bending deformations in the shell wall during the buckling and 

collapse response. 

Overall, the pretest predictions showed good correlation with the measured prebuckling, 

buckling, and postbuckling behavioral characteristics of TA01 and indicate that the 

modeling approach used can produce physically meaningful results that are suitable for 

pretest predictions and test planning. 
48 

In particular, the pretest predictions indicated similar load versus displacement and load 

versus strain response trends including an accurate representation of the axial stiffness 

and axial strain distribution around the circumference of the cylinder (±5% difference or 

better). In addition, the overall character of the prebuckling full-field radial displacements 

agreed well with the measured digital image correlation displacements including the 

development of a single ellipse-shaped dimple that initiated a transient buckling response. 

However, the predicted prebuckling radial displacement amplitudes were typically 

greater than the corresponding measured displacements. It is not known at this time what 

has caused the differences between the predicted and measured radial displacement 

amplitudes and buckling loads; however, it is likely that several of the modeling 

assumptions used in the pretest analysis may have some influence. For example, the 

fillets between the stiffeners and the skin and the fillets at the intersections between 

circumferential and longitudinal stiffeners (often referred to as nodes; see Section 2.2) 

were omitted from the model for simplicity. These fillet details would contribute 

additional bending and torsional stiffness to the stiffener and skin, which could reduce the 

predicted prebuckling radial displacements in the shell wall. In addition, the models 

assume idealized boundary conditions in which the ends of the test article are rigidly 

clamped in the attachment rings. The actual as-tested boundary conditions consisted of 

the test article potted in a low-melting-temperature alloy (see Section 2.3) that may allow 

some rotation of the test article in the attachment ring due to the relatively low stiffness 

of the potting and thus change the load introduction into the test article. 

Future detailed analysis studies shall be performed to determine the effects of selected 

modeling assumptions on the predicted response and improve the test and analysis 

correlation. In addition, the effects of manufacturing tolerances associated with the asbuilt skin and stiffener dimensions should be investigated. 

Archival Information 

A complete listing of all test and analysis data, data files, and drawings is provided in 

Appendix A and includes archival directory names, file names and file format 

descriptions, and example data plots. All data, reports, drawings, and other supporting 

materials for TA01 design, fabrication, and testing is located in the 

SBKF_TA01_Archive directory in the SBKF Archive Directory on the NASA Langley 

central storage system (CSS). 
49 

6.0 References 

1. Hilburger, M. W.; and Thornburgh, R. P.: “Shell Buckling Knockdown Factor 

Program SBKF-P2-CYL-TA01 Test Plan v1.2,” 6 November 2008. 

2. Roberts, M. G.: “Test and Checkout Procedure: Shell Buckling Knockdown 

Factor (SBKF) Test #1,” TCP-ED30.1.MGR.102708, November 10, 2008. 

3. Thornburgh, R. P.; and Hilburger, M. W.: “Design of Orthogrid Cylinder Test 

Articles for the Shell Buckling Knockdown Factor Assessment,” NASA/TM‒

2010-216866 and ARL-TR-5122, November 2010. 

4. Weingarten, V.; Seidi, P.; Peterson, J. P.; Buckling of Thin-Walled Circular 

Cylinders. NASA SP-8007, September 1965, revised August 1968. 

5. Drawing No. 1167189, Revision B: “Panels Checkout Test Panel,” NASA 

Langley Research Center, Hampton, Virginia, 19 March 2008. 

6. Bjorkman, G.: “TD 6456F NASA LaRC Shell Buckling Knockdown Factor 

Assessment Support: Task 3 - Barrel Fabrication,” ETTP-3913-08-001, 

June 11, 2008. 

7. Drawing No. 1238206: “NESC Shell Buckling Test Barrel Assembly,” NASA 

Langley Research Center, Hampton, Virginia, 17 March 2009. 

8. Drawing No. 1238205, Revision B: “NESC Shell Buckling Test Panel Mounting 

Ring,” NASA Langley Research Center, Hampton, Virginia, 17 March 2009. 

9. Drawing 90M12370: “Test Assembly,” NASA Marshall Space Flight Center, 

Huntsville, Alabama, 28 October 2008. 

10. Drawing 90M12375: “Load Structure Assembly,” NASA Marshall Space Flight 

Center, Huntsville, Alabama, 20 February 2008. 

11. Drawing No. 1238207, Revision B: “NESC Shell Buckling Test Checkout Test 

Panel Instrumentation,” NASA Langley Research Center, Hampton, Virginia, 

22 July 2008. 

12. Rankin, C. C.; Brogan, F. A.; Loden, W. A.; Cabiness, H. D.; STAGS Users 

Manual, Version 5.0. Lockheed Martin Missiles & Space Co., Inc., Advanced 

Technology Center, Report LMSC P032594, January 2005. 

13. Thornburgh, R. P.; and Hilburger, M. W.: “Pre-Test Analysis Predictions for the 

Shell Buckling Knockdown Factor Checkout Tests – TA01 and TA02,” 

NASA/TM‒2011-216875 ARL-TR-5123, January 2011. 

14. Hastings, K.; and Malone, T. W.: “Design Allowables Handbook for AluminumLithium 2195 Plates, Extrusions, Forgings, & Welds,” MSFC-HDBK-3513, 

December 2007.
50 

Appendix A Archival Information 

All electronic files associated with the testing of TA01 are stored in the SBKF Data 

Archive located on the NASA Langley Central Storage System (CSS) and the NESC 

NASA Safety Center Knowledge Now (NSCKN) storage site. These files include all test 

data, manufacturing plan, test plan, test procedure, test article and test facility drawings, 

quality assurance reports and data, finite element results, and selected processed data and 

plots. The electronic files are listed in this section along with a short description of the 

format of the files. File names and directory paths are indicated in Arial font throughout 

the Appendix for clarity. 

Plans, Procedures, Drawings, and Reports 

TA01 plans, procedures, drawing files, and reports are found in SBKF_TestData_Archive 

> TA01 > TA01_Docs. Files include: 

Plans and Procedures 

TA01 Test Plan: SBKF-P2-CYL-SD01-TestPlan_v1.2.pdf

TA01 Test Procedure: TCP-ED30.1-MGR-111008.pdf 

TA01 Manufacturing Plan: ETTP-3913-08-001.pdf 

Drawings 

Barrel Panel Design Drawing: Drawing_1167189_Rev._B.pdf

Barrel Test Article Attachment Ring Drawing: Drawing_1238205_Rev._A.pdf

Barrel Test Article Assembly Drawing: Drawing_1238206_Rev._A.pdf

Instrumentation Pattern Drawing: Drawing_1238207_Rev._B.pdf

Load Structure Assembly Drawing: Drawing_90M12375.pdf

Test Assembly Drawing: Drawing_90M12370.pdf

Quality and Manufacturing Reports 

Material Requirements Report: EC-012200_STM11A1-4.pdf 

Material Qualification Report: SBKF_Material_Qualification.pdf 

TA01 Measured Geometry 

The initial geometry of TA01 was measured after fabrication was complete and before 

instrumentation was installed. The raw data were provided in global Cartesian 

coordinates and was converted to cylindrical coordinates. The data were then fit to a bestfit circular cylinder and the deviations from the perfect OML cylinder radius were 

calculated and denoted by the variable imp as shown in Fig. 4.1. The resulting test-article 

geometry data are reported in x, , imp column format, where x and  are the OML 

coordinates as defined in Fig. 4.2 and imp is the measured deviation. The measured data 

are found in SBKF_ TestData Archive > TA01 > TA01_MeasuredGeometry_Data. Files 

include: 

TA01 measured imperfection data file: TA01_cmm.dat

Fortran subroutine used to input the measured imperfection data into the FEM: 

TA01_dimp.F

TA01 measured imperfection plot (Fig. 2.6): TA01_imp.jpg
51 

Test Data 

Test data for all load sequences conducted during the testing of TA01 have been 

archived. Archived test data and plots for Load Sequence 5 (LS_5) are described in this 

section; however, similar data are available for the other load sequences in the archives 

and follows a similar directory and file name format. The data can be found in the 

following directories: 

Load Sequence 1 Data: SBKF_TestData_Archive > TA01 > TA01_LS_1 

Load Sequence 2 Data: SBKF_TestData_Archive > TA01 > TA01_LS_2 

Load Sequence 3 Data: SBKF_TestData_Archive > TA01 > TA01_LS_3 

Load Sequence 4 Data: SBKF_TestData_Archive > TA01 > TA01_LS_4 

Load Sequence 5 Data: SBKF_TestData_Archive > TA01 > TA01_LS_5 

Raw Test Data Files 

The raw test data for LS_5 are in Microsoft® Excel® format and in standard text format in 

the SBKF Data Archive in the following directory: 

SBKF_ TestData Archive > TA01 > TA01_LS5 > TA01_LS5_Raw_Test_Data >

Excel® files: 

TA01_LS5_Raw_Test_Data-EU1of3-11-20-2008.xls 

TA01_LS5_Raw_Test_Data-EU2of3-11-20-2008.xls 

TA01_LS5_Raw_Test_Data-EU3of3-11-20-2008.xls 

TA01_LS5_Raw_Test_Data-LPS1of3-11-20-2008.xls 

TA01_LS5_Raw_Test_Data-LPS2of3-11-20-2008.xls 

TA01_LS5_Raw_Test_Data-LPS3of3-11-20-2008.xls 

Text files: 

TA01_LS5_Raw_Test_Data-EU1of3-11-20-2008.txt 

TA01_LS5_Raw_Test_Data-EU2of3-11-20-2008.txt 

TA01_LS5_Raw_Test_Data-EU3of3-11-20-2008.txt 

TA01_LS5_Raw_Test_Data-LPS1of3-11-20-2008.txt 

TA01_LS5_Raw_Test_Data-LPS2of3-11-20-2008.txt 

TA01_LS5_Raw_Test_Data-LPS3of3-11-20-2008.txt 

The “EU” (Engineering Units) series files are full test data sets and are separated into 

three files due to the size limitations of the software. The “LPS” (Load Point Scans) 

series files contain the tagged scan data. Tagged scan data refers to a subset of the full 

data set in which data from all channels are saved at specific times during the test, 

typically at prescribed load levels defined in the test plan and after prominent response 

events during the test such as buckling. All data channels are clearly labeled in the files 

and are consistent with the name and labeling convention in drawings and other related 

documents. 

Processed Test Data Files and X-Y Data and Plots 

The raw test data have been processed into usable data for plotting and correlation with 

predicted results. The corresponding analysis results were obtained from nonlinear finiteelement analyses (Ref. 13) and were taken from the appropriate locations in the cylinder 

model to correlate directly with the test data. The processed test data files and 

corresponding nonlinear finite-element analysis data files are provided in Tecplot format 
52 

(.plt, similar to tab-delimited text) and are listed here along with selected data plots in 

.pdf format for quick reference. In addition, Tecplot layout files (.lay) are provided and 

can be used to plot the test and analysis data in Tecplot. All files are located in the SBKF 

Data Archive in the following directory: 

SBKF_TestData _Archive > TA01 > TA01_LS5 > TA01_LS5_Formatted_ Data _Files.

Data files: 

Test data: TA01_LS5_Experiment.plt (also called 

TA01_LS5_Experiment_20130712-001.dat)

Predicted STAGS nonlinear transient analysis data: TA01_LS5_STAGS_data.plt 

(also called ta1_ax12_Stags_analysis_20090117-1.dat)

Predicted displacement data: TA01_LS5_STAGS_Disp.data.plt (merged with 

above file)

Tecplot Layout files:

Normalized axial load P/Pcr versus a back-to-back strain gage pair: 

TA01_LS5_B2B_Strains.lay

Normalized axial load P/Pcr versus a displacement transducer: 

TA01_LS5_Displacements.lay

Processed Tagged Scan Data Files and Plots 

Predicted and measured axial strain distributions around the circumference of the test 

article have been obtained from five axial locations, x = ‒32.84-in., ‒18.00-in., ‒2.00-in., 

18.00-in., and 32.84-in. (see Figs. 4.28–4.31). These data are available for several tagged 

scan points that correspond to normalized load levels of P/Pcr = 0.220, 0.440, 0.799 and 

limit loads (for both test and analysis). Pcr corresponds to the predicted linear bifurcation 

buckling load for the corresponding geometrically perfect, uniform cylinder subjected to 

compression and equals 726,800 lb. A summary of the tag scan data files is given in 

Table A3. All files are located in the SBKF Data Archive in the following directory: 

SBKF_TestData _Archive > TA01 > TA01_LS5 > TA01_LS5_Formatted_Data_Files > 

TA01_LS5_Tagged_Scans. 

Digital Image Correlation Data Files and Contour Plots 

A subset of the total DIC images were processed into data due to the extensive number of 

images collected during the testing. However, all images, calibration, and data files have 

been retained for future processing if necessary. Selected files for DIC data and predicted 

data are listed in Table A.4 and include finite-element model analysis load step, DIC 

photo number, raw test data scan number, and corresponding data file names. The raw 

image files (.tiff files), processed digital image correlation data are located in the SBKF 

Data Archive in the following directory: 

SBKF_TestData_Archive > TA01 > TA01_LS5 > TA01_LS5_DIC-3D_Data. 

Within the TA01_LS5_DIC-3D_Data directory there is a directory for each DIC system 

following the convention: 

Test Article name-DIC system number-DIC system location-load sequence 

number (e.g., TA01-sys1-east-LS5) 

Image files and output files within each directory have image number and camera 

number. 
53 

Examples are: 

TA01-sys1-east-LS5-0001_0.tif 

TA01-sys2-north-LS5-0123_1.tif 

TA01-sys4-west-LS5-0024_0.out (processing output file) 

VIC project files and data reports are also included such as: 

TA01-sys5-south-LS5.z3d (VIC-3D project file) 

TA01-sys5-south-LS5-report.csv (projection error report file) 

TA01-sys1-east-LS5.csv (analog data file) 

Similar calibration data and files are included and have a “-cal” appended after the LS# in 

the directory and file name. 

Image files (.jpg) containing contour plots of the u, v, and w displacements were 

generated (e.g., Figs 4.9–4.16). The prebuckling images are stored on the SBKF Data 

Archive in the following directory: SBKF_TestData _Archive > TA01 > TA01_LS5 > 

TA01_LS5_DIC-3D_Data > TA01_LS5_DIC_Prebuckling_Plots. The postbuckling 

images are stored on the SBKF Data Archive in the following directory: 

SBKF_TestData_Archive > TA01 > TA01_LS5 > TA01_LS5_DIC-3D_Data > 

TA01_LS5_DIC_Postbuckling_Plots. 

High-speed video info 

High-speed camera files are stored on the SBKF Data Archive in the following directory: 

SBKF_TestData_Archive > TA01 > TA01_LS5 > TA01_LS5_DIC-3D_Data > 

TA01_LS5_High-Speed_Video. 

The directory and file naming convention is the same as the low-speed DIC systems as 

described above except the sys# portion of the file name will be replaced with a hscam#.

The project file for the single cameras will be a *.z2d instead of a *.z3d file. 

Photos and Video 

Low-resolution and high-resolution photos and video of the test setup and test control 

room were taken November 19‒21 2008 during testing. The photos can be found in the 

following directory: SBKF_TestData _Archive > TA01 > Photos in the following subdirectories:

4619-11-08-lowres 

4619-11-19-08 

4619-11-20-08 

4619-11-21-08 

4619-11-21-08-posttest 

Video is found in the following directory: SBKF_TestData _Archive >TA01 > Video.

Finite-Element Models and Analysis Data 

Finite-Element Models and Analysis Data are found in the following directory: 

SBKF_TestData Archive >TA01 > TA01_LS5 > TA01_LS5_FEM 

Model input file: TA01_LS5.inp (also known as ta1_ax12p.inp) 

Model run file: TA01_LS5.bin (also known as ta1_ax12p.bin) 

Geometric imperfection data: TA01_imp.dat (also known as cmm.dat) 

Geometry definition subroutine: dimp.F (also known as dimp.F) 

Wall definition subroutine: wall.F 

Subroutine to use with initial geometric imperfection data: cmm.F 
54 

Table A1. Electronic Displacement Indicator (EDI) Locations 

EDI EDI ID Angular 

Location, 

deg. 

x, in. Component Location Orientation IML/OML 

Location 

239 D239AA 0° 36.313 Top Attachment Ring Axial IML 

240 D240AA 90° 36.313 Top Attachment Ring Axial IML 

241 D241AA 180° 36.313 Top Attachment Ring Axial IML 

242 D242AA 270° 36.313 Top Attachment Ring Axial IML 

243 D243BR 60° 0.00 Panel A/B Weld Land Radial IML 

244 D244BR 180° 0.00 Panel B/C Weld Land Radial IML 

245 D245BR 300° 0.00 Panel C/A Weld Land Radial IML 

246 D246CR 0° 0.00 Panel A Radial IML 

247 D247CR 120° 0.00 Panel B Radial IML 

248 D248CR 240° 0.00 Panel C Radial IML 

249 D249DR 60° -29.375 Panel A/B Weld Land Radial IML 

250 D250ER 0° -29.375 Panel A Radial IML 

251 D251FR 0° 36.313 Top Attachment Ring Radial IML 

252 D252FR 120° 36.313 Top Attachment Ring Radial IML 

253 D253FR 240° 36.313 Top Attachment Ring Radial IML 

254 D254FR 0° -36.313 Bottom Attachment Ring Radial IML 

255 D255FR 120° -36.313 Bottom Attachment Ring Radial IML 

256 D256FR 240° -36.313 Bottom Attachment Ring Radial IML 

257 D257GH 0° 36.313 Top Attachment Ring Tangential OML 

258 D258GH 0° -36.313 Bottom Attachment Ring Tangential OML 

259 D259AA 0° -36.313 Bottom Attachment Ring Axial IML 

260 D260AA 90° -36.313 Bottom Attachment Ring Axial IML 

261 D261AA 180° -36.313 Bottom Attachment Ring Axial IML 

262 D262AA 270° -36.313 Bottom Attachment Ring Axial IML 

263 D263AA 0° (1) (1) Axial IML 

264 D264AA 90° (2) (2) Axial IML 

265 D265AA 180° (3) (3) Axial IML 

266 D266AA 270° (4) (4) Axial IML 

(1) D263AA = D239AA – D259AA

(2) D264AA = D240AA – D260AA

(3) D265AA = D241AA – D261AA

(4) D266AA = D242AA – D262AA
55 

Table A2. Strain Gage Locations and Orientations for TA01 

OML 

GAGE 

NUMBER 

OML 

GAGE ID 

IML GAGE 

NUMBER 

IML GAGE 

ID 

HOOP DIMENSION, (in.) 

AXIAL DIMENSION, (in.) 

PANEL LOCATION ORIENT

1 001OWA 56 056IWA 50.27 -32.84 A Weld Axi2 002ORA 57 057IRA 48.00 -32.84 A Stiffener Axi

3a 003OSA 58a 058ISA 47.00 -32.84 A Pocket Axi3b 003OSH 58b 058ISH 47.00 -32.84 A Pocket Hoo

4 004OSA 59 059ISA 26.00 -32.84 A Pocket Axi5 005ORA 60 060IRA 24.00 -32.84 A Stiffener Axi

6a 006OSA 61a 061ISA 2.00 -32.84 A Pocket Axi6b 006OSH 61b 061ISH 2.00 -32.84 A Pocket Hoo

7 007ORA 62 062IRA 0.00 -32.84 A Stiffener Axi8 008ORA 63 063IRA -24.00 -32.84 A Stiffener Axi9 009OSA 64 064ISA -26.00 -32.84 A Pocket Axi

10a 010OSA 65a 065ISA -47.00 -32.84 A Pocket Axi10b 010OSH 65b 065ISH -47.00 -32.84 A Pocket Hoo

11 011ORA 66 066IRA -48.00 -32.84 A Stiffener Axi12 012OSH 67 067IRH 47.00 -32.00 A Rib Hoo13 013OSH 68 068IRH 2.00 -32.00 A Rib Hoo14 014OSH 69 069IRH -47.00 -32.00 A Rib Hoo15 015OWA 70 070IWA 50.27 -18.00 A Weld Axi16 016ORA 71 071IRA 48.00 -18.00 A Stiffener Axi17 017OSA 72 072ISA 47.00 -18.00 A Pocket Axi18 018OSA 73 073ISA 2.00 -18.00 A Pocket Axi19 019ORA 74 074IRA 0.00 -18.00 A Stiffener Axi20 020OSA 75 075ISA -47.00 -18.00 A Pocket Axi21 021ORA 76 076IRA -48.00 -18.00 A Stiffener Axi22 022ORH 77 077IRH 47.00 0.00 A Rib Hoo23 023ORH 78 078IRH -47.00 0.00 A Rib Hoo24 024OWA 79 079IWA 50.27 2.00 A Weld Axi25 025ORA 80 080IRA 48.00 2.00 A Stiffener Axi
56 

Table A2. Continued 

OML 

GAGE 

NUMBER 

OML 

GAGE 

ID 

IML GAGE 

NUMBER 

IML GAGE 

ID 

HOOP DIMENSION, (in.) 

AXIAL DIMENSION, (in.) 

PANEL LOCATION ORIENTAT

26a 026OSA 81a 081ISA 47.00 2.00 A Pocket Axial 26b 026OSH 81b 081ISH 47.00 2.00 A Pocket Hoop 

27 027OSA 82 082ISA 26.00 2.00 A Pocket Axial 28 028ORA 83 083IRA 24.00 2.00 A Stiffener Axial 29 029OSA 84 084ISA 2.00 2.00 A Pocket Axial 30 030ORA 85 085IRA 0.00 2.00 A Stiffener Axial 31 031ORA 86 086IRA -24.00 2.00 A Stiffener Axial 32 032OSA 87 087ISA -26.00 2.00 A Pocket Axial 

33a 033OSA 88a 088ISA -47.00 2.00 A Pocket Axial 33b 033OSH 88b 088ISH -47.00 2.00 A Pocket Hoop 

34 034ORA 89 089IRA -48.00 2.00 A Stiffener Axial 35 035OWA 90 090IWA 50.27 18.00 A Weld Axial 36 036ORA 91 091IRA 48.00 18.00 A Stiffener Axial 37 037OSA 92 092ISA 47.00 18.00 A Pocket Axial 38 038OSA 93 093ISA 2.00 18.00 A Pocket Axial 39 039ORA 94 094IRA 0.00 18.00 A Stiffener Axial 40 040OSA 95 095ISA -47.00 18.00 A Pocket Axial 41 041ORA 96 096IRA -48.00 18.00 A Stiffener Axial 42 042ORH 97 097IRH 47.00 32.00 A Rib Hoop 43 043ORH 98 098IRH 2.00 32.00 A Rib Hoop 44 044ORH 99 099IRH -47.00 32.00 A Rib Hoop 45 045OWA 100 100IWA 50.27 32.84 A Weld Axial 46 046ORA 101 101IRA 48.00 32.84 A Stiffener Axial 

47a 047OSA 102a 102ISA 47.00 32.84 A Pocket Axial 47b 047OSH 102b 102ISH 47.00 32.84 A Pocket Hoop 

48 048OSA 103 103ISA 26.00 32.84 A Pocket Axial 49 049ORA 104 104IRA 24.00 32.84 A Stiffener Axial 

50a 050OSA 105a 105ISA 2.00 32.84 A Pocket Axial 
57 

Table A2. Continued 

OML 

GAGE 

NUMBER 

OML 

GAGE 

ID 

IML GAGE 

NUMBER 

IML GAGE 

ID 

HOOP DIMENSION, (in.) 

AXIAL DIMENSION, (in.) 

PANEL LOCATION ORIENTAT

50b 050OSH 105b 105ISH 2.00 32.84 A Pocket Hoop 

51 051ORA 106 106IRA 0.00 32.84 A Stiffener Axial 52 052ORA 107 107IRA -24.00 32.84 A Stiffener Axial 53 053OSA 108 108ISA -26.00 32.84 A Pocket Axial 

54a 054OSA 109a 109ISA -47.00 32.84 A Pocket Axial 54b 054OSH 109b 109ISH -47.00 32.84 A Pocket Hoop 

55 055ORA 110 110IRA -48.00 32.84 A Stiffener Axial 

111 111OWA 143 143IWA 50.27 -32.84 B Weld Axial 112 112ORA 144 144IRA 48.00 -32.84 B Stiffener Axial 113 113OSA 145 145ISA 47.00 -32.84 B Pocket Axial 114 114OSA 146 146ISA 26.00 -32.84 B Pocket Axial 115 115OSA 147 147ISA 2.00 -32.84 B Pocket Axial 116 116ORA 148 148IRA 0.00 -32.84 B Stiffener Axial 117 117ORA 149 149IRA -24.00 -32.84 B Stiffener Axial 118 118OSA 150 150ISA -26.00 -32.84 B Pocket Axial 119 119OSA 151 151ISA -47.00 -32.84 B Pocket Axial 120 120ORA 152 152IRA -48.00 -32.84 B Stiffener Axial 121 121OWA 153 153IWA 50.27 -18.00 B Weld Axial 122 122OWA 154 154IWA 50.27 2.00 B Weld Axial 123 123ORA 155 155IRA 48.00 2.00 B Stiffener Axial 124 124OSA 156 156ISA 47.00 2.00 B Pocket Axial 125 125OSA 157 157ISA 26.00 2.00 B Pocket Axial 126 126OSA 158 158ISA 2.00 2.00 B Pocket Axial 127 127ORA 159 159IRA 0.00 2.00 B Stiffener Axial 128 128ORA 160 160IRA -24.00 2.00 B Stiffener Axial 129 129OSA 161 161ISA -26.00 2.00 B Pocket Axial 130 130OSA 162 162ISA -47.00 2.00 B Pocket Axial 131 131ORA 163 163IRA -48.00 2.00 B Stiffener Axial 
58 

Table A2. Continued 

OML 

GAGE 

NUMBER 

OML 

GAGE 

ID 

IML GAGE 

NUMBER 

IML GAGE 

ID 

HOOP DIMENSION, (in.) 

AXIAL DIMENSION, (in.) 

PANEL LOCATION ORIENTAT

132 132OWA 164 164IWA 50.27 18.00 B Weld Axial 133 133OWA 165 165IWA 50.27 32.84 B Weld Axial 134 134ORA 166 166IRA 48.00 32.84 B Stiffener Axial135 135OSA 167 167ISA 47.00 32.84 B Pocket Axial 136 136OSA 168 168ISA 26.00 32.84 B Pocket Axial 137 137OSA 169 169ISA 2.00 32.84 B Pocket Axial 138 138ORA 170 170IRA 0.00 32.84 B Stiffener Axial139 139ORA 171 171IRA -24.00 32.84 B Stiffener Axial140 140OSA 172 172ISA -26.00 32.84 B Pocket Axial 141 141OSA 173 173ISA -47.00 32.84 B Pocket Axial 142 142ORA 174 174IRA -48.00 32.84 B Stiffener Axial175 175OWA 207 207IWA 50.27 -32.84 C Weld Axial 176 176ORA 208 208IRA 48.00 -32.84 C Stiffener Axial 177 177OSA 209 209ISA 47.00 -32.84 C Pocket Axial 178 178OSA 210 210ISA 26.00 -32.84 C Pocket Axial 179 179OSA 211 211ISA 2.00 -32.84 C Pocket Axial 180 180ORA 212 212IRA 0.00 -32.84 C Stiffener Axial 181 181ORA 213 213IRA -24.00 -32.84 C Stiffener Axial 182 182OSA 214 214ISA -26.00 -32.84 C Pocket Axial 183 183OSA 215 215ISA -47.00 -32.84 C Pocket Axial 184 184ORA 216 216IRA -48.00 -32.84 C Stiffener Axial 185 185OWA 217 217IWA 50.27 -18.00 C Weld Axial 186 186OWA 218 218IWA 50.27 2.00 C Weld Axial 187 187ORA 219 219IRA 48.00 2.00 C Stiffener Axial 188 188OSA 220 220ISA 47.00 2.00 C Pocket Axial 189 189OSA 221 221ISA 26.00 2.00 C Pocket Axial 190 190OSA 222 222ISA 2.00 2.00 C Pocket Axial 191 191ORA 223 223IRA 0.00 2.00 C Stiffener Axial 
59 

Table A2. Concluded 

OML 

GAGE 

NUMBER 

OML 

GAGE 

ID 

IML GAGE 

NUMBER 

IML GAGE 

ID 

HOOP DIMENSION, (in.) 

AXIAL DIMENSION, (in.) 

PANEL LOCATION ORIENTAT

192 192ORA 224 224IRA -24.00 2.00 C Stiffener Axial 193 193OSA 225 225ISA -26.00 2.00 C Pocket Axial 194 194OSA 226 226ISA -47.00 2.00 C Pocket Axial 195 195ORA 227 227IRA -48.00 2.00 C Stiffener Axial 196 196OWA 228 228IWA 50.27 18.00 C Weld Axial 197 197OWA 229 229IWA 50.27 32.84 C Weld Axial 198 198ORA 230 230IRA 48.00 32.84 C Stiffener Axial199 199OSA 231 231ISA 47.00 32.84 C Pocket Axial 200 200OSA 232 232ISA 26.00 32.84 C Pocket Axial 201 201OSA 233 233ISA 2.00 32.84 C Pocket Axial 202 202ORA 234 234IRA 0.00 32.84 C Stiffener Axial203 203ORA 235 235IRA -24.00 32.84 C Stiffener Axial204 204OSA 236 236ISA -26.00 32.84 C Pocket Axial 205 205OSA 237 237ISA -47.00 32.84 C Pocket Axial 206 206ORA 238 238IRA -48.00 32.84 C Stiffener Axial
60 

Table A3. Data Files to Generate X-Y Plots of Axial Membrane Strain Distribution Around the Test Article C

Figures 4.27–4.30) 

STAGS 

Load Step 

P/Pcr(2) Test Tag 

Scan No. 

Axial 

Location, in. 

STAGS Nonlinear Analysis(1) Test 

9 0.440 4257 -32.84 TA01_LS5_STAGS_Load_Step_09_-32.84.dat TA01_LS5_Test_membrane_Step_

 -18.00 TA01_LS5_STAGS_Load_Step_09_-18.00.dat TA01_LS5_Test_membrane_Step_ 2.00 TA01_LS5_STAGS_Load_Step_09_+02.00.dat TA01_LS5_Test_membrane_Step_ 18.00 TA01_LS5_STAGS_Load_Step_09_+18.00.dat TA01_LS5_Test_membrane_Step_ 32.84 TA01_LS5_STAGS_Load_Step_09_+32.84.dat TA01_LS5_Test_membrane_Step_

10 0.550 4609 -32.84 TA01_LS5_STAGS_Load_Step_10_-32.84.dat TA01_LS5_Test_membrane_Step_

 -18.00 TA01_LS5_STAGS_Load_Step_10_-18.00.dat TA01_LS5_Test_membrane_Step_ 2.00 TA01_LS5_STAGS_Load_Step_10_+02.00.dat TA01_LS5_Test_membrane_Step_ 18.00 TA01_LS5_STAGS_Load_Step_10_+18.00.dat TA01_LS5_Test_membrane_Step_ 32.84 TA01_LS5_STAGS_Load_Step_10_+32.84.dat TA01_LS5_Test_membrane_Step_

15 0.799 6308 -32.84 TA01_LS5_STAGS_Load_Step_15_-32.84.dat TA01_LS5_Test_membrane_Step_

 -18.00 TA01_LS5_STAGS_Load_Step_15_-18.00.dat TA01_LS5_Test_membrane_Step_ 2.00 TA01_LS5_STAGS_Load_Step_15_+02.00.dat TA01_LS5_Test_membrane_Step_ 18.00 TA01_LS5_STAGS_Load_Step_15_+18.00.dat TA01_LS5_Test_membrane_Step_ 32.84 TA01_LS5_STAGS_Load_Step_15_+32.84.dat TA01_LS5_Test_membrane_Step_

18 0.853(3) 6537(4) -32.84 TA01_LS5_STAGS_Load_Step_18_-32.84.dat TA01_LS5_Test_membrane_Step_

 -18.00 TA01_LS5_STAGS_Load_Step_18_-18.00.dat TA01_LS5_Test_membrane_Step_

 2.00 TA01_LS5_STAGS_Load_Step_18_+02.00.dat TA01_LS5_Test_membrane_Step_ 18.00 TA01_LS5_STAGS_Load_Step_18_+18.00.dat TA01_LS5_Test_membrane_Step_ 32.84 TA01_LS5_STAGS_Load_Step_18_+32.84.dat TA01_LS5_Test_membrane_Step_

N/A 0.948(5) 6831 -32.84 N/A TA01_LS5_Test_membrane_Step_

 -18.00 N/A TA01_LS5_Test_membrane_Step_ 2.00 N/A TA01_LS5_Test_membrane_Step_ 18.00 N/A TA01_LS5_Test_membrane_Step_ 32.84 N/A TA01_LS5_Test_membrane_Step_

(1) Tecplot format. 

(2) Pcr = 726,800-lb. 

(3) Predicted limit load from STAGS nonlinear analysis. 

(4) Test data tag scan corresponding to predicted limit load. 
61 

(5) Measured limit load from test. 

Table A.4. Files Used to Generate Color Contour Plots (Tecplot Format) 

Test Article 1 STAGS 

Load 

Step 

DIC Photo 

Number 

From Test 

Tagged Scan 

Number 

From Test 

P/Pcr(1) STAGS Data File (for contour plots) DIC Dat

c

Load Sequence 5 6 663 SBKF-

22 3202 SBKF-

2 47 3452 0.1104 TA01_LS5_STAGS_Nonlinear_Load_Step_02.dat SBKF-6 70 3686 0.2202 TA01_LS5_STAGS_Nonlinear_Load_Step_06.dat SBKF-8 93 3919 0.3301 TA01_LS5_STAGS_Nonlinear_Load_Step08.dat SBKF-9 127 4257 0.4397 TA01_LS5_STAGS_Nonlinear_Load_Step09.dat SBKF-

10 163 4609 0.5500 TA01_LS5_STAGS_Nonlinear_Load_Step10.dat SBKF-11 184 4823 0.6048 TA01_LS5_STAGS_Nonlinear_Load_Step11.dat SBKF-

258 SBKF-

12 271 5698 0.6597 TA01_LS5_STAGS_Nonlinear_Load_Step12.dat SBKF-13 289 5871 0.6994 TA01_LS5_STAGS_Nonlinear_Load_Step13.dat SBKF-14 310 6088 0.7494 TA01_LS5_STAGS_Nonlinear_Load_Step14.dat SBKF-15 332 6308 0.7993 TA01_LS5_STAGS_Nonlinear_Load_Step15.dat SBKF-

365 6632 0.8992 SBKF-377 SBKF-378 6831 0.9483 SBKF-384 6940 0.4018 SBKF-395 SBKF-550 9809 0.3462 SBKF-

725 10238 -0.0009 SBKF-741 10663 0.0476 SBKF-798 10891 0.0536 SBKF-

(1) Pcr = 726,800-lb. 
REPORT DOCUMENTATION PAGE Form Approved

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Technical Publication

4. TITLE AND SUBTITLE

Buckling Test Results from the 8-Foot-Diameter Orthogrid-Stiffened 

Cylinder Test Article TA01

Test Dates: 19?21 November 2008

5a. CONTRACT NUMBER

6. AUTHOR(S)

Hilburger, Mark W.; Waters, W. Allen, Jr.; Haynie, Waddy T.

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

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Results from the testing of cylinder test article SBKF-P2-CYL-TA01 (referred to herein as TA01) are presented. TA01 is an

8-foot-diameter (96-inches), 78.0-inch-long, aluminum-lithium (Al-Li), orthogrid-stiffened cylindrical shell similar to those 

used in current state-of-the-art launch-vehicle structures and was designed to exhibit global buckling when subjected to 

compression loads. The testing was conducted at the Marshall Space Flight Center (MSFC), November 19-21, 2008, in 

support of the Shell Buckling Knockdown Factor (SBKF) Project. The test was used to verify the performance of a newly 

constructed buckling test facility at MSFC and to verify the test article design and analysis approach used by the SBKF project 

researchers. 

15. SUBJECT TERMS

Orthogrid, Cylinder, Buckling, Testing, Design, Knockdown Factors

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