Axial-Weld Land Buckling in Compression-Loaded Orthogrid Cylinders

Thornburgh, Robert P.

doi:10.2514/1.49782

Cited by 8 publications

(3 citation statements)

References 1 publication

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“…(For a discussion of some of these joint issues for welded orthogrid metallic structures, see Ref. 7. )…”

Section: Sandwich Composite Jointsmentioning

confidence: 99%

Experimental Study of the Compression Response of Fluted-Core Composite Panels with Joints

Schultz¹,

Rose²,

Guzman³

et al. 2012

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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Fluted-core sandwich composites consist of integral angled web members spaced between laminate face sheets, and may have the potential to provide benefits over traditional sandwich composites for certain aerospace applications. However, fabrication of large autoclave-cured fluted-core cylindrical shells with existing autoclaves will require that the shells be fabricated in segments, and joined longitudinally to form a complete barrel. Two different longitudinal fluted-core joint designs were considered experimentally in this study. In particular, jointed fluted-core-composite panels were tested in longitudinal compression because longitudinal compression is the primary loading condition in dry launch-vehicle barrel sections. One of the joint designs performed well in comparison with unjointed test articles, and the other joint design failed at loads approximately 14% lower than unjointed test articles. The compression-after-impact (CAI) performance of jointed fluted-core composites was also investigated by testing test articles that had been subjected to 6 ft-lb impacts. It was found that such impacts reduced the load-carrying capability by 9% to 40%. This reduction is dependent on the joint concept, component flute size, and facesheet thickness.

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“…(For a discussion of some of these joint issues for welded orthogrid metallic structures, see Ref. 7. )…”

Section: Sandwich Composite Jointsmentioning
confidence: 99%

Experimental Study of the Compression Response of Fluted-Core Composite Panels with Joints
Schultz¹,
Rose²,
Guzman³
et al. 2012
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
0
0
0
0
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“…Second, test results were needed to validate finite-element model predictions of a local weld-land buckling phenomena that was identified in the preliminary design of Ares-1 tank structures. 9 To this end, an optimized design for a full-scale 18-ft-diameter orthogrid-stiffened tank-like structure was developed and then scaled down to an 8-ft-diameter test article configuration. The full-scale acreage design assumed an internal pressure load of 25 psi and uniform axial compression of approximately 6,800 lb/in.…”

Section: Preliminary Design and Analysismentioning
confidence: 99%

Design and Analysis of Subscale and Full-Scale Buckling-Critical Cylinders for Launch Vehicle Technology Development
Hilburger¹,
Lovejoy²,
Thornburgh³
et al. 2012
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
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NASA's Shell Buckling Knockdown Factor (SBKF) project has the goal of developing new analysis-based shell buckling design factors (knockdown factors) and design and analysis technologies for launch vehicle structures. Preliminary design studies indicate that implementation of these new knockdown factors can enable significant reductions in mass and mass-growth in these vehicles. However, in order to validate any new analysis-based design data or methods, a series of carefully designed and executed structural tests are required at both the subscale and full-scale levels. This paper describes the design and analysis of three different orthogrid-stiffened metallic cylindrical-shell test articles. Two of the test articles are 8-ft-diameter, 6-ft-long test articles, and one test article is a 27.5-ftdiameter, 20-ft-long Space Shuttle External Tank-derived test article. Introduction uckling is an important and often critical consideration in the design of lightweight launch-vehicle structures; therefore, robust, validated design criteria for thin-walled shells are needed to achieve optimal designs of these structures. Unfortunately, the current design guidelines 1-4 have not been updated since they were first published in the late 1960's and early 1970's, and may not be able to take full advantage of the modern materials, precision manufacturing processes, and new structural concepts needed to produce the next generation of affordable and efficient launch vehicles. To this end, a design technology development program at NASA, the Shell Buckling Knockdown Factor (SBKF) project, is currently working to revise the existing design factors and recommendations for buckling-critical shell structures. 5 To support the development and validation of these new design factors, the SBKF project is conducting a series of shell buckling tests on large-scale, integrally-stiffened aluminum cylinders. Currently, SBKF is targeting specific structural configurations including isogrid-stiffened and orthogrid-stiffened cylinders for large-diameter heavy-lift launch vehicles. These large metallic cylinders are typically constructed by welding several curved panel sections together along longitudinal weld lands to form a complete circular cylinder (Fig. 1). The validation testing requires that the test article designs and data obtained from the tests are representative of these types of large-scale launch vehicle cylinder structures, and that certain behavioral characteristics and failure modes shall be isolated and studied. For example, these types of integrally-stiffened, welded structures can exhibit several different failure modes including global buckling, local skin-pocket buckling (i.e., buckling of the thin skin between stiffeners), weld land buckling (buckling of the unstiffened welded joint regions), and stiffener buckling and crippling. NomenclatureOne of the challenges in the test program is to design each test article to exhibit a specific failure mode or sequence of failure modes. However, imperfection sensitivity in these buckl...

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“…The digital image correlation that was used for the tanking test was a commercial system which had previously been used to validate LS-DYNA models of foam impact on the Orbiter wing reinforced carbon-carbon panels during the Columbia Return to Flight program [3][4][5]. Three dimensional digital image correlation has been successfully used to capture motion in a wide range of research areas from material characterization tests [6][7][8][9] to structural tests [10][11][12], to biomechanics [13][14][15][16].…”

Section: Fig 1 Cracks In the Et Foam At The Lo2 Flange On Panel 2 Dumentioning
confidence: 99%

Photogrammetry Measurements During a Tanking Test on the Space Shuttle External Tank, ET-137
Littell
¹
,
Schmidt
²
,
Tyson
³

et al. 2012
Conference Proceedings of the Society for Experimental Mechanics Series
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On November 5, 2010, a significant foam liberation threat was observed as the Space Shuttle STS-133 launch effort was scrubbed because of a hydrogen leak at the ground umbilical carrier plate. Further investigation revealed the presence of multiple cracks at the tops of stringers in the intertank region of the Space Shuttle External Tank. As part of an instrumented tanking test conducted on December 17, 2010, a three dimensional digital image correlation photogrammetry system was used to measure radial deflections and overall deformations of a section of the intertank region. This paper will describe the experimental challenges that were overcome in order to implement the photogrammetry measurements for the tanking test in support of STS-133. The technique consisted of configuring and installing two pairs of custom stereo camera bars containing calibrated cameras on the 215-ft level of the fixed service structure of Launch Pad 39-A. The cameras were remotely operated from the Launch Control Center 3.5 miles away during the 8 hour duration test, which began before sunrise and lasted through sunset.The complete deformation time history was successfully computed from the acquired images and would prove to play a crucial role in the computer modeling validation efforts supporting the successful completion of the root cause analysis of the cracked stringer problem by the Space Shuttle Program. The resulting data generated included full field fringe plots, data extraction time history analysis, section line spatial analyses and differential stringer peak-valley motion. Some of the sample results are included with discussion. The resulting data showed that new stringer crack formation did not occur for the panel examined, and that large amounts of displacement in the external tank occurred because of the loads derived from its filling. The measurements acquired were also used to validate computer modeling efforts completed by NASA Marshall Space Flight Center (MSFC). Background

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Axial-Weld Land Buckling in Compression-Loaded Orthogrid Cylinders

Cited by 8 publications

References 1 publication

Experimental Study of the Compression Response of Fluted-Core Composite Panels with Joints

Experimental Study of the Compression Response of Fluted-Core Composite Panels with Joints

Design and Analysis of Subscale and Full-Scale Buckling-Critical Cylinders for Launch Vehicle Technology Development

Photogrammetry Measurements During a Tanking Test on the Space Shuttle External Tank, ET-137

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