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  • 1
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    High-performance equation solvers and their impact on finite element analysis (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The role of equation solvers in modern structural analysis software is described. Direct and iterative equation solvers which exploit vectorization on modern high-performance computer systems are described and compared. The direct solvers are two Cholesky factorization methods. The first method utilizes a novel variable-band data storage format to achieve very high computation rates and the second method uses a sparse data storage format designed to reduce the number od operations. The iterative solvers are preconditioned conjugate gradient methods. Two different preconditioners are included; the first uses a diagonal matrix storage scheme to achieve high computation rates and the second requires a sparse data storage scheme and converges to the solution in fewer iterations that the first. The impact of using all of the equation solvers in a common structural analysis software system is demonstrated by solving several representative structural analysis problems.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 33; 855-868
    Format: text
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  • 2
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    Structural behavior of the space shuttle SRM tang-clevis joint (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The space shuttle Challenger accident investigation focused on the failure of a tang-clevis joint on the right solid rocket motor. The existence of relative motion between the inner arm of the clevis and the O-ring sealing surface on the tang has been identified as a potential contributor to this failure. This motion can cause the O-rings to become unseated and therefore lose their sealing capability. Finite element structural analyses have been performed to predict both deflections and stresses in the joint under the primary, pressure loading condition. These analyses have demonstrated the difficulty of accurately predicting the structural behavior of the tang-clevis joint. Stresses in the vicinity of the connecting pins, obtained from elastic analyses, considerably exceed the material yield allowables indicating that inelastic analyses are probably necessary. Two modifications have been proposed to control the relative motion between the inner clevis arm and the tang at the O-ring sealing surface. One modification, referred to as the capture feature, uses additional material on the inside of the tang to restrict motion of the inner clevis arm. The other modification uses external stiffening rings above and below the joint to control the local bending in the shell near the joint. Both of these modifications are shown to be effective in controlling the relative motion in the joint.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 4; 317-327
    Format: text
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  • 3
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    Postbuckling behavior of selected curved stiffened graphite-epoxy panels loaded in axial compression (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 26; 344-352
    Format: text
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  • 4
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    Error analysis and correction of discrete solutions from finite-element codes (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal (ISSN 0001-1452); 26; 446-453
    Format: text
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  • 5
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    CSM research: Methods and application studies (1989)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Computational mechanics is that discipline of applied science and engineering devoted to the study of physical phenomena by means of computational methods based on mathematical modeling and simulation, utilizing digital computers. The discipline combines theoretical and applied mechanics, approximation theory, numerical analysis, and computer science. Computational mechanics has had a major impact on engineering analysis and design. When applied to structural mechanics, the discipline is referred to herein as computational structural mechanics. Complex structures being considered by NASA for the 1990's include composite primary aircraft structures and the space station. These structures will be much more difficult to analyze than today's structures and necessitate a major upgrade in computerized structural analysis technology. NASA has initiated a research activity in structural analysis called Computational Structural Mechanics (CSM). The broad objective of the CSM activity is to develop advanced structural analysis technology that will exploit modern and emerging computers, such as those with vector and/or parallel processing capabilities. Here, the current research directions for the Methods and Application Studies Team of the Langley CSM activity are described.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA Workshop on Computational Structural Mechanics 1987, Part 2; p 521-570
    Format: application/pdf
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  • 6
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    Nonlinear response of a blade-stiffened graphite-epoxy panel with a discontinuous stiffener: Work in progress (1989)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The problem of calculating detailed stress distributions around discontinuities in buckled, composite structural components for use with the various analytical failure prediction techniques has not been thoroughly explored. The purpose here is the application of computational methods to the detailed stress analysis problem which is the focus of this session of the workshop. One approach to uncovering the difficulties of this type of analysis and to providing specific directions for future research in this area is a direct attack on the problem using currently available analysis tools. A candidate problem has been selected and experiences from calculating its structural response are described.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computational Methods for Structural Mechanics and Dynamics, Part 1; p 51-65
    Format: application/pdf
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  • 7
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    Improved assumed-stress hybrid shell element with drilling degrees of freedom for linear stress, buckling, and free vibration analyses (1992)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: An improved four-node quadrilateral assumed-stress hybrid shell element with drilling degrees of freedom is presented. The formulation is based on Hellinger-Reissner variational principle and the shape functions are formulated directly for the four-node element. The element has 12 membrane degrees of freedom and 12 bending degrees of freedom. It has nine independent stress parameters to describe the membrane stress resultant field and 13 independent stress parameters to describe the moment and transverse shear stress resultant field. The formulation encompasses linear stress, linear buckling, and linear free vibration problems. The element is validated with standard tests cases and is shown to be robust. Numerical results are presented for linear stress, buckling, and free vibration analyses.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-192816 , NAS 1.26:192816
    Format: application/pdf
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  • 8
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    Nonlinear structural response using adaptive dynamic relaxation on a massively-parallel-processing system (1994)
    In:  CASI
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    Publikationsdatum: 2019-06-28
    Beschreibung: A parallel adaptive dynamic relaxation (ADR) algorithm has been developed for nonlinear structural analysis. This algorithm has minimal memory requirements, is easily parallelizable and scalable to many processors, and is generally very reliable and efficient for highly nonlinear problems. Performance evaluations on single-processor computers have shown that the ADR algorithm is reliable and highly vectorizable, and that it is competitive with direct solution methods for the highly nonlinear problems considered. The present algorithm is implemented on the 512-processor Intel Touchstone DELTA system at Caltech, and it is designed to minimize the extent and frequency of interprocessor communication. The algorithm has been used to solve for the nonlinear static response of two and three dimensional hyperelastic systems involving contact. Impressive relative speedups have been achieved and demonstrate the high scalability of the ADR algorithm. For the class of problems addressed, the ADR algorithm represents a very promising approach for parallel-vector processing.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-196491 , NAS 1.26:196491
    Format: application/pdf
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  • 9
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    Comparison of symbolic and numerical integration methods for an assumed-stress hybrid shell element (1993)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Hybrid shell elements have long been regarded with reserve by the commercial finite element developers despite the high degree of reliability and accuracy associated with such formulations. The fundamental reason is the inherent higher computational cost of the hybrid approach as compared to the displacement-based formulations. However, a noteworthy factor in favor of hybrid elements is that numerical integration to generate element matrices can be entirely avoided by the use of symbolic integration. In this paper, the use of the symbolic computational approach is presented for an assumed-stress hybrid shell element with drilling degrees of freedom and the significant time savings achieved is demonstrated through an example.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-CR-195945 , NAS 1.26:195945
    Format: application/pdf
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  • 10
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    Computational methods for global/local analysis (1992)
    In:  CASI
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    Publikationsdatum: 2019-06-28
    Beschreibung: Computational methods for global/local analysis of structures which include both uncoupled and coupled methods are described. In addition, global/local analysis methodology for automatic refinement of incompatible global and local finite element models is developed. Representative structural analysis problems are presented to demonstrate the global/local analysis methods.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: NASA-TM-107591 , NAS 1.15:107591
    Format: application/pdf
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