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  • 1
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    Technology integration box beam failure study (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The objective of this paper is to describe current results from an on-going study of the mechanisms that led to the failure of the TIBB. Experimental and analytical results are presented. Experimental results include load, strain, and deflection data for the TIBB (Technology Integration Box Beam). An analytical investigation was conducted to compliment the experimental investigation and to gain additional insight into the TIBB structural response. Analytical results include strain and deflection results from a global analysis of the TIBB. A local analysis of the failure region is being completed. These analytical results are validated through comparisons with the experimental results from the TIBB tests. The experimental and analytical results from the TIBB tests are used to determine a sequence of events that may have resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Typical analytical results are presented for a stiffener runout specimen that is being defined to simulate the TIBB failure mechanisms. The results of this study are anticipated to provide better understanding of potential failure mechanisms in composite aircraft structures, to lead to future design improvements, and to identify needed analytical tools for design and analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: FAA, Ninth DOD(NASA)FAA Conference on Fibrous Composites in Structural Design, Volume 2; p 673-68
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Technology integration box beam failure study (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Composite structures have the potential to be cost-effective, structurally efficient primary aircraft structures. The Advanced Composites Technology (ACT) Program has the goal to develop the technology to exploit this potential for heavily loaded aircraft structures. As part of the ACT Program, Lockheed Aeronautical Systems Company completed the design and fabrication of the Technology Integration Box Beam (TIBB). The TIBB is an advanced composite prototype structure for the center wing section of the C-130 aircraft. Lockheed subjected the TIBB to downbending, upbending, torsion and combined upbending and torsion load conditions to verify the design. The TIBB failed at 83 percent of design ultimate load for the combined upbending and torsion load condition. The objective of this paper is to describe the mechanisms that led to the failure of the TIBB. The results of a comprehensive analytical and experimental study are presented. Analytical results include strain and deflection results from both a global analysis of the TIBB and a local analysis of the failure region. These analytical results are validated by experimental results from the TIBB tests. The analytical and experimental results from the TIBB tests are used to determine a sequence of events that resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Analytical and experimental results are also presented for a stiffener runout specimen that was used to simulate the TIBB failure mechanisms.
    Keywords: STRUCTURAL MECHANICS
    Type: Third NASA Advanced Composites Technology Conference, Volume 1, Part 2; p 951-965
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Fatigue failure load indicator (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test is described. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time the specimen is subjected to a compression load, means are provided for applying a positive voltage to the rest of the peak detector to reset it. During the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are provided for disconnecting the load cell from the peak detector when there is a failure in the specimen.
    Keywords: STRUCTURAL MECHANICS
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Consumption-based pollution accounting [Physical Sciences] (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-07-02
    Description: In their letter (1), López et al. propose “control-based” accounting of air pollution that assigns pollution to countries according to the nationality of corporations producing the pollution. For example, pollution produced in China by US corporations would be assigned to the United States regardless of where the related goods are...
    Keywords: Letters, Sustainability Science
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
  • 5
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    An accurate nonlinear finite element analysis and test correlation of a stiffened composite wing panel (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: State-of-the-art nonlinear finite element analysis techniques are evaluated by applying them to a realistic aircraft structural component. A wing panel from the V-22 tiltrotor aircraft is chosen because it is a typical modern aircraft structural component for which there is experimental data for comparison of results. From blueprints and drawings, a very detailed finite element model containing 2284 9-node Assumed Natural-Coordinate Strain elements was generated. A novel solution strategy which accounts for geometric nonlinearity through the use of corotating element reference frames and nonlinear strain-displacement relations is used to analyze this detailed model. Results from linear analyses using the same finite element model are presented in order to illustrate the advantages and costs of the nonlinear analysis as compared with the more traditional linear analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: In: AHS National Technical Specialists' Meeting on Rotorcraft Structures, Williamsburg, VA, Oct. 29-31, 1991, Proceedings (A93-27951 10-05); 15 p.
    Format: text
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  • 6
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    High-performance equation solvers and their impact on finite element analysis (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: 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.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 33; 855-868
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    The spacecraft communications repeater (1963)
    In:  CASI
    Details
    Publication Date: 2006-10-26
    Description: Microwave communications repeater of telstar
    Keywords: STRUCTURAL MECHANICS
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Perturbation solution of a hyperbolic equation governing longitudinal wave propagation in certain nonuniform bars (1970)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Longitudinal wave propagation in variable section bars, solving hyperbolic equation of motion by perturbation method
    Keywords: STRUCTURAL MECHANICS
    Type: ; YAL SOCIETY (
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Interactive design of large end rings on stiffened conical shells using composites (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Design study methods and results for a composite reinforced base ring for the conical aeroshell structure of the planetary lander vehicle for Project Viking, an unmanned mission to Mars, are presented. The aeroshell is a ring and stringer-stiffened conical shell structure having a half angle of 70 degrees with a large base ring mounted at the outer edge of the cone and a large pay-load ring in the interior with many smaller rings spaced along the inside shell surface. The purpose of the structure is to develop the aerodynamic drag required to decelerate the lander in the Mars atmosphere to facilitiate a soft landing. The design of a shell structure of this complexity requires the use of the latest technology available in a large general-purpose shell buckling program. The large general-purpose non-linear shell buckling program (BOSOR 2) which was used for this purpose is described.
    Keywords: STRUCTURAL MECHANICS
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Experiences in porting NASTRAN (R) to non-traditional platforms (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The 1990 UNIX version of NASTRAN was ported to two new platforms that are not supported by COSMIC: the Sun SPARC workstation and the Apple Macintosh using the A/UX version of UNIX. The experiences of the authers in porting NASTRAN is summarized here. Suggestions for users who might attempt similar ports are given.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Software Management and Information Center, Nineteenth NASTRAN (R) Users' Colloquium; p 14-21
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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