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  • GEOPHYSICS  (53)
  • STRUCTURAL MECHANICS  (26)
  • 2005-2009
  • 1990-1994  (40)
  • 1965-1969  (39)
  • 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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  • 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
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  • 3
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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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  • 4
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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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  • 5
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    Rocket measurements of midlatitude Sq currents (1966)
    In:  CASI
    Details
    Publication Date: 2006-10-26
    Description: Nike-Apache rocket ionospheric current measurements using rubidium-vapor magnetometer
    Keywords: GEOPHYSICS
    Format: text
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  • 6
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    A compressed marine data set for geomagnetic field modeling (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Some 13 million scalar magnetic field data points that have been collected from the world's ocean areas reside in the collection of the National Geophysical Data Center. In order to derive a suitable data set for modeling the geomagnetic field of the earth, each ship track is divided into 220 km segments. The distribution of the reduced data in position, time and local time is discussed. The along-track filtering process described has proved to be an effective method of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for field modeling. This process also provides the benefits of smoothing short-wavelength crystal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be utilized in the least squares modeling.
    Keywords: GEOPHYSICS
    Type: Journal of Geomagnetism and Geoelectricity (ISSN 0022-1392); 42; 9, 19
    Format: text
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  • 7
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    A latitude survey of the equatorial electrojet with rocket-borne magnetometers. (1967)
    In:  Other Sources
    Details
    Publication Date: 2011-08-11
    Description: Latitudinal cross section of ionospheric current density profile of equatorial electrojet from rocketborne magnetometers
    Keywords: GEOPHYSICS
    Type: JOURNAL OF GEOPHYSICAL RESEARCH
    Format: text
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  • 8
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    Electrons in the Van Allen zone measured with a scintillator on Explorer 14. (1966)
    In:  Other Sources
    Details
    Publication Date: 2011-08-11
    Description: Electron energy spectrum measured near equator by satellite mounted scintillator
    Keywords: GEOPHYSICS
    Type: JOURNAL OF GEOPHYSICAL RESEARCH
    Format: text
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  • 9
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    Rocket measurements of S sub q currents at midlatitude. (1965)
    In:  Other Sources
    Details
    Publication Date: 2011-08-11
    Description: Midlatitude ionospheric currents detected by rocketborne rubidium vapor magnetometers in Nike- Apache rockets
    Keywords: GEOPHYSICS
    Format: text
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  • 10
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    Constraining proposed combinations of ice history and Earth rheology using VLBI determined baseline length rates in North America (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: We predict the present-day rates of change of the lengths of 19 North American baselines due to the glacial isostatic adjustment process. Contrary to previously published research, we find that the three dimensional motion of each of the sites defining a baseline, rather than only the radial motions of these sites, needs to be considered to obtain an accurate estimate of the rate of change of the baseline length. Predictions are generated using a suite of Earth models and late Pleistocene ice histories, these include specific combinations of the two which have been proposed in the literature as satisfying a variety of rebound related geophysical observations from the North American region. A number of these published models are shown to predict rates which differ significantly from the VLBI observations.
    Keywords: GEOPHYSICS
    Type: Smithsonian Astrophysical Observatory, Measurement and Interpretation of Crustal Deformation Rates Associated with Postglacial Rebound; 4 p
    Format: application/pdf
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