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  • Other Sources  (45)
  • STRUCTURAL MECHANICS  (45)
  • 1970-1974  (45)
  • 1965-1969
  • 1950-1954
  • 1935-1939
  • 1972  (45)
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  • Other Sources  (45)
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  • 1970-1974  (45)
  • 1965-1969
  • 1950-1954
  • 1935-1939
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  • 1
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    A non-linear dynamic lumped-parameter model of a rectangular plate. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A lumped-parameter model of a rectangular plate is developed by assuming fundamental mode solutions and using Hamilton's Principle and the Euler equations to set up the differential equation of motion for the system. The plate theory used may be described as the dynamic analogue of the von Karman large-deflection theory. Four sets of symmetrical boundary conditions are considered with the restriction of uniform pressure dynamic loads. The model takes the form of a mass on a cubic-hardening spring with each term defined by algebraic expressions of the plate parameters. The results for some specific problems are compared with two previous solutions. This method is less accurate but simpler to develop and apply.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 21; Apr. 8
    Format: text
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  • 2
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    A comparison of the capabilities of three finite element programs (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Three finite element programs are compared to assess their capabilities as an analysis tool in a structural design process. Because of the need for repetitive analyses as an integral part of a design loop, a candidate program must be capable of handling large problems, operate efficiently, and be readily adaptable for use in computer-aided design. The three programs considered in the study, ELAS,SNAP, and NASTRAN, range from a relatively small finite element program limited to static structural analysis (ELAS) to a large complex general analysis system (NASTRAN). Results are given for comparative speeds and computer resources required for each program in the analysis of sample fuselage problems representative of practical aircraft design.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 277-287
    Format: application/pdf
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  • 3
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    Experiences in interfacing NASTRAN with another finite element program (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The coupling of NASTRAN to another finite element program developed for the static analysis of automotive structures is discussed. The two programs were coupled together to use the substructuring capability of the in-house program and the normal mode analysis capability of NASTRAN. Modifications were made to the NASTRAN program in order to make the coupling feasible.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 111-119
    Format: application/pdf
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  • 4
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    Coupling between structure and liquids in a parallel stage space shuttle design (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study was conducted to determine the influence of liquid propellants on the dynamic loads for space shuttle vehicles. A parallel-stage configuration model was designed and tested to determine the influence of liquid propellants on coupled natural modes. A forty degree-of-freedom analytical model was also developed for predicting these modes. Currently available analytical models were used to represent the liquid contributions, even though coupled longitudinal and lateral motions are present in such a complex structure. Agreement between the results was found in the lower few modes.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-127631 , AIAA PAPER 72-347-REV
    Format: application/pdf
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  • 5
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    Multimaterial lamination as a means of retarding penetration and spallation failures in plates (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experimental data are presented which show that hypervelocity impact spallation and penetration failures of a single solid aluminum plate and of a solid aluminum plate spaced a distance behind a Whipple meteor bumper may be retarded by replacing the solid aluminum plate with a laminated plate. Four sets of experiments were conducted. The first set of experiments was conducted with projectile mass and velocity held constant and with polycarbonate cylinders impacted into single plates of different construction. The second set of experiments was done with single plates of various construction and aluminum spherical projectiles of similar mass but different velocities. These two experiments showed that a laminated plate of aluminum and polycarbonate or aluminum and methyl methacrylate could prevent spallation and penetration failures with a lower areal density than either an all-aluminum laminated plate or a solid aluminum plate. The aluminum laminated plate was in turn superior to the solid aluminum plate in resisting spallation and penetration failures. In addition, through an example of 6061-T6 aluminum and methyl methacrylate, it is shown that a laminated structure ballistically superior to its parent materials may be built. The last two sets of experiments were conducted using bumper-protected main walls of solid aluminum and of laminated aluminum and polycarbonate. Again, under hypervelocity impact conditions, the laminated main walls were superior to the solid aluminum main walls in retarding spallation and penetration failures.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-6989 , L-8444
    Format: application/pdf
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  • 6
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    Fatigue flaw growth and NDI evaluation for preventing through cracks in spacecraft tankage structures (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A program was conducted to determine the fatigue-crack propagation behavior of parent and welded 2219-T87 aluminum alloy sheet under controlled cyclic stress conditions in room temperature air and 300 F air. Specimens possessing an initial surface defect of controlled dimensions were cycled under constant load amplitude until the propagating fatigue crack penetrated the back surface of the specimen. A series of precracked specimens were prepared to determine optimum penetrant, X-ray, ultrasonic, and eddy current nondestructive inspection procedures.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-128600 , LR-25387
    Format: application/pdf
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  • 7
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    Lumped parameter analysis of a stringer reinforced plate excited by band limited noise (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The maximum root-mean-square response of a square clamped plate, subjected to a stationary random excitation, was determined both theoretically and empirically. For the tests, a 40 x 40 x 1/4 aluminum sheet was milled out to provide a thin waffle plate with 9 panels. The plate was acoustically excited, with the frequency range limited between 25 Hz and 500 Hz. The root-mean-square power of the random excitations, 149 decibels, was nearly constant for all natural frequencies of the plate system. Strain gage readings at 14 points were plotted as power spectral densities and root-mean-square displacements. A modal damping ratio matrix was determined from the response curves. Damping ratios were found to be a function of frequency, but not of location on the plate. For comparisons with the theoretical response, the plate was subdivided into 14 modes and anlayzed as a damped, lumped parameter system by use of an approximate normal-mode method. This method gave the best predictions of the power spectral densities for the lower frequencies. That prediction errors increased for the higher frequencies is attributed to improper assumptions for mass distribution and the insufficient number of lumped mass points.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-129301
    Format: application/pdf
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  • 8
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    Strongly coupled stress waves in heterogeneous plates. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Consideration of coupled stress waves generated by an impulsive load applied at one end of a semiinfinite plate. For the field equations governing the one-dimensional coupled waves a hyperbolic system of equations is obtained in which a strong coupling in the second derivatives exists. The method of characteristics described by Chou and Mortimer (1967) is extended to cover the case of strong coupling, and a study is made of the transient stress waves in a semiinfinite plate subjected to an initial step input. Coupled discontinuity fronts are found to propagate at different velocities. The normal plate stress and the bending moment at different time regimes are illustrated by graphs.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 10; Aug. 197
    Format: text
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  • 9
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    Vibrations of circular elastic plates due to sonic boom. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The problem of transient axisymmetric vibrations of thin circular elastic plates due to sonic boom excitation is investigated. The equation of motion for a solid circular plate is solved by applying the modified finite Hankel transform and the Laplace transform, and the numerical results are obtained with the help of the digital computer. From the analysis of the data, obtained for the dynamic deflections of the plates for the boom duration, it is concluded that for a normal flight the boom duration has a significant effect on the vibrations of plates as compared to the overpressure of the boom.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America; vol. 52
    Format: text
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  • 10
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    Some aspects of the NASTRAN program output (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The NASTRAN program output is discussed from a structural analysts point of view, and the simple modifications which were made to the program in order to improve it are also described. The convenience of the output for use in original design work is critically appraised and compared with the output from ASTRAL. It is shown that considerable hand calculation is necessary in order to extract useful load distribution data from the available NASTRAN output. For this reason, some effort was directed toward providing additional force output for the NASTRAN shear panel element.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 337-360
    Format: application/pdf
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