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  • STRUCTURAL MECHANICS  (41)
  • 2015-2019
  • 1975-1979  (41)
  • 1950-1954
  • 1930-1934
  • 1925-1929
  • 1976  (41)
  • 1
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    Implementation on a nonlinear concrete cracking algorithm in NASTRAN (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A computer code for the analysis of reinforced concrete structures was developed using NASTRAN as a basis. Nonlinear iteration procedures were developed for obtaining solutions with a wide variety of loading sequences. A direct access file system was used to save results at each load step to restart within the solution module for further analysis. A multi-nested looping capability was implemented to control the iterations and change the loads. The basis for the analysis is a set of mutli-layer plate elements which allow local definition of materials and cracking properties.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 479-494
    Format: application/pdf
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  • 2
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    A study of the effect of subcritical crack growth on the geometry dependence on nonlinear fracture toughness parameters (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The effect of subcritical crack growth on the geometry dependence of nonlinear fracture toughness parameters was studied by comparing the toughness values for different specimen geometries at the onset of subcritical crack growth and at the initiation of unstable crack propagation. Center-cracked thin sheet specimens of 2024-T3 and 7075-T6 aluminum alloys were tested by varying the specimen length L, width w, and crack length-to-width ratio c/w. When the onset of unstable crack propagation was selected as the critical point, the nonlinear energy toughness and the R curve toughness increased with increasing w and decreasing L and c/w. However, when the onset of subcritical crack growth was taken as the critical point, energy toughness and the linear toughness values were independent of these geometrical variables.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 257-266
    Format: text
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  • 3
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    Lattice theory of three-dimensional cracks (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The problem of the stability of a three-dimensional crack is analyzed within a lattice-statics approximation. The consequence of introducing a jog into the crack face as well as the effects of various nonlinear-force laws are studied. The phenomenon of lattice trapping (upper and lower bounds on the applied stress for an equilibrium crack of given length) is again obtained. It is possible to obtain some physical insight into which aspects of the force law are critical for crack stability. In particular, the inadequacy of a thermodynamic approach - which relates the critical stress to a surface energy corresponding to the area under the cohesive-force-vs-displacement curve - is demonstrated. Surface energy is a global property of the cohesive-force law. Crack stability is sensitive to much more refined aspects of the cohesive-force law. Crack healing is sensitive to the long-range portion of the cohesive force. Crack expansion is sensitive to the position of the maximum in the cohesive-force relation.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Applied Physics; 47; Feb. 197
    Format: text
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  • 4
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    Automated fully-stressed design with NASTRAN (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An automated strength sizing capability is described. The technique determines the distribution of material among the elements of a structural model. The sizing is based on either a fully stressed design or a scaled feasible fully stressed design. Results obtained from the application of the strength sizing to the structural sizing of a composite material wing box using material strength allowables are presented. These results demonstrate the rapid convergence of the structural sizes to a usable design.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 53-66
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  • 5
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    NASA's plans for future NASTRAN capability (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Improvements in the NASTRAN systems management office are presented. Among the improvements are the following items: (1) the FEER eigenmethod and its extension to complete eigenvalue problems; (2) the addition of a supersonic flutter package which allows gust response calculations and active control effects as membrane In addition to capabilities mentioned, an error correction information system is also introduced.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 1-2
    Format: application/pdf
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  • 6
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    Simulation of the atmospheric boundary layer in the wind tunnel for modeling of wind loads on low-rise structures (1976)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: The lower part of the atmospheric boundary layer (strong wind conditions) was simulated in low speed wind tunnel for the modeling of wind loads on low-rise structures. The turbulence characteristics of the turbulent boundary layer in the wind tunnel are compared with full scale measurements and with measurements made at NASA Wallops Flight Center. Wind pressures measured on roofs of a 1:70 scale model of a small single family dwelling were compared with results obtained from full scale measurements. The results indicate a favorable comparison between full scale and model pressure data as far as mean, r.m.s. and peak pressures are concerned. In addition, results also indicate that proper modeling of the turbulence is essential for proper simulation of the wind pressures.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 3; p 1167-1176
    Format: text
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  • 7
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    Sound radiation from randomly vibrating beams of finite circular cross section (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The radiation of sound from vibrating cylindrical beams is analyzed based on the frequency of the beam vibrations and the physical characteristics of the beam and its surroundings. A statistical analysis of random beam vibrations allows this result to be independent of the boundary conditions at the ends of the beam. The acoustic power radiated by the beam can be determined from a knowledge of the frequency band vibration data without a knowledge of the individual modal vibration amplitudes. A practical example of the usefulness of this technique is provided by the application of the theoretical calculations to the prediction of the octave band acoustic power output of the picking sticks of an automatic textile loom. Calculations are made of the expected octave band sound pressure levels based on measured acceleration data. These theoretical levels are subsequently compared with actual sound pressure level measurements of loom noise.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 3; p 1071-1081
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  • 8
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    The prediction and measurement of sound radiated by structures (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Theories regarding the radiation of sound are reviewed and the implementation in strategies for explaining or measuring the sound produced by practical strucutres are discussed. Particular attention is given to those aspects that relate to the determination of the relative amounts of sound generated by various parts of a machine or structure, which can be very useful information for noise reduction efforts.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 3; p 1031-1042
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  • 9
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    Fluid-plasticity of thin cylindrical shells (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Dynamic plastic response of a thin cylindrical shell, immersed in a potential fluid initially at rest and subjected to internal pressure pulse of arbitrary shape and duration, is examined. The shell is assumed to respond as a rigid-perfectly plastic material while the fluid is taken as inviscid and incompressible. The fluid back pressure is incorporated into the equation of motion of the shell as an added mass term. Since arbitrary pulses can be reduced to equivalent rectangular pulses, the equation of motion is solved only for a rectangular pulse. The influence of the fluid in reducing the final plastic deformation is demonstrated by a numerical example.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 2; p 627-637
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  • 10
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    Finite element solutions for crack-tip behavior in small-scale yielding (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The subject considered is the stress and deformation fields in a cracked elastic-plastic power law hardening material under plane strain tensile loading. An incremental plasticity finite element formulation is developed for accurate analysis of the complete field problem including the extensively deformed near tip region, the elastic-plastic region, and the remote elastic region. The formulation has general applicability and was used to solve the small scale yielding problem for a set of material hardening exponents. Distributions of stress, strain, and crack opening displacement at the crack tip and through the elastic-plastic zone are presented as a function of the elastic stress intensity factor and material properties.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 76-MAT-O
    Format: text
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