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  • STRUCTURAL MECHANICS  (66)
  • SPACE VEHICLES
  • 1990-1994  (66)
  • 1970-1974
  • 1990  (66)
  • 1
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    Exponential approximations in optimal design (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: One-point and two-point exponential functions have been developed and proved to be very effective approximations of structural response. The exponential has been compared to the linear, reciprocal and quadratic fit methods. Four test problems in structural analysis have been selected. The use of such approximations is attractive in structural optimization to reduce the numbers of exact analyses which involve computationally expensive finite element analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Langley Research Center, Research in Structures, Structural Dynamics and Materials, 1990; p 137-150
    Format: application/pdf
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  • 2
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    Postbuckling of long thick plates in compression including higher order transverse shearing effects (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Aluminum plates of various length/width ratios loaded in compression are examined analytically in terms of buckling and postbuckling for comparison with classical theory. The plates are considered to be subjected to longitudinal compressive displacement with no edge stress and are assumed to be simply supported at the side edges. The average longitudinal direct stresses are computed to plot characteristic curves by means of the following theories: 3D flexibility, higher-order shear deformation, first-order shear deformation, and classical von Karman. The 3D flexibility approach yields the lowest results with more unknowns than the higher-order shear-deformation method. The 3D flexibility approach is considered to be the most accurate, and it is shown that the calculated resultants and displacements tend to vary when consideration is given to the effects of transverse shear.
    Keywords: STRUCTURAL MECHANICS
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  • 3
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    A stiffness tailored wing cover concept for structural efficiency and postbuckling application (1990)
    In:  CASI
    Details
    Publication Date: 2004-12-04
    Description: The weight savings due to usage of composite materials in aircraft structural applications is well known. Significant weight and cost benefits are achievable by developing structurally tailored concepts and efficiently integrating them with suitable material and manufacturing technologies. The proposed paper will describe such an efficient concept for application to primary aircraft structures.
    Keywords: STRUCTURAL MECHANICS
    Type: The Third Air Force(NASA Symposium on Recent Advances in Multidisciplinary Analysis and Optimization; p 353-356
    Format: text
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  • 4
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    An analytical investigation of delamination front curvature in double cantilever beam specimens (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An analytical investigation is conducted to determine the shape of a growing delamination and the distribution of the energy release rate along the delamination front in a laminated composite double cantilever beam specimen. Distributions of the energy release rate for specimens with straight delamination fronts and delamination front contours for delaminations whose growth is governed by the fracture criterion that G = Gc at all points are predicted as a function of material properties and delamination length. The predicted delamination front contours are utilized to ascertain the effect of the changing shape of the delamination front on the value of the critical strain energy release rate as computed from double cantilever beam fracture toughness test data.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials (ISSN 0021-9983); 24; 1124-113
    Format: text
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  • 5
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    Thick plate bending wave transmission using a mobility power flow approach (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The mobility power flow (MPF) approach is used in this paper to describe the flexural behavior of an L-shaped plate structure consisting of thick plates with rotary inertia and shear deformation effects included in the analysis. The introduction of the thick plate effects significantly increases the complexity of the structural mobility functions used in the definitions of the power flow terms; however, because of the substructuring that is used in the MPF approach, the complexity of the problem is significantly reduced as compared to solving for the global structure. Additionally, with the MPF approach the modal behavior is described. The MPF analysis of the L-shaped plate is performed for the case of point force excitation on one plate, with the two plates being identical in both size and thickness. The results of this analysis are compared to results from the finite-element analysis (FEA) and the statistical energy analysis (SEA) and show very good agreement in the low- and high-frequency regimes, respectively.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America, Journal (ISSN 0001-4966); 88; 1472-147
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  • 6
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    An integrated methodology for optimizing the passive damping of composite structures (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A method is presented for tailoring plate and shell composite structures for optimal forced damped dynamic response. The damping of specific vibration modes is optimized with respect to dynamic performance criteria including placement of natural frequencies and minimization of resonance amplitudes. The structural composite damping is synthesized from the properties of the constituent materials, laminate parameters, and structural geometry based on a specialty finite element. Application studies include the optimization of laminated composite beams and composite shells with fiber volume ratios and ply angles as design variables. The results illustrate the significance of damping tailoring to the dynamic performance of composite structures, and the effectiveness of the method in optimizing the structural dynamic response.
    Keywords: STRUCTURAL MECHANICS
    Type: Polymer Composites (ISSN 0272-8397); 11; 328-336
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  • 7
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    Dynamic effects in thermoviscoplastic structures (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An algorithm for three-dimensional thermoviscoplasticity with inertial effects is presented. The algorithm utilizes a unified thermoviscoplastic constitutive model with directional hardening (Bodner-Partom). An example problem is shown in which thermally induced vibrations lead to material yielding at elevated temperatures. Significant dampening caused by inelastic strain is shown to take place in the structure.
    Keywords: STRUCTURAL MECHANICS
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  • 8
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    Mechanics of damping for fiber composite laminates including hygrothermal effects (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 28; 1813-181
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  • 9
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    Load biaxiality and fracture - Synthesis and summary (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The question of load biaxiality strongly affecting almost all of the characteristics of brittle fracture behavior of a cracked body is investigated. Results of research published piecemeal over the years by the authors have shown that the stress and displacement fields, the elastic strain energy density, and the maximum shear stress near the crack tip are all altered by loads applied parallel to the crack, as are the angle of initial crack extension, the strain energy of the entire body, the fracture load, and the rate of fatigue crack growth. A synthesis and summary of this research is presented showing the shortcomings inherent in both Griffith's global energy rate theory for crack instability and Irwin's local crack-tip stress intensity theory for fracture toughness. In both theories only the tensile load perpendicular to the crack influences fracture behavior of the body.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics (ISSN 0013-7944); 36; 4, 19; 537-549
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  • 10
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    The effects of transverse shearing and anisotropy on vibration frequencies of laminated cylinders (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The natural vibration frequencies of orthotropic and anisotropic, simply supported right circular cylinders are predicted using a theory which takes into account higher-order transverse shear deformation effects. A comparison between results based on first-order transverse shear deformation theory and the higher-order theory indicates that an additional allowance for transverse shear deformation has a negligible effect on the predicted natural vibration frequencies associated with long wavelengths, but significantly reduces the natural vibration frequencies associated with short wavelengths. Results of a parametric study of ply orientation for two classes of laminates indicates that while stacking sequence affects natural vibration frequencies, cylinder geometry and mode shape are more important in accurately predicting transverse shear deformation effects. Transverse shearing effects are less important in predicting natural vibration frequencies associated with long wavelength than in predicting axial compressive buckling loads.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 138; 389-404
    Format: text
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