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  • Other Sources  (214)
  • STRUCTURAL MECHANICS  (214)
  • 2005-2009
  • 1980-1984  (214)
  • 1965-1969
  • 1980  (214)
  • 1
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    Measurements of mixed-mode crack surface displacements and comparison with theory (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The problem of a finite-width tension specimen containing a crack oriented at various angles to the load axis is attacked from experimental and theoretical viewpoints. Displacements of an electro-machined slot, 12.5 mm long and oriented at angles of 0, 15, 30, 45, 60, and 75 deg, are measured using a laser-based in-plane measuring technique. Various width specimens, ranging from a crack-length/width ratio of 0.167 to 0.794, are tested. A boundary-integral equation method is extended to deal with the presence of a sharp crack. Agreement between the two approaches is generally good except near the tips of the cracks.
    Keywords: STRUCTURAL MECHANICS
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  • 2
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    Green's function for a crack emanating from a circular hole in an infinite sheet (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Stress-intensity factors, K/I/ and K/II/, are obtained for a point loaded crack emanating from a circular hole in an infinite plate. A series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity are used to derive the solution. The applicability of the solution is demonstrated by using it as a Green's function to obtain K/I/ and K/II/ and the case of (1) biaxial tension of an infinite plate and (2) bending of a wide strip.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 16; Aug. 198
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  • 3
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    Response of a panel to a supersonic turbulent boundary layer - Studies on a theoretical model (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A study of the response of a clamped panel to a supersonic turbulent boundary layer, based on a recently developed theoretical model, is presented. It is demonstrated that the model incorporates the effect of coupling between the panel motion and the flow of the surrounding fluid. Further, a Ritz-Galerkin method is used to obtain approximate solutions for the statistics of the panel response to the turbulence. The numerical results are compared with previous experimental data and the theoretical model is assessed.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 71; July 22
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  • 4
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    Vibration and buckling of rectangular plates under in-plane hydrostatic loading (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Numerical solutions are presented for the fundamental natural frequency and mode shape of a rectangular plate loaded by in-plane hydrostatic forces for a wide variety of aspect ratios, boundary conditions, and load magnitudes. All six possible combinations of simply supported and clamped edges are considered. The limiting conditions of unloaded vibration and buckling are discussed in detail, with emphasis on the preferred mode shape. Design curves and approximate formulae are presented which provide a simple means of determining the fundamental frequency parameter.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 70; June 22
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  • 5
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    An assessment of buffer strips for improving damage tolerance of composite laminates (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Graphite/epoxy panels with buffer strips were tested in tension to measure their residual strength with crack-like damage. Panels were made with (45/0/-45/90)2S and (45/0/-45/0)2S layups. The buffer strips were parallel to the loading direction. They were made by replacing narrow strips of the 0 deg graphite plies with strips of either 0 deg S-Glass/epoxy or Kevlar-90/epoxy on either a one-for-one or a two-for-one basis. In a third case, 0 deg graphite/epoxy was used as the buffer material and thin, perforated Mylar strips were placed between the 0 deg plies and the cross-plies to weaken the interfaces and thus to isolate the 0 deg plies. Some panels were made with buffer strips of different width and spacings. The buffer strips arrested the cracks and increased the residual strengths significantly over those of plain laminates without buffer strips. A shear-lag type stress analysis correctly predicted the effects of layup, buffer material, buffer strip width and spacing, and the number of plies of buffer material
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials Supplement; 14; 1, 19; 1980
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  • 6
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    Development and evaluation of two non-linear shell elements (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Two plate and shell displacement elements are developed for use in large deflection non-linear analysis. The elements are of the 'stability' type, in which non-linear strains are included, with their values optimized by added higher order membrane functions and special types of elemental level constraints. The paper summarizes formulation and computational procedures, and discusses numerical results in detail. Conclusions are given regarding the effectiveness of the elements for solving both linear and non-linear shell analysis problems.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 16; Oct. 198
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  • 7
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    Mode I fracture behavior of nonlinear materials (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A finite element analysis is presented for the Mode I fracture behavior of cracked plates (stationary crack) made of different nonlinear materials (elastoplastic or elastic locking). The assumed stress-strain behavior of the nonlinear materials was piecewise linear. For each given 'stationary' crack size, the corresponding critical remote tensile stress was calculated based on the maximum crack-tip stress failure criterion. It was found that in the log-log plots of the critical remote stress versus critical crack length, the fracture data of the piecewise linear materials obey a 'stepwise-linear-inverse-square-root' fracture law. It is also shown how the fracture data of the piecewise linear materials can be fitted by proper piecewise graphical shifting of the classical 'inverse-square-root' fracture curve for the linearly elastic materials.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 16; June 198
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  • 8
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    Energy minimization versus pseudo force technique for nonlinear structural analysis (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effectiveness of using minimization techniques for the solution of nonlinear structural analysis problems is discussed and demonstrated by comparison with the conventional pseudo force technique. The comparison involves nonlinear problems with a relatively few degrees of freedom. A survey of the state-of-the-art of algorithms for unconstrained minimization reveals that extension of the technique to large scale nonlinear systems is possible.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 11; May 1980
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  • 9
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    Recent developments in the design, testing and impact-damage tolerance of stiffened composite panels (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The structural technology of laminated filamentary-composite stiffened-panel structures under combined in-plane and lateral loadings is discussed. Emphasis is on analyzing the behavior of the structures under load, determining appropriate structural proportions for weight efficient configurations, and effects of impact damage and geometric imperfections on structural performance. Experimental data on buckling of panels under in-plane compression validate the analysis and sizing methods, and illustrate structural performance and efficiency obtained from representative structures. It is shown that the strength of panels under in-plane compression can be degraded by low-velocity impact damage, and data are presented which indicate that the matrix is a significant factor influencing tolerance to impact damage.
    Keywords: STRUCTURAL MECHANICS
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  • 10
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    Thermally induced response of flexible structures - A method for analysis (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The phenomenon of a thermally induced spacecraft instability became apparent during the flight of the OGO-IV spacecraft in the late 1960s. The paper presents a generalized approach to the problem of obtaining a computationally practical simulation model for a thermally driven structure. The formulation is such that it can be utilized in a stand-along manner or be meshed into a general multibody simulation model such as that reported by Bodley et al. (1978). As presented, the formulation is restricted to the dynamic range for which linearized radiation is a valid assumption.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Guidance and Control; 3; Jan
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  • 11
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    Stress-intensity factors for internal surface cracks in cylindrical pressure vessels (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper presents stress-intensity factors for a wide range of semi-elliptical surface cracks on the inside of pressurized cylinders. The ratio of crack depth to crack length ranged from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 to to 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method using singularity elements along the crack front and linear-strain elements elsewhere. An equation for the stress-intensity factors was obtained which applies over a wide range of configuration parameters and was within about 5 percent of the present results. A comparison was also made between the results and other analyses of internal surface cracks in cylinders. The results from a boundary-integral equation method were in agreement and those from another finite-element method were in fair agreement (+ or - 8 percent) with the results.
    Keywords: STRUCTURAL MECHANICS
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  • 12
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    A wide range stress intensity factor expression for the C-shaped specimen (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Testing and Evaluation; 8; Nov. 198
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  • 13
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    A consistent set of trial functions for conical shells (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A consistent approach is developed for the determination of trial functions for a class of shells of revolution. The trial functions satisfy the in-plane and out-of-plane boundary conditions at the shell ends and include the effects of tangential inertia. The resulting expressions converge rapidly for the problem of linear free vibration
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 73; Nov. 8
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  • 14
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    Improvements to the NASAP code (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The FORTRAN code, NASAP was modified and improved for the capability of transforming the CAD-generated NASTRAN input data for DESAP II and/or DESAP I. The latter programs were developed for structural optimization.
    Keywords: STRUCTURAL MECHANICS
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 76 p
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  • 15
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    Buckling of axially compressed conical shells (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The buckling of a truncated elastic conical shell subjected to an axial compression is a classical problem in shell structures. The paper reinvestigates the buckling of an axially compressed truncated conical shell with rigid bulkheads. Two improvements are achieved. First, the condition that the total horizontal displacement must vanish due to rigid bulkhead and axisymmetry is treated as a constraint. This constraint is incorporated into the system through the use of the Lagrange multiplier; then the variational method is used to derive a complete set of boundary conditions for conical shells. Second, the stability is evaluated in the deformed state using the asymptotic solutions of the pair of Donnell-type equations for axisymmetric configuration. The results indicate that the buckling strength of conical shells depends mainly on the condition of the smaller end. In addition to the vertex angle, the distance ratio plays, at least, an equally important role.
    Keywords: STRUCTURAL MECHANICS
    Type: American Society of Civil Engineers; Journal
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  • 16
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    Maintenance of NASTRAN (R) as a state-of-the-art computer program (1980)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The maintenance requirements for a large, general purpose, finite element computer program are presented. The program is maintained as state-of-the-art on three computer systems (IBM, CDC, and UNIVAC) with respect to both finite element and computer technology. There are four primary areas involved in the maintenance effort: (1) error correction; (2) incorporation of advances in technology; (3) documentation; and (4) new level generation. The complexity of the maintenance effort is compounded by the sizes of the program (400,000 lines of code) and the documentation (7000 pages divided into seven manuals).
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD The Use of Computers as a Design Tool; 12 p
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  • 17
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    Comparison of finite element analysis of a piping tee using NASTRAN and CORTES/SA (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A comparison of finite element analyses of a piping tee was made using NASTRAN and CORTES/SA, a modified version of SAP3 having a special purpose input processor for generating geometries for a wide variety of tee joints. Four finite element models were subjected in force, moment, and pressure loadings. Flexibility factors and principal stresses were computed for each model and compared with results obtained experimentally by Combustion Engineering, Inc. Results from the NASTRAN analyses were in good agreement with experimental results for all loadings except internal pressure. The CORTES/SA analyses gave good results for the internal pressure loading, but poorer results for out of plane bending moments or forces resulting in out of plane bending. Two of the basic load cases in CORTES/SA were found to contain errors that could not be easily corrected. COST COMPARison of NASTRAN and CORTES/SA showed NASTRAN to be less expensive to two than CORTES/SA for identical meshes.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 224-242
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  • 18
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    On the application of nonlinear load elements to thermal analyses using the NASTRAN thermal analyzer (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The nonlinear load elements in thermal analysis are used to simulate an undocumented nonlinear thermal boundary condition. The treatment of the nonlinearity arising from the temperature-dependent convective film coefficients is shown in detail. As an illustration, emphasis is placed on the modeling techniques and their interrelationships with the solution accuracy as affected by a specific integration algorithm of the transient thermal analysis used in the NASTRAN Thermal Analyzer. Briefly shown is the underlying theory on which the maneuvering of terms pertinent to the modeling depends. This demonstration provides some insight into the intricacies of the method that would be general to all applications. A recommendation is also made to modify a nonlinear load element that will enhance the solution capability and broaden the scope of application.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 121-139
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  • 19
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    Solution of enforced boundary motion in direct transient and harmonic problems (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The current versions of NASTRAN, i.e., NASA, MSC, and MAC support nonzero boundary displacements only in the static analysis. Forcing functions in the dynamic analysis formats allow only forces and pressures to exercise the mathematical model. A DMAP alter sequence to circumvent this limitation is described. For the direct harmonic problem, a simple change to module FRRD is incorporated to effect a more efficient use of the code.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 96-120
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  • 20
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    Solution sensitivity and accuracy study of NASTRAN for large dynamic problems involving structural damping (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Large dynamic problems involving NASTRAN SOLUTION 8 (i.e., the steady state dynamic response option wherein all response quantities vary as e sub i omega t, where omega is the driving frequency and t is time) are considered. Using a submerged steel plate with a viscoelastic layer layer as the bench mark sample, the solution sensitivity and solution accuracy are checked. The solution sensitivity is examined by running the same finite element model on different computers, different versions of NASTRAN, and different precision levels. The solution accuracy is evaluated for these same runs by comparing the NASTRAN results with the exact solution of the same problem.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 49-62
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  • 21
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    Iterative methods based upon residual averaging (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Iterative methods for solving boundary value problems for systems of nonlinear partial differential equations are discussed. The methods involve subtracting an average of residuals from one approximation in order to arrive at a subsequent approximation. Two abstract methods in Hilbert space are given and application of these methods to quasilinear systems to give numerical schemes for such problems is demonstrated. Potential theoretic matters related to the iteration schemes are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 91-96
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  • 22
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    New capacities and modifications for NASTRAN level 17.5 at DTNSRDC (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Since 1970 DTNSRDC has been modifying NASTRAN to suite various Navy requirements. These modifications include capabilities as well as user conveniences and error corrections. The new features added to NASTRAN Level 17.5 are described. The subject areas of the additions include magnetostatics, piezoelectricity, fluid structure interactions, isoparametric finite elements, and shock design for shipboard equipment.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 1-13
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  • 23
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    Solutions of contact problems by the assumed stress hybrid model (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A method was developed for contact problems which may be either frictional or frictionless and may involve extensive sliding between deformable bodies. It was based on an assumed stress hybrid approach and on an incremental variational principle for which the Euler's equations of the functional include the equilibrium and compatibility conditions at the contact surface. The tractions at an assumed contact surface were introduced as Lagrangian multipliers in the formulation. It was concluded from the results of several example solutions that the extensive sliding contact between deformable bodies can be solved by the present method.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 211-224
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  • 24
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    Finite element analysis of hyperelastic structures (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The use of the penalty function, to account for near incompressibility is discussed and compared to that of Lagrange multiplier. A scheme to use Lagrange multiplier, without having to treat it as unknown, is also presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 197-209
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  • 25
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    Study of solution procedures for nonlinear structural equations (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A method for the redution of the cost of solution of large nonlinear structural equations was developed. Verification was made using the MARC-STRUC structure finite element program with test cases involving single and multiple degrees of freedom for static geometric nonlinearities. The method developed was designed to exist within the envelope of accuracy and convergence characteristic of the particular finite element methodology used.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 129-139
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  • 26
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    Thermal stress response of General Purpose Heat Source (GPHS) aeroshell material (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A thermal stress test was conducted to determine the ability of the GPHS aeroshell 3 D FWPF material to maintain physical integrity when exposed to a severe heat flux such as would occur from prompt reentry of GPHS modules. The test was performed in the Giant Planetary Facility at NASA's Ames Research Center. Good agreement was obtained between the theoretical and experimental results for both temperature and strain time histories. No physical damage was observed in the test specimen. These results provide initial corroboration both of the analysis techniques and that the GPHS reentry member will survive the reentry thermal stress levels expected.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 11th Space Simulation Conf.; p 378-389
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  • 27
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    Finite circular plate on elastic foundation centrally loaded by rigid spherical indenter (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The analytical solution of a finite circular plate on an elastic foundation centrally loaded by the rigid indenter is discussed. The procedure to use NASTRAN as a subroutine to iteratively converge to this solution numerically is described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 173-190
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  • 28
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    A NASTRAN investigation of simulated projectile damage effects on a UH-1B tail boom model (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A NASTRAN model of a UH-1B tail boom that had been designed for another project was used to investigate the effect on structural integrity of simulated projectile damage. Elements representing skin, and sections of stringers, longerons and bulkheads were systematically deleted to represent projectile damage. The structure was loaded in a manner to represent the flight loads that would be imposed on the tail boom at a 130 knot cruise. The deflection of four points on the rear of the tail boom relative to the position of these points for the unloaded, undamaged condition of the tail boom was used as a measure of the loss of structural rigidity. The same procedure was then used with the material properties of the aluminum alloys replaced with the material properties of T300/5208 high strength graphite/epoxy fibrous composite material, (0, + or - 45, 90)s for the skin and (0, + or - 45)s for the longerons, stringers, and bulk heads.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 161-172
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  • 29
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    Ring element dynamic stresses (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The stresses in the CTRAPRG and CTRIARG ring elements are not calculated for any of the dynamic solutions in the current COSMIC version of NASTRAN. A DMAP alter sequence for Solution 8 and post-processing program, NASTPOST, are presented to calculate these stresses. Test cases are used which describe the method. The stiffness and the consistent versus concentrated mass problems ascribed to this element are reviewed. The DMAP alter sequence introduces Solution 8 displacements to a Solution 1 module to calculate real and imaginary stress components during the execution of Solution 8. The post-processor, NASTPOST, calculates the magnitude/phase stress results. The DMAP sequence was written specifically for level 52 MSC/NASTRAN, but can certainly be used for any COSMIC version with slight modification.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 63-78
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  • 30
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    Improvements in sparse matrix operations of NASTRAN (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A "nontransmit" packing routine was added to NASTRAN to allow matrix data to be refered to directly from the input/output buffer. Use of the packing routine permits various routines for matrix handling to perform a direct reference to the input/output buffer if data addresses have once been received. The packing routine offers a buffer by buffer backspace feature for efficient backspacing in sequential access. Unlike a conventional backspacing that needs twice back record for a single read of one record (one column), this feature omits overlapping of READ operation and back record. It eliminates the necessity of writing, in decomposition of a symmetric matrix, of a portion of the matrix to its upper triangular matrix from the last to the first columns of the symmetric matrix, thus saving time for generating the upper triangular matrix. Only a lower triangular matrix must be written onto the secondary storage device, bringing 10 to 30% reduction in use of the disk space of the storage device.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 14-48
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  • 31
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    Corotational velocity strain formulations for nonlinear analysis of beams and axisymmetric shells (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Finite element formulations for large strain, large displacement problems are formulated using a kinematic description based on the corotational components of the velocity strain. The corotational components are defined in terms of a system that rotates with each element and approximates the rotation of the material. To account for rotations of the material relative to this element system, extra terms are introduced in the velocity strain equations. Although this formulation is incremental, in explicitly integrated transient problems it compares very well with formulations that are not.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 263-276
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  • 32
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    Finite elements for contact problems in two-dimensional elastodynamics (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A finite element approach for contact problems in two dimensional elastodynamics was proposed. Sticking, sliding, and frictional contact were taken into account. The method consisted of a modification of the shape functions, in the contact region, in order to involve the nodes of the contacting body. The formulation was symmetric (both bodies were contactors and targets), in order to avoid interpenetration. Compatibility over the interfaces was satisfied. The method was applied to the impact of a block on a rigid target. It is shown that the formulation can be applied to fluid structure interaction, and to problems involving material nonlinearity.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 225-235
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    Post-buckling behavior of a beam-column on a nonlinear elastic foundation with a gap (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The structural behavior of an elastic beam-column placed with a gap between two nonlinearity elastic layers each resting on a rigid foundation was examined. The beam-column was laterally supported at both ends and subjected to a uniform transverse load and axial compression. Its slenderness was such that the axial compressive force exceeds the amount that would be necessary to buckle it as a simple supported column. The elastic layers were represented by an elastic foundation with a strongly nonlinear specific reaction taken as a rapidly increasing function of the layer compression. The analytical model developed simulated the entire pattern of the deflection and stress state including layer and end support reactions, under gradually increasing axial force.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 165-173
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  • 34
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    Straightening of a wavy strip: An elastic-plastic contact problem including snap-through (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The nonlinear behavior of a wave like deformed metal strip during the levelling process were calculated. Elastic-plastic material behavior as well as nonlinearities due to large deformations were considered. The considered problem lead to a combined stability and contact problem. It is shown that, despite the initially concentrated loading, neglecting the change of loading conditions due to altered contact domains may lead to a significant error in the evaluation of the nonlinear behavior and particularly to an underestimation of the stability limit load. The stability was examined by considering the load deflection path and the behavior of a load-dependent current stiffness parameter in combination with the determinant of the current stiffness matrix.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 175-185
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  • 35
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    Computational strategy for the solution of large strain nonlinear problems using the Wilkins explicit finite-difference approach (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The STEALTH code system, which solves large strain, nonlinear continuum mechanics problems, was rigorously structured in both overall design and programming standards. The design is based on the theoretical elements of analysis while the programming standards attempt to establish a parallelism between physical theory, programming structure, and documentation. These features have made it easy to maintain, modify, and transport the codes. It has also guaranteed users a high level of quality control and quality assurance.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 97-114
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  • 36
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    Newton's method: A link between continuous and discrete solutions of nonlinear problems (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Newton's method for nonlinear mechanics problems replaces the governing nonlinear equations by an iterative sequence of linear equations. When the linear equations are linear differential equations, the equations are usually solved by numerical methods. The iterative sequence in Newton's method can exhibit poor convergence properties when the nonlinear problem has multiple solutions for a fixed set of parameters, unless the iterative sequences are aimed at solving for each solution separately. The theory of the linear differential operators is often a better guide for solution strategies in applying Newton's method than the theory of linear algebra associated with the numerical analogs of the differential operators. In fact, the theory for the differential operators can suggest the choice of numerical linear operators. In this paper the method of variation of parameters from the theory of linear ordinary differential equations is examined in detail in the context of Newton's method to demonstrate how it might be used as a guide for numerical solutions.
    Keywords: STRUCTURAL MECHANICS
    Type: Res. in Nonlinear Struct. and Solid Mech.; p 27-46
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  • 37
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    Analysis of reinforced concrete structures with occurrence of discrete cracks at arbitrary positions (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A nonlinear analysis of in-plane loaded plates is presented, which eliminates the disadvantages of the smeared crack approach. The elements used and the computational method are discussed. An example is shown in which one or more discrete cracks are dominant.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 1-12
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  • 38
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    Computational models for the nonlinear analysis of reinforced concrete plates (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A finite element computational model for the nonlinear analysis of reinforced concrete solid, stiffened and cellular plates is briefly outlined. Typically, Mindlin elements are used to model the plates whereas eccentric Timoshenko elements are adopted to represent the beams. The layering technique, common in the analysis of reinforced concrete flexural systems, is incorporated in the model. The proposed model provides an inexpensive and reasonably accurate approach which can be extended for use with voided plates.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 13-26
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  • 39
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    Elastic-plastic analysis using a triangular ring element in NASTRAN (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An elastic plastic triangular ring element is implemented in NASTRAN computer program. The plane strain problem of partially plastic thick walled cylinder under internal pressure is solved and compared with the earlier finite difference solution. A very good agreement has been reached. In order to demonstrate its application to more general problems, an overloaded thread problem for the British Standard Buttress is examined. The maximum axial and principal stresses are located and their values are determined as functions of loadings.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 190-200
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  • 40
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    An enhancement of NASTRAN for the seismic analysis of structures (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: New modules, bulk data cards and DMAP sequence were added to NASTRAN to aid in the seismic analysis of nuclear power plant structures. These allow input consisting of acceleration time histories and result in the generation of acceleration floor response spectra. The resulting system contains numerous user convenience features, as well as being reasonably efficient.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 79-95
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  • 41
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    Microcomputer system for medium-sized and experimental finite element analysis (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of a microcomputer system is described. A series of finite element analysis programs are evaluated in terms of their cost effective application within the microcomputer system. It is shown that the system is practically maintenance free and can be sustained by individual laboratories of standard scale in the educational or academic environment.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 277-289
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  • 42
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    Nonlinear soil-structure interaction calculations simulating the SIMQUAKE experiment using STEALTH 2D (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 47-66
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  • 43
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    Application of a data base management system to a finite element model (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In today's software market, much effort is being expended on the development of data base management systems (DBMS). Most commercially available DBMS were designed for business use. However, the need for such systems within the engineering and scientific communities is becoming apparent. A potential DBMS application that appears attractive is the handling of data for finite element engineering models. The applications of a commercially available, business-oriented DBMS to a structural engineering, finite element model is explored. The model, DBMS, an approach to using the DBMS, advantages and disadvantages are described. Plans for research on a scientific and engineering DBMS are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 223-234
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  • 44
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    Applications of NASTRAN in Gust Response Analysis at Northrop (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A comprehensive gust response analysis was performed on a complete model of an airplane using the NASTRAN aeroelastic package. The analysis investigated random response to atmospheric turbulence and transient response to a discrete gust, including control system dynamics in both cases. It is shown that NASTRAN is an effective tool for aeroelastic analysis and active control system design.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 165-188
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  • 45
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    Condensing loaded points for transients by substructuring (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A technique for condensing dynamic loading points is described. The method was applied to substructure transient solutions and was found to be very effective.
    Keywords: STRUCTURAL MECHANICS
    Type: Eighth NASTRAN User's Colloq.; p 79-100
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  • 46
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    Stress concentrations in screw threads (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The concept of stress concentration in screw threads was defined using the sheer transfer rate as the fundamental quantity. The stress concentration is plotted for a fixed geometry. The Heywood equation was used to generate the basic plots and NASTRAN was used to extend the analysis to the case both where flanks of an individual thread tooth are in contact. The case where a finite axial stress is superimposed is discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 65-77
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  • 47
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    On the congruent feature in NASTRAN (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The congruent feature, which is a capability in NASTRAN that can contribute to significant increases in computational efficiencies, is discussed. The usage of the capability and the software design characteristics affecting it are explained. The factors affecting the efficiency of the feature are pointed out. The details pertaining to the software design of the congruent feature are presented; in particular, the congruent element table is described. Serveral examples employing the congruent feature are considered and comparisons of Element Matrix Generator module computer program update times with and without this feature are presented. The results clearly demonstrate the role of the congruent feature in increasing computational efficiencies and its applicability to large-size problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 1-10
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  • 48
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    Implementation of NASTRAN on the IBM/370 CMS operating system (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The NASA Structural Analysis (NASTRAN) computer program is operational on the IBM 360/370 series computers. While execution of NASTRAN has been described and implemented under the virtual storage operating systems of the IBM 370 models, the IBM 370/168 computer can also operate in a time-sharing mode under the virtual machine operating system using the Conversational Monitor System (CMS) subset. The changes required to make NASTRAN operational under the CMS operating system are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 189-203
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    Steady state solutions to dynamically loaded periodic structures (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 131-164
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  • 50
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    Implementation of a trapezoidal ring element in NASTRAN for elastic-plastic analysis (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The explicit expressions for an elastic-plastic trapezoidal ring element are presented and implemented in NASTRAN computer program. The material is assumed to obey the von Mises' yield criterion, isotropic hardening rule and the Prandtl-Reuss flow relations. For the purpose of demonstration, two elastic-plastic problems are solved and compared with previous results. The first is a plane-strain tube under uniform internal pressure and the second, a finite-length tube loaded over part of its inner surface. A very good agreement was found in both test problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 101-112
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  • 51
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    Tensioning of a belt around a drum using membrane element (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An application of the membrane element to the problem of the tensioning of a conveyer belt which wraps around a drum is presented. Two cases were investigated: (1) belt tension increase due to drum edge wear; and (2) material trapped between the drum and the belt. In both cases it was found that the increase in belt tension was due to the additional stretching of the belt resulting from the drum radius change rather than from the transverse deflection of the belt.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 33-39
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  • 52
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    Stress distribution in a semi-infinite body symmetrically loaded over a circular area (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Algorithms are developed for computing stresses in a semi-infinite body when loaded by a uniform pressure acting over a circular area. The algorithm allows easy determination of any stress component in a semi-infinite body having a known Poisson's ratio. Example curves are plotted for Portland cement grout and metal representative values.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition Rept.; p 123-130
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  • 53
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    IFEMS, an Interactive Finite Element Modeling System Using a CAD/CAM System (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method of coupling a CAD/CAM system with a general purpose finite element mesh generator is described. The three computer programs which make up the interactive finite element graphics system are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 205-221
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  • 54
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    Development of the Learjet 28/29 Wing Using NASTRAN Analysis (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The structural development work performed on the Learjet 28/29 wing using NASTRAN analysis is discussed. The work included the basic sizing of primary structural members such as wing skins, wing skin splices, and spar caps, as well as the calculation of preliminary weight estimates utilizing the weight computation routine in NASTRAN. The eight spar redundancy of the Learjet wing made this task somewhat more complex than for more determinate type wing structures. Some of the problems that were encountered and the solutions and methods that were used are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center Eighth NASTRAN User's Colloq.; p 11-32
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  • 55
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    Nonlinear finite element analysis: An alternative formulation (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A geometrical nonlinear analysis based on an alternative definition of strain is presented. Expressions for strain are obtained by computing the change in length of the base vectors in the curvilinear element coordinate system. The isoparametric element formulation is assumed in the global Cartesian coordinate system. The approach is based on the minimization of the strain energy, and the resulting nonlinear equations are solved by the modified Newton method. Integration of the first and second variation of the strain energy is performed numerically in the case of two and three dimensional elements. Application is made to a simple long cantilever beam.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 251-261
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  • 56
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    Development and analysis of the learjet 54/55 fuselage NASTRAN model using substructure techniques (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Development and analysis of the Learjet 54/55 fuselage NASTRAN model is presented. This structure was broken down into several substructures to make the modeling and analysis effort more manageable. Since the geometry was fairly complex in some areas and in order to provide flexibility for future configuration studies, a series of local coordinate systems were used to describe the model. This work was accomplished using several different computer systems, the more recent of which were connected by a high speed data communications lines to perform the tasks of model generation and NASTRAN analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: 9th NASTRAN (R) Users' Colloq. p 201-223; 9th NASTRAN
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    NASTRAN analysis of heat-transfer fluid fill pipe failure (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An example that shows the difficulties of failure analyses and the advantage of the finite element method (NASTRAN) in assisting in determining the true cause of a failure is presented. In this example, cracks were developing along a pipe weld. After discarding several possible causes for the failures, it was finally determined that the problem was due to stress corrosion cracking associated with a rather unusual and novel environmental condition.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Kennedy Space Center 9th NASTRAN (R) Users' Colloq.; p 140-160
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  • 58
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    Lattice-statics approach to fracture and plasticity (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The lattice-statics approach to the problem of providing a quantitative description of the microstructure near a defect is outlined. The method deals with an effectively infinite lattice and hence avoids interface problems; the lattice-statics method is not restricted by the range of the potential. The lattice-statics solution requires a harmonic solution for the lattice which is shown to be always obtainable by suitable Fourier transforms. Applications of the method to fracture and dislocations are discussed and areas that warrant further research are specified.
    Keywords: STRUCTURAL MECHANICS
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    Application of the cubic polynomial strength criterion to the failure analysis of composite materials (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A comparative failure analysis is presented based on the application of quadratic and cubic forms of the tensor polynomial lamina strength criterion to various composite structural configurations in a plane stress state. Failure loads have been predicted for off-angle laminates under simple loading conditions and for symmetric-balanced laminates subject to varying degrees of biaxial tension, including configurations subject to multimode failures. Some experimental data are also provided to support these calculations. From these results, the necessity of employing a cubic strength criterion to accurately predict the failure of composite laminae is demonstrated.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials Supplement; 14; 1, 19; 1980
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  • 60
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    An improved approximate theory for the bending of laminated plates (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: STRUCTURAL MECHANICS
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    NASTRAN level 16 demonstration manual updates for aeroelastic analysis of bladed discs (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer program based on state of the art compressor and structural technologies applied to bladed shrouded discs was developed and made operational in NASTRAN level 16. The problems encompassed include aeroelastic analyses, modes, and flutter. The demonstration manual updates are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159826 , D2536-941005
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    NASTRAN level 16 programmer's manual updates for aeroelastic analysis of bladed discs (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The programming routines for the NASTRAN Level 16program are presented. Particular emphasis is placed on its application to aeroelastic analyses, mode development, and flutter analysis for turbomachine blades.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159825 , D2536-941004
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    Nastran level 16 theoretical manual updates for aeroelastic analysis of bladed discs (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer program based on state of the art compressor and structural technologies applied to bladed shrouded disc was developed and made operational in NASTRAN Level 16. Aeroelastic analyses, modes and flutter. Theoretical manual updates are included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159823 , D2536-941002
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    NASTRAN level 16 user's manual updates for aeroelastic analysis of bladed discs (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The NASTRAN aeroelastic and flutter capability was extended to solve a class of problems associated with axial flow turbomachines. The capabilities of the program are briefly discussed. The aerodynamic data pertaining to the bladed disc sector, the associated aerodynamic modeling, the steady aerothermoelastic 'design/analysis' formulations, and the modal, flutter, and subcritical roots analyses are described. Sample problems and their solutions are included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159824 , D2536-941003
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    Aeroelastic and dynamic finite element analyses of a bladder shrouded disk (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The delivery and demonstration of a computer program for the analysis of aeroelastic and dynamic properties is reported. Approaches to flutter and forced vibration of mistuned discs, and transient aerothermoelasticity are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159728 , D2536-941001
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    Experimental compliance calibration of the compact fracture toughness specimen (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Compliances and stress intensity coefficients were determined over crack length to width ratios from 0.1 to 0.8. Displacements were measured at the load points, load line, and crack mouth. Special fixturing was devised to permit accurate measurement of load point displacement. The results are in agreement with the currently used results of boundary collocation analyses. The errors which occur in stress intensity coefficients or specimen energy input determinations made from load line displacement measurements rather than from load point measurements are emphasized.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81665 , E-685
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    ACCESS 3. Approximation concepts code for efficient structural synthesis: User's guide (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A user's guide is presented for ACCESS-3, a research oriented program which combines dual methods and a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and dual algorithms of mathematical programming are applied in the design optimization procedure. This program retains all of the ACCESS-2 capabilities and the data preparation formats are fully compatible. Four distinct optimizer options were added: interior point penalty function method (NEWSUMT); second order primal projection method (PRIMAL2); second order Newton-type dual method (DUAL2); and first order gradient projection-type dual method (DUAL1). A pure discrete and mixed continuous-discrete design variable capability, and zero order approximation of the stress constraints are also included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159260
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  • 68
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    Dynamic response of a forward-swept-wing model at angles of attack up to 15 deg at a Mach number of 0.8 (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Root mean square (rms) bending moments for a dynamically scaled, aeroelastic wing of a proposed forward swept wing, flight demonstrator airplane are presented for angles of attack up to 15 deg at a Mach number of 0.8 The 0.6 size semispan model had a leading edge forward sweep of 44 deg and was constructed of composite material. In addition to broad band responses, individual rms responses and total damping ratios are presented for the first two natural modes. The results show that the rms response increases with angle of attack and has a peak value at an angle of attack near 13 deg. In general, the response was characteristic of buffeting and similar to results often observed for aft swept wings. At an angle of attack near 13 deg, however, the response had characteristics associated with approaching a dynamic instability, although no instability was observed over the range of parameters investigated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81863 , L-13872
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  • 69
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    Preliminary study on the potential usefulness of array processor techniques for structural synthesis (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of the use of array processor techniques within the structural analyzer program, SPAR, are simulated in order to evaluate the potential analysis speedups which may result. In particular the connection of a Floating Point System AP120 processor to the PRIME computer is discussed. Measurements of execution, input/output, and data transfer times are given. Using these data estimates are made as to the relative speedups that can be executed in a more complete implementation on an array processor maxi-mini computer system.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-163801
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  • 70
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    An analytical technique for approximating unsteady aerodynamics in the time domain (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An analytical technique is presented for approximating unsteady aerodynamic forces in the time domain. The order of elements of a matrix Pade approximation was postulated, and the resulting polynomial coefficients were determined through a combination of least squares estimates for the numerator coefficients and a constrained gradient search for the denominator coefficients which insures stable approximating functions. The number of differential equations required to represent the aerodynamic forces to a given accuracy tends to be smaller than that employed in certain existing techniques where the denominator coefficients are chosen a priori. Results are shown for an aeroelastic, cantilevered, semispan wing which indicate a good fit to the aerodynamic forces for oscillatory motion can be achieved with a matrix Pade approximation having fourth order numerator and second order denominator polynomials.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1738 , L-13255
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  • 71
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    Stress singularities at the vertex of a cylindrically anisotropic wedge (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The plane elasticity problem for a cylindrically anisotropic solid is formulated. The form of the solution for an infinite wedge shaped domain with various homogeneous boundary conditions is derived and the nature of the stress singularity at the vertex of the wedge is studied. The characteristic equations giving the stress singularity and the angular distribution of the stresses around the vertex of the wedge are obtained for three standard homogeneous boundary conditions. The numerical examples show that the singular behavior of the stresses around the vertex of an anisotropic wedge may be significantly different from that of the isotropic material. Some of the results which may be of practical importance are that for a half plane the stress state at r = 0 may be singular and for a crack the power of stress singularity may be greater or less than 1/2.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-165639
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  • 72
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    Stresses in adhesively bonded joints: A closed form solution (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The plane strain of adhesively bonded structures which consist of two different orthotropic adherents is considered. Assuming that the thicknesses of the adherends are constant and are small in relation to the lateral dimensions of the bonded region, the adherends are treated as plates. The transverse shear effects in the adherends and the in-plane normal strain in the adhesive are taken into account. The problem is reduced to a system of differential equations for the adhesive stresses which is solved in closed form. A single lap joint and a stiffened plate under various loading conditions are considered as examples. To verify the basic trend of the solutions obtained from the plate theory a sample problem is solved by using the finite element method and by treating the adherends and the adhesive as elastic continua. The plate theory not only predicts the correct trend for the adhesive stresses but also gives rather surprisingly accurate results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-165638
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  • 73
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    Crack problems for a rectangular plate and an infinite strip (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-165637
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  • 74
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    Stress intensity factors in a hollow cylinder containing a radial crack (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An exact formulation of the plane elasticity problem for a hollow cylinder or a disk containing a radial crack is given. The crack may be an external edge crack, an internal edge crack, or an embedded crack. It is assumed that on the crack surfaces the shear traction is zero and the normal traction is an arbitrary function of r. For various crack geometries and radius ratios, the numerical results are obtained for a uniform crack surface pressure, for a uniform pressure acting on the inside wall of the cylinder, and for a rotating disk.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-165640
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  • 75
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    Method for estimating crack-extension resistance curve from residual strength data (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A method is presented for estimating the crack extension resistance curve (R curve) from residual strength (maximum load against initial crack length) data for precracked fracture specimens. The method allows additional information to be inferred from simple test results, and that information is used to estimate the failure loads of more complicated structures. Numerical differentiation of the residual strength data is required, and the problems that it may present are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1753 , E-439
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  • 76
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    Failure analyses of composite bolted joints (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The complex failure behavior exhibited by bolted joints of graphite epoxy (Hercules AS/3501) was investigated for the net tension, bearing and shearout failure modes using combined analytical and experimental techniques. Plane stress, linear elastic, finite element methods were employed to determine the two dimensional state of stress resulting from a loaded hole in a finite width, semiinfinite strip. The stresses predicted by the finite element method were verified by experiment to lend credence to the analysis. The influence of joint geometric parameters on the state of stress and resultant strength of the joint was also studied. The resulting functional relationships found to exist between bolted joint strength and the geometric parameters, were applied in the formulation of semiempirical strength models for the basic failure modes. A point stress failure criterion was successfully applied as the failure criterion for the net tension and shearout failure modes.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-163732 , CCM-80-16
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  • 77
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    Hybrid-finite-element analysis of some nonlinear and 3-dimensional problems of engineering fracture mechanics (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In this paper, efficient numerical methods for the analysis of crack-closure effects on fatigue-crack-growth-rates, in plane stress situations, and for the solution of stress-intensity factors for arbitrary shaped surface flaws in pressure vessels, are presented. For the former problem, an elastic-plastic finite element procedure valid for the case of finite deformation gradients is developed and crack growth is simulated by the translation of near-crack-tip elements with embedded plastic singularities. For the latter problem, an embedded-elastic-singularity hybrid finite element method, which leads to a direct evaluation of K-factors, is employed.
    Keywords: STRUCTURAL MECHANICS
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  • 78
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    Three dimensional finite element analysis of layered fiber-reinforced composite materials (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A three-dimensional finite element analysis was performed for a biaxially loaded composite laminate (with a centered hole) consisting of several fiber-reinforced composite layers each with a specified fiber orientation. The detailed stress distribution around the hole was determined. Also, the locations of initial damage zones due to different failure mechanisms were indicated.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 12; Sept
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  • 79
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    Discrete-continuous variable structural synthesis using dual methods (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Approximation concepts and dual methods are extended to solve structural synthesis problems involving a mix of discrete and continuous sizing type of design variables. Pure discrete and pure continuous variable problems can be handled as special cases. The basic mathematical programming statement of the structural synthesis problem is converted into a sequence of explicit approximate primal problems of separable form. These problems are solved by constructing continuous explicit dual functions, which are maximized subject to simple nonnegativity constraints on the dual variables. A newly devised gradient projection type of algorithm called DUAL 1, which includes special features for handling dual function gradient discontinuities that arise from the discrete primal variables, is used to find the solution of each dual problem. Computational implementation is accomplished by incorporating the DUAL 1 algorithm into the ACCESS 3 program as a new optimizer option. The power of the method set forth is demonstrated by presenting numerical results for several example problems, including a pure discrete variable treatment of a metallic swept wing and a mixed discrete-continuous variable solution for a thin delta wing with fiber composite skins.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 18; Dec. 198
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  • 80
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    Thermal fatigue performance of integrally cast automotive turbine wheels (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fluidized bed thermal fatigue testing was conducted on 16 integrally cast automotive turbine wheels for 1000-10,000 (600 sec total) thermal cycles at 935/50 C. The 16 wheels consisted of 14 IN-792 + 1% Hf and 2 gatorized AF2-1DA wheels; 6 of the IN-792 + Hf wheels contained crack arrest pockets inside the blade root flange. Temperature transients during the thermal cycling were measured in three calibration tests using either 18 or 30 thermocouples per wheel. Thermal cracking based on crack length versus accumulated cycles was greatest for unpocketed wheels developing cracks in 8-13 cycles compared to 75-250 cycles for unpocketed wheels. However, pocketed wheels survived up to 10,000 cycles with crack lengths less than 20 mm, whereas two unpocketed wheels developed 45 mm long cracks in 1000-2000 cycles.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-165227 , DOE/NASA/9696-1 , IITRI-M06003-54
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  • 81
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    Convergence rates for finite element problems with singularities. Part 1: Antiplane shear (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The problem of a finite crack in an infinite medium under antiplane shear load is considered. It is shown that the nodal forces at the tip of the crack accurately gives the order of singularity, that n energy release methods can give the strength to better than 1 percent with element size 1/10 the crack length, and that nodal forces give a much better estimate of the stress field than do the elements themselves. The finite element formulation and the factoring of tridiagonal matrices are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-164633 , IR-18 , VPI-E-80-8
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  • 82
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    Graphite composite truss welding and cap section forming subsystems. Volume 2: Program results (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The technology required to develop a beam builder which automatically fabricates long, continuous, lightweight, triangular truss members in space from graphite/thermoplastics composite materials is described. Objectives are: (1) continue the development of forming and welding methods for graphite/thermoplastic (GR/TP) composite material; (2) continue GR/TP materials technology development; and (3) fabricate and structurally test a lightweight truss segment.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-160932 , GDC-ASP-80-007-VOL-2
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  • 83
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    Effects of angle of attack and vertical fin on transonic flutter characteristics of an arrow-wing configuration (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental transonic flutter results are presented for a simplified 1/50 size, aspect ratio 1.77, wind tunnel model of an arrow wing design. Flutter results are presented for two configurations; namely, one with and one without a ventral fin mounted at the 0.694 semispan station. Results are presented for both configurations trimmed to zero lift and in a lifting condition at angles of attack up to 4 deg. The results show that the flutter characteristics of both configurations are similar to those usually observed. Increasing angle of attack reduces the flutter dynamic pressure by a small amount (about 13 percent maximum) for both configurations. The addition of the fin to the basic wing increases the flutter dynamic pressure. Calculated results for both configurations in the nonlifting condition obtained by using subsonic doublet lattice unsteady aerodynamic theory correlate reasonably well with the experimental results. Calculated results for the basic wing obtained by using subsonic kernal function unsteady aerodynamic theory did not agree as well with the experimental data.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81914 , L-14114
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  • 84
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    A new look at numerical analyses of free-edge stresses in composite laminates (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The edge stress problem for a + or - 45 deg graphite/epoxy laminate was examined. The reliability of the displacement formulated finite element method in analyzing the edge stress problem was investigated. Analyses of two well known elasticity problems, one involving a stress discontinuity and one a singularity, showed that the finite element analysis yields accurate stress distributions everywhere except in two elements closest to the stress discontinuity of singularity. Stress distributions for a + or - 45 deg laminate showed the same behavior near the singularity found in the well known problems with exact solutions. The displacement formulated finite element method appears to be a highly accurate technique for calculating interlaminar stress in composite laminates. The disagreement among the numerical methods was attributed to the unsymmetric stress tensor at the singularity.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1751 , L-13777
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  • 85
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    Normal and shear impact of layered composite with a crack - Dynamic stress intensification (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The dynamic response of a layered composite under normal and shear impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. One of the objectives was to develop an analytical method for determining dynamic stress solutions which should lead to a numerical method which utilizes Fourier transform for the space variable and Laplace transform for the time variable. The time-dependent angle loading is separated into two parts: a symmetric and a skew-symmetric with reference to the crack plane. By superposition, the transient boundary conditions consist of applying normal and shear tractions to a crack embedded in a layered composite; one phase of the composite could represent the fiber while the other could be the matrix. Mathematically, these conditions reduce the problem to a system of dual integral equations solved in the transform plane for the transform of the dynamic stress-intensity factor.
    Keywords: STRUCTURAL MECHANICS
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  • 86
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    A mixed-mode crack analysis of isotropic solids using conservation laws of elasticity (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A simple and convenient method of analysis for studying two-dimensional mixed-mode crack problems is presented. The analysis is formulated on the basis of conservation laws of elasticity and of fundamental relationships in fracture mechanics. The problem is reduced to the determination of mixed-mode stress-intensity factor solutions in terms of conservation integrals involving known auxiliary solutions. One of the salient features of the present analysis is that the stress-intensity solutions can be determined directly by using information extracted in the far field. Several examples with solutions available in the literature are solved to examine the accuracy and other characteristics of the current approach. This method is demonstrated to be superior in its numerical simplicity and computational efficiency to other approaches. Solutions of more complicated and practical engineering fracture problems dealing with the crack emanating from a circular hole are presented also to illustrate the capacity of this method
    Keywords: STRUCTURAL MECHANICS
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  • 87
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    Stresses in a three-dimensional unidirectional composite containing broken fibers (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An approximate solution is developed for the determination of the interlaminar normal and shear stresses in the vicinity of a crack in a three dimensional composite containing unidirectional linearly elastic fibers in an infinite linearly elastic matrix. In order to reduce the complexity of the formulation, certain assumptions are made as to the physically significant stresses to be retained. These simplifications reduce the partial differential equations of elasticity to differential-difference equations which are tractable using Fourier transform techniques. This 'material modeling' approach is in contrast with solutions developed by considering each lamina as a homogeneous, orthotropic layer. The resulting solution does not contain the classical singular stress field for the fibers and the influence of broken fibers on unbroken fibers is felt by a change in stress concentration factors. The matrix stresses however, are unbounded as the fiber spacing vanishes and an equivalent fiber-matrix geometry is proposed which gives the correct singular behavior. The numerical solution is considered in detail and several specific examples are presented. The potential for damaged or debonded zones to be generated by an embedded crack is discussed, and stress concentration factors for fibers near the crack are given. Detailed comparisons are made between the present solution, the analogous two-dimensional problem, and corresponding shear-lag models.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 13; 2, 19; 1980
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  • 88
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    Inelastic behavior of structural components (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A more accurate procedure was developed for the determination of the inelastic behavior of structural components. The actual stress-strain curve for the mathematical of the structure was utilized to generate the force-deformation relationships for the structural elements, rather than using simplified models such as elastic-plastic, bilinear and trilinear approximations. relationships were generated for beam elements with various types of cross sections. In the generational of these curves, stress or load reversals, kinematic hardening and hysteretic behavior were taken into account. Intersections between loading and unloading branches were determined through an iterative process. Using the inelastic properties obtained, the plastic static response of some simple structural systems composed of beam elements was computed. Results were compared with known solutions, indicating a considerable improvement over response predictions obtained by means of simplified approximations used in previous investigations.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 237-250
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  • 89
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    Combustion: Structural interaction in a viscoelastic material (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The effect of interaction between combustion processes and structural deformation of solid propellant was considered. The combustion analysis was performed on the basis of deformed crack geometry, which was determined from the structural analysis. On the other hand, input data for the structural analysis, such as pressure distribution along the crack boundary and ablation velocity of the crack, were determined from the combustion analysis. The interaction analysis was conducted by combining two computer codes, a combustion analysis code and a general purpose finite element structural analysis code.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 67-90
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  • 90
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    Statistical energy analysis of complex structures, phase 2 (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A method for estimating the structural vibration properties of complex systems in high frequency environments was investigated. The structure analyzed was the Materials Experiment Assembly, (MEA), which is a portion of the OST-2A payload for the space transportation system. Statistical energy analysis (SEA) techniques were used to model the structure and predict the structural element response to acoustic excitation. A comparison of the intial response predictions and measured acoustic test data is presented. The conclusions indicate that: the SEA predicted the response of primary structure to acoustic excitation over a wide range of frequencies; and the contribution of mechanically induced random vibration to the total MEA is not significant.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-161576 , MDC-G9203
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  • 91
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    Dynamic modal estimation using instrumental variables (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A method to determine the modes of dynamical systems is described. The inputs and outputs of a system are Fourier transformed and averaged to reduce the error level. An instrumental variable method that estimates modal parameters from multiple correlations between responses of single input, multiple output systems is applied to estimate aircraft, spacecraft, and off-shore platform modal parameters.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-152396 , TR-6419-01
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  • 92
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    Self-adaptive incremental Newton-Raphson algorithms (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Multilevel self-adaptive Newton-Raphson type strategies are developed to improve the solution efficiency of nonlinear finite element simulations of statically loaded structures. The overall strategy involves three basic levels. The first level involves preliminary solution tunneling via primative operators. Secondly, the solution is constantly monitored via quality/convergence/nonlinearity tests. Lastly, the third level involves self-adaptive algorithmic update procedures aimed at improving the convergence characteristics of the Newton-Raphson strategy. Numerical experiments are included to illustrate the results of the procedure.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 115-127
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  • 93
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    Response of nonlinear panels to random loads (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Lightweight aircraft structures exposed to a high intensity noise environment can fatigue prematurely if adequate consideration is not given to the problem. Design methods and design criteria for sonic fatigue prevention were developed based on analytical and experimental techniques. Most of the analytical work was based upon small deflection or linear structural theory which did not agree with the experimental results. A large deflection geometrical nonlinearity was incorporated into the analysis methods for determining the structural response to high intensity noise. The Karman-Herrmann large deflection equations with a single mode Galerkin approximation, and the method of equivalent linearization were used to predict mean square amplitude, mean square stresses, and nonlinear frequency at various acoustic loadings for rectangular panels. Both simply supported and clamped support conditions with immovable or movable inplane edges are considered. Comparisons with experimental results are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Nonlinear Struct. and Solid Mech.; p 141-163
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  • 94
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    Design and analysis of a stiffened composite fuselage panel (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The design and analysis of stiffened composite panel that is representative of the fuselage structure of existing wide bodied aircraft is discussed. The panel is a minimum weight design, based on the current level of technology and realistic loads and criteria. Several different stiffener configurations were investigated in the optimization process. The final configuration is an all graphite/epoxy J-stiffened design in which the skin between adjacent stiffeners is permitted to buckle under design loads. Fail safe concepts typically employed in metallic fuselage structure have been incorporated in the design. A conservative approach has been used with regard to structural details such as skin/frame and stringer/frame attachments and other areas where sufficient design data was not available.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159302 , LG80ER0137
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  • 95
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    Lateral density variations in elastic Earth models from an extended minimum energy approach (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Kaula's minimum energy approach was extended to include the nonhydrostatic gravitational potential energy and the density perturbation field was obtained to degree and order eight. The depth profiles for the density perturbation show a stratification with density excesses and deficiencies alternating with depth. The addition of the gravitational potential energy in the minimization process does not change significantly the conclusions based on results for the minimum shear strain energy case, concerning the inability of the mantle to withstand the lateral loading elastically.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-80742
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  • 96
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    Effects of substrate deformation and sip thickness on tile/sip interface stresses for shuttle thermal protection (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A nonlinear analysis was used to study the effects of substrate deformation characteristics and strain isolator pad (SIP) thickness on TILE/SIP interface stresses for the space shuttle thermal protection system. The configuration analyzed consisted of a 5.08 cm thick, 15.24 cm square tile with a 12.7 cm square SIP footprint bordered by a 1.27 cm wide filler bar and was subjected to forces and moments representative of a 20.7 kPa aerodynamic shock passing over the tile. The SIP stress deflection curves were obtained after a 69 kPa proof load and 100 cycles conditioning at 55 kPa. The TILE/SIP interface stresses increase over flat substrate values for zero to peak substrate deformation amplitudes up to 0.191 cm by up to a factor of nearly five depending on deformation amplitude, half wave length, and location. Stresses for a 0.23 cm thick SIP found to be up to 60 percent greater than for a 0.41 cm thick SIP for identical loads and substrate deformation characteristics. A simplified method was developed for approximating the substrate location which produces maximum TILE/SIP interface stresses.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81855
    Format: application/pdf
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    Some space shuttle tile/strain-isolator-pad sinusoidal vibration tests (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Vibration tests were performed on the tile/strain-isolator-pad system used as thermal protection for the space shuttle orbiter. Experimental data on normal and in-plane vibration response and damping properties are presented. Three test specimens exhibited shear type motion during failures that occurred in the tile near the tile/strain-isolator-pad bond-line. A dynamic instability is described which has large in-plane motion at a frequency one-half that of the nominal driving frequency. Analysis shows that this phenomenon is a parametric response.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81853
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  • 98
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    Application of fully stressed design procedures to redundant and non-isotropic structures (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An evaluation is presented of fully stressed design procedures for sizing highly redundant structures including structures made of composite materials. The evaluation is carried out by sizing three structures: a simple box beam of either composite or metal construction; a low aspect ratio titanium wing; and a titanium arrow wing for a conceptual supersonic cruise aircraft. All three structures are sized by ordinary fully-stressed design (FSD) and thermal fully stressed design (TFSD) for combined mechanical and thermal loads. Where possible, designs are checked by applying rigorous mathematical programming techniques to the structures. It is found that FSD and TFSD produce optimum designs for the metal box beam, but produce highly non-optimum designs for the composite box beam. Results from the delta wing and arrow wing indicate that FSD and TFSD exhibits slow convergence for highly redundant metal structures. Further, TFSD exhibits slow oscillatory convergence behavior for the arrow wing for very high temperatures. In all cases where FSD and TFSD perform poorly either in obtaining nonoptimum designs or in converging slowly, the assumptions on which the algorithms are based are grossly violated. The use of scaling, however, is found to be very effective in obtaining fast convergence and efficiently produces safe designs even for those cases when FSD and TFSD alone are ineffective.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81842
    Format: application/pdf
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  • 99
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    Substructure procedure for including tile flexibility in stress analysis of shuttle thermal protection system (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A substructure procedure to include the flexibility of the tile in the stress analysis of the shuttle thermal protection system (TPS) is described. In this procedure, the TPS is divided into substructures of (1) the tile which is modeled by linear finite elements and (2) the SIP which is modeled as a nonlinear continuum. This procedure was applied for loading cases of uniform pressure, uniform moment, and an aerodynamic shock on various tile thicknesses. The ratios of through-the-thickness stresses in the SIP which were calculated using a flexible tile compared to using a rigid tile were found to be less than 1.05 for the cases considered.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81864
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  • 100
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    Photoelastic tests on models of thermal protection system for space shuttle orbiter (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The thermal protection system (TPS) of the space shuttle orbiter vehicle, consisting of ceramic tile/adhesive/strain isolator pad/adhesive/aluminum substructure, was modeled photoelasticity. A highly sensitive photoelastic material was used in the models to show the nature of the stress-transfer between the strain isolation pad (SIP) and the ceramic tile through the RTV-adhesive layer. Isochromatic fringe patterns were obtained for models subjected to tension and combined tension and bending. Tests indicated that the load-transfer between the SIP and the photoelastic material occurred at discrete locations causing stress concentrations in the photoelastic material. Stress concentration factors of the order of 1.9 were measured, but as the observed photoelastic response was an integrated effect through the model thickness, the local stress concentration factors at the SIP/tile interface could be even higher.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81866
    Format: application/pdf
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