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  • Other Sources  (591)
  • STRUCTURAL MECHANICS  (591)
  • 1980-1984  (591)
  • 1950-1954
  • 1984  (314)
  • 1983  (277)
  • 1952
  • 101
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    Constitutive modeling of inelastic anisotropic material response (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A constitutive equation was developed to predict the inelastic thermomechanical response of single crystal turbine blades. These equations are essential for developing accurate finite element models of hot section components and contribute significantly to the understanding and prediction of crack initiation and propagation. The method used was limited to unified state variable constitutive equations. Two approaches to developing an anisotropic constitutive equation were reviewed. One approach was to apply the Stouffer-Bodner representation for deformation induced anisotropy to materials with an initial anisotropy such as single crystals. The second approach was to determine the global inelastic strain rate from the contribution of the slip in each of the possible crystallographic slip systems. A three dimensional finite element is being developed with a variable constitutive equation link that can be used for constitutive equation development and to predict the response of an experiment using the actual specimen geometry and loading conditions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 4 p
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  • 102
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    High temperature stress-strain analysis (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The objectives are threefold: to assist in developing predictive tools needed to improve design analyses and procedures for the efficient and accurate prediction of burner liner structural performance and response; to calibrate, validate, and evaluate these predictive tools by comparing the predicted results with the experimental data; and to evaluate existing as well as advanced temperature and strain measurement instrumentation, through both contact and noncontact efforts, in a simulated turbine engine combustor environment. As the predictive tool, tests, test methods, instrumentation, and data acquisition and reduction methods are developed and evaluated, a proven, integrated analysis/experiment method will be developed that will permit the accurate prediction of the cyclic life of a burner liner.
    Keywords: STRUCTURAL MECHANICS
    Type: Turbine Engine Hot Section Technology, 1984; 14 p
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  • 103
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    Life prediction and constitutive behavior (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: One of the primary drivers that prompted the initiation of the hot section technology (HOST) program was the recognized need for improved cyclic durability of costly hot section components. All too frequently, fatigue in one form or another was directly responsible for the less than desired durability, and prospects for the future weren't going to improve unless a significant effort was mounted to increase our knowledge and understanding of the elements governing cyclic crack initiation and propagation lifetime. Certainly one of the important factors is the ability to perform accurate structural stress-strain analyses on a routine basis to determine the magnitudes of the localized stresses and strains since it is these localized conditions that govern the initiation and crack growth processes. Developing the ability to more accurately predict crack initiation lifetimes and cyclic crack growth rates for the complex loading conditions found in turbine engine hot sections is of course the ultimate goal of the life prediction research efforts. It has been found convenient to divide the research efforts into those dealing with nominally isotropic and anisotropic alloys; the latter for application to directionally solidified and single crystal turbine blades.
    Keywords: STRUCTURAL MECHANICS
    Type: Turbine Eng. Hot Sect. Technol. (HOST); p 205-207
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  • 104
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    Turbine engine Hot Section Technology (HOST) project (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Hot Section Technology (HOST) Project is a NASA-sponsored endeavor to improve the durability of advanced gas turbine engines for commercial and military aircraft. Through improvements in the analytical models and life prediction systems, designs for future hot section components , the combustor and turbine, will be more accurately analyzed and will incorporate features required for longer life in the more hostile operating environment of high performance engines.
    Keywords: STRUCTURAL MECHANICS
    Type: Turbine Eng. Hot Sect. Technol. (HOST); p 1-6
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  • 105
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    Nonlinear Analysis of a Bolted Marine Riser Connector Using NASTRAN Substructuring (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of an investigation of the behavior of a bolted, flange type marine riser connector is reported. The method used to account for the nonlinear effect of connector separation due to bolt preload and axial tension load is described. The automated multilevel substructing capability of COSMIC/NASTRAN was employed at considerable savings in computer run time. Simplified formulas for computer resources, i.e., computer run times for modules SDCOMP, FBS, and MPYAD, as well as disk storage space, are presented. Actual run time data on a VAX-11/780 is compared with the formulas presented.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC Twelfth NASTRAN (R) Users' Colloq.; p 210-236
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  • 106
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    Elevated temperature crack growth (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Critical gas turbine engine hot section components such as blades, vanes, and combustor liners tend to develop minute cracks during early stages of operations. The ability of currently available path-independent (P-I) integrals to correlate fatigue crack propagation under conditions that simulate the turbojet engine combustor liner environment was determined. To date, an appropriate specimen design and a crack displacement measurement method were determined. Alloy 718 was selected as the analog material based on its ability to simulate high temperature behavior at lower temperatures in order to facilitate experimental measurements. Available P-I integrals were reviewed and the best approaches are being programmed into a finite element post processor for eventual comparison with experimental data. The experimental data will include cyclic crack growth tests under thermomechanical conditions, and, additionally, thermal gradients.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 10 p
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  • 107
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    The 3-D inelastic analysis methods for hot section components (base program) (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A series of computer codes are sought that would permit more accurate and efficient three-dimensional inelastic structural analysis of combustor liners, turbine blades, and turbine vanes. Each code embodies a progression of mathematical models for increasingly comprehensive representation of the geometrical features, loading conditions, and forms of nonlinear material response that distinguish these three groups of hot section components.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 4 p
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  • 108
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    Finite Element Prediction of Acoustic Scattering and Radiation from Submerged Elastic Structures (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A finite element formulation is derived for the scattering and radiation of acoustic waves from submerged elastic structures. The formulation uses as fundamental unknowns the displacement in the structure and a velocity potential in the field. Symmetric coefficient matrices result. The outer boundary of the fluid region is terminated with an approximate local wave-absorbing boundary condition which assumes that outgoing waves are locally planar. The finite element model is capable of predicting only the near-field acoustic pressures. Far-field sound pressure levels may be determined by integrating the surface pressures and velocities over the wet boundary of the structure using the Helmholtz integral. Comparison of finite element results with analytic results show excellent agreement. The coupled fluid-structure problem may be solved with general purpose finite element codes by using an analogy between the equations of elasticity and the wave equation of linear acoustics.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC Twelfth NASTRAN (R) Users' Colloq.; p 192-209
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  • 109
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    Design Spectrum Analysis in NASTRAN (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The utility of Design Spectrum Analysis is to give a mode by mode characterization of the behavior of a design under a given loading. The theory of design spectrum is discussed after operations are explained. User instructions are taken up here in three parts: Transient Preface, Maximum Envelope Spectrum, and RMS Average Spectrum followed by a Summary Table. A single DMAP ALTER packet will provide for all parts of the design spectrum operations. The starting point for getting a modal break-down of the response to acceleration loading is the Modal Transient rigid format. After eigenvalue extraction, modal vectors need to be isolated in the full set of physical coordinates (P-sized as opposed to the D-sized vectors in RF 12). After integration for transient response the results are scanned over the solution time interval for the peak values and for the times that they occur. A module called SCAN was written to do this job, that organizes these maxima into a diagonal output matrix. The maximum amplifier in each mode is applied to the eigenvector of each mode which then reveals the maximum displacements, stresses, forces and boundary reactions that the structure will experience for a load history, mode by mode. The standard NASTRAN output processors have been modified for this task. It is required that modes be normalized to mass.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC Twelfth NASTRAN (R) Users' Colloq.; p 78-91
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  • 110
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    The Design and Usage of the New Data Management Features in NASTRAN (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two new data management features are installed in the April 1984 release of NASTRAN. These two features are the Rigid Format Data Base and the READFILE capability. The Rigid Format Data Base is stored on external files in card image format and can be easily maintained and expanded by the use of standard text editors. This data base provides the user and the NASTRAN maintenance contractor with an easy means for making changes to a Rigid Format or for generating new Rigid Formats without unnecessary compilations and link editing of NASTRAN. Each Rigid Format entry in the data base contains the Direct Matrix Abstraction Program (DMAP), along with the associated restart, DMAP sequence subset and substructure control flags. The READFILE capability allows an user to reference an external secondary file from the NASTRAN primary input file and to read data from this secondary file. There is no limit to the number of external secondary files that may be referenced and read.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC Twelfth NASTRAN (R) Users' Colloq.; p 11-25
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  • 111
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    Passive Sun seeker/tracker and a thermally activated power module (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Development and testing of two mechanisms using a shape memory alloy metal (NITINOL) as the power source are described. The two mechanisms developed are a passive Sun Seeker/Tracker and a generic type power module. These mechanisms use NITINOL wire initially strained in pure torsion which provides the greatest mechanical work capacity upon recovery, as compared to other deformation modes (i.e., tension, helical springs, and bending).
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 171-185
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  • 112
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    Structural optimization - Challenges and opportunities (1983)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: A review of developments in structural optimization techniques and their interface with growing computer capabilities is presented. Structural design steps comprise functional definition of an object, an evaluation phase wherein external influences are quantified, selection of the design concept, material, object geometry, and the internal layout, and quantification of the physical characteristics. Optimization of a fully stressed design is facilitated by use of nonlinear mathematical programming which permits automated definition of the physics of a problem. Design iterations terminate when convergence is acquired between mathematical and physical criteria. A constrained minimum algorithm has been formulated using an Augmented Lagrangian approach and a generalized reduced gradient to obtain fast convergence. Various approximation techniques are mentioned. The synergistic application of all the methods surveyed requires multidisciplinary teamwork during a design effort.
    Keywords: STRUCTURAL MECHANICS
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  • 113
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    Postbuckling behavior of axially compressed graphite-epoxy cylindrical panels with circular holes (1984)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: The results of an experimental and analytical study of the effects of circular holes on the postbuckling behavior of graphite-epoxy cylindrical panels loaded in axial compression are presented. The STAGSC-1 general shell analysis computer code is used to determine the buckling and postbuckling response of the panels. The loaded, curved ends of the specimens were clamped by fixtures and the unloaded, straight edges were simply supported by knife-edge restraints. The panels are loaded by uniform end shortening to several times the end shortening at buckling. The unstable equilibrium path of the postbuckling response is obtained analytically by using a method based on controlling an equilibrium-path-arc-length parameter instead of the traditional load parameter. The effects of hole diameter, panel radius, and panel thickness on postbuckling response are considered in the study. Experimental results are compared with the analytical results and the failure characteristics of the graphite-epoxy panels are described.
    Keywords: STRUCTURAL MECHANICS
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  • 114
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    Advances and trends in structural and solid mechanics; Proceedings of the Symposium, Washington, DC, October 4-7, 1982 (1983)
    In:  Other Sources
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    Publication Date: 2016-03-09
    Description: The mechanics of materials and material characterization are considered, taking into account micromechanics, the behavior of steel structures at elevated temperatures, and an anisotropic plasticity model for inelastic multiaxial cyclic deformation. Other topics explored are related to advances and trends in finite element technology, classical analytical techniques and their computer implementation, interactive computing and computational strategies for nonlinear problems, advances and trends in numerical analysis, database management systems and CAD/CAM, space structures and vehicle crashworthiness, beams, plates and fibrous composite structures, design-oriented analysis, artificial intelligence and optimization, contact problems, random waves, and lifetime prediction. Earthquake-resistant structures and other advanced structural applications are also discussed, giving attention to cumulative damage in steel structures subjected to earthquake ground motions, and a mixed domain analysis of nuclear containment structures using impulse functions.
    Keywords: STRUCTURAL MECHANICS
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  • 115
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    Design sensitivity analysis with Applicon IFAD using the adjoint variable method (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A numerical method is presented to implement structural design sensitivity analysis using the versatility and convenience of existing finite element structural analysis program and the theoretical foundation in structural design sensitivity analysis. Conventional design variables, such as thickness and cross-sectional areas, are considered. Structural performance functionals considered include compliance, displacement, and stress. It is shown that calculations can be carried out outside existing finite element codes, using postprocessing data only. That is, design sensitivity analysis software does not have to be imbedded in an existing finite element code. The finite element structural analysis program used in the implementation presented is IFAD. Feasibility of the method is shown through analysis of several problems, including built-up structures. Accurate design sensitivity results are obtained without the uncertainty of numerical accuracy associated with selection of a finite difference perturbation.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-181101 , NAS 1.26:181101 , TR-84-17
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  • 116
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    Stress concentration measurement in a rectangular plate using an array of embedded optical fibers (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Embedded single mode optical fiber waveguide has been used to determine the two-dimensional stress distribution produced by point loading on a simply supported rectangular plate. Each of the fifty individual fibers in the rectangular grid array attached to the plate yields a measurement of the stress integrated along the length of that fiber on the specimen. By using information from all the fibers, both the functional form and the amplitude of the distribution may be determined. Limits on the dynamic range and spatial resolution are indicated. Applications in the measurement of internal stress and the monitoring of physically small critical structural components are suggested.
    Keywords: STRUCTURAL MECHANICS
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  • 117
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    Residual thermal stresses in cross-ply graphite-epoxy tubes (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Elasticity solutions for the residual stress state in cross-ply graphite-epoxy tubes subjected to a spatially uniform temperature below the cure temperature are derived. The solutions are valid away from the ends of the tube. Numerical results are presented for three tubes. It is seen that stacking arrangement can affect the residual stresses and that the radial stresses are smaller than the other stress components. The results show that classical lamination theory is in considerable error when the tube radius to wall thickness ratio is less than 20.
    Keywords: STRUCTURAL MECHANICS
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  • 118
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    On dynamics of laminated anisotropic plates using a refined mixed plate element (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An analysis of the free vibration and transient response of laminates using a mixed shear flexible element is presented. The element is based on a refined theory that accounts for a parabolic distribution of the transverse shear stresses through each lamina and requires no shear correction coefficients. The mixed formulation of the theory treats the five displacement functions and six stress resultants independently so that they are nodal degrees of freedom in the finite element model. Sample problems using the element are analyzed and the results of free vibration and transient response are presented. Compared to the existing shear deformation plate theory the present refined theory gives more accurate results for frequencies, displacements and stresses.
    Keywords: STRUCTURAL MECHANICS
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  • 119
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    Extensions of the Ritz-Galerkin method for the forced, damped vibrations of structural elements (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Ritz-Galerkin methods were used to obtain approximate solutions for free undamped, vibration problems. It is demonstrated that these same methods may be used straightforwardly to analyze forced vibrations with damping without requiring the free vibration eigenfunctions. It was shown that the Galerkin method is an effective technique for these types of problems. The Ritz method has the advantage that it does not need to satisfy the force-type boundary conditions, which is particularly important for plates and shells. Proper functionals representing the forcing and damping terms were developed. Two types of damping--viscous and material (hysteretic) are discussed. Distributed and concentrated exciting forces are treated. Numerical results are obtained for cantilevered beams and rectangular plates. The rates of convergence of the solutions are shown. Approximate solutions from the present methods are compared with the exact solutions for the cantilever beam.
    Keywords: STRUCTURAL MECHANICS
    Type: AFWAL Vibration Damping 1984 Workshop Proceedings; 21 p
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  • 120
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    A comparison of measured spacecraft modal damping values (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The prediction and the measurement of modal damping values of spacecrafts for use in the determination of design loads were summarized. Realistic transient forcing functions were used. The solution of complex eigenvalue response solutions resulting from modal synthesis of subsystems in which each subsystem is assigned modal damping values is discussed. Damping data on both the Voyager and the Galileo spacecrafts using up to eight different types of techniques to analyze modal data are presented. It is concluded that it is difficult to estimate the true damping of a structure and the measured damping values which are dependent on the analysis method of the data.
    Keywords: STRUCTURAL MECHANICS
    Type: AFWAL Vibration Damping 1984 Workshop Proceedings; 6 p
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  • 121
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    Shape optimization including finite element grid adaptation (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The prediction of optimal shape design for structures depends on having a sufficient level of precision in the computation of structural response. These requirements become critical in situations where the region to be designed includes stress concentrations or unilateral contact surfaces, for example. In the approach to shape optimization discussed here, a means to obtain grid adaptation is incorporated into the finite element procedures. This facility makes it possible to maintain a level of quality in the computational estimate of response that is surely adequate for the shape design problem.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 10 p
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  • 122
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    Problems in large-scale structural optimization (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A general design optimization model for large complex systems is defined. Major features of the model that challenge various optimization algorithms are discussed. Requirements of a model optimization algorithm are identified. Objectives of the study of various algorithms are defined and a basis for conducting such a study is developed. Primal as well as transformation methods are analytically studied and a unified viewpoint of various methods is presented. Several numerical examples are solved using different methods to study their performance. Conclusions drawn from the study are presented and discussed. Areas of future research in nonlinear programming as well as structural optimization are identified and discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 26 p
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  • 123
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    High-temperature constitutive modeling (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Thermomechanical service conditions for high-temperature levels, thermal transients, and mechanical loads severe enough to cause measurable inelastic deformation are studied. Structural analysis in support of the design of high-temperature components depends strongly on accurate mathematical representations of the nonlinear, hereditary, inelastic behavior of structural alloys at high temperature, particularly in the relatively small strain range. Progress is discussed in the following areas: multiaxial experimentation to provide a basis for high-temperature multiaxial constitutive relationships; nonisothermal testing and theoretical development toward a complete thermomechanically path dependent formulation of viscoplasticity; and development of viscoplastic constitutive model accounting for initial anisotropy.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 11 p
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  • 124
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    Turbine Engine Hot Section Technology, 1984 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Presentations were made concerning the hot section environment and behavior of combustion liners, turbine blades, and waves. The presentations were divided into six sessions: instrumentation, combustion, turbine heat transfer, structural analysis, fatigue and fracture, and surface properties. The principal objective of each session was to disseminate research results to date, along with future plans. Topics discussed included modeling of thermal and fluid flow phenomena, structural analysis, fatigue and fracture, surface protective coatings, constitutive behavior, stress-strain response, and life prediction methods.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CP-2339 , E-2267 , NAS 1.55:2339
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  • 125
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    On the solution of problems involving impact type loading (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The response of beam and plate members to pulse and impact loading is investigated, and numerical methods are analyzed and compared. The equations of motion, the finite difference and finite element methods, the time integration/Runge-Kutta techniques, and material modeling are discussed in detail. It is found that both the finite difference and the finite element methods could be accurately employed to discretize the spatial variation in the displacements. Central differences or a fourth order Runge-Kutta algorithm could be used for the time integration. The total energy of the system would give the stability and accuracy of the solution. Results showed that the finite element method provided better efficiency in obtaining accurate solution than the finite difference method when a scalar processor is used. However, the finite difference method was more efficient on the vector processor. Therefore, the most efficient method of solution depends on the type of computer present for the analysis.
    Keywords: STRUCTURAL MECHANICS
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  • 126
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    Time dependency of strainrange partitioning life relationships (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of exposure time (or creep rate) on the CP life relationship is established by conducting isothermal CP tests at varying exposure times on 316 Ss at 1300 and 1500 F. A reduction in the CP cycle life is observed with an increase in the exposure time of the CP test at a given inelastic strain-range. This phenomenon is characterized by modifying the Manson-Coffin type of CP relationship. Two new life relationships: (1) the Steady State Creep Rate (SSRC) Modified CP life relationship, and (2) the Failure Time (FT) Modified CP life relationship, are developed in this report. They account for the effect of creep rate and exposure time within the CP type of waveform. The reduction in CP cyclic life in the long exposure time tests is attributed to oxidation and the precipitation of carbides along the grain boundaries.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-174946 , NAS 1.26:174946
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  • 127
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    NASTRAN Structural Model for the Large 64-meter Antenna Pedestal. Part 3: Applications to Hydrostatic Bearing Oil Film (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: Investigations are conducted on the 64-meter antenna hydrostatic bearing oil film thickness under a variety of loads and elastic moduli. These parametric studies use a NASTRAN pedestal structural model to determine the deflections under the hydrostatic bearing pad. The deflections form the input for a computer program to determine the hydrostatic bearing oil film thickness. For the future 64-meter to 70-meter antenna extension and for the 2.2-meter (86-in.) haunch concrete replacement cases, safe oil film thickness (greater than 0.13 mm (0.005 in.) at the corners of the pad) are predicted. The effects of varying moduli of elasticity for different sections of the pedestal and the film height under distressed runner conditions are also studied.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition Rept.; p 172-183
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  • 128
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    Nonlinear Analysis for High-temperature Composites: Turbine Blades/vanes (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: An integrated approach to nonlinear analysis of high-temperature composites in turbine blade/vane applications is presented. The overall strategy of this approach and the key elements comprising this approach are summarized. Preliminary results for a tungsten-fiber-reinforced superalloy (TFRS) composite are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: Nonlinear Struct. Anal.; p 131-147
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  • 129
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    Interactive Finite Elements for General Engine Dynamics Analysis (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: General nonlinear finite element codes were adapted for the purpose of analyzing the dynamics of gas turbine engines. In particular, this adaptation required the development of a squeeze-film damper element software package and its implantation into a representative current generation code. The ADINA code was selected because of prior use of it and familiarity with its internal structure and logic. This objective was met and the results indicate that such use of general purpose codes is viable alternative to specialized codes for general dynamics analysis of engines.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Struct. Anal.; p 119-130
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  • 130
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    A Shear Deformable Shell Element for Laminated Composites (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: A three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Struct. Anal.; p 31-43
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    NASTRAN Structural Model for the Large 64-meter Antenna Pedestal, Part 1 (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: Static analysis and a computer structural model for the large 64-m antenna pedestal are developed using the MSC version of the NASTRAN program. This model was necessary to conduct a variety of hydrostatic bearing rehabilitation studies. The results obtained from the model show that the top surface deflections due to pad loads are in good agreement with the results previously obtained from a simplified "shortcut' analytical model, and also in agreement with field measurements. In addition, the displacement and force distributions as well as the state of stress and strain are obtained.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition Rept.; p 86-96
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  • 132
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    Determination of Elevator and Rudder Hinge Forces on the Learjet Model 55 Aircraft (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The empennage structure on the Learjet 55 aircraft was quite similar to the empennage structure on earlier Learjet models. However, due to an important structural change in the vertical fin along with the new loads environment on the 50 series aircraft, a structural test was required on the vertical fin, but the horizontal tail was substantiated by a comparative analysis with previous tests. NASTRAN analysis was used to investigate empennage deflections, stress levels, and control surface hinge forces. The hinge force calculations were made with the control surfaces in the deflected as well as undeflected configurations. A skin panel buckling analysis was also performed, and the non-linear effects of buckling were simulated in the NASTRAN model to more accurately define internal loads and stress levels. Comparisons were then made between the Model 55 and the Model 35/36 stresses and internal forces to determine which components were qualified by previous tests. Some of the methods and techniques used in this analysis are described.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 226-248
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    Dynamic certification of a thrust-measuring system for large solid rocket motors (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The J-4 Rocket Test Cell and its Thrust Measuring System (TMS) at Arnold Engineering Development Center were modified to provide multicomponent force measurement of large solid rocket motors having nozzle gimbaling capability. To verify the structural integrity of a combined TMS and motor system, a large finite element model of the TMS and motor was developed using the NASTRAN computer program. Due to the importance of obtaining accurate estimates for the dynamic force levels, it was necessary to certify that the model adequately simulated the physical system. This was accomplished by performing a modal analysis test on the TMS and motor combination. The objectives were to discuss the physical characteristics of the TMS and motor that influence the NASTRAN model; to compare the frequency response characteristics computed using the NASTRAN model to those obtained from the modal analysis test; to discuss the experiences gained in modal analysis testing; and to demonstrate how state-of-the-art experimental and analytical methods are used in the design of ground test facilities.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 207-225
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  • 134
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    Propagation of flexural and membrane waves with fluid loaded NASTRAN plate and shell elements (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Modeling of flexural and membrane type waves existing in various submerged (or in vacuo) plate and/or shell finite element models that are excited with steady state type harmonic loadings proportioned to e(i omega t) is discussed. Only thin walled plates and shells are treated wherein rotary inertia and shear correction factors are not included. More specifically, the issue of determining the shell or plate mesh size needed to represent the spatial distribution of the plate or shell response is of prime importance towards successfully representing the solution to the problem at hand. To this end, a procedure is presented for establishing guide lines for determining the mesh size based on a simple test model that can be used for a variety of plate and shell configurations such as, cylindrical shells with water loading, cylindrical shells in vacuo, plates with water loading, and plates in vacuo. The procedure for doing these four cases is given, with specific numerical examples present only for the cylindrical shell case.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 178-206
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  • 135
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    Propagating plane harmonic waves through finite length plates of variable thickness using finite element techniques (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An analysis is given using finite element techniques which addresses the propagaton of a uniform incident pressure wave through a finite diameter axisymmetric tapered plate immersed in a fluid. The approach utilized in developing a finite element solution to this problem is based upon a technique for axisymmetric fluid structure interaction problems. The problem addressed is that of a 10 inch diameter axisymmetric fixed plate totally immersed in a fluid. The plate increases in thickness from approximately 0.01 inches thick at the center to 0.421 inches thick at a radius of 5 inches. Against each face of the tapered plate a cylindrical fluid volume was represented extending five wavelengths off the plate in the axial direction. The outer boundary of the fluid and plate regions were represented as a rigid encasement cylinder as was nearly the case in the physical problem. The primary objective of the analysis is to determine the form of the transmitted pressure distribution on the downstream side of the plate.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 161-177
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  • 136
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    A NASTRAN DMAP procedure for calculation of base excitation modal participation factors (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: This paper presents a technique for calculating the modal participation factors for base excitation problems using a DMAP alter to the NASTRAN real eigenvalue analysis Rigid Format. The DMAP program automates the generation of the seismic mass to add to the degrees of freedom representing the shaker input directions and calculates the modal participation factors. These are shown in the paper to be a good measure of the maximum acceleration expected at any point on the structure when the subsequent frequency response analysis is run.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 113-140
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  • 137
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    Finite element analysis of fluid-filled elastic piping systems (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two finite element procedures are described for predicting the dynamic response of general 3-D fluid-filled elastic piping systems. The first approach, a low frequency procedure, models each straight pipe or elbow as a sequence of beams. The contained fluid is modeled as a separate coincident sequence axial members (rods) which are tied to the pipe in the lateral direction. The model includes the pipe hoop strain correction to the fluid sound speed and the flexibility factor correction to the elbow flexibility. The second modeling approach, an intermediate frequency procedure, follows generally the original Zienkiewicz-Newton scheme for coupled fluid-structure problems except that the velocity potential is used as the fundamental fluid unknown to symmetrize the coefficient matrices. From comparisons of the beam model predictions to both experimental data and the 3-D model, the beam model is validated for frequencies up to about two-thirds of the lowest fluid-filled labor pipe mode. Accurate elbow flexibility factors are seen to be crucial for effective beam modeling of piping systems.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 141-160
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  • 138
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    An alternative method of analysis for base accelerated dynamic response in NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An alternative method of analysis to determine the dynamic response of structures subjected to base accelerations is presented. The method is exact as opposed to the approximate technique of using unusually large masses and loads to enforce desired base accelerations. This paper presents the relevant equations to motion, ALTERs for direct and modal frequency-, random- and transient-response rigid formats, and illustrative examples.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 89-112
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  • 139
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    Acoustical modes of arbitrary volumes using NASTRAN transient heat transfer RF9 (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An equivalence between temperature and pressure, heat conduction and stiffness and heat capacity and mass is defined, enabling acoustical modal analysis of arbitrary three dimensional volumes. The transient heat transfer analysis rigid format in NASTRAN, RF9, has been altered providing the acoustical analysis capability. Examples and ALTERs are included.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 82-88
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  • 140
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    Generalizing the TRAPRG and TRAPAX finite elements (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The NASTRAN TRAPRG and TRAPAX finite elements are very restrictive as to shape and grid point numbering. The elements must be trapezoidal with two sides parallel to the radial axis. In addition, the ordering of the grid points on the element connection card must follow strict rules. The paper describes the generalization of these elements so that these restrictions no longer apply.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 76-81
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  • 141
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    The GPRIME approach to finite element modeling (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: GPRIME, an interactive modeling system, runs on the CDC 6000 computers and the DEC VAX 11/780 minicomputer. This system includes three components: (1) GPRIME, a user friendly geometric language and a processor to translate that language into geometric entities, (2) GGEN, an interactive data generator for 2-D models; and (3) SOLIDGEN, a 3-D solid modeling program. Each component has a computer user interface of an extensive command set. All of these programs make use of a comprehensive B-spline mathematics subroutine library, which can be used for a wide variety of interpolation problems and other geometric calculations. Many other user aids, such as automatic saving of the geometric and finite element data bases and hidden line removal, are available. This interactive finite element modeling capability can produce a complete finite element model, producing an output file of grid and element data.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 33-45
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  • 142
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    Orthotropic hole element (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A finite element was developed to adequately represent the state of stress in the region around a circular hole in orthotropic material experiencing reasonably general loading. This has been achieved through a complementary virtual work formulation of the stiffness and stress matrices for a square element with a center circular hole. The element has been incorporated into COSMIC/NASTRAN as a dummy element. Sample problems have been solved and these results are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 46-75
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  • 143
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    NASA/MSFC NASTRAN auxiliary I/O routines (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Since the initial installation of NASTRAN on the UNIVAC 1100/82 computer at the Marshall Space Flight Center (MSFC), a number of local codes have been incorporated as user routines. This paper describes four of these codes and how interested users may obtain additional information.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 6-20
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  • 144
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    Using PAFEC as a preprocessor for COSMIC/NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Programs for Automatic Finite Element Calculations (PAFEC) is a general purpose, three dimensional linear and nonlinear finite element program (ref. 1). PAFEC's features include free format input utilizing engineering keywords, powerful mesh generating facilities, sophisticated data base management procedures, and extensive data validation checks. Presented here is a description of a software interface that permits PAFEC to be used as a preprocessor for COSMIC/NASTRAN. This user friendly software, called PAFCOS, frees the stress analyst from the laborious and error prone procedure of creating and debugging a rigid format COSMIC/NASTRAN bulk data deck. By interactively creating and debugging a finite element model with PAFEC, thus taking full advantage of the free format engineering keyword oriented data structure of PAFEC, the amount of time spent during model generation can be drastically reduced. The PAFCOS software will automatically convert a PAFEC data structure into a COSMIC/NASTRAN bulk data deck. The capabilities and limitations of the PAFCOS software are fully discussed in the following report.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 21-32
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    BANDIT in NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: BANDIT has been implemented into the NASTRAN April '83 release. It is now a permanent feature in NASTRAN and will be included in all future releases for all four computing machines (IBM, CDC, UNIVAC, and VAX). Originally BANDIT operated as a preprocessor of NASTRAN. It read the NASTRAN input cards and produced a set of resequencing (SEOGP) cards that would greatly reduce the computational time required by the matrix decomposition module of NASTRAN for a large structure. In the past, many computer centers had installed BANDIT in their systems together with the NASTRAN program. The user would run the BANDIT program and NASTRAN as if they were one program (or two separated programs depending on how the two programs were actually tied together in the computer systems). In some cases, the user was required to pass the input cards and the output SEQGP cards between the two programs, and n others, the data was manipulated through the use of cataloged disc files. Although there is nothing wrong with this BANDIT-NASTRAN arrangement, there are, however, several shortcomings which are mentioned in this paper. The BANDIT in the NASTRAN April '83 release has removed all the deficiencies, and it comes in one version applicable to the four computing machines.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 1-5
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  • 146
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    NASTRAN structural model for the large 64-meter antenna pedestal. Part 2: Improved model (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Static analysis and a computer structural model for the large 64-m antenna pedestal are developed using the MSC version of the NASTRAN program. This improved pedestal model includes the launch areas and the actual pressure pattern of the oil under the hydrostatic bearing pad. The results obtained from the new improved model have indicated that the deflections due to pad loads are in good agreement with field measurements. The top surface deflection of the pedestal obtained from the NASTRAN model is used as an input to the oil film computer program to determine the minimum oil film thickness under the pad.
    Keywords: STRUCTURAL MECHANICS
    Type: The Telecommun. and Data Acquisition Rept.; p 105-113
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  • 147
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    Constitutive Models Based on Compressible Plastic Flows (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The need for describing materials under time or cycle dependent loading conditions has been emphasized in recent years by several investigators. In response to the need, various constitutive models describing the nonlinear behavior of materials under creep, fatigue, or other complex loading conditions were developed. The developed models for describing the fully dense (non-porous) materials were mostly based on uncoupled plasticity theory. The improved characterization of materials provides a better understanding of the structual response under complex loading conditions. The pesent studies demonstrate that the rate or time dependency of the response of a porous aggregate can be incorporated into the nonlinear constitutive behavior of a porous solid by appropriately modeling the incompressible matrix behavior. It is also sown that the yield function which wads determined by a continuum mechanics approach must be verified by appropriate experiments on void containing sintered materials in order to obtain meaningful numbers for the constants that appear in the yield function.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 267-282
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    A New Uncoupled Viscoplastic Constitutive Model (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A new uncoupled viscoplastic model has been proposed along with experiments and analysis to define the various material constraints. Distinguishing between rate sensitive and rate insensitive strain allows the rate sensitive strain to be modelled over a wide range of temperatures with very little variation in the stress component 'n'. Furthermore, it allows the rounded corners on stress-strain hysteresis loops to be achieved very naturally.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 217-234
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  • 149
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    Application of an Uncoupled Elastic-plastic-creep Constitutive Model to Metals at High Temperature (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A uniaxial, uncoupled constitutive model to predict the response of thermal and rate dependent elastic-plastic material behavior is presented. The model is based on an incremental classicial plasticity theory extended to account for thermal, creep, and transient temperature conditions. Revisions to he combined hardening rule of the theory allow for better representation of cyclic phenomenon including the high rate of strain hardening upon cyclic reyield and cyclic saturation. An alternative approach is taken to model the rate dependent inelastic deformation which utilizes hysteresis loops and stress relaxation test data at various temperatures. The model is evaluated and compared to experiments which involve various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy-X.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 185-190
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  • 150
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    Some Recent Developments in the Endochronic Theory with Application to Cyclic Histories (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Constitutive equations with only two easily determined material constants predict the stress (strain) response of normalized mild steel to a variety of general strain (stress) histories, without a need for special unloading-reloading rules. The equations are derived from the endochronic theory of plasticity of isotropic materials with an intrinsic time scale defined in the plastic strain space. Agreement between theoretical predictions and experiments are are excellent quantitatively in cases of various uniaxial constant amplitude histories, variable uniaxial strain amplitude histories and cyclic relaxation. The cyclic ratcheting phenomenon is predicted by the present theory.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 191-216
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    On the Application of Deformation Kinetics to Nonlinear Constitutive Relations at Higher Temperatures (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A single phenomenological constitutive equation is derived theoretically from first principles and applied to aluminum, tin and lead. The theory is based on deformation kinetics of steady creep in which the fundamental mechanism is atomic transport over potential barriers whose conformation is distorted by the application of a stress field. The form of the functional dependence of barrier distortion and stress over the entire temperature range is found to be a sigmoidal curve which tends to straight lines of a unit slope in the small and high stress regions. With this form of barrier distortion, the constitutive equation prediction the steady creep behavior of aluminum, tin and lead over a wide range of temperature and stress.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 139-152
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  • 152
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    Evaluation of Inelastic Constitutive Models for Nonlinear Structural Analysis (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The influence of inelastic material models on computed stress-strain states, and therefore predicted lives, was studied for thermomechanically loaded structures. Nonlinear structural analyses were performed on a fatigue specimen which was subjected to thermal cycling in fluidized beds and on a mechanically load cycled benchmark notch specimen. Four incremental plasticity creep models (isotropic, kinematic, combined isotropic-kinematic, combined plus transient creep) were exercised. Of the plasticity models, kinematic hardening gave results most consistent with experimental observations. Life predictions using the computed strain histories at the critical location with a Strainrange Partitioning approach considerably overpredicted the crack initiation life of the thermal fatigue specimen.
    Keywords: STRUCTURAL MECHANICS
    Type: Nonlinear Constitutive Relations for High Temp. Appl.; p 89-106
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  • 153
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    Multiaxial Cyclic Thermoplasticity Analysis with Besseling's Subvolume Method (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A modification was formulated to Besseling's Subvolume Method to allow it to use multilinear stress-strain curves which are temperature dependent to perform cyclic thermoplasticity analyses. This method automotically reproduces certain aspects of real material behavior important in the analysis of Aircraft Gas Turbine Engine (AGTE) components. These include the Bauschinger effect, cross-hardening, and memory. This constitutive equation was implemented in a finite element computer program called CYANIDE. Subsequently, classical time dependent plasticity (creep) was added to the program. Since its inception, this program was assessed against laboratory and component testing and engine experience. The ability of this program to simulate AGTE material response characteristics was verified by this experience and its utility in providing data for life analyses was demonstrated. In this area of life analysis, the multiaxial thermoplasticity capabilities of the method have proved a match for the actual AGTE life experience.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 69-88
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    Evaluation of Three Constitutive Models for the Prediction of Hastelloy X Elevated Temperature Cyclic Response (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The approach for the method development assumes that, for a thermally loaded structure, the overall strain history is defined by linear elastic analysis. The local stress history at a fatigue critical location is then determined from a one dimensional material behavior model and the local strain and temperature conditions. Three material models are currently being evaluated to assess their ability to predict relevant high temperature cyclic material response characteristics. They are: a time independent classical plasticity and creep representation, a time dependent viscoplastic model capable of predicting combined creep and plasticity effects, and an approximate elastic analysis approach that uses a series of stress-strain curves and a cyclic hardening model to determine reverse plasticity.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 43-46
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  • 155
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    Correlation of Rupture Life, Creep Rate, and Microstructure for Type 304 Stainless Steel (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The stress and temperature sensitivites of the rupture life and secondary creep rate were examined in detail for a single heat of type 304 stainless steel (9T2796). Assuming that the rupture life has a power law stress dependency, relatively small differences in the stress exponent were observed over a broad range of stress and temperature. In contrast, large changes were observed for equivalent parameter for secondary creep rate. As a result of these differences, the Monkman-Grant correlation was sensitive to stress and temperature below 650 C. Metallurgical studies based on light and transmission electron microscopy suggested that the temperature and stress sensitivities of secondary creep rate at temperatures below 650 C were related to features of the substructure not present at higher temperature. Specifically, the presence of a fine dislocation network stabilized by precipitates altered the stress and temperature sensitivities relative to what might be expected from high temperature studies.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Constitutive Relations for High Temp. Appl.; p 1-12
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  • 156
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    A new method for generating and maintaining rigid formats in NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A new method for generating and updating Rigid Formats in NASTRAN is discussed. The heart of this method is a Rigid Format data base that is in card-image format and that can therefore be easily maintained by the use of standard text editors. Each Rigid Format entry in this data base will contain the Direct Matrix Abstraction Program (DMAP) for that Rigid Format along with the related restart, subset and substructure control tables. NASTRAN will read this data base directly in every NASTRAN run and perform the necessary transformations to allow the DMAP to be processed and compiled by the NASTRAN executive. This approach will permit Rigid Formats to be changed without unnecessary compilations and relinking of NASTRAN. Furthermore, this approach will also make it very easy for users to make permanent changes to existing Rigid Formats as well as to generate their own Rigid Formats. This new method will be incorporated in a future release of the public version of NASTRAN.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 249-254
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  • 157
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    Design and operation of a deployable truss structure (1984)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A concept for the one dimensional deployable truss structure is presented. The deployed configuration of the structure consists of the repetition of a longitudinal octahedral truss module. The principal mechanical feature of the truss is that the lateral members comprising the lateral triangular truss are telescoping beams. Contracting of the lateral members results in the deployment of the truss structure. The geometric transformation of this truss of variable geometry is presented. Both simultaneous and sequential modes of transformation are possible. The validity of the transformation applied to the deployment is verified through design of a conceptual model.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 49-63
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  • 158
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    Elastic-plastic analysis of annular plate problems using NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The plate elements of the NASTRAN code are used to analyze two annular plate problems loaded beyond the elastic limit. The first problem is an elastic-plastic annular plate loaded externally by two concentrated forces. The second problem is stressed radially by uniform internal pressure for which an exact analytical solution is available. A comparison of the two approaches together with an assessment of the NASTRAN code is given.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 281-292
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    Implementation of elastic-plastic structural analysis into NASTRAN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 255-280
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  • 160
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    Bolt in bore boundaries (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The factors that must be taken into consideration when applying NASTRAN's linear analysis to structures whose principle boundaries are formed by bolting, and for which localized stress peaking is important are discussed. An illustration is given in an application to a mounting bracket.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC 11th NASTRAN User's Colloq.; p 293-303
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  • 161
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    The effect of matrix properties and fiber properties on impact failure mechanics (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The low-velocity impact problem in graphite/epoxy composite sheets must be solved before large amounts of that material can be used in commercial aircraft. Many of the low-velocity impacts that affect aircraft parts occur during normal ground operations and maintenance. Service equipment and tools have masses above 1 kg, and at velocities of less than 3 m/s can impact structural parts with energies higher than composites can endure without degradation of stiffness or strength. Simple solutions were developed for large-mass, low-velocity impacts which can be modeled as quasi-static events. Static test data and impact data show that the fiber properties control the impact energy which can be absorbed before penetration. Matrix shear strength and peel resistance control the extent of delamination. Comparison of results from tough matrix and brittle matrix composites show that although tough matrices reduce the extent of delamination, they lead to more fiber damage in the contact area.
    Keywords: STRUCTURAL MECHANICS
    Type: Delaware Univ. Abstr. of the 20th Ann. Meeting, Society of Engineering Science, Inc.; p 57
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  • 162
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    A nonlinear fracture mechanics approach to the growth of small cracks (1983)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: An analytical model of crack closure is used to study the crack growth and closure behavior of small cracks in plates and at notches. The calculated crack opening stresses for small and large cracks, together with elastic and elastic plastic fracture mechanics analyses, are used to correlate crack growth rate data. At equivalent elastic stress intensity factor levels, calculations predict that small cracks in plates and at notches should grow faster than large cracks because the applied stress needed to open a small crack is less than that needed to open a large crack. These predictions agree with observed trends in test data. The calculations from the model also imply that many of the stress intensity factor thresholds that are developed in tests with large cracks and with load reduction schemes do not apply to the growth of small cracks. The current calculations are based upon continuum mechanics principles and, thus, some crack size and grain structure exist where the underlying fracture mechanics assumptions become invalid because of material inhomogeneity (grains, inclusions, etc.). Admittedly, much more effort is needed to develop the mechanics of a noncontinuum. Nevertheless, these results indicate the importance of crack closure in predicting the growth of small cracks from large crack data.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Behaviour of Short Cracks in Airframe Components; 26 p
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  • 163
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    Cannon launched electromechanical control actuation system development (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The evolution of an electromechanical control actuation system from trade study results through breadboard test and high-g launch demonstration tests is summarized. Primary emphasis is on design, development, integration and test of the gear reduction system.
    Keywords: STRUCTURAL MECHANICS
    Type: JPL The 17th Aerospace Mech. Symp.; p 181-198
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  • 164
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    Optimal damping for a two-dimensional structure (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Criteria for selection of optimal damper locations are presented. A damping synthesis problem was formulated and applied to a NASA grillage model.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Structual Dyn. and Control of Large Space Struct., 1982; p 249-262
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  • 165
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    Active control of a flexible beam (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Because of inherent low damping and high flexibility, large space structures may require some form of active control of their dynamics. Because of the apparent inability to accurately model the dynamics of these structures, methods for parameter adaptive control are now being developed at Langley. This approach uses a digital computer to process discrete sensor data, identify modal parameters, calculate modal control gains, and then convert the modal forces to real forces. Some of the problems considered are: (1) the possibility that there may be modes to control with limited amounts of hardware, and (2) the required accuracy of identified structural parameters.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Dyn. and Control of Large Space Struct., 1982; p 235-247
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  • 166
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    Structural design for dynamic response reduction (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A computer program for redesigning structural modes to reduce response has been initiated. The linear regulator approach in modal coordinates has been implemented. It is noted that the transformation of solution to physical structure is a major problem. It is concluded that the solution of stiffness equations and damping equations can be done separately as NXN set of (matrix Riccati) equations.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Dyn. and Control of Large Space Struct., 1982; p 141-150
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  • 167
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    Nonlinear effect on modal data analysis method (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: How the presence of nonlinearities in structural test data can be detected when using modern linear modal data analysis methods is discussed. The extent to which linear algorithms can provide useful information on nonlinear systems was discussed. The modal data analysis method successfully identified the frequency components (but not damping) of the true solution of a nonlinear systems. It was found that the approximate modal parameters of the linear system can be identified by the modal method when low levels of nonlinearities are present. The modal method successfully identified the modal parameters of a linear mode in the presence of a nonlinear response.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Dyn. and Control of Large Space Struct., 1982; p 135-140
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  • 168
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    Decoupling and observation theory applied to control of a long flexible beam in orbit (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Techniques which use decoupling theory and state variable feedback to control the pitch attitude and the flexible mode amplitudes of a long, thin beam are discussed. An observer based on the steady state Kalman filter was incorporated into the control design procedure in order to estimate the values of the modal state variables required for the feedback control law.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Dyn. and Control of Large Space Struct., 1982; p 9-38
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  • 169
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    Active damping of a flexible beam (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of an algorithm that will determine actuator and sensor locations on a flexible beam is discussed. Large space structures will have many locations where actuators can be placed. This research seeks to determine the optimum locations. In addition, the best locations are determined while certain constraints are satisfied which guarantee that mission performance requirements are achieved. The approach adopted is to consider actuators and sensors to be collocated so as to produce an equivalent viscous damper. Ultimately, the experimental results of measuring the log decrement during free decay will correlate with the analytical predictions.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Dyn. and Control of Large Space Struct., 1982; p 1-8
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  • 170
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    Results from recent NASA tire thermal studies (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The testing technique and some results from an experimental study to determine tire temperature profiles to aid in defining the strength and fatigue limitations of the tire carcass structure are described. This effort is part of a program to explore analytically and through experiment the temperature distribution in an aircraft tire during free roll and braked and yawed rolling conditions.
    Keywords: STRUCTURAL MECHANICS
    Type: Tire Modeling; p 211-222
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  • 171
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    Adhesion testing of aircraft tires (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Adhesion testing appeared to offer a less burdensome alternative to replace some of the dynamometer tests. Accordingly, test results and data were requested from retreaders who had used adhesion testing.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 175-192
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  • 172
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    Heat generation in aircraft tires (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A method was developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions of the wheel and runway surface. Comparison with data obtained with buried thermocouples in tires shows good agreement.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 193-210
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  • 173
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    Overview of NASA tire experimental programs (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Ongoing aircraft tire experimental programs are reported. These programs are designed to measure profile growth due to inflation pressure and vertical loading, contact pressures in the tire footprint, and a number of tire mechanical properties including spring, damping, and relaxation characteristics.
    Keywords: STRUCTURAL MECHANICS
    Type: Tire Modeling; p 163-174
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  • 174
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    Experimental and finite element study of a standing torus under normal and tangential loads (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effect of a combined external load consisting of a normal component and a tangential braking force applied to an inflated torus is addressed. Experimental results obtained by photographic study of the contact area between the torus and load plate are presented as well as measurements of the vertical and horizontal displacement of the torus under load. A numerical procedure for displacement analysis is developed in which the finite element program STAGS (Structural Analysis of General Shells) is used in an iterative manner to produce a flat, horizontal footprint surface under force loading. The redistributed force distribution obtained by the iterative process is displayed along with computed meridional and circumferential stresses. Finally, an extension of the iterative method is introduced which eliminates the need to experimentally determine the footprint area.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 141-162
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  • 175
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    A tire contact solution technique (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An efficient method for calculating the contact boundary and interfacial pressure distribution was developed. This solution technique utilizes the discrete Fourier transform to establish an influence coefficient matrix for the portion of the pressurized tire surface that may be in the contact region. This matrix is used in a linear algebra algorithm to determine the contact boundary and the array of forces within the boundary that are necessary to hold the tire in equilibrium against a specified contact surface. The algorithm also determines the normal and tangential displacements of those points on the tire surface that are included in the influence coefficient matrix. Displacements within and outside the contact region are calculated. The solution technique is implemented with a finite-element tire model that is based on orthotropic, nonlinear shell of revolution elements which can respond to nonaxisymmetric loads. A sample contact solution is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 95-122
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  • 176
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    Analytical and experimental study of a standing torus with normal loads (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Finite element analysis is applied to study the large deflection and stress of a thin-walled pressurized torus loaded by normal contact with a plane. Experimentally determined stresses are compared to those resulting from finite element analysis at various meridional and circumferential coordinates of the torus, including the footprint area. Circumferential strains compare favorably while meridional strains are higher in the finite element analysis, probably due to slippage of the boundary at the rim. The STAGS finite element computer program was used. The purpose of the study was to evaluate the various program options for structural loading, for material modeling, for stress analysis, and for grid refinement. The experimental model, a thin-walled rubber tube mounted on a steel cylindrical rim, provided measured results to compare with various analytical trade-offs. It was found that there was almost no difference in predicted deflections or stress distributions between linear and nonlinear material description. However, the difference between linear analysis and that of geometric nonlinearities utilizing incremental loading was marked.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 123-140
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  • 177
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    Application of tire dynamics to aircraft landing gear design analysis (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The tire plays a key part in many analyses used for design of aircraft landing gear. Examples include structural design of wheels, landing gear shimmy, brake whirl, chatter and squeal, complex combination of chatter and shimmy on main landing gear (MLG) systems, anti-skid performance, gear walk, and rough terrain loads and performance. Tire parameters needed in the various analyses are discussed. Two tire models are discussed for shimmy analysis, the modified Moreland approach and the von Schlippe-Dietrich approach. It is shown that the Moreland model can be derived from the Von Schlippe-Dietrich model by certain approximations. The remaining analysis areas are discussed in general terms and the tire parameters needed for each are identified. Accurate tire data allows more accurate design analysis and the correct prediction of dynamic performance of aircraft landing gear.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 71-94
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  • 178
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    Finite element methods for nonlinear elastostatic problems in rubber elasticity (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A number of finite element methods for the analysis of nonlinear problems in rubber elasticity are outlined. Several different finite element schemes are discussed. These include the augmented Lagrangian method, continuation or incremental loading methods, and associated Riks-type methods which have the capability of incorporating limit point behavior and bifurcations. Algorithms for the analysis of limit point behavior and bifurcations are described and the results of several numerical experiments are presented. In addition, a brief survey of some recent work on modelling contact and friction in elasticity problems is given. These results pertain to the use of new nonlocal and nonlinear friction laws.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 39-70
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  • 179
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    Finite element modeling and analysis of tires (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Predicting the response of tires under various loading conditions using finite element technology is addressed. Some of the recent advances in finite element technology which have high potential for application to tire modeling problems are reviewed. The analysis and modeling needs for tires are identified. Reduction methods for large-scale nonlinear analysis, with particular emphasis on treatment of combined loads, displacement-dependent and nonconservative loadings; development of simple and efficient mixed finite element models for shell analysis, identification of equivalent mixed and purely displacement models, and determination of the advantages of using mixed models; and effective computational models for large-rotation nonlinear problems, based on a total Lagrangian description of the deformation are included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Tire Modeling; p 1-38
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  • 180
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    Water impact laboratory and flight test results for the space shuttle solid rocket booster aft skirt (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: A series of water impact tests was conducted using full-scale segment representations of the Space Shuttle Solid Rocket Booster (SRB) aft skirt structure. The baseline reinforced structural design was tested as well as various alternative design concepts. A major portion of the test program consisted of evaluating foam as a load attenuation material. Applied pressures and response strains were measured for impact velocities from 40 feet per second (ft/s) to 110 ft/s. The structural configurations, test articles, test results, and flight results are described.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Information Center The Shock and Vibration Bull. 54, Pt. 2; p 87-98
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  • 181
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    Transient vibration test criteria for spacecraft hardware (1984)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Transient vibration test criteria, developed for spacecraft hardware, provide a test rationale to verify the capability of the hardware to withstand the low and mid frequency transient vibration environments induced by launch vehicle events. A test method, consisting of a series of discrete frequency, limited cycle, modulated sine wave pulses, was developed to avoid the slow swept sine drawbacks, yet provide a repeatable test that would excite all frequencies. The shape of the waveform is that of the classic response of the mass of a one degree of freedom system when it is base-excited by an exponentially decayed sine wave transient. Criteria were developed to define pulse amplitudes, shapes, and center frequencies from spacecraft loads analyses. Test tolerance criteria were also developed and specified. The transient vibration test criteria were implemented on spacecraft flight hardware and provided a more realistic test simulation (i.e., less conservative) for qualification of spacecraft hardware without risk of undertest.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Information Center The Shock and Vibration Bull. 54, Pt. 3; p 99-110
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  • 182
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    Keynote address (1984)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Shock and vibration research relative to manned spacecraft is surveyed. Past, present, and future research projects are discussed. Dynamic response, structural modeling, rotor dynamics, reliability, large space sttructures, and testing are among the topics discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Information Center The Shock and Vibration Bull. 54, Pt. 1; p 3-21
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  • 183
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    Inelastic work and thermomechanical coupling in viscoplasticity (1983)
    In:  Other Sources
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    Publication Date: 2018-12-01
    Description: The inelastic deformation of engineering alloys was recently shown to be rate (time)-dependent at room temperature. Experiments reported herein demonstrate that inelastic strain path length is a suitable measure for the modeling of work hardening for these materials, whereas inelastic work is not appropriate. The measured deformation induced temperature change is well predicted by a previously proposed theory of thermomechanical coupling. It has been derived by neglecting the stored energy of cold work and by assuming tha the internal energy expression for thermoelasticity is valid even when the mechanical deformation is inelastic.
    Keywords: STRUCTURAL MECHANICS
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  • 184
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    Biaxial load effects in the mechanics of fracture (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Experimental findings on the effects of biaxial loading on fracture toughness, non-self-similar growth problems, fatigue crack propagation, and subcritical growth properties are reviewed, together with the fundamental analytical solutions for problems of crack in an elastic solid under biaxial loading. Basic asymptotic field representations, and some stress-intensity factor solutions are presented. The effects of biaxial loading on problems involving plastic deformation are illustrated with recent numerical results. Early asymptotic solutions for a nonlinear elastic solid are discussed with emphasis on the solution of problems with significant plastic deformation, and on stable crack growth. A brief survey of the applications literature, and recommendations for future studies are included.
    Keywords: STRUCTURAL MECHANICS
    Type: Aeronautical Society of India, Journal (ISSN 0001-9267); 36; 221-236
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  • 185
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    Demonstration test of burner liner strain measurement systems: Interim results (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Work is in progress to demonstrate two techniques for static strain measurements on a jet engine burner liner. Measurements are being made with a set of resistance strain gages made from Kanthal A-1 wire and via heterodyne speckle photogrammetry. The background of the program is presented along with current results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 41-44
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  • 186
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    Quasi-static solution algorithms for kinematically/materially nonlinear thermomechanical problems (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This paper develops an algorithmic solution strategy which allows the handling of positive/indefinite stiffness characteristics associated with the pre- and post-buckling of structures subject to complex thermomechanical loading fields. The flexibility of the procedure is such that it can be applied to both finite difference and element-type simulations. Due to the generality of the algorithmic approach developed, both kinematic and thermal/mechanical type material nonlinearity including inelastic effects can be treated. This includes the possibility of handling completely general thermomechanical boundary conditions. To demonstrate the scheme, the results of several benchmark problems is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Thermal Stresses (ISSN 0149-5739); 7; 3-4; 227-257
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  • 187
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    Analysis of large, non-isothermal elastic-visco-plastic deformations (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The development of a general mathematical model and solutions of test problems to analyze large nonisothermal elasto-visco-plastic deformatisms of structures is discussed. Geometric and material type nonlinearities of higher order are present in the development of the mathematical model and in the developed solution methodology.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-176220 , NAS 1.26:176220
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  • 188
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    Three-dimensional finite element and dynamic analysis of composite laminate subjected to impact (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A three dimensional finite element and dynamic analysis has been made for a layered fiber-reinforced composite laminate subjected to a given impact loading. Central difference method is employed in this analysis. The numerical results for the transient response of the laminate are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 19; 5-6
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  • 189
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    Computation of eigenpairs of Ax = lambda Bx for vibrations of spinning deformable bodies (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It is shown that, when linear theory is used, the general eigenvalue problem related with the free vibrations of spinning deformable bodies is of the type AX = lambda Bx, where A is Hermitian, and B is real positive definite. Since the order n of the matrices may be large, and A and B are banded or block banded, due to the economics of the numerical solution, one is interested in obtaining only those eigenvalues which fall within the frequency band of interest of the problem. The paper extends the well known method of bisections and iteration of R to the n power to n dimensional complex spaces, i.e., to C to the n power, so that it can be applied to the present problem.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 19; 5-6
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  • 190
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    Development and testing of stable, invariant, isoparametric curvilinear 2- and 3-D hybrid-stress elements (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Linear and quadratic Serendipity hybrid-stress elements are examined in respect of stability, coordinate invariance, and optimality. A formulation based upon symmetry group theory successfully addresses these issues in undistorted geometries and is fully detailed for plane elements. The resulting least-order stable invariant stress polynomials can be applied as astute approximations in distorted cases through a variety of tensor components and variational principles. A distortion sensitivity study for two- and three-dimensional elements provides favorable numerical comparisons with the assumed displacement method.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 47; 331-356
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  • 191
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    Geometrically nonlinear analysis of laminated elastic structures (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Laminated composite plates and shells that can be used to model automobile bodies, aircraft wings and fuselages, and pressure vessels among many other were analyzed. The finite element method, a numerical technique for engineering analysis of structures, is used to model the geometry and approximate the solution. Various alternative formulations for analyzing laminated plates and shells are developed and their finite element models are tested for accuracy and economy in computation. These include the shear deformation laminate theory and degenerated 3-D elasticity theory for laminates.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-175609 , NAS 1.26:175609 , PB85-127173 , VPI-E-84-36
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  • 192
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    Structural sensitivity analysis: Methods, applications and needs (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Innovative techniques applicable to sensitivity analysis of discretized structural systems are reviewed. The techniques include a finite difference step size selection algorithm, a method for derivatives of iterative solutions, a Green's function technique for derivatives of transient response, simultaneous calculation of temperatures and their derivatives, derivatives with respect to shape, and derivatives of optimum designs with respect to problem parameters. Computerized implementations of sensitivity analysis and applications of sensitivity derivatives are also discussed. Some of the critical needs in the structural sensitivity area are indicated along with plans for dealing with some of those needs.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-85827 , NAS 1.15:85827 , Symp. on Recent Experiences in Multidisciplinary Analysis and Optimization; Hampton, VA; United States
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  • 193
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    Transverse vibration and buckling of a cantilevered beam with tip body under constant axial base acceleration (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The planar transverse bending behavior of a uniform cantilevered beam with rigid tip body subject to constant axial base acceleration was analyzed. The beam is inextensible and capable of small elastic transverse bending deformations only. Two classes of tip bodies are recognized: (1) mass centers located along the beam tip tangent line; and (2) mass centers with arbitrary offset towards the beam attachment point. The steady state response is studied for the beam end condition cases: free, tip mass, tip body with restricted mass center offset, and tip body with arbitrary mass center offset. The first three cases constitute classical Euler buckling problems, and the characteristic equation for the critical loads/accelerations are determined. For the last case a unique steady state solution exists. The free vibration response is examined for the two classes of tip body. The characteristic equation, eigenfunctions and their orthogonality properties are obtained for the case of restricted mass center offset. The vibration problem is nonhomogeneous for the case of arbitrary mass center offset. The exact solution is obtained as a sum of the steady state solution and a superposition of simple harmonic motions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-175567 , NAS 1.26:175567 , CSDL-R-1675
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  • 194
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    Planar dynamics of a uniform beam with rigid bodies affixed to the ends (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The planar dynamics of a uniform elastic beam subject to a variety of geometric and natural boundary conditions and external excitations were analyzed. The beams are inextensible and capable of small transverse bending deformations only. Classical beam vibration eigenvalue problems for a cantilever with tip mass, a cantilever with tip body and an unconstrained beam with rigid bodies at each are examined. The characteristic equations, eigenfunctions and orthogonality relations for each are derived. The forced vibration of a cantilever with tip body subject to base acceleration is analyzed. The exact solution of the governing nonhomogeneous partial differential equation with time dependent boundary conditions is presented and compared with a Rayleigh-Ritz approximate solution. The arbitrary planar motion of an elastic beam with rigid bodies at the ends is addressed. Equations of motion are derived for two modal expansions of the beam deflection. The motion equations are cast in a first order form suitable for numerical integration. Selected FORTRAN programs are provided.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-175566 , NAS 1.26:175566 , CSDL-R-1629
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  • 195
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    On stress analysis of a crack-layer (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This work considers the problem of elastic interaction of a macrocrack with an array of microcracks in the vicinity of the macrocrack tip. Using the double layer potential techniques, the solution to the problem within the framework of the plane problem of elastostatics has been obtained. Three particular problems of interest to fracture mechanics have been analyzed. It follows from analysis that microcrack array can either amplify or reduce the resulting stress field of the macrocrack-microcrack array system depending on the array's configuration. Using the obtained elastic solution the energy release rate associated with the translational motion of the macrocrack-microcrack array system has been evaluated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-174774 , NAS 1.26:174774
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  • 196
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    Stability and Convergence of Underintegrated Finite Element Approximations (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of underintegration on the numerical stability and convergence characteristics of certain classes of finite element approximations were analyzed. Particular attention is given to hourglassing instabilities that arise from underintegrating the stiffness matrix entries and checkerboard instabilities that arise from underintegrating constrain terms such as those arising from incompressibility conditions. A fundamental result reported here is the proof that the fully integrated stiffness is restored in some cases through a post-processing operation.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Struct. Anal.; p 95-103
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  • 197
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    Three-dimensional Stress Analysis Using the Boundary Element Method (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The boundary element method is to be extended (as part of the NASA Inelastic Analysis Methods program) to the three-dimensional stress analysis of gas turbine engine hot section components. The analytical basis of the method (as developed in elasticity) is outlined, its numerical implementation is summarized, and the approaches to be followed in extending the method to include inelastic material response indicated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center Nonlinear Struct. Anal.; p 149-160
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  • 198
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    Statistical failure prediction models for brittle materials (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 13, p. 2107, Accession no. A82-30104
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 22; 135-140
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  • 199
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    Experimental stress analysis of a thin walled pressurized torus loaded by contact with a plane (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 13, p. 2108, Accession no. A82-30114
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 22; 124-127
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  • 200
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    Analyses of large quasistatic deformations of inelastic bodies by a new hybrid-stress finite element algorithm - Applications (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A new hybrid-stress finite element algorithm suitable for analyzing large quasistatic deformations of inelastic solids is presented and its feasibility and performance are demonstrated with examples. The algorithm provides extremely accurate bifurcation analysis which is stable with respect to variation in the finite element mesh, so long as the same type of element is used in every mesh. When the mesh element is varied, the result changes in a predictable manner. The method does not necessarily lead to an upper or lower bound for the critical load. An explicit forward gradient scheme is used to improve stability and is shown to be useful also for elongation-dominated deformations. The application of the method to the onset of necking in plane extension and to deformation and stress in plane extension of an elasticoviscous fluid with an array of cylindrical voids is given in detail.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 40; 171-198
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