摘要 :
A thermodynamic foundation using the concept of internal state variables is presented for the kinematic description of a viscoplastic material. Three different evolution equations for the back stress are considered. The first is t...
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A thermodynamic foundation using the concept of internal state variables is presented for the kinematic description of a viscoplastic material. Three different evolution equations for the back stress are considered. The first is that of classical, nonlinear, kinematic hardening. The other two include a contribution that is linear in stress rate. Choosing an appropriate change in variables can remove this stress rate dependence. As a result, one of these two models is shown to be equivalent to the classical, kinematic hardening model; while the other is a new model, one which seems to have favorable characteristics for representing ratchetting behavior. All three models are thermodynamically admissible.
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摘要 :
A thermodynamic foundation using the concept of internal state variables ispresented for the kinematic description of a viscoplastic material. Three different evolution equations for the back stress are considered. The first is th...
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A thermodynamic foundation using the concept of internal state variables ispresented for the kinematic description of a viscoplastic material. Three different evolution equations for the back stress are considered. The first is that of classical, nonlinear, kinematic hardening. The other two include a contribution that is linear in stress rate. Choosing an appropriate change in variables can remove this stress rate dependence. As a result, one of these two models is shown to be equivalent to the classical, kinematic hardening model; while the other is a new model, one which seems to have favorable characteristics for representing ratchetting behavior. All three models are thermodynamically admissible.
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摘要 :
The salient aspects of the theoretical modeling of a conventional triaxial test (CTC) of a cohesionless granular medium with stress and strain rate loading are described. Included are a controllable gravitational body force and pr...
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The salient aspects of the theoretical modeling of a conventional triaxial test (CTC) of a cohesionless granular medium with stress and strain rate loading are described. Included are a controllable gravitational body force and provision for low confining pressure and/or very low intergranular stress. The modeling includes rational, analytic, and numerical phases, all in various stages of development. The numerical evolutions of theoretical models will be used in final design stages and in the analysis of the experimental data. In this the experimental design stage, it is of special interest to include in the candidate considerations every anomaly found in preliminary terrestrial experimentation. Most of the anomalies will be eliminated by design or enhanced for measurement as the project progresses. The main aspect of design being not the physical apparatus but the type and trajectories of loading elected. The major considerations that have been treated are: appearance and growth of local surface aberrations, stress-power coefficients, strain types, optical strain, radial bead migration, and measures of rotation for the proper stress flux.
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摘要 :
Three methods of photoelastic analysis are examined. The first method is an extension of the oblique incidence technique in which the model (or the light beam) is rotated about one of the material symmetry axes. In the second meth...
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Three methods of photoelastic analysis are examined. The first method is an extension of the oblique incidence technique in which the model (or the light beam) is rotated about one of the material symmetry axes. In the second method, transmission and reflection photoelastic responses are combined. The third method requires the drilling of small holes and the determination of the fringe orders at selected points on the hole boundary. The three methods are applied to an orthotropic circular disk under diametral compression. Results are compared with strain gage data.
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摘要 :
A shear flexible quadratic isoparametric beam element with three degrees of freedom per node is critically examined from the point of view of the consistency of the constrained strain fields that arise in the thin beam limits. The...
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A shear flexible quadratic isoparametric beam element with three degrees of freedom per node is critically examined from the point of view of the consistency of the constrained strain fields that arise in the thin beam limits. The errors, in terms of convergence of displacement fields and violent oscillations of stress fields that emerge when exactly integrated elements are used, are predicted a priori and confirmed with numerical experiments. The rationale behind the use of optimal stress sampling at Gaussian points is also derived directly from these arguments.
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摘要 :
Stress-dependent terms in the mechanical equation of state; strain-dependent terms in the mechanical equation of state; strain-rate history effects and constitutive relations for strain-rate jump tests are discussed. Use of an int...
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Stress-dependent terms in the mechanical equation of state; strain-dependent terms in the mechanical equation of state; strain-rate history effects and constitutive relations for strain-rate jump tests are discussed. Use of an internal structure sensitive parameter is described. Experimental data at strain rates up to 10,000/sec were obtained.
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