Parameter evaluation for a unified constitutive model

Article Abstract:

The parameters contained in the constitutive equations of the unified model MATMOD are evaluated. Laboratory tests are performed on specimens of rock salt to produce mechanical histories corresponding to stress relaxation, constant strain rate and creep. All data are collected using specially calibrated transducers and are subsequently evaluated by means of nonlinear least squares. The parameter values obtained from this approach are found to differ substantially from those obtained using traditional methods of parameter evaluation.

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On testing requirements for viscoplastic constitutive parameter estimation

Article Abstract:

The sensitivity coefficients for the constitutive parameters of a dynamic system were calculated by means of a nine-parameter isothermal fitted model. The model was fitted to data obtained from tests conducted on a clean, fine-grained natural rock salt. It was used to determine the sensitivity coefficients for each of the load histories imposed and establish the reliability of the test matrix. Results show that the efficiency of the test matrix can be improved by reducing the duration of the stress relaxation and creep tests.

Testing, Plasticity, Materials, Materials testing

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Parameter estimation for an internal variable model using nonlinear optimization and analytical/numerical response sensitivities

Article Abstract:

A parameter estimation method that uses nonlinear optimization and analytical/numerical response sensitivities was applied on a viscoplastic model for braze alloys. Results have shown that correlation between parameters was significantly reduced when material constants are evaluated with an adequate database than with an inadequate database. Moreover, incorrect sets of material parameters can be obtained from insufficient data.

Research, Alloys

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