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n this work we present a unified strategy for identification of material parameters of visco-plastic models from test data of complex smctum. For consideration of the associated inhomogeneous deformations and stresses the finite-element method is used. The objective function of least-squares type is minimired by a method based on gradient evaluations. such as an SQP method or a projection algorithm due to Bertsekas The sensitivity analysis, i.e. the determination of the gradient of the objective function, is explained in detail. As a mult a recursion formula is obtained. In the numerical examples we compare gradient-based methods with evolutionaty methods for homogeneous problems. Concerning inhomogeneous problems we discuss the results obtamed for a material law due to Steck.

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This contribution addresses various topics on parameter identification for constitutive equations on the basis of experimental data. Starting from basic characteristics of inverse problems illustrated by simple examples, four different identification methods are introduced. Then particular aspects of the least squares approach are outlined, such as optimization, local minima, sensitivity analysis, consequences of instabilities, and stochastic methods. Uniform small strain problems and nonuniform large strain problems are considered, where for the latter finite element results are incorporated into the optimization process. The examples are concerned with a perturbation technique in order to detect possible instabilities, a stochastic analysis in order to examine the uncertainty of parameter estimates, and a necking problem observed with an optical method in order to take into account nonuniform large strains during the experiment.