The identification of parameters for visco-plastic models via finite-element methods and gradient methods

In this work we present a unified strategy for identification of material parameters of visco-plastic models from test data of complex structures. For consideration of the associated inhomogeneous deformations and stresses the finite-element method is used. The objective function of least-squares type is minimized 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 result a recursion formula is obtained. In the numerical examples we compare gradient-based methods with evolutionary methods for homogeneous problems. Concerning inhomogeneous problems we discuss the results obtained for a material law due to Steck.