THE IDENTIFICATION OF RATE-DEPENDENT MATERIAL PROPERTIES IN FOAMS USING LS-OPT

In the past years more and more complex materials, e. g. plastic and metallic foams, honey-comb materials, different types of glues, epoxy-glass materials etc., were incorporated in a wide range of products, particularly in the automotive industry. For the modeling of such materials within nonlinear dynamic problems numerous material models are available in LS-DYNA. However, the application of these material models require the knowledge of the ma-terial parameters describing the behavior of the specific material. The accuracy of the Finite-Element simulations depend authoritatively on the quality of the involved material parame-ters. In order to obtain these material parameters the calibration of the model is necessary through comparison with experimental data. The main objective of this paper is to demonstrate the calibration of a nonlinear material model by minimizing the difference of the model response and the experimental tests. As an example, a low density styrofoam is considered which is described by a material model with strain rate effects (Fu-Chang Model (LS-DYNA, 1999)). The minimization problem is solved via the Response Surface Method (Myers, 1995) using the commercial optimization code LS-OPT.