Modelling and identification of voids nucleation and growth effects in porous media plastic flow

In the paper the effects of nucleation and growth of voids in the plastic porous media are investigated. Three different forms of the model are considered: the augmented Gurson model (total porosity model) with variable nucleation and growth material function, the same model with constant growth material function and the separated porosity model. The identification of the material functions parameters is based on Fischer’s experimental data set for axisymmetric tension of steel specimens and formulated as a typical nonlinear regression problem using the least squares approach. The resulting minimization problem is solved by means of our own implementation of the Boender at al. global minimization method. Calculations and statistical analysis (Akaike, FPE and Vuong tests) have led to a conclusion that the growth material function in the uniaxial tension for steel may be assumed to be constant although not necessarily equal to one.