Influence of Strain Localization on Parameter Identification

In the present contribution, the parameter identification of ductile materials is reconceived in the frame of localization phenomena. To describe the damage process on a continuum mechanical basis, the Gurson–Tvergaard–Needleman damage model is implemented in the finite element system Scientific Parallel Computing-Program Module Hyperelastic Plastic (SPC-PMHP), which was developed for parallel computers to solve nonlinear initial boundary value problems within large strain formalism. The softening of the material is responsible for the loss of ellipticity of the differential equations and for the strain localization. A general localization criterion is given to determine when numerical solutions cease to show convergence. This criterion is based on an analysis of the determinant of the acoustic tensor, which includes the material tangent, the stresses, and the deformation gradient. On this account, the onset of localization is significantly affected by material parameters. The parameters are identified on the basis of locally measured displacement fields. As additional information, the strain localization criterion is included in the identification process. A numerical example shows the influence of the localization criterion on the parameter identification.