Finite Element Investigation of Hole‐Expansion Formability of Dual‐Phase Steels Using RVE Approach

Abstract

Qualitative analysis on the formability of dual-phase (DP) steels was carried out by employing the realistic microstructure based finite element (FE) method. The microstructure-based model was generated using image processing of scanning electron micrographs and mesh generation with a boundary smoothing algorithm. The model was applied to hole-expanding formability tests for two DP steels with distinct volume fractions and morphological features: Steel A with continuous ferritic phase and Steel B with continuous martensitic phase. The micromechanical simulations showed that the high volume fraction of martensite and its morphological characteristics of Steel B prohibited the plastic deformation and damage evolution in ferritic phase, thus delayed the material's failure, while considerable damage propagation occurred along the phase boundaries in Steel A. The observed difference in hole-expansion ratio for the two microstructures was consistent with results from the FE model.