Modelling of ductile failure in materials with heterogeneous particle structure using localization analysis

Abstract

In this study, we evaluate the use of strain localization analysis based on the imperfection band approach to model the effect of heterogeneous particle distribution on the ductile failure of structural metallic materials. To this end, tensile tests are performed on smooth and notched samples made of aluminium alloy AA6110 with an equiaxed grain structure and an inhomogeneous distribution of the constituent particles. The constituent particles are assumed to be the main contributors to the ductile failure of the alloy. By varying the heat treatment of the alloy, three different materials are considered with different strength, work hardening, and ductility, while the grain structure and constituent particle distribution are unaltered. Finite element simulations of the tension tests are conducted using both metal and porous plasticity models and the stress–strain histories of the elements in the minimum section of the specimen are used in strain localization analyses. In these analyses, ductile failure is assumed to occur when the strain rate inside a thin, planar imperfection band becomes infinite. The imperfection band is modelled with porous plasticity, using either a higher initial porosity than in the bulk material or by adding void nucleation. It is found that the ductility of the materials is most accurately captured by modelling the imperfection band by stress-enhanced nucleation.