A hybrid model for analysis of ductile fracture in micro-scaled plastic deformation of multiphase alloys

As a critical issue in micro-scaled plastic deformation, viz., microforming, the effects of workpiece geometry and material grain sizes on ductile fracture behavior have been studied. However, the flow stress contribution of each phase in multiphase alloys to the ductile fracture and deformation behaviors in microforming has not yet been fully addressed. In this paper, a hybrid model is proposed for modeling and representing the fracture and deformation behaviors in microforming processes. The proposed model calculates fracture energy and then predicts the fracture strain of the alloys with single or multiphase. The model is considered to be more accurate in fracture prediction as it considers the influence of size effect on material fracture energy. Using brass C3602 with different grain sizes obtained via heat treatment as the testing material, the grain and feature size effects are investigated. Through the finite element simulation by using the developed hybrid model and physical experiment, the methodology to represent and model the influence of metal phase on deformation and fracture behaviors in micro-scaled plastic deformation of multiphase alloys is presented. Also, to compare the difference between grain and geometry size effects, the stress-induced fracture map, which articulates the relationship of size effect, fracture energy and the expected fracture strain in microforming, is proposed and constructed for fracture prediction in microforming processes. (C) 2013 Published by Elsevier Ltd.