Evaluation of ductile fracture in sheet metal forming using a damage model

Abstract

Continuous Damage Mechanics (CDM) may constitute an alternative to the traditional use of Forming Limit Diagrams (FLDs) to predict the onset of formability in sheet metal forming [1]. In CDM, at the constitutive level, a damage variable is introduced to model, at the macro scale, the internal material degradation due to micro-defects that occur during plastic loading. This approach is used in this work and the implementation of a continuum damage model in a commercial code is described, in order to identify ductile fracture in sheet metal forming. The model includes Lemaitre's ductile damage evolution law coupled with an orthotropic plasticity criterion and the resulting constitutive equations are implemented and assessed in the prediction of fracture initiation in sheet metal forming processes comparing the obtained numerical solutions with experimental results.