Numerical Analyses of Strain Rate and Temperature Effects on Localization of Plastic Flow and Ductile Fracture - Applications to Metal Forming Processes

Abstract The analysis of damage in rate sensitive and temperature sensitive materials is of a primary importance to be able to predict the loss of strength capacity, due to localization of plastic flow or due to ductile fracture. This paper gives an extension of the Gurson model to deal with rate sensitive and temperature effects. The model, which is mainly based on growth and coalescence of voids is applicable in warm conditions where the steels begin to exhibit a viscoplastic behaviour. A large strain implicit algorithm is presented for the integration of the constitutive equations and the elastic-viscoplastic resulting finite element analysis is shown to be inconditionally stable. Numerical applications are given for industrial problems. First application concerns the analysis of fracture in upsetting tests using a plastic flow localization criterion. The second example concerns an axisymmetric wire drawing problem, where the influence of strain rate and temperature increasing are analysed.