Numerical Prediction of Ductile Failure Onset under Tensile and Compressive Stress States

Prediction of ductile failure onset in fracture-free materials has instigated several research works in the last few years. The literature shows basically two general approaches: (i) post-processed fracture indicators and (ii) damage-based material modeling. The former has shown successful to predict failure initiation in specific forming operations, whereas the latter has proved greater potential in assessing failure processes under general stress—strain paths. This work extends an existing isotropic damage model to account for separately tensile and compressive stress effects. Material modeling is based on finite strain elastoplasticity fully coupled to the damage evolution law. An assessment of some post-processed failure indicators is also presented. The damage model and fracture criteria are verified against tensile tests of notched specimens (tensile-dominant stress states) and the upsetting test of cylindrical billets (compressive-dominant stress states).