Identification of a continuum damage model from micro-hardness measurements: application to a backward extrusion process

摘要

In many forming processes - like backward extrusion - the material is subjected to very high local strains that can lead to microcracks and subsequently to in-service failure of the final piece. In order to model the defects nucleation and growth, a ductile damage model proposed by Lemaitre is introduced. The parameters of the constitutive equations are identified from micro-hardness measurements performed on a tensile test specimen after rupture. Numerical simulations of upsetting tests and their comparisons with experimental results are used to validate the introduction of a unilateral effect in the damage evolution law to take into account the case of high compressive stress states.