Crystal-plasticity modelling of the yield surfaces and anelasticity in the elastoplastic transition of metals

The paper presents a full-field crystal-plasticity computational investigation of 10με small-strain-offset yield surfaces with pointed vertexes that are seen in the elastoplastic transition of pre-strained polycrystal metals. It is concluded that the shape of these yield surfaces obtained with a full-field spectral solver compares reasonably well with calculated ones by a simple aggregate Taylor model. The influence of material strength, work hardening, and texture are discussed. An assessment is made of the origin of anelasticity and Bauschinger effects at small strains, considering two mechanisms. Firstly, there is a built-in composite effect in crystal elastoplastic simulations due to the mixture of elastically and plastically loaded grains. Secondly, kinematic hardening of reverse slip systems will contribute to the Bauschinger effect. Based on analyses of the computed selected cases and comparison to previously published measurements, it is concluded that both mechanisms are important.