Konstitutiv modellering av elastoplasticitet med hänsyn till spännings-kompressionsasymmetri

This thesis aims to develop a plastic simulation method for a ductile Aluminium, having asymmetric characteristics, which effectively captures the effective plastic strain (PEEQ) values coming from tension and compression.A UMAT is developed which efficiently makes the split in tension and compression. It distinguishes between tensile and compressive yield strengths and also different hardening exponent in tension and compression. It is based on small-strain plasticity with an additive decomposition of strain and a von Mises-type yield criterion. Trial stresses are calculated using the assumption of elastic response, and plastic correction is applied using a newton raphson return mapping algorithm. In order to guide the model to the proper yield strength and hardening law, hydrostatic stress is employed to ascertain whether the current loading condition is in tension or compression.Additionally, the subroutine retains distinct state variables for the history of plastic strain under tension and compression, as well as tracking effective plastic strain (PEEQ).A post-processing approach is introduced to separate tensile and compressive contributions to the equivalent plastic strain (PEEQ). The effect of machining on the casted components is also investigated in this study.The resulting material is applied to gearbox components at Scania to predict failure locations as well as to dogbone specimens with and without notches where strains are measured using a digital image correlation method. FEMFAT Break was used to estimate static strength and found to be a conservative approach. The split proposed, as well as an industrial alternative using a field operation under post processing show improvements on the capabilities for failure predicition withrespect of location and load magnitude, although machining was found to have a big impact in the local material modifications.