Considerations on parameter identification and material response for Gurson-type and Lemaitre-type constitutive models

The ongoing pursuit of quality improvement and cost reduction in metal forming operations has instigated intense research on both material modelling and identification of constitutive parameters. Metal forming applications involving large plastic deformations are subject to mechanical degradation and failure, thereby recommending use of damage models. Notwithstanding, accurate predictions require material parameters able to describe realistic stress-strain paths, especially when involving large inelastic deformations under non-uniform stress states. The present work addresses identification of material parameters for Gurson-type and Lemaitre-type constitutive models for a low alloy steel based on a hybrid global-local optimization technique. The simulations show that, in the featured examples, material degradation takes place under non-uniform stress states precluding application of classical calibration techniques. The material response to loading also shows that the Lemaitre-type material provides a somewhat better approximation to the experimental data than the Gurson-type model.