Investigation and implementation of nonlinear micro plasicity in abaqus

Abstract: This thesis is aimed to investigate different approaches in FEM simulation of sheet metal forming to accurately predict the final geometry. These approaches are mainly focused on the behavior of material models used in the forming process. Two sets of test results are available that play important roles in this project. The first set is the cyclic test which depicts the behavior of the material model in large deformations. The material model in simulations is modified according to the cyclic test results. Second set of tests is Bending Under Tension (BUT) test which represents the forming process of sheets. BUT test is simulated with the material model that is modified according to the cyclic test results. The deformed profiles of the BUT simulations are compared with BUT test results to check the accuracy of the modified material models. The influence of friction on the final geometry in the BUT simulations is investigated. All of the modified material models are implemented in simulations with and without considering friction and the results are compared. Friction provides a realistic condition in BUT simulation and has a great impact in spring-back results. Friction reduces the bending stiffness of sheets and consequently the more spring-back is observed. The modified model with single step reduction in elastic modulus (with friction) makes an improvement in prediction of spring-back magnitude in BUT simulation.