Plastic temperature-dependent constitutive modeling of pure aluminum diaphragms at large strains by using bulge test

Abstract

A plastic temperature-dependent constitutive model is developed for 0.05 mm thickness pure aluminum diaphragms at large strains by using bulge test method. Rupture strain of the material is recorded below two percent according to tensile tests. In order to achieve the material behavior at larger strains, an own bulge test apparatus is used to extract equi-biaxial stress–strain curves at different temperatures, i.e. from room to 150 °C. Effective stress–strain behavior is then computed via a transformation scheme using the plastic work definition as well as the room temperature uniaxial stress–strain curve. It is illustrated that the Johnson–Cook constitutive model is not able to capture this stress–strain behavior. Thus, a modified Johnson–Cook model is developed in which the strain hardening is assumed to be temperature-dependent accompanying by a novel thermal softening relation. Using the Least-square method as well as the Ant colony optimization algorithm, the material parameters of the both models are calculated. It is depicted that the new model follows the material behavior more precisely than the Johnson–Cook model. The new model is then numerically implemented into finite element software via a user subroutine. In order to compare the accuracy of both models in capturing the hot bi-axial deformation of pure aluminum, an experiment is performed and numerically simulated.