Material modeling of pure titanium sheet and its application to bulge test simulation

Abstract

The hydraulic bulge test is widely used to obtain stress–strain data over large strain ranges. This study identifies plastic characteristics of pure titanium sheet by conducting several tensile tests and a hydraulic bulge test. Distortional hardening behavior of the tested material is examined experimentally by comparing the uniaxial tensile results of three specimens taken from different orientations. In addition, three stages of deformation were observed in biaxial stress–strain data obtained from the bulge test. Therefore, a constitutive model based on a non-associated flow rule is developed to describe the material characteristics. Evolution Hill’s quadratic functions are adapted to reproduce the yield surface and potential surface transients during plastic deformation. Additionally, a modified Voce hardening model is used to represent the effective stress–strain curve over large strain ranges to capture the three-stage hardening phenomenon of titanium sheet. The developed material model is then applied to simulate the bulge test to verify its accuracy. Based on simulation results, it is concluded that the distortional hardening behavior strongly affects the evaluation of apex height in the bulge test.