A finite element modelling for superplastic bulging of titanium alloy tube and pressure path optimization

Superplastic bulging process of Ti-alloy tube has been simulated by a Finite Element Method (FEM). A commercial code, MARC, was employed to analyze the whole deformation by an incremental approach based on rigid-plastic flow formulation. Simulation programs have been carried out under two kinds of pressure control, ''constant pressure'' and ''nearly constant apex strain rate'' to understand the influence of the pressure path on bulging shape and diameter, and to predict process characteristics such as deformation pressure, time and thickness distribution. Results of FEM calculations confirmed that ''nearly constant apex strain rate'' pressure control is superior to the ''constant pressure'' for obtaining larger deformation. A very good agreement was seen in the comparison of thickness distribution between simulation and experimentally deformed ''SP-700'' tube.