Evaluation of Superplastic Material Characteristics Using Multi-Dome Forming Test

Abstract

Superplastic characteristics of Ti-alloy Ti-4.5Al-3V-2Fe-2Mo have been evaluated by multi-domed single sheet forming instead of commonly used tensile test. The flow stress versus strain rate relationship was established from a circular sheet containing four different domes, with diameters of 20, 25, 30, and 35mm. Multi-dome forming experiments were conducted under constant pressure at a superplastic temperature of 800°C. Membrane theory was used to calculate the flow stress and the strain rate at the apex of each dome. Forming processes such as superplastic hemispherical and box forming were simulated by FEM using material characteristics obtained from multi-dome forming and tensile tests. Finally the results of estimated bulging time and final thickness distribution obtained from the simulation were compared to those of experiments. Material characteristics obtained from multi-dome forming experiments showed good agreements with the FEM simulation in the estimated bulging time, whereas the tensile tests had some discrepancies with regard to the estimated bulging time Almost the same final thickness distribution were obtained in the simulations by using two material characteristics, multi-dome forming and tensile jump test, but the one from multi-dome forming was more close to real experiments.