Ductile fracture criterions for hot forming process of Ti-6Al-2Zr-1Mo-1V alloy sheets

To accurately predict the fracture during the hot forming process of Ti-6Al-2Zr-1Mo-1V alloy sheets, ductile fracture criterions(DFCs) for the hot forming process of titanium alloy sheets was proposed based on C&L, R&T and Oyane criterions by the combination method of experiments with finite element(FE) simulation. Firstly, uniaxial isothermal tension tests were conducted at different temperatures under various strain rates and the fracture strains were obtained. Then, with the fracture strains, the damage parameters of different DFCs were obtained by FE method and point trace method. By introducing the Zener-Holloman parameter ln Z, the damage parameter model considering the effects of temperature and strain rate was established. Finally, the DFCs for hot forming process of titanium alloy sheets based on C&L, R&T and Oyane criterions were established by considering the deformation history, temperature and strain rate. The established criteria was applied in the hot shear spinning process of titanium alloy. The results show that fracture strains increase with the increase of temperature and decrease of strain rate; the changes of damage parameters of different DFCs are the same as that of fracture strains; Oyane criterion is the most accurate in predicting the fracture occurrence.