Material characterization, constitutive modeling and validation in hot stretch bending of Ti-6Al-4V profile

Ti-6Al-4V, as one of the most frequently used titanium alloy in aerospace applications, is characterized by its excellent mechanical and corrosion properties. However, it is well known that Ti-6Al-4V is difficult to be formed at room temperature. Therefore, hot stretch bending has been used to improve formability and reduce springback in forming Ti-6Al-4V profile. In the virtual development of designing suitable hot stretch bending processes for Ti-6Al-4V, numerical simulations are considered desirable. However, the reliability of numerical simulations depends on the models and methods used as well as the accuracy of material data. In this work, a set of uniaxial tension tests was performed on Ti-6Al-4V at the temperatures ranging from 923 to 1023K and strain rate from 0.005 to 0.05s(-1). Moreover, a set of stress relaxation tests was conducted on Ti-6Al-4V at the temperature range between 773 and 973K and pre-stretch elongation ranging from 0.7% to 10%. The Johnson-Cook and Arrhenius models were used to characterize the uniaxial tension and the stress relaxation behavior, respectively. Finite element model of hot stretch bending was created according to the laboratorial experiment setup in ABAQUS based on the constitutive models calculated above. The finite element simulation indicates that the residual stress in the profile decreases greatly in the secondary stage of hot stretch bending due to the stress relaxation behavior. The predicted springback shows promising agreement with the corresponding experimental observations.