Modelling of Fracture Onset in Ti6Al4V Sheets Deformed at Elevated Temperature

The reliability of FE-based simulations, employed to assess the application of sheet forming process at elevated temperature to the production of high surface-to-thickness ratio components, depends on the accuracy of the models used to describe the material behavior. In this paper, a modified version of the uncoupled Johnson-Cook fracture criterion is proposed to predict the fracture onset when deforming Ti6Al4V sheets of 1 mm thickness in a wide range of temperature spanning from room temperature to 900̊C. Tensile tests were performed at different temperatures and strain rates on smooth and notched samples, leading to different values of the stress triaxiality factor. The resulting strains at fracture were used to both calibrate and validate the modified fracture criterion in two temperature ranges, namely 25-600̊C and 600-900̊C.