Forming limit in thermal cruciform biaxial tensile testing of titanium alloy

In this study, a new cruciform biaxial tensile testing technology was employed to evaluate the thermal limit strains of a TAI titanium alloy, which is widely used as an aircraft structural component, so as to prevent fracture defects during thermoplastic processing. The effect of specimen shape on the forming limit and its measurement range is discussed. The results of this study show that a design that reduces the semispherical thickness results in localized necking and fracture at the center of the specimen when normal stress is applied to it. The forming limit diagrams obtained at different angles with respect to the material rolling direction suggested that the limit strain was anisotropic in nature. The experimental results were in good agreement with the substituted values obtained from the finite element analysis and Oyane ductile fracture criterion. Finally, the efficacy of the related test and prediction methods was corroborated. (C) 2016 Elsevier B.V. All rights reserved.