Biaxial tensile behavior of Ti-6Al-4V under proportional loadings at high strain rates

To study the mechanical performance of materials under dynamic and proportional biaxial tensile loadings, the electromagnetic Hopkinson bar system was employed. Dynamic biaxial tensile experiments were conducted by this novel system. Dynamic uniaxial tensile and compressive tests were also performed. The digital image correlation (DIC) technique combined with the high-speed camera was utilized to analyze the deformation in the gauge section of the improved cruciform specimens. The cruciform specimen design was improved by finite element method (FEM) method to adapt to dynamic biaxial loadings. An inverse analysis (IA) method was adapted to deduce the true stresses in cruciform specimens. Based on the Yoon criterion, a strain rate and stress state dependent yield criterion and a related constitutive model were developed to account for the asymmetric yielding and strengthening behaviors under high strain rates. The new constitutive model was implemented in the FEM analysis and the numerical results agreed well with the experiments.