Investigation of the constitutive relationship and formability of Ti-6Al-4V alloy considering anisotropy and mesoscopic damage at elevated temperatures

This study investigates the high-temperature mechanical behavior of Ti-6Al-4V alloy, focusing on the effects of temperature, strain rate, and anisotropy on damage evolution, ductility, and fracture behavior. Uniaxial tensile tests were conducted at 650 degrees C, 700 degrees C, and 750 degrees C with strain rates from 0.001 s-1 to 0.1 s-1 , revealing nearly isotropic behavior when the temperature exceeds 700 degrees C and the strain rate falls below 0.01 s-1 . A modified Gurson-Tvergaard-Needleman (GTN) damage model was developed to simultaneously account for temperature, strain rate, and anisotropy, integrating a custom numerical algorithm along with a modified Backofen plastic flow model and the Hill48 and Yld2000-2D yield criteria. The Yld2000-based GTN model demonstrated superior accuracy over the Hill48-based model, particularly in predicting fracture morphology and forming limit curves under complex stress states. The Yld2000 model also offered more precise predictions of stress-strain curves, yield strength, and R-values, exhibiting less than 5 % error across different directions. Leveraging the precision of the Yld2000-based GTN model, this study explored the effects of various parameters, including temperature, strain rate, blank-holding force, and friction coefficient on the limit dome height (LDH). Optimal results during the bulging process were achieved with a friction coefficient between 0.10 and 0.15, and a blank-holding force between 30 and 35 KN.