Predicting hot deformation behaviors under multiaxial loading using the Gurson-Tvergaard-Needleman damage model for Ti?6Al?4V alloy sheets

Abstract

In this study, the hot deformation behavior of Ti?6Al?4V alloy sheets was investigated at a temperature of 650 ?C after being subjected to various forming histories. The studied behaviors included empirical testing of uniaxial stress, plane strain, and biaxial stretch deformation modes. The results were then quantified using a damage modeling approach. Limiting dome height tests at elevated temperatures were conducted to characterize the mechanical behavior under various deformation modes. Constitutive modeling followed the Gurson-TvergarrdNeedleman damage model of plasticity, including flow softening, strain rate sensitivity, and adiabatic heating. The material constants of the model were calibrated using hot uniaxial tension at various strain rates. Thermomechanical finite element simulations coupled with the plastic and damage modeling were conducted to predict the plastic deformation and failure behaviors of the Ti?6Al?4V alloy sheets under hot forming conditions. The damage behavior for hot uniaxial tension and limiting dome height tests was also analyzed via the hybrid methods of fractography and quantitative assessment. The macro-damage quantitative simulations reproduced the observed plastic behaviors, including the load-displacement responses and the fracture states of Ti?6Al?4V alloy sheets at elevated temperatures, after experiencing complex-forming conditions. The research results thus provide a basis of optimal hot forming process for titanium alloys.