Numerical Prediction and Experimental Investigation of Ductile Damage During Cold Upsetting of TC16 Titanium Alloy for Manufacturing Fasteners

Based on the continuum damage mechanics theory, a new set of unified visco-plastic damage constitutive equations for TC16 titanium alloy was developed by using the internal state variable modeling method to couple the stress state, stress triaxiality ratio (STR) and normalized Lode angle (NLA), and to predict the damage evolution of TC16 alloy during cold upsetting. The coupled damage constitutive equations were determined and programmed into FE software DEFORM-3D via user subroutine. A numerical simulation of the cold upsetting was conducted to simulate the manufacturing fasteners. The distribution of microstructure, stress state, and the ductile damage was predicted during the cold upsetting using the developed FE simulation system. Furthermore, the cold upsetting experiments of fasteners were carried out to validate the FE simulation results. Results showed that predicted ductile damage and experimental results are consistent. This indicates that constitutive model of the proposed multiaxial visco-plastic damage is well predictive for manufacturing fasteners.