Characterization and numerical modeling of high strain rate mechanical behavior of Ti-15-3 alloy for machining simulations

Metastable beta titanium alloys combine light weight, high strength, and excellent corrosion and fatigue resistance, and can therefore be very useful in many demanding applications. However, they are also difficult to machine and the machining costs of titanium components can be significant compared to the overall costs of the component. Finite element simulations can be used to optimize the cutting conditions and reduce the machining costs. However, any attempt to simulate the rather complex machining processes needs reliable material models that can only be generated when the mechanical behavior of the material is understood well. In this work, the mechanical properties and behavior of titanium 15-3 alloy was studied in a wide range of strain rates and temperatures, and a constitutive model was generated for simulating orthogonal cutting of the alloy. The strain-hardening rate of Ti-15-3 is a strong function of strain rate, and it decreases rapidly as the strain rate is increased. Also, the strain rate sensitivity of the material was found to depend strongly on temperature. Johnson–Cook plasticity model, based on isothermal stress–strain curves, was used to model the behavior of the material. The isothermal stress–strain response was calculated from the experimental data, and the model used in the simulations was modified to account also for the adiabatic heating and consequent thermal softening of the material. The current model is able to simulate the serrated chip formation frequently observed for titanium alloys at high cutting speeds.