Cutting Force Prediction in Drilling of Titanium Alloy

Cutting force in drilling of Ti-6Al-4V is studied with simulation based on a predictive model. In the force model, three-dimensional chip flow is made by piling up the orthogonal cuttings in the planes containing the cutting velocities and the chip flow velocities, where the cutting model in each plane is made using the orthogonal cutting data. The chip flow direction is determined to minimize the cutting energy. The cutting force is predicted in the determined chip flow model. The force model is verified in comparison between the predicted and the measured cutting forces. In the rolled titanium alloy, anisotropy is observed in the cutting force. Because the cutting edges rotate in drilling, the cutting force changes periodically with the cutting direction with respect to the rolling direction. Hardness change in subsurface is also measured with a nano indenter. The hardness of the titanium alloy increases around 10 mu m underneath the machined surface. Meanwhile, hardness of 0.50% carbon steel does not change. The strain hardening effect is considered by the shear stress on the shear plane in the orthogonal cutting data in the force model.