Numerical and experimental investigations on the laser assisted machining of the TC6 titanium alloy

Abstract

In order to improve the machinability of difficult-to-machine materials in aviation, laser-assisted cutting technology has received extensive attention. This method of machining allows the workpiece to obtain a localized high temperature prior to cutting in order to benefit from thermal softening. A 3D transient laser heating model was developed for the finite element method to predict the preheating temperature of the cutting layer. The effect of cutting parameters (cutting speed, feed rates, depth of cut) on the magnitude, frequency and amplitude of the cyclic cutting forces was investigated both in conventional machining and in laser assisted machining. It is founded that the laser assistance decreases the flow stress of the material, magnitude of cutting forces and the amplitude of cutting forces. But the frequency of circulating cutting forces increase comparing with the CM (conventional machining). In addition, this paper considers the effect of the LAM (laser-assisted machining) technique on reducing the magnitude of cutting force fluctuations, which results in a flatter machined surface profile and reduces the number of surface defects. A chip morphology different from that of CM is created due to the influence of the cutting force by the temperature field in LAM. Furthermore, a “transitional chip” is discovered, which is a transition from a continuous chip to a segmented chip. The completely thermal-mechanical coupled orthogonal cutting model was established to reveal the evolution mechanism of shear band formation with laser assistance. The results show that shear bands can be formed faster and with less stress in LAM compared to CM. The model can effectively predict the shear angle and keep the prediction error within 10 %. The shear band formation processes in both machining methods were uncovered according to the models. The developed model is very useful for understanding the chip formation process and the cutting force variation in laser assisted machining.