Effect of thermo-mechanical loading on machining induced residual stresses in ultrasonic vibration assisted turning of Ti6Al4V alloy

The study of residual stresses induced during machining is of considerable importance due to their effect on fatigue life of machined components. The metallurgical changes occurred due to thermo-mechanical phenomenon in cutting process affects the distribution of residual stress in machined components. Ultrasonic vibration assisted turning (UVAT) is effective machining process for low thermal conductivity materials like Ti6Al4V alloy and improves the surface characteristics by reducing cutting force and cutting temperature. In this paper, experimental and finite element (FE) studies are conducted to study the circumferential and axial residual stress distribution in UVAT of Ti6Al4V alloy. FE model is developed to study the effect of vibrating parameter (ultrasonic power intensity) and cutting parameters (cutting speed, feed rate, and depth of cut) on the residual stress profiles of machined surface. The FE simulation results of cutting force and cutting temperature are validated with experimental results. The circumferential and axial surface residual stresses obtained from FE simulation are also compared with experimental results using X-ray diffraction method. The effect of thermo-mechanical loading on residual stress distribution is analyzed with respect to force components (cutting force and feed force) and cutting temperature. Finally, the effect of each cutting parameter on subsurface layer of machined component is analyzed.