Mechanical analysis and machinability evaluation of a new EDM-turning hybrid machining process

Abstract

This study developed an accurate electrical discharge-assisted turning (EDAT) technique for Ti–6Al–4 V alloy and a precise EDAT cutting force prediction model considering theoretical multi-physics fields with metallurgical transformation. A heat-fluid coupled model of multi-pulse discharge in the EDAT process was developed to obtain the thickness of the removal layer (RL) and modified layer (ML) together with the temperature field of the cutting layer. Subsequently, the shear flow stresses under different machining parameters were obtained using the oblique cutting and flow softening constitutive models. Within the cutting layer, the pure thermal softening effect reduces the flow stresses by more than 25% in the unmodified matrix layer (UML) and by more than 60% in the ML, which is dominated by the metallurgical transformation softening (MTS) effect. Finally, the cutting force model of EDAT under multi-physical fields was established and the accuracy was verified by relevant experiments. The results showed that the increase in discharge number accelerated the rise of workpiece surface temperatures, and the small cutting parameters were favorable to the machining performance of the EDAT. The MTS effect significantly reduces cutting forces while improving the quality of the machined surface.