Experimental study of machining residual stresses in plasma-assisted turning process

The possibility of workpiece deformation after or during machining due to residual stresses is of crucial importance in precise components. These stresses are induced mainly due to plastic deformation or heat generation during the metal cutting process. Therefore, the magnitude of machining residual stresses is affected by mechanical and thermal stresses. Mechanical stresses depend on the cutting forces and thermal stresses originate from the magnitude of heat generation during cutting action. Therefore, it is expected that machining processes with lower cutting forces and cutting temperatures, will induce lower machining residual stresses as well. Plasma assisted machining is a process that uses a heat source to increase workpiece local temperature and thereby decrease the strength of the material which is to be removed; therefore lower values of cutting forces, temperatures, and residual stresses are expected. In this research work, the effects of undeformed chip temperature, cutting speed, and feed have been investigated on the machining induced residual stresses in the plasma-assisted orthogonal turning of AISI 4140. According to the achieved results, undeformed chip temperature is the most effective parameter on machining residual stresses and by increasing this parameter from 75 to 220˚C, machining induced surface residual stresses became more compressive averagely by 85.30%.