Process parameters influence on laser-assisted machining-induced residual stresses

Residual stresses are induced mainly due to the plastic deformation or heat generation during metal cutting process. Mechanical stresses are themselves dependent on machining forces while thermal stresses depend on the magnitude of the produced heat during cutting process. Laser-assisted machining is a process in which a controlled laser source is used to increase the local temperature in some parts of a workpiece which are about to be cut. Therefore, the material resistance against the cutting will be reduced and machining process will lead to smaller values of cutting forces and temperatures which will finally decrease the induced residual stress in workpiece surface. In this paper, the impact of laser source parameters (power and spot size) and also machining parameters (cutting speed and feed) on surface residual stress in laser-assisted machining of AISI 4140 was experimentally studied. Based on the obtained results, by increasing laser source power, the machining-induced surface residual stresses in the selected range of machining parameters became more compressive; with an increase in P s from 200 to 500 W, the average value of machining-induced surface residual stresses became more compressive by 48.47%.