Three-Dimensional Analysis of Residual Stress in EDM Process

Abstract

In electrical discharge machining(EDM) process, the residual stress is generated generally in the surface layer of the workpiece due to the effects of the heating and cooling process. The stress causes decrease of fatigue strength, delayed fracture and stress corrosion which affect quality of the workpiece. In the present paper, based on thermal elastic-plastic theory, a new calculation procedure of the three-dimensional analysis of thermal stress and residual stress is developed by utilizing the FEM in which the temperature dependencies of physical-mechanical properties of workpiece material are taken into consideration. The analysis shows that the radial stress and the circumferential stress in the layer below the crater are beyond the tensile strength of the material, and result in the generation of the crack.