Quantitative Expressions for Some Aspects of Surface Integrity of Electro Discharge Machined Components

Abstract

An on-line adaptive control of the Electrical Discharge Machining (EDM) process needs proper quantitative relationships between output parameters and input variables of the process. This paper presents an attempt to develop mathematically simple expressions for the depth of cracks, the depth of damaged layer, and the depth of martensitic layer in terms of pulse duration and current. The transient temperature distribution developed by Data Dependent Systems analysis of the EDM process is used in obtaining thermal stress expressions. The hypothesis that the cracks are the consequence of thermal stresses exceeding the fracture level leads to the expression for the depth of occurrence of cracks. The estimation of the thickness of martensitic layer is based on the phase transformation temperature isothermal obtained from the temperature distribution. A simple expression for the depth of the damaged layer is also obtained using the experimental conclusions reported in the literature. Regression equations suitable for the on-line adaptive control of the EDM process are developed. The theoretical estimates are compared with the experimental measurements.