Effect of electrical resistivity on the electrical discharge machining process

• Type: Chapter or Part of a Book
• Date: 2016-07

Authors

José Duarte Marafona (Author) FEUP; Joaquim Fonseca (Author) FEUP; I. M. F. Bragança (Author) Other; L.L. Alves (Author) Other; P. A. R. Rosa (Author) Other

Book

Title: Metal Cutting Technologies: Progress and Current Trends

Pages: 143-170

ISBN: 978-3-11-044942-6

Electronic ISBN: 978-3-11-045174-0

Publisher: Walter De Gruyter

Other information

Abstract (EN): The electrical discharge machining (EDM) involves the transition from the ionization of the dielectric fluid at atmospheric pressure to the generation of micro-plasmas subjected to high temperature and pressure. Hence, to understand the material removal mechanism it is of great importance to have knowledge of the physics behind the plasma channel. Knowing how electrical properties change with the operating conditions over the discharge time, how this eventually affects heat transfer at the electrode surface and how erosion of workpiece occurs have an important role to achieve an accurate modelling of the process This chapter provides some answers to these issues by means of independent numerical and experimental investigations of the electrical resistivity of plasma channel and of the eroded craters morphology resulting from the plasma-solid interaction. Numerical modelling was performed by means of a coupled electric-thermal approach based on the finite element formulation, and the numerical simulation was carried out with input data exclusively obtained from literature. The experimental tests were performed on AA1050 specimens subjected to single point-to-plane spark discharge, using laboratory-controlled experiments carried out on an innovative testing machine that was designed, fabricated, and instrumented by the authors. The experimental achievements are intended to provide some reference boundaries for the physical parameters required to evaluate the numerical simulation performance of the EDM process. The results suggest that the numerical estimates based on electrical resistivity at a fixed value provides good estimates of the depth and the radius of the craters experimentally observed for the smallest discharge times. However, it always underestimates the radius-to-depth ratio when, independently determined electrical properties of the plasma, at the correct applied power rates, temperatures and pressure, are employed. The contribution of a realistic resistivity behavior is essential for obtaining good estimates for the temperature and consequently of the morphology of the eroded craters. These results raised the need to time-dependent calibration of the electrical resistivity in time to address the right input data parameters to numerical simulations of the EDM.

Type (Professor's evaluation): Scientific

Notes: https://www.researchgate.net/publication/308993800_Effect_of_electrical_resistivity_on_the_electrical_discharge_machining_process

No. of pages: 28