Process simulation and residual stress estimation of micro-electrodischarge machining using finite element method

A mathematical model based on heat transfer principles has been developed for the simulation of single-spark machining during micro-electrodischarge machining (mu EDM) of a titanium alloy (Ti-6Al-4V). The model is solved by using a commercially available finite element method. A Gaussian distribution of the heat source and temperature-dependent material properties have been used to perform transient thermal analysis to estimate the crater size, the temperature distribution on the workpiece and the residual stress on and near the crater. Simulated crater dimensions and residual stresses were compared with experimentally obtained values by atomic force microscope (AFM) and a nanoindentation technique. The diameter-to-depth ratios of the crater obtained by simulation and by experiment are 3.45 and 3.99, respectively. The simulated stress exceeds the ultimate tensile strength (860MPa) of the material near the spark center and gradually diminishes as the distance from the center increases. The stress values measured by nanoindentation of the spark-eroded surface are within 300 MPa.