Finite Element Modeling and Simulation of Inconel 718 Using WEDM

Abstract

Wire Electrical Discharge Machining (WEDM) is a versatile process to generate intricate and complex shapes on conductive work material with high dimensional accuracy and surface finish. Since the process is stochastic, its input parameters play critical role for achieving desired accuracy and precision of the component. Inconel 718, High-Strength-Temperature-Resistant (HSTR) material, has wide applications in the field of aerospace, automobile, mould making and medical industries. Hence, machining of Inconel 718 using WEDM is a challenging task. Also experimentation on Inconel 718 with WEDM is costly as well as time consuming process. Therefore to study the behavior of WEDM process with different process parameters for effective and efficient operation, process modeling and simulation using appropriate software is highly essential. In the present investigation, a 3-D single spark finite element thermal model for WEDM process has been developed using ANSYS software. This model has some more realistic assumptions like heat flux following Gaussian distribution and spark radius as a function of time and energy. Plasma incident region is meshed by keeping elemental size equal to one tenth of entire plasma radius, so that exact ten elements can be fitted. Identified elements were thermally loaded by applying element wise different temperatures for getting more accurate temperature distribution profile. This profile was found to be having crater shape matching with earlier Finite Element Models (FEM) available in the literature. Along with the shape, it also helps to decide the elements having temperatures greater or equal to melting point leading to estimate Material Removal Rate (MRR). Later on single spark MRR can be used to estimate multi-discharge-MRR by calculating pulse rate. Model MRR is validated with the experimental MRR which show a very good agreement, but little variation. This variation in the modeling could possibly due to assumptions like no delay in ignition, non-deposition of recast layer (100% flushing efficiency), etc. The factors like incomplete flushing of debris and inter-electrode gap arcing cause the variation in machining conditions thus reducing the actual MRR. In the present investigation, the use of dielectric is considered only for convection, but in reality, it acts as an insulator, coolant and also as debris remover. Melting and vaporization of material is the main phenomena for material removal. Dielectric fluid partially removes the molten metal because at the same time, the molten metal is under very high pressure due to plasma channel. Its adhesive property resists the material removal. It is very difficult to incorporate all real effects in the model, however the obtained results in the present study show good agreement between model MRR and experimental MRR within 10% variation.