Drilling Force Characterization during Inconel 718 Drilling: A Comparative Study between Numerical and Analytical Approaches

In drilling operations, cutting forces are one of the major machinability indicators that contribute significantly towards the deviations in workpiece form and surface tolerances. The ability to predict and model forces in such operations is also essential as the cutting forces play a key role in the induced vibrations and wear on the cutting tool. More specifically, Inconel 718—a nickel-based super alloy that is primarily used in the construction of jet engine turbines, nuclear reactors, submarines and steam power plants—is the workpiece material used in the work presented here. In this study, both mechanistic and finite element models were developed. The finite element model uses the power law that has the ability to incorporate strain hardening, strain rate sensitivity as well as thermal softening phenomena in the workpiece materials. The model was validated by comparing it against an analytical mechanistic model that considers the three drilling stages associated with the drilling operation on a workpiece containing a pilot hole. Both analytical and FE models were compared and the results were found to be in good agreement at different cutting speeds and feed rates. Comparing the average forces of stage II and stage III of the two approaches revealed a discrepancy of 11% and 7% at most. This study can be utilized in various virtual drilling scenarios to investigate the influence of different process and geometric parameters.