Finite element simulation of straight plunge grinding for advanced ceramics

The objective of this work is to model the grinding forces and the associated stress and deformation fields generated in a ceramic workpiece during plunge surface grinding. A two-dimensional finite element model is constructed with the grinding parameters and the mechanical properties of the workpiece as input variables. The size of the geometric model is several times larger than the size of the cutting zone, using approximately 5200 rectangular solid elements with a finer mesh in the cutting zone and with fixed remote boundaries. The loading in the cutting zone is imposed by displacement vectors proportional to the local undeformed chip thickness, which is a function of grinding parameters. For a given set of inputs, the model predicts the normal and tangential forces generated by the grinding wheel, as well as the deformation and the stress fields within the workpiece. As an example, the simulation is applied to a silicon nitride workpiece. Analysis of the stress fields developed in this material suggests that shear failure within the cutting zone is the dominant mode of subsurface failure, which could lead to the formation of shear micro- cracks at the grain interfaces. The depth of the subsurface shear failure zone increases with an increase in maximum undeformed chip thickness or the wheel depth of cut. The resulting local grinding force vectors, maximum stresses and damage zone sizes are predicted as a function of maximum undeformed chip thickness (or the wheel depth of cut).