Numerical simulation of crack formation process in lapping fused silica optics

The conventional finite element method is over-reliance on the mesh dimension, specifically, the mesh distortion is usually serious in the contact area of the abrasive particle and workpiece which makes it more difficult to simulate the formation process of internal cracks in brittle materials. To simulate the lapping process of fused silica optics, FE/SPH model of the machining process for a single abrasive particle was established. Then a new way to simulate the cutting process of brittle materials was provided. The formation process of subsurface crack and the influence of cutting parameters on subsurface damage depths were analyzed. Simulation results show that the brittle material is in the elastic-plastic deformation stage when abrasive particle is just beginning to cut into the workpiece, further amounts of microcracks arise under the extrusion and tear effects of the abrasive particle. The combination and extension of microcracks produced transverse and longitudinal cracks, which are parallel and perpendicular to the workpiece surface, respectively. Consequently, brittle-fracture removal of the workpiece material is completed.