Effect of single grit impacts on initiation and propagation of cracks in ultrasonic assisted grinding of ceramics by using SPH method

In order to investigate the material removal mechanism in vertical ultrasonic assisted grinding (VUAG) of ceramics, single-grit impact simulation is performed by using smoothed particle hydrodynamics (SPH) method. The initiation and propagation of cracks in grinding of Al2O3 ceramics are analysed. In this simulation, the grit is modelled as a rectangular pyramid diamond indenter and the process of grit impacting on workpiece under different impact speeds is simulated. The critical depth of initiation and propagation of lateral crack is observed. The results show that within a certain range of impact speed, the critical depth of lateral crack decreases with the increasing of impact speed. This means that the brittle fractures are more prone to occur in VUAG. Considering that the material micro-fracture is the main mode in ceramics material grinding under ordinary processing conditions, the material removal rate in VUAG can be improved. Moreover, by observing the surface topography, it can be found that the surface roughness becomes smaller when the impact speed increases.