ROLE OF INDENTATION FRACTURE IN FREE ABRASIVE MACHINING OF CERAMICS

Free abrasive machining (FAM) is widely used for stock removal and sur face finishing of ceramics. In FAM, material removal results from mech anical action between the abrasive slurry, which is trapped between th e workpiece and a rotating lapping block, and the workpiece. Microscop ic observations of the machined surface show that lateral cracking due to indentation by the abrasive particles contributes substantially to material removal. A simple model of FAM is developed which is based o n indentation fracture and takes into account the abrasive particle di stribution in the slurry. The model is used to predict the number of p articles actually involved in the machining process, the distribution of load among these particles, and the depth of the plastically deform ed layer on the workpiece surface. Many of the predictions of the mode l are well supported by experimental observations from the FAM of alum inum oxide, Ni-Zn ferrite, and glass using a silicon carbide slurry.