ROLE OF INDENTATION FRACTURE IN FREE ABRASIVE MACHINING OF CERAMICS

Free abrasive machining (FAM) is widely used for stock removal and surface finishing of ceramics. In FAM, material removal results from mechanical action between the abrasive slurry, which is trapped between the workpiece and a rotating lapping block, and the workpiece. Microscopic 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 on indentation fracture and takes into account the abrasive particle distribution in the slurry. The model is used to predict the number of particles actually involved in the machining process, the distribution of load among these particles, and the depth of the plastically deformed layer on the workpiece surface. Many of the predictions of the model are well supported by experimental observations from the FAM of aluminum oxide, Ni-Zn ferrite, and glass using a silicon carbide slurry.