Predicting subsurface damage in silicon nitride ceramics subjected to rotary ultrasonic assisted face grinding

Silicon nitride is an advanced ceramic used in high performance applications. One of the main problems in machining of brittle materials such as silicon nitride is subsurface damage (SSD). On the other hand, rotary ultrasonic assisted face grinding (RUAFG) is considered as state of the art machining process for brittle and hard to machining materials such as ceramics and optical glasses. In this research, a new study on SSD generation in RUAFG by establishing both ductile deformation and brittle fracture conducted. To achieve this goal, initially single diamond grit cutting force based on Vickers hardness correlation and indentation fracture mechanics established and placed in crack propagation formulas to anticipate SSD. Verification tests performed and average 8% error detected. Moreover, RUAFG depicted up to 30% SSD reduction in comparing to conventional face grinding (CFG). Besides, scanning electron microscope utilized to investigate cracks morphology.