Material removal behavior and crack-inhibiting effect in ultrasonic vibration-assisted scratching of silicon nitride ceramics

To investigate the material removal mechanism and crack-inhibiting effect of ultrasonic vibration-assisted grinding of ceramic materials, a series of double-scratch tests with variable scratching depths and interval distances was conducted. Ultrasonic vibration-assisted scratching (UVS) and conventional scratching (CS) were compared in terms of cutting force, scratch morphology, crack system, and material removal mode, and the effects of ultrasonic vibration and scratch interval distance on the material removal mode and crack-inhibiting effect were analyzed. The results indicate that the crack-inhibiting effect between scratches gradually decreases with an increase in the scratch interval distance. In comparison with CS, UVS can increase the critical load of the brittle-ductile transition and promote the propagation of shallow lateral cracks to the surface. Meanwhile, ultrasonic vibration increases the critical scratch interval distance of the crack-inhibiting effect. The research results also reveal that the material is mostly removed by the interlacing of shallow lateral cracks in UVS; however, this is due to the combined action of deep lateral cracks and radial cracks in CS.