Fundamental Machining Characteristics of Ultrasonic Assisted Internal Grinding of SiC Ceramics

Silicon carbide (SiC) ceramics has been utilized in a variety of engineering applications because of its desirable properties. Meanwhile, SiC ceramics is a typical hard-brittle material; hence it is difficult to machine. In this study, ultrasonic assisted internal grinding (UAIG) technique was proposed for the precision internal grinding of SiC ceramics, and its fundamental machining characteristics were investigated experimentally. Conventional internal grinding (CIG) test was also carried out on the same experimental rig but without ultrasonic vibration for comparison. The experimental results of UAIG compared with those of CIG show that (1) the normal force and tangential force in UAIG are considerably smaller than those in CIG by up to 30.7% and 56.25%, respectively; (2) the improvement of the form accuracy and the surface roughness become greater, i.e., in CIG, the roundness and cylindricity of workpiece are improved by 67.4% and 56%, respectively, after grinding, whereas in UAIG by 86% for both the roundness and cylindricity; the surface roughness R ( a ) in CIG is decreased by 76.5% after grinding, whereas in UAIG by 84.9%; (3) grinding cracks occurring on the work-surface are considerably restrained; (4) grain cutting edge protrusions are sufficiently observed; (5) subsurface damages are alleviated, i.e., the fracture depth is decreased by 17% and cracks are reduced.