Longitudinal-torsional coupled rotary ultrasonic machining end surface grinding of SiCf/SiC composites: a mechanical model of cutting force.

Composites with a silicon carbide fiber-reinforced silicon carbide matrix (SiCf/SiC) are difficult to be machined by the conventional processing due to its hardness and brittleness. The longitudinal-torsional coupled rotary ultrasonic machining (LTC-RUM) is regarded as an effective processing for the material; however, the SiCf/SiC composite's material removal mechanism in LTC-RUM has not been reported, as well as the cutting force. In order to better understand the material removal mechanism of SiCf/SiC composites, this study proposed a cutting force model of LTC-RUM end surface grinding of SiCf/SiC composites. Firstly, the motion path of a single abrasive grain was analyzed, and the micromechanical analysis was used to convert a heterogeneous material into an equivalent homogeneous material. Then, a single abrasive grain material removal mechanism was explored by considering the three material removal regions, including ductile region, ductile-to-brittle transition region, and brittle region. The corresponding material removal mechanism of single abrasive grain during each region was analyzed in detail, and the normal and tangential cutting forces were obtained. Finally, a number of designed experiments were carried to verify the developed model and found that the predicted values were in good agreement with the experimental ones, and the maximum relative errors of normal and tangential cutting forces were 8.51 and 10.19%, respectively. Compared with conventional grinding, the cutting force shows a nonlinear decline in LTC-RUM end surface grinding. The results of this study provide a valuable reference for the LTC-RUM SiCf/SiC composites. [ABSTRACT FROM AUTHOR]