Drilling induced tearing defects in rotary ultrasonic machining of C/SiC composites

Drilling induced tearing defects at the hole exit restrict the reliability of C/SiC production. In this study, the drilling induced tearing defects in rotary ultrasonic machining of C/SiC composites were investigated quantitatively. The mechanism of tearing defect formation was studied through the detailed observation of thrust force. Experimental results indicate a positive dependence of tearing defect on the thrust force. A larger thrust force corresponds to a larger drill displacement during the formation process of tearing defect, resulting in larger tearing defect. RUM can averagely reduce the tearing defect at the hole exit more than 60%. Tearing defects can be further reduced by increasing the spindle speed and the ultrasonic amplitude, or decreasing the feed rate.