A new method for drilling holes in engineering ceramics by using a rotary ultrasonic tool has been developed. In this method, a drilling tool impregnated with abrasive particles is simultaneously rotated and vibrated. The mechanism of ultrasonic drilling is analysed using the concept of fracture mechanics and a new theoretical model of material removal rate (MRR) is proposed. According to this model, the material removal rate increases with increases of applied static load, amplitude of vibration and rotation speed of the drilling tool. Test results show that ultrasonic drilling is an eective method for machining engineering ceramics.

The widespread utilization of engineering ceramics has been limited by fracture in the machining process. A technical basis for avoiding fracture requires a fundamental understanding of the fracture mechanisms in machining. The present paper is intended to discuss the fracture mechanisms during the vibration drilling of holes in engineering ceramics. In this paper, the stress distribution during the vibration drilling of holes in ceramics has been analysed. The results show that, in the terminal period of vibration drilling, the stress on the periphery of the hole exit is at its maximum. It is the main reason for fracture at the exit of holes in engineering ceramics. The condition for no fracture at the exit is given, and an eVective method is proposed to avoid such fracture.