Dynamics of Ultrasonic Drilling of Hard Materials

Most research in ultrasonic drilling has been concentrated on experimental aspects of the process, and this has led to a substantial gap in a depth of treatment of experimental and theoretical investigations. The basic aim of this chapter is to review and develop appropriate mathematical models, which can be used to predict the main features of the ultrasonic drilling of hard materials. Among them, an impact oscillator and dry friction models are used to provide a valuable insight into this complex process involving dynamic fracture of brittle materials. It is postulated that the main mechanism of the enhancement of material removal rate (MRR) in ultrasonic machining is associated with high amplitudes forces generated by impacts, which act on the workpiece and help to develop micro-cracks in the cutting zone. Novel procedures for calculating the MRR are proposed, which for the first time explain the experimentally observed fall in MRR at higher static forces. These theoretical studies are verified by the experimental investigations carried out in our laboratory.