Finite element analysis of coupling effects of weight on bit and vibration amplitude on ultrasonic vibration assisted drilling rock

Ultrasonic vibration as a novel and advanced auxiliary lithotripsy technology possesses great potential in the fields of deep mine drilling. This paper carries out a finite element (FE) analysis to investigate the coupling effects of weight on bit (WOB) and ultrasonic vibration amplitude on the ultrasonic vibration assisted drilling (UVAD) of hard rock. The critical model of WOB and amplitude for hard rock breaking is established to explore the coupling effects quantitatively. The results show that the ultrasonic-frequency axial percussive motion significantly enhances the drilling rate. During the UVAD process, the principle stress undergoes severe fluctuation, constituting more than 50 % of the maximum principal stress, and larger ultrasonic amplitudes correspond to more pronounced stress fluctuations. There are critical coupling values of WOB and ultrasonic amplitude for the rock breaking, with the amplitude increases from 0 µm to 15 µm, the critical WOB for rock breaking reduces by 25 %.