Modelling of vibro-impact penetration of self-exciting percussive-rotary drill bit

The penetration of a drilling tool into a hard medium under periodic impact action is analyzed and the simulation model presented. This is further development of previously investigated model of a self-excited percussive-rotary drilling system. The system used the stick–slip phenomenon to generate an impact action superimposed on the drilling process. A phenomenological visco-elasto-plastic model of the media is used and the system response is studied numerically, first as a forced vibration and second as a result of a self-excited vibro-impact process. Relief of the main drive has been obtained and an increase in the rate of penetration is observed with increased impact intensity and hardening of the medium. Results of the preliminary drilling experiment with superimposed dynamic action have shown an improvement in the rate of penetration.