Abstract: In order to promote the auxiliary effect of axial impact in rotary-percussive drilling, an experimental set-up for testing the indenter-rock interaction is developed, the nonlinear dynamics of this vibro-impact system is studied numerically and experimentally by varying three control parameters, including frequency and amplitude of excitation, and static force applied on the indenter, and the obtained experimental measurements and the numerical simulations show good agreements. Bifurcation analysis and phase-plane analysis indicate that the dynamic responses are mainly period-one motions with varied impact numbers, which can further develop into period-two motions via period-doubling bifurcations, but will go back to period-one motion via inverse period-doubling bifurcation or fold bifurcation. Since the vibration condition of the indenter determines the impact force, and thus the drilling efficiency, to obtain the most powerful percussion, the ideal vibration of the indenter is the period-one one-impact motion. Therefore, the high excitation frequency and amplitude are suggested, but the high static force should be avoided since it triggers harmful chattering for percussive drilling.

Key words: dynamics, nonlinear, vibro-impact, bifurcation