Experimental verification of the percussive drilling model

This paper focuses on the experimental verification of a dynamical model describing percussive drilling. The design of the experimental apparatus is introduced firstly, and then the dynamic interactions between rock and indenter are studied experimentally by varying three control parameters, including frequency and amplitude of excitation, and pneumatic pressure applied on the indenter. Additionally, the influence of rock stiffness is analyzed by testing different rock-indenter combinations. Meanwhile, the corresponding numerical simulations were conducted showing good agreements with the experimental results. According to the detailed bifurcation analyses, the dynamic responses of indenter mainly display period-one motions which can further develop into period-two motions via period-doubling bifurcation scenarios, or even chaotic motions by period-doubling cascade. The chaotic vibration of indenter can also return to periodic motions via inverse period-doubling bifurcation or fold bifurcation. Although the period-one motion is the main dynamic response in the considered parameter ranges, its impact number per excitation period varies with parameters, which directly affects the maximal impact acceleration of indenter. This results in more energy being dissipated during repeated weak impacts. Therefore, strong impacts are obtained if the indenter is exhibiting the period-one with one-impact motion. For such a purpose, high excitation frequency and amplitude are suggested, however, the high pneumatic pressure should be avoided since it can trigger chattering of the indenter. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This paper focuses on experimentally verifying a dynamical model of percussive drilling, finding that the dynamic response of the indenter mainly exhibits period-one motions, which can develop into period-two or chaotic motions via period-doubling bifurcation scenarios. The impact number of the indenter directly affects its maximum impact acceleration, suggesting that repeated weak impacts should be avoided to obtain strong impacts, with high excitation frequency and amplitude recommended.