Dynamic method of stiffness identification in impacting systems for percussive drilling applications

This paper introduces a dynamic method for the stiffness identification of an impacted object via analysis of its corresponding impact duration. To accurately detect the impact durations from experimental signals, nonlinear time series methods are applied. Two low-dimensional dynamical systems, including a piecewise-linear impact oscillator and a rock impacting system, are studied experimentally and numerically to demonstrate the proposed method. Meanwhile, the analytical prediction of the impact duration for the period-one one-impact motion is developed. The results of both systems indicate that, for a certain stiffness, the impact duration of the period-one one-impact motion is nearly constant. The higher the stiffness, the lower the impact duration. This monotone correlation provides a mechanism to estimate the stiffness of the impacted object once the impact duration has been accurately detected. The developed method can be used to optimise percussive drilling parameters.