Dynamics of resonance impact drilling based on constant depth-of-cut and state-dependent time delay models

Key words:  resonance impact drilling system  dynamic characteristics  constant depth-of-cut  state-dependent time delay  box-plot

Abstract:

In order to study the dynamics of resonance impact drilling, two dynamic models of the drilling system were proposed based on the constant depth-of-cut method and the state-dependent time delay method, respectively, considering the load of axial dynamic-static composite impact and axial-torsional coupled motion of the drill string. The Duhamel integral and a fourth-order Runge-Kutta method were used to solve the dynamic models, and the influences of frequency and amplitude of harmonic dynamic load on the dynamic characteristics of the resonance drilling system were analyzed. The dynamic characteristics of the two models were compared and discussed based on the numerical solution results and box-plots. The results indicate that, when the frequency of the harmonic dynamic load increases from 25 Hz to 100 Hz, the drilling bit bouncing phenomenon in the axial direction and the stick-slip effect in the torsional direction can be obviously weakened under the given initial conditions, and when the amplitude of the harmonic dynamic load increases from 30 kN to 60 kN, the both phenomena can be further exacerbated. Besides, under the same initial and harmonic dynamic load conditions, the dynamic characteristic response curves obtained by the two models are different both in the shape and response frequency, and the data points calculated by the state-dependent time delay model are closer to the actual drilling condition. It is concluded that high-frequency and low-amplitude harmonic dynamic loads can improve the dynamic characteristics of the resonance impact drilling system, thereby improving the drilling efficiency.