Numerical Simulation of Rock Breaking by Single Worn Cutting Tooth
Keywords:Worn cutter, Tooth edge stress, Numerical simulation, Plastic strain.
The cutting teeth on PDC bits have been working under wear for a long time, but the understanding of their rock breaking mechanism is not deep enough. In this paper, the influence of key factors such as wear height, passivation type, invasion depth, lithology, rake angle and tooth diameter on the load distribution of the cutting tooth edge, as well as the equivalent plastic strain form of the rock section, are investigated by means of numerical simulation. The results show that under the same rock breaking parameters, with the increase of wear height, the stress concentration at both ends of the cutting tooth edge is obvious, and the load in the middle section of the cutting tooth edge decreases with the increase of wear height, and the load fluctuation of the cutting tooth edge increases; The load on the tooth edge of the worn cutting gear decreases with the increase of the tooth diameter, and the fluctuation of the load on the tooth edge increases; The load distribution of the cutting tooth edge with an inclination of 15° is uniform, while the stress concentration at both ends of the cutting tooth edge with an inclination of 10° and the load drop at the middle section are obvious; Compared with the cutting teeth of the other two types of wear, the conventional wear cutting teeth have longer effective rock breaking length, larger load on the cutting edge, more uniform distribution and better rock breaking effect; According to the relevant simulation results, it is believed that the wear height, design parameters and wear types will affect the size and distribution of the tooth edge stress in the cutting process of worn cutting teeth, and then affect the wear trend in the cutting process. In addition, by observing the equivalent plastic strain form of the rock section after cutting, it is found that the rock cuttings under the action of new teeth are semicircular blocky, while the rock cuttings under the condition of worn teeth are flake. It is believed that the new teeth are more likely to form large blocky rock cuttings in the process of rock breaking, and the rock breaking effect is better than that of worn teeth.
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