Numerical study on optimal impact angle of a single PDC cutter in impact rock cutting

Abstract

In previous work (Liu et al., 2020), we studied the differences between conventional rock cutting and cutting with compound vertical and horizontal impact force. In this work, we investigated the relationship between the impact force direction and cutting efficiency, which is the key to the impactor design. We established an impact rock cutting model with a single sharp polycrystalline diamond compact (PDC) cutter, and the direction of the impact force was described by an impact angle (β), which ranged from 0 to 90°. Simulations with different β were conducted, and the fragmentation process, forces, and mechanical specific energy (MSE) were analyzed. We also investigated the effects of the amplitude and duration of the impact forces on the MSE. The results showed that there is an optimal β, for which the MSE is the lowest and cutting efficiency is the highest. The effects of the vertical and horizontal impact forces on the rock cutting process were different, and excessive vertical or horizontal impact forces were not conducive to improving the cutting efficiency. The optimal β decreased with an increase in the impact amplitude, and a similar relationship was found between the optimal β and the duration of the impact force. In practice, designers are suggested to set the β of the impactor between 30° and 60°, and a lower β may be necessary to adapt to a higher impact amplitude and lower frequency.