## 4 Results and Discussion
### Cutting Force Analysis  
To find the best cutter arrangement scheme, 18 different combination schemes of cylindrical (No. 1), axe (No. 2), and triangular prism (No. 3) cutters were numerically simulated. The scheme numbers in Figures 10-12 have the following implications: Taking \"\(1+2+2\)\" as an example, the first digit represents the cutter arrangement type of the front row of the drill bit. The second and third digits represent the cutter arrangement types of the rear row of the drill bit, with the second digit indicating the left-side cutter arrangement type of the rear row and the third digit indicating the right-side cutter arrangement type of the rear row. The cutting force curves corresponding to the six strategies utilizing cylindrical cutters in the frontal row are shown in Figure 10. As evidenced in the figure, the application of cylindrical cutters as the leading row has a considerable impact on the overall cutting force under varying rear row arrangements. In instances where the rear row incorporates a cylindrical cutter, the cutting force exhibits a notably amplified peak and fluctuation compared to the other arrangements. The underlying cause of this occurrence is predominantly linked to the fracturing properties of the cutter. Being flat, the cutting face of the cylindrical cutter relies primarily on its periphery's shear force to split the rock. However, it encounters considerable difficulty when presented with more rigid rock types. Additionally, incorporating excessive numbers of cylindrical cutters into the arrangement can complicate the drilling process, leading to heightened resistance. These conditions can significantly compromise the overall efficiency and lifespan of the drill bit. As shown in Figure 10, the optimal configuration utilizes the cylindrical cutter in the front row, followed by the axe cutter, resulting in a substantial reduction in overall cutting force fluctuations and peaks. This outcome is primarily due to the cylindrical cutter's pre-crushing effects on the rock in the front row. Meanwhile, the axe cutter not only exerts a shearing impact on the rock but also induces an additional crushing effect. Consequently, this setup enhances penetration into granite structures compared to exclusively using cylindrical cutters, thereby minimizing resistance. Figure 11 shows the various force curves associated with the axe cutter in the vanguard position across six assorted scenarios. Upon comparison with data from Figure 10, it is concluded that when the axe cutter operates in the front row, it yields lesser stress peaks in all scenarios, as opposed to when the cylindrical cutter is placed in the same position. This is attributable to the axe cutter's superior capacity to induce a crushing effect on rock compared to the cylindrical cutter. Consequently, this facilitates more efficient granite penetration in its initial phases, engenders an enhanced pre-crushing influence, and alleviates formation stress. This sequence of events collectively enables subsequent rows of cutters to crush rock more effortlessly. The data presented in Figure 11 reveals an imperfect effect of utilizing both front and rear row axe cutters. This is largely due to the resultant interference in the force exerted by the front row cutters when the rear row attempts to crush the rock, causing instability and a significant fluctuation in the overall cutting force, therefore hindering the anticipated effect. However, when the frontal row is equipped with an axe cutter and the rear row consists of a triangular prism cutter and an axe cutter, the peak and fluctuation of cutting forces attain a minimal level. This is attributed to the weaker impact of the triangular prism cutter  
Figure 11: Axe cutter with different cutting forces in the front row. Figure 10: Different cutting forces with a cylindrical cutter in the front row. on the rock, resulting in less interference with the front row's performance. The harmonic interplay between the two cutter types yields a more optimal result.