Investigation on force responses in ridged diamond element breaking granite

Abstract

Ridged diamond element (RDE), a new 3D shaped PDC cutter, has higher impact and wear resistance than conventional plane PDC cutter. Furthermore, RDE also can significantly improve the rock-breaking efficiency of PDC drill bits in hard rock. The investigation on force response during the RDE breaking rock is a critically important work for revealing the rock breakage mechanism and designing the AxeBlade PDC bit. However, to our best knowledge, there is still a lack of systematic and in-depth research on the force response of RDE cutting hard rock. This paper conducted a series of single cutter tests on granite, and measured the triaxial forces of RDE under different depth of cut (DOC) and back rake angle. Then, a mechanical model of interaction between RDE and rock was established through theoretical derivation. The model accuracy is validated by experimental data, and the average error of prediction cutting force and normal force is 3.13% and 3.68% respectively. Lastly, the influence of DOC, back rake angle, cutter diameter and ridge angle on cutting force and normal force was analyzed, and the influence weights of four parameters were revealed by random forest method. The results show that the cutting force and the normal force increase with DOC in a quadratic polynomial relationship. With the increase in back rake angle, cutter diameter and ridge angle, the cutting force and normal force show an increasing trend, but there are significant differences in the rate of increase. When the back rake angle increases from 10° to 30° for DOC of 2 mm, the cutting force and normal force increases by 416.22 and 1008.04 N respectively. The cutter diameter increases from 10 to 20 mm, the cutting force and normal force increases by 1318.13 and 1739.10 N respectively. The ridge angle increases from 100° to 165°, the cutting force and normal force increases by 1276.03 and 750.87 N respectively. The DOC has the largest influence weight on the force response of RDE in four parameters. The findings of this work can provide theoretical guidance for the cutter arrangement of AxeBlade PDC bit.