Research on rock breaking mechanism of composite cone single cone bit

Composite cone single cone bit is a new type of single cone bit based on spherical single cone bit. Its unique structure changes the rock breaking method of traditional single cone bit, and the rock breaking efficiency and service life of the bit are improved in hard rock formation. One of the most influential is the shape of cone, which changes the trajectory and the cutter loads of the bit at the bottom of well, affecting the drilling efficiency and service life of bit. Based on experimental and numerical analysis methods, the rock breaking mechanism of two kinds of bits with different structural shapes was analyzed, and the following conclusions were obtained. 1) Rock breaking of composite single cone bit can be divided into three areas: long-distance scratch area, dense short distance scratch area and crushing pit area. 2) The direction of cutter load is determined by structure and motion mode of the cone. 3) Impact and scraping proportion of cutter with different bits structures is different, resulting in different rock breaking modes of cutter with different cutter row. This research has a profound understanding of the influence of cone shape on cutter load and cutter failure of bit, and it is of great significance for the study of composite cone single cone bit with long service life and high rock breaking efficiency.