Experimental study of the force response and chip formation in rock cutting

Abstract

Mechanical rock cutting is one kind of rock breaking methods which is extensively used in oil gas drilling engineering. The force response and chip formation in rock cutting process plays an important role in studying the rock breaking mechanism of polycrystalline diamond compact (PDC) cutter, which is essential to the determination of optimum cutting parameters. In this paper, the experimental setup and discrete element model of rock cutting are developed; the force response and chip formation under various depths of cut (DOC), cutting velocities, and rake angles of PDC cutter are performed. This study shows that the average cutting force is proportional to the DOC when it is shallow; however, the average cutting force tends to deviate from the linear relationship while the DOC reaches to a threshold value. The cutting chips generated during rock cutting process can be divided into three parts, the crushed zone near the cutter tip and the plastic flow zone in front of the cutter surface, both of them in a powdery form, and another is the main part of chip in front of the crushed zone in a block-shaped form. The crushed zone will create a wedging effect on the initiation of macro-crack which causes the propagation of macro-crack in an opening mode. The cutting velocity has no obvious influence on the size and number of the formed chips. The smaller the rake angle is, the smaller size the chips will be. The research results are of great significance for deep understanding of the mechanism of rock cutting and for guiding the design of PDC bit and optimization of the drilling parameters.