Numerical Simulation and Experimental Study on Novel Rock-Breaking Concept—Layered Spalling

Cutter, the fundamental cutting element of PDC (Polycrystalline Diamond Compact) bit, directly determines the overall performance of PDC bit and thus influences Rate of Penetration (ROP), drilling efficiency and drilling cost. Bit scrapped caused by cutter failure accounts for about 90% of all the failure in field operations. A majority of researches have been conducted on PDC cutter design, which were mainly concentrated on structure itself, such as stress state, self-sharpening and interface bonding strength, while neglecting the closely related factor of the rock-breaking method. This paper presents a novel PDC cutter which is designed based on the bionics theory to illustrate the layered spalling concept of rock-breaking. This paper has paid much attention to studying the numerical simulation of dynamic rock-breaking process under new bionic PDC cutter to illustrate the rock-breaking mechanism. Meanwhile, the corresponding experiments have been performed with a single cutter to validate the theory. The results indicate that: (a) the process of rock-breaking under the new bionic PDC cutter is characterized as “layered spalling” with slight oscillation comparing to the property-“Block Dropping” of conventional cutter. (b) the cutting process of bionic cutter is more stable with minor impact vibration, which contributes to improving the cutter’s life to some extent. The amplitude of cutting force reduces by 42% and the average value of the new bionic PDC cutter is 460N while the conventional PDC cutter is 790N.