孕镶金刚石钻头多级胎块螺旋式分布结构设计及其仿真优化OA

Objectives:To address the low drilling efficiency and frequent"bit balling"or slipping issues encountered by conventional impregnated diamond bits when drilling through hard,dense,and weakly abrasive formations characterized by rock Mohs hardness exceeding 7 in a major hydropower project exploration area in Tibet,this study aims to design an innovative impregnated diamond bit featuring a multi-stage matrix block with helical distribution structure.The core objective is to enhance the proportion of volumetric rock fragmentation by modifying the bit-rock interaction mechanism,thereby improving the rate of penetration and drilling efficiency in such challenging formations.The research focuses on elucidating the rock fragmentation mechanism of the novel bit and optimizing its key structural parameters through finite element simulation,providing a new technical approach for drilling difficulties in these formations.Methods:Firstly,based on the rock fragmentation principle of impregnated diamond bits,a bit with a multi-stage helically distributed matrix block structure was designed from the perspective of increasing rock fracture free surfaces and inducing volumetric fragmentation.The innovation lies in the bit face configuration,where wear-resistant spiral matrix blocks and weakened ordinary matrix are alternately arranged,forming a unique helical pattern.Additionally,annular gauge blocks are set at the inner and outer diameters of the bit to ensure drilling stability.Based on theoretical analysis of its rock fragmentation mechanism including ridge formation,increased free surfaces,and radial thrust action,finite element simulation using Abaqus software was employed to optimize the bit structural parameters.The Drucker-Prager model was selected as the rock constitutive model to simulate elastoplastic deformation and progressive damage failure processes of rock.Taking the block-to-slot ratio(the ratio of spiral block thickness to inter-block slot width)as the key variable,the force and torque characteristics of five bit types with block-to-slot ratios of 1∶0,1∶1,1∶2,1∶3,and 1∶4 were comparatively analyzed under fixed conditions of 1.5 mm block thickness,6 mm/s penetration rate,and 6 r/s rotational speed.Based on this,internal and external gauge structures were further introduced to comparatively analyze the mechanical responses of bits with different gauge parameters,determining the optimal bit face structure combination.Results:The simulation results indicate that:(1)Without gauge structure,the reaction force on the bit in the z-axis(drilling direction)decreases as the block-to-slot ratio reduces,being maximum at 1∶0 and minimum at 1∶4,with no significant differences among the reaction forces at ratios of 1∶2,1∶3,and 1∶4.(2)Regarding torque,the z-axis torque on the bit is maximum at a block-to-slot ratio of 1∶1 and minimum at 1∶2;the z-axis torques on bits with ratios of 1∶2,1∶3,and 1∶4 are all lower than those on bits with ratios of 1∶0 and 1∶1,with no significant differences among the three.(3)All helically arranged bits exhibit significant eccentric forces and eccentric torques in the x and y axes directions,while such eccentric phenomena are not pronounced for the flat-bottom bit with a ratio of 1∶0.(4)The addition of gauge structures increases the bit face area,leading to a certain increase in z-axis reaction force,but shows no significant effect on z-axis torque.However,the incorporation of gauge structures significantly reduces the eccentric forces and eccentric torques on the bit in the x and y axes directions,effectively enhancing drilling stability.Conclusions:This study has successfully designed an impregnated diamond bit with multi-stage helically distributed matrix blocks,and verified through simulation its feasibility for application in hard,dense,and weakly abrasive formations.The research reveals the mechanism by which the helical arrangement structure enhances rock fragmentation efficiency through inducing ridge formation and volumetric fragmentation.The optimal bit face structural parameters are determined as follows:spiral block thickness of 1.5 mm,inter-block slot spacing of 4.5 mm(corresponding to a block-to-slot ratio of 1∶2)or 4.0 mm,and gauge block thickness of 1.5 mm.This parameter combination can reduce the reaction force and torque required for drilling while effectively controlling eccentric loads,achieving a balance between drilling efficiency and stability.The innovation of this study lies in introducing the helical distribution concept into the matrix block design of impregnated diamond bits,addressing the hard rock slipping problem by altering the bottom-hole stress field and increasing volumetric fragmentation,rather than simply relying on contact area reduction.