Research On Subsurface Damage Of Hard And Brittle Materials By Discrete Element Method In Lapping

Hard and brittle materials have been widely used in aerospace,optics,semiconductor,energy,machinery and military fields because of the high hardness,brittleness,wear resistance,cor rosion resistance and other excellent features.With its extensive application,more severe processing precision and surface quality have promoted the rapid development of corresponding precision and ultra-precision machining technology,and the subsurface damage has gradually become the focus of research.In this paper,the prediction method of subsurface damage of hard and brittle materials(magnesia-alumina spinel and quartz glass)was studied based on the fixed-abrasive lapping technology,and used the discrete element method to explore the feasibility of subsurface damage prediction in lapping process.To convert subsequent detection to previous prediction will reduce detection cost and provide reference and guidance for the follow-up lapping and polishing process parameters.The main contents of this paper are as follows:(1)Based on the discrete element method,the influence of microscopic parameters on the macroscopic mechanical properties of two hard and brittle material particle models was analyzed and the corresponding mechanical properties were confirmed;Utilized compression,Brazilian tensile and fracture toughness test,both in two-dimension and three-dimension,to ensure the performance of corresponding material model is consistent with the mechanical properties of the material.Finally,discrete-element particle models of two hard and brittle materials were established respectively.(2)Based on the characteristics of fixed-abrasive lapping,the mathematical model of single abrasive cutting depth was established,and converted the lapping process into micro cutting movement of single abrasive under the fixed cutting depth.Based on the established material models,the micro cutting process of single abrasive was simulated to obtain the corresponding micro-crack depth,type and extension by discrete element method.(3)Based on three-dimensional material particle models of two hard and brittle materials,the simulation of micro-cutting process of single abrasive was carried out under different depths of cutting,with curve trajectory,to compensate the disadvantage of linear motion of abrasive in two-dimension,and improve the precision of prediction.Next,the multipoint micro-cutting process of two abrasive sizes(17μm and 5μm)was studied to predict the subsurface damage depth under the condition of lapping.(4)Based on the single-factor experiment method,the lapping experiments of spinel and quartz glass samples were carried out,and the single polishing method was used to detect the subsurfac e damage(form and depth of microcracks)of two materials after lapping.At the same time,compared simulation results with experimental results to verify effectiveness of the prediction by discrete element method.