Simulation And Experimental Study Of Single Crystal SiC Ultre-precision Cutting

SiC single crystal has excellent material properties and is widely used in high-power and high-frequency power devices,such as turbine engine components,optical devices,space telescopes and other industrial products.Due to the high hardness and brittleness of SiC single crystal,it is very difficult to cut it,and the surface machining accuracy of materials in these fields has reached the nanometer level,which requires ultra-precision cutting theory and method as support.Because the experimental study of ultra-precision machining is expensive and time-consuming,it is necessary to adopt new research methods to study the micro-mechanism of ultra-precision machining of SiC single crystal.Molecular dynamics is an important method to study the mechanism of ultra-precision machining.In this thesis,the molecular dynamics simulation model of diamond cutting tools for 4H-SiC single crystal was established,and the influences of different cutting speeds,cutting depths and cutting Angle on the surface damage layer,main cutting force,system potential energy and cutting temperature were studied.Simulation results show that high cutting speed,suitable cutting depth and positive fore-angle cutting tool are beneficial to the machining of 4H-SiC single crystal in the plastic domain.Based on the constitutive model of JH-2 hard and brittle materials,the two-dimensional and three-dimensional simulation of 4H-SiC single crystal machining by LS-DYNA was carried out,and the stress distribution,cutting force changes and cutting surface damage of the machining process at different cutting depths and cutting speeds were analyzed.The simulation results show that the machining efficiency can be improved and the machining surface can be obtained by using the appropriate cutting speed and cutting depth.The effects of different scratch depth on the surface morphology and surface damage of 4H-SiC single crystal were studied.The finite element simulation results of SiC machining with diamond cutters at different depths are compared with the scratch experimental results at different depths.The results show that with the increase of machining depth,there will be more cracks and cracks and pits on the workpiece surface,and the surface quality of the workpiece is poor.The experimental results are in good consistency with the simulation results.