Research On Grinding Removal Mechanism And Subsurface Crack Of Silicon Carbide

With the enlarging of the size of space optical system mian mirror, it hasmore demanding for the mechanical and physical properties of primary mirror’smaterials.Silicon carbide is an ideal material for the space primary mirror reflector.But the high hardness and low fracture toughness of SiC result in poormachinability and easily introduce sub-surface damage such as cracks in thegrinding process.So the intensive research on the mechanism of material removaland subsurface crack during the grinding process has important siginificance onthe improvement of the quality of the griding surface.In this paper, particle flow code discrete element method is used to model thesilicon carbide ceramic material,material model calibration and simulation of thegrinding process is performed under the help of discrete element simulation test.The crack formation during the grinding process and the impact of machiningprocess parameters to the grinding force and grinding crack are analysed. Vickersindentation test is performed to analyse silicon carbide hardness and fracturetoughness and Vickers indentation crack system. Vickers indenter is used toperform the micro scratch test of silicon carbide, the way of material removalunder single grain scratch test is studied.Grinding test of silicon carbide ceramic is carried out to analyse the grindingsurface topography and material removal methods, the writer also use ion beamprocessing technology to perform section polishing on the grinding surface, theaccuracy grinding subsurface damage characteristics of silicon carbide ceramicgrinding is acquired, different process methods and process parameters’s impacton the form of sub-surface cracks and depth are stuied in this paper. Studies showultrasonic vibration assisted grinding not only reduces the grinding surfaceroughness, but also observably restrains the generation of subsurface cracks, thenumber and the depth of sub-surface cracks of which are both less than that ofother way. the formation and depth distribution of silicon carbide grindingsubsurface cracks and the inpact of grinding depth and speed on the crack depthare concluded through statistic analyses and observation on the sub-surface cracksof the face grinding.