Research On Scratch Force And Surface Damage Of Single Abrasive Particle Scratching Silicon Carbide Ceramic Matrix Composite

SiC_f/SiC ceramic matrix composite material has the advantages of low density,high temperature resistance,impact resistance and oxidation resistance.It has become the most potential thermal structure material and has been used in aero engines,nuclear reactors and single crystal furnaces and other high-end equipment core components.However,the high cost,low efficiency,and easy surface damage of its manufacturing process have severely restricted the popularization and application of SiC_f/SiC ceramic matrix composites,and the research on precision grinding of this type of materials at home and abroad is still in the preliminary stage.Due to the uneven strength and anisotropy of the ceramic matrix composite material,higher requirements are put forward for its high-efficiency and low-damage precision grinding processing technology.The precision grinding of SiC_f/SiC ceramic matrix composites is a formative manufacturing process in which the material structure and mechanical properties,the structure of the grinding wheel,the grinding process and its stress and strain fields are intertwined.Aiming at the problem of the lack of damage mechanism of SiC_f/SiC ceramic matrix composites grinding materials,this paper uses a combination of experimental research and simulation analysis to determine the scratching force and surface/surface of a single abrasive particle scratching SiC_f/SiC ceramic matrix composites.Subsurface material damage was studied.A single diamond abrasive particle was prepared by electroplating,and a single diamond abrasive particle scratching experiment platform was built based on the design of a surface grinder.The horizontal and vertical scratching experiments of SiC_f/SiC ceramic matrix composites were carried out,and the cutting depth and grinding depth were measured in real time.Scratch force related to particle shape and fiber orientation and validated the scratch force model.Qualitative analysis of the surface morphology characteristics of the scratched composite material,clarified the main damage form of the SiC_f/SiC ceramic matrix composite material and proposed a method to reduce material damage,and combined with the SPH finite element simulation results of a single abrasive particle scratching for verification.The main research contents and innovations of this article are as follows:(1)Starting from the grinding movement process of a single diamond abrasive grain,the characteristics of different stages in the grinding and removal process of ceramic matrix composites are analyzed,and the relationship between the maximum undeformed chip thickness and the grinding process parameters is obtained.The force is orthogonally decomposed,and the relationship between the grinding force and the grinding process parameters is further deduced.The theoretical model will further guide the experiment and finite element simulation.(2)The bonding mechanism of the SiC_f fiber-SiC matrix coating interface was studied,and the surface/subsurface damage form of SiC_f/SiC ceramic matrix composites was clarified.The analysis shows that with the increase of load,microscopic cracks occur and grow in SiC_ffibers,radial cracks lead to fracture of SiC_f/SiC ceramic matrix composites,and transverse crack propagation is the main reason for chip removal from material removal.(3)In order to study the grinding damage mechanism of SiC_f/SiC ceramic matrix composites,the electroplating preparation of diamond abrasive grains was carried out in the early stage,and the electroplating parameters of#35/40 diamond abrasive grains were optimized.A test platform was built to carry out a single abrasive particle scratch test,the scratch force was measured and the surface damage form was observed,and the influence of abrasive particle shape,scratch depth and SiC_f orientation on the grinding mechanism of composite materials was studied.The test results show that the scratch damage forms of SiC_f/SiC ceramic matrix composites mainly include matrix collapse,fiber cracks,fracture,and pullout.In the scratching process of SiC_f/SiC ceramic matrix composites,the scratching force of sharp abrasive particles is smaller,and the surface damage range of the entire scratch is smaller than that of flat abrasive particles.When scratched with flat abrasive grains but the fiber orientation?=0°,there are fewer damage forms such as fiber breakage and fiber pull-out in the scratch morphology.(4)Combining the composition and structure of SiC_f/SiC ceramic matrix composites,a single-component material model was constructed with SiC matrix,SiC_f fiber and SiC-SiC_finterface respectively,and a single diamond abrasive particle was established to scratch the SiC_f/SiC ceramic matrix.SPH simulation model of composite materials.As the scratch depth increases,the scratch force gradually increases.There is a certain difference in the simulation results of the scratching force at 0°and 90°fiber orientation.At the same scratch depth,the radial crack propagation of 90°fibers is more serious.The results of SPH finite element simulation of single abrasive particle scratching and single abrasive particle scratching experiment qualitatively describe the grinding mechanism and damage mechanism of SiC_f/SiC ceramic matrix composites.