Study On The Machining Mechanism Of Grinding SiC Ceramic Under Biaxial Compressive Pre-stressing

Industrial ceramics have been widely used in machinery, automobiles, aerospace engineering, energy projects, electronics and other fields due to their excellent physical and chemical properties. As modern industry progresses and its products gradually become more sophisticated, there are increasingly high requirements for ceramic components, such as high quality, high precision and high reliability. However, due to the high hardness and brittleness of engineering ceramics, it is hard to avoid damage and cracks in the process of machining them, which greatly reduces its reliability. Therefore, developing high efficiency and low damage processing of engineering ceramic materials has been an important issue for research scholars. This thesis presents a new method which applies a biaxial compressive pre-stress on the ceramic material before processing.The main contents of this thesis are as follows:Based on ceramic fracture mechanics theory, a theoretical model of scratching stress distribution of ceramics under biaxial compressive stressing was established. The effects of biaxial compressive pre-stress and the load ratio on SiC ceramic scratching stress distribution were analyzed.Scratch test on SiC ceramics was performed in which different biaxial compressive pre-stress and normal load were used as test parameters. The surface and subsurface damage of the scratches and crack propagation were observed using ultra-depth field optical microscope. Furthermore, the change regulation of tangential force and acoustic emission signals during scratching were analyzed. based on the observation and analysis of the results above, the influence of biaxial compressive pre-stress on damage and scratches crack propagation was extrapolated.The grinding experiments of SiC ceramic were carried out in which different biaxial compressive pre-stress, depth of grinding and grinding direction were chosen as test parameters. The surface topography and subsurface damage were observed using scanning electron microscope. The influence of biaxial compressive pre-stress on the grinding damage, grinding force, grinding force ratio and grinding surface quality was discussed using the gathered data.The SiC ceramic discrete element model was established using Cluster method. Discrete element simulation of SiC ceramic was carried out under different biaxial compressive pre-stress and depth of scratches. The influence of biaxial compressive pre-stress on crack propagation and tangential force was analyzed. Afterwards, the simulation results and experimental results in the third chapter were compared to verify the reliability of simulation.From the results of this study, it can be seen that applying biaxial compressive pre-stress in the process of ceramic grinding, to some extent, limits the propagation of radial cracks, improves the quality of grinding surface, and reduces the damage induced by grinding. This shows that ceramic grinding damage is inhibited when taking a great grinding depth by applying biaxial compressive pre-stress in the process of grinding, achieving high efficiency and low damage.