Molecular Dynamics Simulations Of Diamond Tool Graphitization Wear In Ultra-precision Cutting Of Single Crystal Silicon

In ultra-precision cutting of single-crystal silicon using a diamond tool, the groove wear happens at the flank face of the diamond tool, and it seriously affects the quality of machined surface of the workpiece. The mechanism of the the groove wear that happened at the flank face of the diamond tool is not very clear currently. This thesis has confirmed the generation of graphitization of the tool during cutting the single-crystal silicon by molecualr dynamics, then analyzed the process of the graphitization wear, and studied the graphitization wear extents of the tool at different cutting parameters and cutting edge radius.The main contents of this thesis are as follows:1) The model of that think about the wear of the diamond tool while cutting the single-crystal silicon is established, then analyzed the temperature and cutting force of the different zone of the diamond tool during the cutting process by molecualr dynamics, obtained the wear images of the tool, measured the change of C-C bond angle and bond length at the surface or subsurface layer of the the cutting edge of the tool by the visualization software VMD. Observed the graphitization of the diamond tool and researched the process of the graphitization by molecualr dynamics, and analysed the mechanism of the graphitization wear.2) Confirmed the generation of graphitization of the tool on the other side by calculating the changes of coordination numbers of the tool atoms at different moment during the cutting process, then obtained the percentage graphitization of the tool atoms at different moments and its changing trends.3) Analysed the graphitization wear extents of the tool at different cutting conditions by changing the cutting parameters and the cutting edge radius. It can be found that the bigger the cutting thickness, the higher the wear rate, the degree of graphitization wear of the diamond tool is the more intense; as the cutting edge radius of the tool decreases, the graphitization wear will more severe; no matter the cutting speed is fast or slow, the effects on the graphitization rate of tool is not that much, however, the faster the cutting speed, the faster the transformation of graphitization of the diamond tool, also, if the cutting speed slows down, the velocity of the transformation of the graphitization will reduce.