The Simulation Of The Graphitization On The Flank Face Of The Diamond Tool With Initial Damage

In the process of nanoscale ductile mode ultra-precision cutting of brittle materials,such as moncrystalling silicon, the occurrence of the micro/nano groove wear on the flankface of cutting tool makes a serious impact on the cutting process and the quality of thefinish surface of the workpiece. By summing up and analyzing the literature on wear ofdiamond, it can be found that the occurrence of the micro/nano groove wear is usuallyaccompanied by the emergence of some of initial damages on the cutting tool. Theseinitial damages can be mainly divided into the following two types: the hard particlesplough on the tool flank face which lead to nano-scratch damages and nano-chippingdamage on the cutting tool edge. In this thesis, the cutting progress have been investigatedthrough molecular dynamics (MD) simulation using diamond tools with the two typesinitial damages on the flank face. In the cutting process, the changes of temperature andthe atom energy are calculated. The transformation of tetrahedral diamond into hcpgraphite on the place of initial damage is observed. The present thesis also analyzes theeffect of cutting parameters and crystal parameters of the flank face on the rate ofgraphitization conversion. Finally, the influence of initial damage on groove wearformation is studied.The main contents of this thesis are as follows:1) Considering the plough effect of hard particles as well as the chipping damage onthe cutting edge, the ultr-precision cutting modle model is established and the model isbased on the tool with nano-scratch and nano-chipping damage. When the MD simulationof the cutting processes is executed, the motion of the workpiece material on the place oftool damage is observed by visualization software VMD. A mount of MD simulations areexecuted by changing the cutting parameters. The simulation results show that thepresence of tool damage will change the temperature and the energy of atoms in thecutting process.2) The momentary position of atoms and the crystal structure on the place of initialdamage are analyzed by visualization software and radial distribution function respectively. The results show that there is diamond-graphite transformation during thecutting process. A lot of MD simulations are carried out by adopting different cuttingparameters and flank face crystal parameters. The rule of the graphitization conversion onthe damage place is studied through bond angle analyse which calculation by usingFortran programming.3) In this thesis, the process that atoms which with low coordination number atomscome off from the place of the initial damage are observed via visualization software. Thegraphite transition of the diamond and low coordination number atoms come off from theplace of the initial damage are consided to be the two important aspects that give rise tothe formation of the groove wear in the process of nanoscale ductile mode ultra-precisioncutting of brittle materials.