| Micro-grinding technology is an extension of traditional grinding technology and a New Ultra-Precision micro-processing technology,which can realize high precision surface processing of micro-parts or micro-structures of hard and brittle materials with high hardness and strength at low cost.Because this new technology is still in the stage of development and improvement,and the material removal mechanism of traditional grinding can not be fully applied to micro-grinding technology;In micro-grinding of brittle materials,edge crack damage and subsurface damage of brittle materials become more serious quality problem than that of surface roughness;There is no uniform evaluation criterion for brittle material edge collapse as an evaluation of the processing quality of brittle material microstructures.In view of the above problems,the following work has been done in this dissertation.(1)Based on the deeply understanding of micro-grinding mechanism,the cutting models of single grits including cone,sphere,triangular pyramid and rectangular pyramid were established,which took the radius of edge arc into account.The grit shape and distribution of the micro-grinding tool with?0.5mm?#600 were observed and counted by super depth optical microscope VHX1000.Then the micro-grinding force models based on single grit models and that based on comprehensive grit models were established.The micro-grinding experiment was performed on the ZCuZn38 and the measured micro-grinding force was compared with that obtained from micro-grinding models.And the change of micro-grinding force with process parameters was discussed according to the proposed micro-grinding force models.(2)Based on the phase transition-dislocation theory,the mechanism of phase transition-Increase of phase transition zone-Stagnation zone appears-Dislocation nucleation-Dislocation accumulation-Crack nucleation-Crack random occurrence and removal of single crystal silicon materials with the increase of sliding depth during abrasive sliding is proposed.Analytical relationships between the friction depth h and scratch force F and unit scratch force F_p of single abrasive grains in the process of sliding friction on the surface of single crystal silicon were established.The rationalit y of material removal mechanism and analytical relationship is verified by nanoindentation test and nanoscratch test.The model can explain micro-structure crack initiation and size effect in micro-grinding well.Atomic force microscopy(AFM)was used to observe the morphology of nano-scratches,and each region of scratch morphology was clearly distinguished.Confocal Raman spectroscopy was used to verify the existence of phase transition in the sliding process of monocrystalline silicon,which indicated the rationality of the proposed material removal mechanism.(3)By analyzing the current situation of edge collapse and damage of micro-structure in micro-grinding process,the edge collapse and damage evaluation factor F_r is established,and the feasibility of the evaluation factor for edge collapse is discussed.F_r was applied to the optimization of boundary cracking,da mage parameters and tool parameters of micro-grinding micro-structure on the surface of monocrystalline silicon.Finally,two kinds of surface microstructures are machined by selecting the optimized micro-grinding parameters,and the boundary cracking and damage degree of the microstructures are evaluated by Fr,which shows the feasibility of the edge damage evaluation factor. |
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