Research On Grinding Mechanism Based On Elastoplastic Deformation Of Hard And Brittle Materials During High Speed Scratching

The deformation scale is usually micro-nano scale in the ductile region grinding process of hard and brittle material.Hard and brittle materials usually have higher yield strength at this deformation scale,which results in that elastic deformation accounts for a larger proportion of total deformation.Large proportion of elastic deformation leads to serious elastic recovery during the grinding process.Therefore,study of the elastic recovery during the grinding process is of great significance for further understanding of the grinding mechanism.In this study,a systematic study of the elastic recovery in the ductile region grinding process of hard and brittle material is carried out based on the elastoplastic interaction between the single grit and workpiece.A high-speed scratching method is proposed and the corresponding equipment is developed.The elastic recovery model of the quasi-static scratching process is established.Based on the quasi-static model,the elastic recovery model during the high speed scratching process is established.Monocrystalline silicon is selected as the workpiece.The high-speed scratch process of monocrystalline silicon has been studied.A plunge grinding model for monocrystalline silicon considering elastic recovery is established and the plunge grinding experiments of monocrystalline silicon is carried out.The systematic study of the grinding mechanisms of monocrystalline silicon is conducted.The proposed high-speed scratching method provides a solution for obtaining a high-speed and stable scratching process by extending the length of the scratch.The maximum stable scratching speed can reach 50m/s.The scratching experiments with constant and variable depths could be carried out based on the proposed method.For the scratching process with constant depth,online ultra-precision cutting and in-situ dynamic balance are used to improve the stability of the scratching process.For the scratching process with variable depth,in-situ precise adjustment assisted by laser displacement sensor and the in-situ dynamic balance are used to achieve precise gradation of the scratching depth,which improves the stability of the scratching process.The proposed high-speed scratching method could realize the precise control of the scratching depth at the micrometer scale,which is suitable for the study of elastic recovery of hard and brittle materials during the scratching process.The relationship between elastic recovery of indentation and that of scratching is studied by finite element method.It is found that they have consistency.Based on this conclusion,a general elastic recovery model of quasi-static scratching is established indirectly by establishing an elastic recovery model of indentation.Due to the difference between the dynamic mechanical properties and the quasi-static mechanical properties,the elastic recovery of dynamic scratching is different from that of quasi-static scratching.The dynamic mechanical and temperature models of single grit high-speed scratching are established.The stress state of the scratch under the thermo-mechanical coupling equilibrium state during the high-speed scratching process is calculated by the means of iterative calculation,which is combined with the elastic recovery model of quasi-static scratching to establish the elastic recovery model of high-speed scratching.The high-speed scratching experiments of monocrystalline silicon with diamond grit are carried out.The elastic recovery model of monocrystalline silicon during the high-speed scratching process is established.The experimental research and theoretical analysis of the high-speed scratching process of monocrystalline silicon are carried out.The results show that the elastic recovery of monocrystalline silicon during high-speed scratching process is serious and the elastic recovery ratio is higher than 50%.It is found that the calculated elastic recovery depths of scratches agree well with that of experimental ones,which proves that the established elastic recovery model of monocrystalline silicon has high prediction accuracy.The topography of the grinding wheel is measured and analyzed statistically.The digital model of the grinding wheel is established based on the results of the statistical analysis.Based on the digital model of the grinding wheel,a plunge grinding model considering the elastic recovery is established.The plunge grinding mechanisms of monocrystalline silicon are studied systematically.The results show that the theoretical calculated results considering elastic recovery agree well with the experimental results and there is a big difference between the theoretical calculation results considering the elastic recovery and that without considering elastic recovery.The research results show that increasing the grinding speed properly is beneficial to realize the ductile region grinding monocrystalline silicon.