Numerical Simulation And Experimental Research Of Ultraprecision Machining

Ultraprecision machining is one of advanced manufactuing technology. In this thesis, the size effect of material behaviors at micron level has been studied by using strain gradient plasticity, molecular dynamics simulation and finite element simulation are employed to investigate the process of ulatraprecision. Grinding surface has been measured and analysed.Molecular dynamics is important major means for nano scale machining. Based on the molecular dynamics theory, molecular dynamics simulation model of cutting between diamond tool and single crystal silicon workpiece is built in nanometer scale, and the mechanism of material removal and surface generation are simulated when the depth of cut and the geometries of diamond tool change.Constitutive relationship and minimum chip thickness are theoretical foundations of ultraprecision machining. A constitutive relationship is formulated to model the size effect of material behaviors at micron level by using strain gradient plasticity; formula of minimun chip thickness is deduced; stress and minimum chip thickness are caculated and analysed. Some conclusions can be drawn: new constitutive relationship can reflect size effect of material at micron level, size effect become more notable with the depth cutting decreased, the rake angle increased and the radiu of tool decreased in the curve of mechanical property. The minimun chip thickness is decreased with the coefficient of friction increased and the radiu tool decreased.Utilizing meco scale constitutive relationship, a finite element model has been established, the process of ultraprecision machining is simulated. Results show that the maximum effective stress and displacement can be increase with clearance angle grown up. The tool edge radius have influence on surface quality, surface quality increase with the tool edge radius decreased. The effect of cutting depth on surface quality is not obvious. Cutting speed influences both surface quality and machining efficiency. when the grinding speed is grown up, the grinding force is decreased; displacement increase and surface quality can be decreased.The ground surface with difference surface topography have been measured using surface roughness tester. the original sample data have been obtained, Through the decomposition and reunited of minor wave, the form error, cockles degree and roughness have been succeed in separating from the primitive outline signal. Reseach of character of surface have been studied by system of surface measurement, parameter set of evaluating surface has been build.