Simulation Analysis And Experimental Study On Ductile Cutting Of Single Crystal Silicon

Single crystal silicon is widely used in integrated circuits,solar cells,infrared detection and military technology.Brittle fracture is easy to occur in the process of machining because single crystal silicon is a kind of brittle material and its fracture toughness is very low,which seriously affect the surface quality and performance.The key of ultra-precision cutting is to control the processing conditions to make the single crystal silicon undergo brittle-ductile transition,and ensur that the material is removed by ductile deformation rather than brittle fracture.In this paper,the cutting in ductile region of single crystal silicon was taken as the research object.Firstly,the brittle-ductile transition mechanism of single crystal silicon was analyzed,and the realization conditions of cutting in ductile region were given.Then,a simulation model of single crystal silicon cutting was established,and the influence of tool and cutting parameters on the cutting process were discussed,and the cutting thickness of brittle-ductile transition was predicted.Finally,the ultra-precision cutting experiment of single crystal silicon was carried out.The brittle-ductile transition cutting thickness of single crystal silicon was obtained by the oblique cutting experiment,and then the depth of cut was determined according to the calculation model of the maximum undeformed chip thickness,and other optimal machining parameters were obtained by the single crystal silicon turning experiment.The main research contents of this paper are as follows:(1)The origin of brittle-ductile transition of single crystal silicon was analyzed from material phase transition and scale effect by nano indentation and scratch experiments.According to the brittle-ductile transition mechanism of single crystal silicon,a cutting model based on negative rake angle and arc edge tool was established.Based on the analysis of the relationship between the cutting thickness of brittle-ductile transition,the minimum cutting thickness and the maximum undeformed chip thickness,the realization conditions of cutting in the ductile region of single crystal silicon were given.(2)The finite element model of ultra-precision cutting of single crystal silicon was established,and the cutting process of single crystal silicon was simulated and analyzed.The influences of rake angle,back angle,edge radius,cutting thickness and cutting speed on chip shape,stress distribution,cutting force and machining surface quality were emphatically discussed.The cutting thickness of brittle-ductile transition of single crystal silicon was predicted,and the relationship between the minimum cutting thickness and the edge radius was analyzed.The simulation analysis provided the basis for parameter selection of the final ultra-precision cutting experiment of single crystal silicon.(3)Ultra-precision cutting experiments of single crystal silicon were carried out.Considering the influence of material anisotropy on the cutting thickness of brittle-ductile transition,the minimum cutting thickness of brittle-ductile transition of single crystal silicon was obtained by oblique cutting experiments.On this basis,the main parameters of the single crystal silicon turning experiment were determined.And the optimal machining parameters such as tool rake angle,cutting speed and depth of cut were obtained.The research results can be used as a guide for ultra-precision turning of single crystal silicon,and also provide references for ultraprecision machining technology of other brittle materials.