Research On Cutting Force Detection Based On SEM Online Nanometric Cutting

With the continuous development of ultra-precision machining technology,improving the surface quality of processed parts,precision and processing integrity is of great significance.Nano-cutting experimental verification and other related basic research are important foundations for promoting the development of nano-cutting technology.In order to solve the problem of cutting force detection in nano-cutting process,based on the self-developed SEM nano-cutting platform,the real-time observed nanoscale cutting video is collected.Based on the image visual processing method,a series of researches are carried out for typical brittle materials cutting force detection in SEM nano-machining of monocrystalline silicon,mainly including the related researches of the correspondence relationship between the deflection fluctuation of the nano-scale cutting tool and the cutting force in SEM monocrystalline silicon nano-machining as well as the detection precision and error analysis of toolbar deflection.The main contents of this paper are summarized as follows:(1)According to the influence of material processing anisotropy on the cutting force,the structure and mechanical properties of monocrystalline silicon are analyzed.Besides,the anisotropic distribution of elastic modulus and shear modulus of monocrystalline silicon cutting is established by means of three-dimensional modeling.Analyzing of the distribution of elastic modulus and shear modulus with the crystal direction changes,the theoretical value of shear angle with the cutting direction changes is estimated.A theoretical calculation model for the monocrystalline silicon plastic region cutting process is established by combining the properties of monocrystalline silicon with the distribution of cutting force.In addition,finite element analysis is used to simulate the cutting process of monocrystalline silicon,analyzing the influence of cutting parameters and crystal parameters change on the cutting force qualitatively.(2)With the structural simulation design of the toolbar integrated in the SEM nano-cutting platform,the method of getting the cutting force in the process of nano-cutting by detecting the deformation of the toolbar is improved.Five kinds of different toolbar structures are designed.The finite element method is used to analyze the relationship between the position force and deflection of the tool tip,and the stiffness calibration is carried out for each toolbar.Besides,the relational expression between the cutting force and deflection of the toolbar is established by data fitting,which can meet the needs of the design of toolbar in different nano machining experiments.(3)Based on the SEM image processing method of nanoscale cutting video,this paper studies the cutting force variation law of brittle and plastic cutting of monocrystalline silicon.In order to realize the online detection of the cutting force under the scanning electron microscopy,with the high-resolution microscopic characterization of SEM,the target detection of toolbar is carried out by extracting the monocrystalline silicon nano-cutting video,as well as realizing the target tracking of extract features.The coordinate of the target pixel is extracted in the course of tracking,by the size calibration and the target matching in realization of deflection measurement in the process of cutting,the toolbar deflection curve is obtained.Combined with the change relationship between the deflection and the cutting force,the change of cutting force in cutting process is derived and the change law of cutting force during brittle and plastic removal of monocrystalline silicon is compared and analyzed as well.Finally,the actual speed of the toolbar is obtained based on the tool cutting video processing,the deflection testing accuracy and error are analyzed by comparing with the actual and ideal running speed of the toolbar and analyzing image processing algorithm.