Mechanism And Experimental Study Of Laser-Assisted Ultra-precision Cutting Of Monocrystalline Silicon

Monocrystalline silicon has the characteristics of high brittleness and low toughness,so it is difficult to achieve high quality surface machining in conventional turning process.The traditional machining method is inefficient and easy to produce surface and subsurface cracks.By changing mechanical properties and plastic deformation ability of monocrystalline silicon at high temperature,laser heating assisted turning technology can effectively reduce surface/subsurface damage and inhibit the propagation of microcracks during material processing,which has become an effective way to process high quality monocrystalline silicon surface.In this paper,the material machinability of laser-heating assisted diamond turning of monocrystalline silicon was studied,focusing on the influence of temperature on mechanical properties and plastic deformation mechanism of monocrystalline silicon.Firstly,the crack propagation process of monocrystalline silicon under different loads was simulated by discrete element method.Then,high temperature indentation experiment and scratch experiment were carried out to explore the inhibition effect of heating temperature on material surface/subsurface microcracks.Finally,laser-assisted turning experiments were carried out to achieve high quality machining of monocrystalline silicon surface.The main research contents are as follows:（1）Discrete element modeling and scratching/indentation simulation of monocrystalline silicon:PFC^3D software was used to establish the initial bonding model of monocrystalline silicon,and the mechanical properties of the high temperature model were calibrated to be consistent with the actual mechanical properties by adjusting the microscopic parameters of the bonding bonds between the models.After the calibration,the nano indenting head was used to conduct the indentation and scratch experiments of monocrystalline silicon,and the inhibition effect of temperature on monocrystalline silicon damage was studied according to the change law of crack.The effects of different machining parameters and temperature on crack propagation were studied by simulation experiments.（2）Mechanical properties and plastic deformation mechanism of monocrystalline silicon at high temperature:the high temperature indentation and scratch experiments of monocrystalline silicon were carried out,to study the influence of temperature on the hardness and elastic modulus of monocrystalline silicon in the range of 200℃-600℃,and to study the growth law of microcracks on the surface and subsurface of monocrystalline silicon,and the change of crystal structure in the range of 200℃-400℃;The variation trend of the plastic deformation zone and brittle fracture zone on the surface of monocrystalline silicon during the process of temperature rise were studied by high temperature scratching experiment.The influence of the change of subsurface crystal structure on the plastic deformation of the material was analyzed,and the mechanism of high temperature plastic deformation of monocrystalline silicon was explored.（3）Laser-assisted turning monocrystalline silicon experiment:according to the plastic variation rule in high-temperature indentation and scratching experiment,laser-assisted ultra-precision turning monocrystalline silicon experiment under different laser heating temperature and processing parameters was carried out.The surface roughness,chip morphology and phase transformation of monocrystalline silicon after turning were analyzed to obtain the changing rule of processing performance of monocrystalline silicon,and the laser heating temperature and turning parameters were optimized.