Temperature Field Analysis And Experiment Research For Laser Assisted Cutting Of Fused Silica

Fused silica has many excellent properties such as high temperature resistance,thermal shock resistance,and good optical performance.It has been widely used in precision instruments and equipment working in extreme environments,such as window materials of photolithography and optical lens of laser fusion device.However,the high brittleness and hardness of fused silica makes processing difficult and inefficient.In order to improve the machinability and tool life,Laser Assisted Machining（LAM）is used in this paper.Based on the interaction mechanism of CO₂ laser and fused silica,Gauss laser heating model is built.The emissivity is obtained by comparison the contact and noncontact measurement of temperature.Experiments and simulations are combined to determine the temperature dependent absorption.The three-dimensional transient heat conduction model is proposed,and the finite element simulation is operating in software of COMSOL after the thermophysical parameters are measured.The thermal model is validated by measuring the temperature of different points.Moreover,the thermal model is used to analyze the response time of heating,temperature distribution in surface and interior,the influence of parameters on temperature.The heat affected zone of workpiece is investigated by magnetron sputtering gold plating and heating experiments.The optimal preheating time under fixed point preheating is analyzed.The range of machining parameters are discussed by using simulations based on cutting temperature limit.The temperature in cutting zone is researched under considering the cutting heat and contact heat transfer.The results show that temperature gradient in material removing layer is great,and there is a temperature gap between this layer and PCD cutting tool.Higher temperature of material and lower temperature of tool is good for cutting process.After cutting experiments the surface and subsurface quality of machined workpiece,chip morphology and tool wear are analyzed and compared to conventional cutting,which verifies the feasibility and superiority of LAM.The material removing mechanism is presumed to be combination of ductile machining and brittle fracture.Artificial neural network（ANN）is used to build the mathematic relationship between machining parameters and cutting force,and the generalization ability is validated.The optimal parameters are obtained by genetic algorithm（GA）,and the accuracy and reliability are validated by experiments.Moreover,the melt flow model is constructed in COMSOL.The flow mechanism,influence factors of temperature,and effect of temperature on optimization results and flow velocity are studied.The optimal repair temperature is obtained in micron scale grain of fused silica.