| In this paper,the laser polishing process of TC4 titanium alloy is studied,and the optimization of laser polishing process is studied.This paper introduces the principle and characteristics of laser polishing,studies the theory of laser polishing,and analyzes the influencing factors of laser polishing.It includes SSM and SOM mechanisms based on heat conduction,spatial frequency analysis based on Fourier decomposition when laser polishing metal materials,and laser thermal conductivity welding model when molten pool fluid convection occurs on the polished surface.In laser single line polishing,the influence of laser power,polishing speed and defocusing amount on the polished surface morphology is analyzed and explored.The surface after laser single line polishing presents a thin line shape,and it is difficult to analyze quantitatively.In this paper,the surface morphology after single line polishing is qualitatively described from two aspects of width and surface micro morphology observation,and is divided into four categories.In order to facilitate the classification of the surface morphology of single line polishing during a large number of experiments in the later stage,Easy DL image module is used to classify,mark and train the existing graphics,The classification model of single line polished surface morphology is obtained and the accuracy of the model classification is verified.Combined with BP neural network,the width prediction model of single line polishing is constructed.The temperature field of laser single line polishing is simulated by COMSOL,and the energy changes at different times in different single line polishing are analyzed.The surface morphology after laser polishing increases with the polishing speed,and the corresponding surface quality shows a trend of first increasing and then decreasing;In the selected defocus range,the surface morphology is the best when the laser power is 100 W and the polishing speed is 3.5m/min.With the increase of laser power,the polished surface morphology of titanium alloy with defocus of-2mm and 0mm shows a trend that the surface quality first improves,and then there is a dense molten pool caused by the phenomenon of over melting,which reduces the surface quality;When the defocusing amount is 2mm,when the laser power increases,there will be dense molten pools along the single line polishing direction,which will reduce the surface quality of laser polishing.However,when the defocusing amount becomes larger,the overall width of the polishing area will exceed the width when the defocusing amount is small.When this change law is applied to surface polishing,the wider the single line polishing area is,the less single line polishing times are required for the surface polishing area formed by its array.Therefore,low energy consumption and short-term surface polishing can be achieved.When the polishing speed and laser power are selected,increasing the defocusing amount is conducive to the improvement of the polished surface morphology.In the plane polishing experiment with five different paths,the surface roughness,surface morphology,surface residual stress and surface hardness after the surface polishing experiment with increased defocus and different path parameters are analyzed under the selected polishing speed,laser power and surface polishing overlap rate.The experiments show that the surface morphology of the polished surface tends to improve with the increase of defocusing amount under the same polishing path.The overall roughness Ra of the path of two surface polishing is lower than that of one surface polishing with the same path.When path D is selected,the optimal surface roughness Ra is 0.629 μm when the defocus amount is 8mm μm.Compared with the initial surface roughness Ra 2.623 μm decreased by 76%. |
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