Research On Laser Transmission Welding Of Polycarbonate Based On Aluminum Powder Absorber

Laser transmission welding has an important position in the plastics processing industry due to the advantages of high speed,small heat affected zone,no contact,precision,etc.In the laser transmission welding process,the light absorbing agent can absorb the radiant energy emitted by the laser,convert the radiant energy into heat energy,and fuse the thermoplastic by heat conduction.Common light absorbing agents are generally divided into two methods:a lower layer solder material filling color master and an intermediate layer filling absorbing film.Compared with the underlying filling color master,the intermediate layer absorbing film can realize laser transmission welding of double transparent materials,and has more advanced industrial application prospects.In this paper,a preparation method of intermediate layer aluminum powder light absorbing agent is proposed to research the double transparent material welding of polycarbonate.The addition of aluminum powder light absorbing agent to polymer is analyzed.The influence of welding property and heat transfer is established.The influence model between welding process parameters and welding performance is established to optimize the welding process parameters.The three-dimensional finite element model with intermediate layer light absorbing agent is constructed to discuss the welding process and the influence mechanism of parameters on temperature field,flow field and two coupled fields.The research contents are as follows:Firstly,the weldability of aluminum powder absorber to polycarbonate was discussed.The parameters of polycarbonate welding were analyzed from the aspects of thermal physical properties,optical properties and thermal kinematics of polycarbonate.The thermal physical properties and particle hydrodynamics of aluminum powder absorbers were discussed.The formula for calculating the thermal physical properties of the powdered light absorbing agent and the motion model of the powder particles in the molten region were obtained.The heat source model and heat transfer model based on the lap joint were established.Secondly,the single-factor experimental method was used to verify the weldability of laser transmission welding.The influence of different factors(power,speed,aluminum powder content and surface roughness)on the welding performance was analyzed.The effects of the breaking force and the cross-sectional shape after the breaking were researched.The effects of the tiny bubbles and the central pores on the welding strength were researched.Thirdly,the combination of the rotating center composite method and the machine learning support vector machine algorithm(LibSVM)were used to analyze the experimental results,and the regression prediction model between process parameters and welding strength and welding width was established.The process parameters were analyzed based on the principle of maximum tensile strength to obtain the optimal process parameters.The random verification experiment was carried out to ensure the prediction accuracy of the regression model.Finally,a three-dimensional finite element model with intermediate layer light absorbing agent was constructed by finite element analysis software.The temperature field,flow field and the distribution of the two coupled fields during the welding process were numerically simulated.According to the thermal physical properties and optical properties of the welding materials,the material properties of each layer were defined.Considering the actual light absorption in the welding process,the temperature field and the flow field were coupled and analyzed by applying the surface heat source model to the intermediate layer.The temperature field-flow field coupling field simulation results were post-processed,and combined with the experimental data,the influence of welding process parameters(laser power,welding speed,light absorption agent aluminum powder content)on temperature field and flow field was obtained.In this paper,a method for preparing an intermediate layer light absorbing agent is proposed,in which aluminum powder and carbon black powder were uniformly mixed and pressed onto the surface of the polycarbonate to form an intermediate layer light absorbing agent,thereby realizing laser transmission welding of the double transparent polycarbonate.The preparation method and the welding operation of the light absorbing agent are relatively simple,the welding area formed is neat and beautiful,and has a large-scale industrial production and application prospect,and has far-reaching practical significance for the development of the automobile industry,aerospace and biomedical equipment manufacturing industries.