| Laser transmission welding is widely used in modern industry due to its small deformation,clean,efficient,and small heat affected zone.Conventional laser transmission welding research necessarily requires the use of a light absorbing agent to absorb infrared wavelength light,and filling absorbent in the middle of polymer has a broader application background than filling color masterbatch and other absorbents in the underlying material.The addition of the intermediate heat conduction layer has an important influence on the energy transfer law,the heat absorption conversion process of the polymer and the formation of the weld zone during the welding process,which makes the application and equipment of laser transmission welding technology further developed.In this paper,polycarbonate(PC)was used as the research object,and the metal aluminum film with different widths was added to absorb heat in the middle,and the influence of aluminum film on the solderability and heat transfer of the polymer was analyzed.The mathematical model between laser transmission welding parameters and welding strength and weld width was established,and the laser transmission welding parameters with aluminum film were optimized.The influence mechanism of welding parameters on temperature field and stress field in Thermo-Solid coupling was discussed by using dimensional finite element model.The research contents were as follows:Firstly,the influence of aluminum film on the solderability of laser transmission welded polycarbonate was analyzed,the interaction between laser beam and welded specimens was discussed,and the optical properties of PC specimens and aluminum film were measured.According to the laser beam passing through the test piece,the energy was absorbed and transmitted by the aluminum film of different widths,and the laser energy density model of the spot existence margin was established.Secondly,the single-factor experimental method was used to verify the solderability of aluminum film and polycarbonate.The influence of different factors(power,speed,aluminum film)on the welding quality was analyzed,and the presence or absence of aluminum film was compared to analyze the effect of layer on welding strength.The analysis of the microstructure and element distribution of the welded area after the break,and the influence of the extrusion deformation of the aluminum film on the joint quality of the joint were analyzed.The micromechanical riveting effect between high-pressure uniform small bubble molten polymer produced by thermal degradation in the weld zone was analyzed.Then,the response surface method combined with genetic algorithm(RSM-GA)to optimize the process parameters of the experimental process was used.A three-factor and five-level design scheme was established by using RSM.Based on the experimental data,a mathematical model between process parameters and welding strength and weld width was established.Based on the principle of maximum welding strength and minimum weld width,genetic algorithm was used to optimize the process parameters and obtain the Pareto Front.The accuracy of the model by comparing the predicted results with the experimental results was verified.Finally,the numerical simulation of the laser transmission welding process of the intermediate layer of the aluminum film was carried out by using COMSO1.Considering the influence of the optical properties of the transparent PC on the model,a surface heat source model was established based on the interaction of the aluminum film conducting layer coated with the light absorbing agent and the laser.The temperature field and the coupling of temperature field and stress field in laser transmission welding PC were studied,and the influence of welding parameters on the thermal-solid coupling was discussed.The theory and application value of laser transmission welding with aluminium interlayer are preliminarily explored in this resaeach,and the practical field of laser transmission welding with double transparent thermoplastic polymer is broadened. |
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