| Borosilicate glass serves as a substrate and cover for biological microfluidic chip or micro pump chip,because of its excellent insulation,optical transparency,mechanical properties,corrosion resistance,high temperature resistance,and oxidation resistance.Hence,borosilicate glass is widely used in aerospace,electronic products and MEMS device packaging fields.However,the effective connection of transparent and fragile materials such as glasses at this stage has been regarded as a major challenge to scientists and manufacturing industries.Compared to existing traditional borosilicate glass material joining technologies,ultrashort pulse laser welding technology(UPLW)has many outstanding advantages such as high processing precision,small heat-affected zone and considerable joint strength.Ultrashort pulse laser welding technology requires no intermediate layer and can be selectively processed in the interior of transparent materials.In recent years,it has received much more attention in the field of laser welding.In this paper,borosilicate glass was used as the research object.The connection mechanism,process and temperature field evolution of ultrashort pulse laser welding borosilicate glass was studied by the combination of theoretical analysis,experimental research and numerical simulation.The main research contents are as follows:(1)The mechanism of interaction between ultrashort pulse laser and borosilicate glass material was systematically studied.This included the non-linear transmission process,thermal conduction model and non-linear absorption effects such as nonlinear photoionization,avalanche ionization and free carrier absorption of plasma,etc.These provided a theoretical basis for the subsequent research process and numerical simulation.(2)A special fixture for laser welding of borosilicate glass material was designed,and the platform of ultrashort pulse laser welding borosilicate glass was built;after which the ultrashort pulse laser welding experiments were carried out under different process parameters to study the diffusion and migration of network formers and micro-hardness distribution.It was found that the diffusion of Si and O elementsoccurs during the laser welding process,which was also one of the reasons for the improvement of the micro-hardness of the weld area.The weld width and microstructure were observed,and the influence of the microstructure of the weld on the fracture form of the glass welded specimen was analyzed.From the analysis,it was found that the welding quality was higher when there was a large amount of adherends at the weld seam of borosilicate glass.(3)The effects of laser power,welding speed and repetition frequency on weld width and lap-shear strength were analyzed to determine the range of process parameters for response surface methodology analysis.Multi-parameter experiments of ultrashort pulse laser welding borosilicate glass were designed by Design-Expert V8.0.The interactive effects of process parameters(laser power,welding speed and repetition frequency)on welding quality(weld width and lap-shear strength)were analyzed.The results showed that the laser power,welding speed and repetition frequency have a significant interactive effect on the welding quality.The reliability of the established mathematical model was demonstrated by the analysis of variance and experimental verification.The optimal process parameter combination under different optimization criteria was obtained by combining the satisfaction function.(4)A finite element model of transient temperature field of ultrashort pulse laser welding borosilicate glass material was established by finite element analysis software ANSYS.The temperature field distribution and the influence of different process parameters on temperature field were studied.It was found that the influence of process parameters on the weld width was consistent with the experimental trend.The reliability of the numerical model was verified by comparing the simulated values of the weld width with the experimental values. |
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