| More and more people are highlighting laser transmission welding of thermoplastic because of so many advantages, such as excellent welding quality, easy to control, available for micro-welding (seam less than 500μm) and so on. Especially thermoplastic in automobile industry, laser transmission welding is the first choice in this field. However, there are few domestic studies on this research subject, which results huge gap between domestic and foreign on theory and industrialization. Therefore, research on laser transmission welding of thermoplastic has a significant meaning.First of all, the paper study the mechanism of plastic laser transmission welding and reach a conclusion: not only the light matter interaction must take into consideration, but also the thermal behavior of polymer (such as glass temperature, viscosity, heat conductivity, heat expansion), because these behaviors are quite different from metal. It is proved that overlap weld is the preferred geometry.Then, experimental scheme is plotted, including choosing laser equipment, welding materials, welding method and designing new fixture which is special for laser transmission welding. And destroying tensile strength and metallographic microscopy are conducted for experimental samples in order to investigate the influence of welding factors on welding quality. As a result, PMMA/ABS laser transmission welding, in the condition of clamping, can use the Energy Density (ED) to determine the welding quality quantificationlly. When seam width is 5mm and feed rate is 5mm/s, if ED is equal to 0.364 J/mm2, the welding intensity is the highest and the welding quality is the best. If ED is less than 0.364 J/mm2, there is no weld, just an adhesion in the interface of PMMA and ABS. If ED is between 0.368 J/mm2and 0.376 J/mm2, it is commonly thought to weld, but because the ED is higher than the optimal ED, the absorbing material ABS is decomposed. And the decomposition is combustible, causing the black cavities and the welding intensity down. If ED is above 0.376 J/mm2, the absorbing material ABS is decomposed largely, therefore, the black cavities can connect together and the welding intensity is obviously down. All the above cause bad weld.At last, the paper attempt to use the ANSYS software to simulate the welding temperature field, in order to reduce the cost of the manpower and material resources because of the large numbers of experiments. Respectively we simulate the temperature field of the laser power 20W, 28W and 35W at the same time the seam width 3mm and the feed rate 30mm/s. And the results of the simulation can match the real experiments.
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