添加中间层的PMMA与PBT激光透射焊接实验研究与数值模拟

发布时间：2018-02-27 21:03

本文关键词： 激光透射焊接相容性焊接强度工艺优化温度场　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：激光透射焊接技术以其焊接效率高、焊接质量好、残余应力小、易于控制等优点,广泛应用于医疗器械、汽车零部件、电子器件产品和包装工业等领域。然而,由于异种聚合物材料之间的相容性比同种材料的相容性差,导致异种材料的激光透射焊接强度不是很高,所以需要进一步研究。本文选用PMMA(聚甲基丙烯酸甲酯)和PBT(聚对苯二甲酸丁二醇酯)作为激光透射焊接的上下层材料。这两者相容性较差,焊接强度低。本文通过在激光透射焊接PMMA和PBT中间添加一层PC(聚碳酸酯)薄膜,来增强两者的焊接强度,探究材料之间的可焊性机理,并对焊接工艺和温度场的数值模拟进行研究。首先,根据激光吸收面的选择和薄膜厚度的选择实验来选择激光吸收面和薄膜厚度;在激光透射焊接实验中,通过对比有无PC薄膜焊接件的焊接强度,发现,添加PC薄膜作为中间层的焊接件的焊接强度可达到没有PC薄膜的焊接件的焊接强度4倍左右。其次,从微观角度,激光透射焊接有PC薄膜作为中间层的PMMA与PBT的焊缝区的气泡比直接激光透射焊接PMMA与PBT的焊缝区的气泡多,在一定程度上,气泡在焊缝区域可以形成微铆接来提高焊接强度;根据流变实验的结果和蠕动模型来分析计算PMMA、PC和PBT的蠕动时间,发现三个时间都处于毫秒级别,PMMA的蠕动时间最大,PBT的蠕动时间最小,通常蠕动时间比材料熔融状态的时间越小,焊接强度就越高,这可以得出PC与PBT的焊接强度比PMMA与PC的焊接强度高;通过计算平衡界面宽度以及相对焊接能力,得出PMMA与PBT的焊接能力差,而PMMA与PC、PC与PBT的焊接能力相对高一点,也说明了添加PC薄膜层提高焊接PMMA与PBT焊接强度的可焊性机理。随后,通过旋转中心复合设计法(CCRD)对实验进行设计与规划,采用响应曲面方法(RSM)构建了添加PC薄膜作为中间层的激光透射PMMA和PBT焊接件的焊接强度与各个工艺参数之间的数学分析模型,分析了各个工艺参数对焊接强度的交互影响,并根据目标优化标准对工艺参数进行了优化。最后,建立激光透射焊接有PC薄膜作为中间层的PMMA与PBT的焊接界面处的温度场有限元模型,得到焊接界面处温度场的变化规律;发现两个界面处的模拟焊缝宽度值随工艺参数的变化而变化的趋势基本保持一致。通过对比焊缝宽度的实验值和模拟值来验证模型的可靠性。本文为研究相容性较差的异种聚合物的激光透射焊接提供一种新途径,并为激光透射焊接添加薄膜的PMMA和PBT奠定理论基础。
[Abstract]:Laser transmission welding technology is widely used in medical devices, automobile parts, electronic devices and packaging industry because of its high welding efficiency, good welding quality, low residual stress, easy control and so on. The miscibility of heterogeneous polymer materials is worse than that of the same materials, so the laser transmission welding strength of dissimilar materials is not very high. In this paper, PMMA (polymethyl methacrylate) and PBT (polybutylene terephthalate) are selected as the upper and lower layers of laser transmission welding. The welding strength is low. In this paper, the welding strength of PMMA and PBT is enhanced by adding a layer of PC-film between laser transmission welding and PBT, and the solderability mechanism between the two materials is explored. The numerical simulation of welding process and temperature field is also studied. Firstly, the laser absorption surface and film thickness are selected according to the selection of laser absorption surface and film thickness. By comparing the welding strength of the welded parts with or without PC thin film, it is found that the welding strength of the welded parts with PC film as the intermediate layer is about 4 times that of the welding parts without PC film. Secondly, from the microscopic point of view, In laser transmission welding, there are more bubbles in the weld zone of PMMA and PBT with PC film as the interlayer than in the weld zone of direct laser transmission welding with PMMA and PBT. To a certain extent, the bubbles can form micro-riveting in the weld zone to improve the welding strength. According to the results of rheological experiments and creep model, the creeping time of PMMA-PC and PBT is analyzed and calculated. It is found that all three times are in the millisecond level, the maximum peristaltic time of PMMA-PBT is the smallest, and the peristaltic time is usually smaller than that of the melting state of the material. The higher the welding strength, the higher the welding strength of PC and PBT is than that of PMMA and PC. By calculating the width of balance interface and the relative welding ability, it is concluded that the welding ability of PMMA and PBT is poor. However, the weldability of PMMA and PC-PC and PBT is relatively high, which also explains the solderability mechanism of adding PC film layer to improve the welding strength of PMMA and PBT. Then, the experiment is designed and planned by the method of rotating center composite design. A mathematical analysis model of laser transmitted PMMA and PBT welds with PC film as intermediate layer was constructed by using response surface method (RSM), and the interaction between each process parameter and welding strength was analyzed. Finally, the finite element model of the temperature field at the interface of PMMA and PBT with PC film as the interlayer is established, and the variation of the temperature field at the interface is obtained. It is found that the variation trend of the simulated weld width at the two interfaces is basically consistent with the change of the process parameters. The reliability of the model is verified by comparing the experimental and simulated weld width values. Laser transmission welding of poor dissimilar polymers provides a new way. It also lays a theoretical foundation for PMMA and PBT of laser transmission welding.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456.7

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