变厚截面材料填粉激光焊接的自适应监控机理研究

Tailor rolled material (TRM) provides an innovative light weight method in optimization technology for modern design and manufacturing. However, connection of tailor rolled material becomes a key manufacturing problem to realize this optimization way. Adaptive laser welding method with powder feeding offers quality guarantee of connection of TRM, for welding of tailor rolled material requires adaptive penetration with variation of the TRM thickness in the different position. To solve the monitoring issue of the adaptive matching between the heat flux and the mass flow in laser welding of TRM with powder feeding, this project proposes following methods: After the measurement position and welding zone are guaranteed to be in agreement, welding line, seam gap, weld width, weld depth and penetration status will be synchronously measured with auxiliary illumination of the weld seam by use of special light source to avoid interference signal from high power laser irradiation. Based on the monitoring of the laser induced plasma, adaptive control of heat flux and mass flow will be used to realize penetration welding and to avoid welding defects as coarse microstructure and pores in the whole process. Level-set method for tracking the boundary between the gas and the liquid, mixture model for tracking the boundary between the liquid and the solid, and the model for coupling among the laser, the powder and the molten pool will be used to simulate the physical process in the laser welding with powder. The research results will improve the ability of light weight technology to the benefit of climbing the academic peak in the optimization technology for modern design and manufacturing.

采用变厚截面优化设计与制造则是实现轻量化的新途径，解决变厚截面材料的连接问题是实现该技术的制造基础。变截面材料焊接要求熔深随厚度变化而适应性变化，填粉激光自适应焊接则为满足该类材料焊接质量要求提供了保障。针对变厚截面材料填粉激光焊接的热输入流量与质量流量的适应性匹配监控问题，本项目提出，为保证测量位置与焊接位置的一致性，通过特定辅助光源照射以避免激光干扰，主动视觉同步监测焊缝位置、对接间隙、熔宽、熔深、熔透等焊缝状态参量，利用激光诱导产生的光致等离子体监测焊缝组织粗大、气孔等缺陷，基于自适应控制热输入流量与质量流量实现熔透、焊缝组织、气孔缺陷等质量控制，并通过level-set方法追踪气-液界面、固-液混合模型追踪固-液界面及光-粉-熔池耦合模型模拟填粉激光焊接变厚截面材料物理过程。本研究将有利于占领汽车轻量化设计及制造领域的学术高点，提升我国自主研发和制造的能力。

汽车车身轻量化已经成为世界汽车技术发展的趋势，采用变厚截面优化设计与制造则是实现汽车轻量化新途径。针对车用变截面材料高效、优质焊接的迫切需求以及焊接熔透性和焊缝位置难以实现原位同步监测的技术难题，本项目搭建了强光干扰下熔透与焊缝同步监测系统，提出强激光辐照干扰条件下焊缝、小孔、熔池等图像轮廓提取算法和成形面积、对接间隙的同步测量方法。开展了光致等离子体与气孔等缺陷的相关性分析。建立了激光能量衰减模型，粉末热输运模型，探明不同光束形态作用下的光-粉耦合能量输运机制。基于level-set方法的填粉激光焊接数值模拟和小孔、熔池特征分析，提出了激光焊接熔透状态的判定算法。搭建了连续变厚截面材料自适应激光焊接平台系统并开发相应监控软件。项目组成员在国内外知名期刊发表高质量论文12篇，其中SCI收录11篇，SCI他引61次。授权发明专利1项，实用新型专利2项，申请发明专利3项。应邀作国际会议特邀报告或分组报告共12人次，国内会议分组报告13人次。培养毕业硕士研究生7人，在读博士生3人，在读硕士研究生3人，其中获湖南省优秀硕士学位论文2人，湖南大学优秀硕士学位论文2人。获2019年国家科技进步二等奖1项。谭建荣院士评价项目成果创新性强，总体技术达到国际先进水平。