多相振荡相关性对激光焊接过程准稳态自平衡机制的表征方法研究

High-power laser welding is gradually becoming a development trend for advanced welding processing technology. Effective monitoring of welding status is considered essential to guarantee desirable welding quality detection. However, the high laser power density and the intense coupling among liquid metal, gaseous metal and plasma tend to cause instability during welding process, which eventually affects the effective monitoring of welding stability. This project is to research on, under controllable pressure, the action law of quasi-steady-state self-balancing mechanism during laser welding process and the design of welding status characterization method based on multiple phrase vibration correlation. It aims at realizing the stability control of welding status. By employing optical multiple sensing fusion technology, the project conducts optical fiber laser welding experiments under the vacuum condition with controllable pressure in order to study the multiphase vibration pattern in stable state, and to discover how circumstance pressure regularly affects multiphase vibration. It also studies the variation pattern of multiphase vibration when technical parameters change in transient state, explains the self-balancing mechanism of multiphase coupling, uncovers the characterization mechanism of multiphase vibration on welding stability and designs a welding status description method based on multiphase vibration correlation. Research work hereunder helps to provide innovative theoretical basis and experimental approaches for effective recognition of status during complicated laser welding process. It is also of great scientific and practical significance for researches on the measurement of multiphase characteristics and stability detection during welding process.

高功率激光焊接是先进焊接工艺的发展趋势，其中，焊接状态的有效识别是焊缝质量检测的关键技术。由于激光能量密度极高，导致焊接过程液态、气态及等离子之间的剧烈耦合，严重制约了焊接稳定性的有效检测。本项目针对焊接缺陷产生前难以准确预判的问题，提出一种通过表征准稳态过渡过程来提高焊接稳定性检测的新思路。项目研究气压可控环境下焊接过程准稳态自平衡机制的作用规律，设计基于多相振荡相关性的焊接状态表征方法，实现焊接状态的准确识别。通过多光学传感融合分析技术，研究稳态下多相的振荡特征，揭示环境气压对多相振荡的影响规律；分析准稳态过程多相振荡随能量输入的变化趋势，阐明多相耦合的自平衡机制。项目为大功率激光焊接过程的有效识别提供新的理论基础及实验方法，对焊接过程多相特征的测量及稳定性检测具有重要的科学和现实意义。

本项目研究搭建了激光焊接多相信号采集系统，基于多光学传感器进行光谱选区重构，分别对近红外、可视域及紫外-可视域进行选区过滤，结合高速成像进行分光测量校正，可以较全面地观察并获取加工过程中可见光、反射光辐射信息，光谱信息，熔池、匙孔、金属蒸汽的几何尺寸等多相信息。通过对不同焊接状态下的多相特征信号振荡规律的研究，揭示了激光焊接过程能量耦合和偏移对于提高焊接稳定性的规律；量化各模态内外参数之间的耦合关系，研究激光焊接过程过程多相振荡特征的耦合机理，针对典型焊接缺陷产生时进行多相振荡特征分析，阐明自平衡机制对稳定焊接过程的作用机理。结合不同焊接工艺参数下的多相振荡特征进行分析，阐明焊接过程匙孔、熔池模型对激光能量的吸收机理，在焊接过程中存在准稳态，并且可以通过同轴光电传感器和视觉检测模块的组合，实现稳态、非稳态以及准稳态的区别，以此建立了稳态过渡过程的多相特征相关性规律以及状态模型，具有重要的科学意义和应用价值。