声信号阵列检测激光焊接熔池基础理论与方法

The monitoring of laser welding processing is the key to ensure the quality of welds. The molten pool has the dual properties, which is the sound source and contains a large number of state information in laser welding processing. However, its application is limited to some extent in laser welding, due to its vulnerability to environmental noise. Recent study shows that sensor array technology and signal processing method could eliminate background noises and localized sound sources, which provide a new way for quality inspection of the laser welding processing.Depending on the foundation of scientific theory and the crossover of forefront of generic technology, the sensor array technology for the acoustic signal detection is first to utilized for explaining some unknown phenomena in welding field. These are very important for further study of acoustic signal detection in laser welding.This project aims to study the propagation characteristics of acoustic signal during welding processing, establish the relationship among the weld pool shape, position and welds quality, reveal the generation rule of sound for weld pools with different cavities and get accurate results of laser seam changing. The relationship between array acquisition signal and sound source during laser welding process is studied on the basis of the calculation of the sound field, molten pool's temperature field, plasma and flow field. By establishing the model and algorithm, dynamic real-time pressure of the sound source are obtained, which makes it possible to evaluate the quality of welding seam. In summary this project has important prospect of theory value and applications.

激光焊接过程检测是保证焊接质量的关键，熔池形状决定焊接质量，同时它也是焊接过程中的声源，具有双重属性，包含大量熔池信息；但由于其易受环境噪声干扰，使它在激光焊接中的应用受到限制。近期研究发现，传感器阵列技术与信号处理方法能够消除噪声，定位声源，这为激光焊接质量检测提供了新的途径。本课题率先将传声器阵列技术用于激光焊接声信号检测，依靠基础科学理论和前沿共性技术交叉研究，解决目前存在未知现象和规律，对提高声信号检测焊接质量非常重要。本项目拟研究焊接过程移动声音信号在声场中传播基本特性，建立熔池形状、位置与焊接质量的关系，揭示不同熔池腔发声的规律，得到激光焊缝变化的准确结果。课题拟计算焊接过程的声场、熔池温场、等离子体和熔体金属的流场，研究阵列采集信号与激光焊接声源发声内在联系，建立有关模型及算法；计算动态声源实时压力，评价焊接过程焊缝的质量，该项研究具有重要科学理论价值和应用前景。

激光焊接过程检测是保证焊接质量的关键，熔池形状决定焊接质量，同时它也是焊接过程中的声源，具有双重属性，包含大量熔池信息；但由于其易受环境噪声干扰，使它在激光焊接中的应用受到限制。近期研究发现，传感器阵列技术与信号处理方法能够消除噪声，定位声源，这为激光焊接质量检测提供了新的途径。因此，本项目率先将传声器阵列技术用于激光焊接声信号检测。. 本项目主要针对激光焊接过程中的声信号易受噪声干扰的问题，应用声学原理、传热传质学及流体力学理论、等离子体物理学等多学科理论，阐明声信号在激光焊接中的产生、传播规律；发现焊接质量与熔池形状尺寸、焊接工艺参数、熔体金属流变等关系；提出激光焊接传声器阵列及阵列信号处理方法，指导焊接声音信号的降噪、声源识别与定位、移动声源声压信号实时跟踪与评价等。其主要研究内容包括：焊接过程移动声音信号在声场中传播基本特性，建立熔池形状、位置与焊接质量的关系，揭示不同熔池腔发声的规律，得到激光焊缝变化的准确结果。计算了焊接过程的声场、熔池温场、等离子体和熔体金属的流场，研究阵列采集信号与激光焊接声源发声内在联系，建立有关模型及算法；计算动态声源实时压力，评价焊接过程焊缝的质量。. 取得成果包括：将传感器阵列及阵列信号处理方法应用于激光深熔焊接过程，完成了激光焊接声信号的降噪、识别与定位、动态声源的实时监测、算法的研究；同时，建立了一套基于传声器阵列的激光深熔焊“小孔”形态监测装置，能够准确检测小孔声音信号、实现声源识别、定位和跟踪；另外，形成样机1台，申请发明专利10 项，发表论文44篇，完成了项目任务。. 从目前所掌握资料看，国际上还没有将阵列声源识别技术和盲信号处理算法应用到激光焊接质量检测领域，本项目在国家自然科学基金委的资助下开展的研究工作，在国内率先开展基于传声器阵列的激光焊接过程质量检测研究，取得的研究成果对激光焊接过程的质量检测奠定良好的基础。