On-Line Weld Quality Monitoring/Control Using Laser Ultrasound and Non-Contact Sensors

本研究项目的目的是开发一种由柔性光纤束线性相控阵(FFBLPA)和聚焦透镜产生体波的焊缝在线监测/控制系统，用于实时监测和控制焊缝熔深。接收器将采用非接触式电磁换能器(EMAT)。这项研究将论证原理的证明，作为开发由超声波传感器控制的自动闭环焊接系统的第一步。随着焊枪的移动，发射和接收传感器将测量熔池深度。通过使用固定式激光相控阵超声发生器和EMAT接收器，测量数据将用于焊接过程的实时控制。该系统将在实际的机器人熔化极气体保护焊过程中实现。具体的项目任务将包括：(1)开发超声产生单元，其中激光产生单元的所有组件将被集成和优化。(2)开发了数据采集与分析子系统。(3)将产生和接收单元与焊接和机器人控制器以及数据采集子系统集成在一起。(4)论证原则证明。这项技术将解决传统超声产生方法的缺点，即通过偶联剂将压电换能器连接到样品表面。通过实时传感反馈控制被焊件的热输入，有望减少热影响区、材料退化和热变形，从而提高产量和焊接质量，降低生产成本。

The objective of this research project is to develop an online weld monitoring/control system consisting of a flexible fiber bundle linear phased array (FFBLPA) and a focusing lens to generate bulk waves, which will be used to monitor and control weld penetration in real-time. A non-contact electromagnetic acoustic transducer (EMAT) will be used as the receiver. The study will demonstrate the proof-of-principle as a first step toward developing an automatic closed loop welding system controlled by ultrasonic sensors. The weld pool depth will be measured with the transmitting and receiving sensors moving along with the welding torch. By using a stationary laser phased array ultrasound generator and an EMAT receiver, the measured data will be used in real-time control of the welding process. This system will be implemented in actual robotic gas metal arc welding process. Specific project tasks will include: (1) Develop an ultrasound generation unit where all the components of the laser generation unit will be integrated and optimized. (2) Develop a data acquisition and analysis sub-system. (3) Integrate the generation and receiving units with the welding and robot controllers and the data acquisition sub-system. (4) Demonstrate the proof-of-principle. The technique will address the shortcomings of the traditional approaches to ultrasound generation in which the piezoelectric transducer is connected to the sample surface through a couplant. Controlling heat input to the parts being welded through a real-time sensory feedback is expected to reduce the heat affected zone, material degradation, and thermal distortion, leading to the increase of throughput and weld quality and the reduction of production cost.