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

本研究的目的是开发一种在线焊缝监测/控制系统，该系统由柔性光纤束线性相控阵（FFBLPA）和聚焦透镜组成，以产生体波，用于实时监测和控制焊缝熔深。 将使用非接触式电磁声换能器（EMAT）作为接收器。 这项研究将证明的原则，作为第一步，发展一个自动闭环焊接系统控制的超声波传感器。 焊接熔池深度的测量将与发射和接收传感器一起沿着焊枪移动。 通过使用固定的激光相控阵超声发生器和EMAT接收器，测量的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得到应用。 具体的项目任务将包括：（1）开发一个超声发生单元，其中激光发生单元的所有组件将被集成和优化。(2)开发数据采集和分析子系统。(3)将生成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。(4)证明原理。该技术将解决传统方法的缺点，超声波发生器中的压电换能器连接到样品表面通过耦合剂。 通过实时传感反馈控制输入到被焊接部件的热量有望减少热影响区、材料降解和热变形，从而提高产量和焊接质量并降低生产成本。

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.