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

点击翻译按钮获取中文摘要

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.