Real-time phased array ultrasonic weld pool monitoring during multi-pass weld deposition

Many industrial sectors such as nuclear and defence, employ ultrasonic Non-Destructive Evaluation (NDE) as a means of ensuring the integrity of welded components at the point of manufacture and throughout their service life. In recent years, there have been increasing industrial and economic drivers to reduce manufacturing costs, particularly as the nuclear sector is being called upon to play a significant role in the delivery of a low-carbon energy future. The development and deployment of innovative in-process inspection and monitoring techniques in one way in which the NDE sector can support the achievement of this aim. Real-time inspection and monitoring of welding processes can help to reduce fabrication costs by detecting defects as they occur, allowing more efficient and cost effective repair.
In this body of work, phased array ultrasonic testing is used to interrogate the molten weld pool in real-time during deposition of multi-pass gas tungsten arc welds. The received ultrasonic signals contain sufficient information to isolate the molten weld pool and monitor key physical transitions occurring within the welding process, namely the melting and solidification of the weldment. Furthermore, it is also found that this technique is capable of discerning weld quality in real-time with significant signal changes occurring when defects such as Lack of Root Penetration (LORP) are present. It is believed that with suitable modification to the deployment strategy to allow for concurrent inspection, the received signals are of sufficient quality to form the basis of a closed-loop weld control system in the future.