In-process phased array ultrasonic weld pool monitoring

In recent years, there have been increasing economic and industrial drivers for the development of real-time non-destructive evaluation directly at the point of manufacture. Real-time inspection and monitoring of welding processes can help to reduce fabrication costs by detecting defects as they occur, enabling more efficient and cost-effective builds. This paper shows, for the first time, the use of phased array ultrasonics to monitor and analyse the molten weld pool during deposition of multi-pass gas tungsten arc welds. The received ultrasonic signals are shown to contain information related to key physical transitions occurring within the welding process, namely the melting and solidification of the weldment. Furthermore, the technique used here is shown to be effective for determining weld quality in real-time with significant signal changes occurring when defects such as Lack of Root Penetration are present. The accurate focusing and steering capabilities offered by phased arrays are used to successfully isolate the molten weld pool from the surrounding solidified weldment during deposition of multiple layers of a multi-pass weld.