In-Line Weld Penetration Monitor Using Laser Ultrasonics

Submerged arc welding is commonly used for joining thick plates in panel-line assembly. This technique normally involves double-sided welding, with significant preparation on the back side to promote adequate weld penetration. Currently, completed welds are inspected by ultrasonic or radiographic techniques after a delay to allow cooling. If incomplete penetration is detected, the flawed region is likely to be extensive, and considerable repair or rework is required. In this proposal we will demonstrate the feasibility of monitoring submerged arc weld penetration in real time, immediately after the weld is formed. Such an in-line technique would eliminate slow, costly post-process inspection and would allow immediate corrective action if a bad weld is detected. The technique we will apply is laser ultrasonics. The use of lasers for generating and detecting ultrasonic waves enables inspection on parts with rough surfaces that can be moving and/or at high temperature. In this project we will establish the best inspection configuration and test welds and analyze shipyard affordability.