TWI

Some numerical and experimental results are presented to illustrate the ability of the SignaStir laser ultrasonic testing system to monitor the occurrence of voids, cavities and lack of root penetration defects during friction stir welding (FSW). A numerical Comsol model was employed to simulate wave propagation through a 3D domain of a friction stir weldment during laser ultrasonic testing. A series of welded joints with different cavities and degrees of lack of root penetration was tested after FSW. Different parameters for the positioning of the pulsed YAG generation laser and continuous YAG detection laser were examined and optimal configurations for each plate thickness, alloy and cavity characteristic were identified. The potential capability to reduce void formation by establishing optimal welding parameters based on the closed-loop feedback of the laser ultrasonic signals to the machine control system is discussed.

9th International Symposium, 15-17 May 2012, Session 2B: Inspection, Paper 04