Fundamental study of the quality measurement for wire arc additive manufacturing process by laser ultrasonic technique

This study is a fundamental study of measurement using the laser ultrasonic for the wire arc additive manufacturing (WAAM) process. WAAM has the feature that large structures can be created in a shorter time and lower cost than conventional manufacturing techniques, but a method to guarantee the quality applicable for in-process is still not established. The laser ultrasonic technique should be a candidate for such a method since it can measure the quality of welded parts even during the welding process. In the presented work, the applicability of the laser ultrasonic through the measurements of artificial defects introduced to the simulated specimen for the deposited shape and actual WAAM deposits was evaluated. Although there were multi-surface wave reflections and low detection sensitivity of the surface in the top side measurement, the defect at 10-mm depth in the actual WAAM deposition was measurable with the surface polishing. In the bottom side measurement, even though the deposition part is narrow (5 mm or less) and tall (30 mm or less), the interfaces, including the defects, could be detected.