レーザ超音波による溶接品質モニタリング技術（1）

（溶接中の溶融池深さのその場計測）

抄録

In order to guarantee the weld quality, the ultrasonic inspection is widely used as a method of checking the presence of weld defects. Conventionally, the defects are detected by a contact type ultrasonic inspection after the welding process because this method cannot be used under a high temperature/noise environment such as during welding. Therefore, we aim at the development of contactless and in-situ measurement system during welding by using laser ultrasonic technique. This system enables to conduct the welding and inspection simultaneously with monitoring. In this study, we first measured the test piece shape of half rounded groove on the top surface to investigate the performance of our system. As a result, we could measure echoes from the bottom of the groove and visualize the test piece shape. Then, we measured the molten pool shape by hammering method and laser ultrasonic technique during the bead on plate welding by TIG arc. In addition, we calculated the 3D heat conduction model to apply the temperature distribution to the results of the measurement because the velocity of laser ultrasonic depends on the temperature. As a result, the measured distance from the bottom of work to the molten pool interface reasonably corresponded to the actual position obtained by the hammering method.