Akira Matsunawa and his co-workers at the Joining and Welding Research Institute at Osaka University devised, created and exploited a series of clever, telling and relevant experiments that has provided us with information on the temperature and the formation of the keyhole in laser beam welding as well as important knowledge as to the flow of the molten pool and the formation of porosity in welds with partial penetration. They have developed a high-speed X-ray transmission observation system to reveal the keyhole, bubble and porosity formation behavior. They utilize two synchronized ultra high-speed synchronized video camera to simultaneously observe keyhole and plasma images.

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