Restoration and characteristic analysis of X-ray images of molten pool during laser deep penetration welding

Owing to a strong ability to go through the objects, the radiography can be used to observe and analyze the formation of a molten pool inside weldments during laser deep penetration welding. The shape of a molten pool and the thermal transfer effect of laser power through keyhole can be monitored and analyzed in real-time. During a high-power fiber laser welding on plate of 304 stainless steel,a high-speed radiography camera was used to capture the molten pool images. These captured X-ray images were degenerated and obscure due to the disturbance and noises from the welding process and radiography devices. An arithmetic to restore and intensify the X-ray images of molten pool was proposed to make the X-ray images more clear and enhance the ability to recognize the characteristics of images. The blind deconvolution method was used to estimate the point spreading function of X-ray image degeneration,which was applied as a parameter to implement the Wiener filtering of X-ray image of a molten pool. Also,the X-ray image of a molten pool was intensified by the grey level transformation,and the dynamic of a molten pool was analyzed. Results showed that the proposed algorithm of image restoration and intensification can improve the quality of X-ray images effectively and make the contour of a molten pool more distinct.