Abstract
A method is developed for applying the d-c potential drop technique to simplified nondestructive evaluation of a circumferential 3-D crack on the inner surface of a welded pipe. The pipe is welded circumferentially and the crack exists vertically to the inner surface at the weld. Potential drop is measured on the outer surface of the pipe. The method is based on 2-D theoretical analysis with modification for considering the actual 3-D nature of current flow. In order to determine the shape and size of the crack, measured distribution of the potential drop is compared with the 2-D analysis for a respective segment, which is based on the stream line, in the circumferential direction of the pipe containing an assumed crack. The effect of weld on the potential drop is treated based on the work reported so far. It is shown that the evaluated shape and size coincide well with those of the actual crack.
