Abstract
Based on the dc-pd (direct-current-potential-drop) technique, an efficient detection procedure is developed to identify the existence of unknown cracks in a pipe. By this procedure, the electric potential on the perfect pipe needs to be calculated first by finite element method. The proposed defect influence factor, which is defined as the electric potential of the defective pipe divided by that of the perfect one, is then employed to reveal the effect of unknown cracks on the electric potential. By depicting the constant contours of the defect influence factor with sufficient resolution, not only the position, but also the shape and size of cracks in the pipe can be identified accurately by the detection criterion devised in this work. Those cracks detected include circumferential crack, inclined crack, and multiple cracks. Good identified results show the merits of the procedure developed for the identification of unknown cracks in the pipe structure.