When the crack of the pipe-flange welded part is evaluated by the direct-current potential difference method (DC-PDM), the result is affected by the weld metal geometry and electrical conductivity. In this paper, a pipe-flange welded component was modeled and the detection of the crack by DC-PDM was discussed based on the results of electric field analyses using the finite element method. In the analysis, the depth of crack and the geometry and electrical conductivity of the weld metal were varied. In all conditions, increase in potential difference by the crack took the maximum value near the boundary of the flange and weld metal, and it was high enough for crack detection. Although the potential difference was affected by the weld metal geometry and electrical conductivity, the normalized potential difference was well correlated with the crack depth ratio, and the relation was formulated by a cubic equation. Based on the equation, the crack depth was evaluated successfully for all conditions with different weld metal geometries and electrical conductivities.

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