Potential drop detection of creep damage in the vicinity of welds

Recent research indicated that directional Alternating Current Potential Drop (ACPD) measurements could be exploited for nondestructive evaluation (NDE) of creep damage. Unfortunately, creep damage is often concentrated in welded sections where the inspection is less straightforward. In this work, a directional square-electrode ACPD probe with spring-loaded contact pins was used to evaluate different levels of creep damage in the vicinity of welds. The electric transfer resistance is measured in two orthogonal directions to detect creep-induced material damage. This is particularly difficult close to weld/base-metal interfaces because the electric conductivity usually changes significantly from one side of the interface to the other and therefore exhibit an apparent anisotropy caused by the influence of the boundary. The feasibility of directional ACPD evaluation of creep damage in the vicinity of such transition regions was studied by experimental, analytical, and numerical means. Finite element simulati...