Applications and limitations for using ACPD in crack depth measurements

Alternating current potential drop (ACPD) testing has been established as a viable means of measuring crack depth. This paper presents experiences in using a commercially available version of this tool to generate results under flaw constraints encountered in industrial usage. Sample geometries with simulated cracks were studied to examine crack depth as a percentage of through-wall thickness and with varying width of contact area adjacent to cracks. A variety of real cracks were also examined, illustrating cracking conditions that may be adequately measured using ACPD, as well as situations where crack depth may be under- or oversized.