Direct current potential difference correlation for open-hole, single-crack coupons

This work provides forward and inverse voltage to crack length correlations for direct current potential difference (DCPD) crack size measurements in open-hole, single-crack fatigue test coupons. A finite element model was used to develop the correlations for a domain with a centrally located open hole in a long finite-width strip with a through crack from one side of the hole. The strip width was varied from 2 to 10 times the hole diameter. The correlations were applied to experimental results and validated by comparing DCPD results to digital photomicroscopic crack length measurements. A conformal mapping of the often-used Johnson solution was found to be inaccurate for the open-hole geometry.

► Crack length to voltage correlations are developed for a single crack at an open hole.
► Correlations are determined from finite element analyses and validated by crack measurements.
► Closed-form expressions provide forward and inverse correlations, for a range of hole size.