Performance of the Direct Current Electric Potential Difference (DCEPD) Method for Crack Extension Measurement in Fracture Mechanics Specimens Exhibiting Split Delaminations

ABSTRACT This work investigates the performance of the direct current electric potential difference (DCEPD) method for measuring crack extension ( ) during fracture toughness tests of ductile steels exhibiting delaminations perpendicular to the main crack plane, known as splits. These delaminations were studied in DH36 and X70 steels using SE(B) specimens, tested at −60°C (DH36) and at room temperature (X70). For comparison, the unloading compliance (UC) method was applied simultaneously. To elucidate trends observed in DCEPD results, morphological and geometric characteristics of the splits were analyzed by computed microtomography and fracture surface examination. Results indicate that splits fully perpendicular to the main crack do not promote crack growth and do not perturb DCEPD measurements. In contrast, splits involving plane changes or branching cause sudden instabilities in , which are reflected as instantaneous increases in the DCEPD signals. Overall, DCEPD and UC showed good agreement and reliable performance in quantifying crack extension in specimens with splits.