Experimental and numerical investigation of crack closure measurements with electrical potential drop technique

Crack closure measurements during fatigue crack propagation using the electrical potential drop (PD) technique is evaluated using a combination of experiments and simulations. From finite element simulations it is shown that variations in the potential drop value over a fatigue cycle can be explained by crack closure and strain induced conductivity changes. It is also demonstrated that closure measurements made with PD are consistent with closure observations made from in situ SEM observations of crack closure. Finally, it was observed that closure measurements made by a compliance-based measuring technique gave a somewhat lower opening load as compared to the PD-measurement.