Optimization of the DCPD technique for monitoring the crack propagation from notch root in localized plasticity

Abstract The Direct Current Potential Drop method is commonly used to monitor the crack growth during fatigue test when optical access to the crack is not possible. The reliability of this method depends on the calibration curve, which correlates the potential drop measurement with the crack length and shape. Using Finite Element Analysis and experimental approaches with heat tints, a procedure for the optimization of the calibration curve has been proposed. The influence of plastic deformation and of the presence of a secondary crack on the calibration curve has been studied. Finally, a test strategy, using two heat tints, has been developed in order to identify the first order parameters for the calculation of calibration curve. This strategy shows higher accuracy of crack length measurement and permit to balance experimental uncertainties out.