combining magnetic flux leakage and optical inspection technique for identification of nearby pittings

Magnetic flux leakage (mfl) is an indirect measurement technique. therefore, calibration curves are generally used to estimate the depths of the defects from the measured mfl signals. this has been shown to give good results on varying degrees of the single defects. however due to the interaction between the leakage fluxes, nearby pittings can-not be discriminated and properly assessed using the conventional mfl technique. in order to ensure reliable measurement for this case, the mfl technique is combined with the optical inspection technique. the main contributions of this study are to develop a new calibration method based on the defect depth, defect area as well as the amplitude of the corresponding mfl signal and propose a novel combined approach for detection and identification of the nearby pittings. mfl and optical inspection techniques are applied to a test specimen containing the nearby pittings. the results obtained from the experimental tests demonstrate the efficacy of the proposed approach.