oa Improvement of eddy current testing method for sheet piles on harbor

The applicability and the feasibility of eddy-current testing method for the detection of defects such as wall thinning, surface crack, pinholes, etc. of steel structure have been practically confirmed by field and laboratory experiments. Qualitative analysis of these defects has been empirically understood by the current practice of eddy current methods based on analog analysis. There has, however, been a growing demand to quantitatively evaluate the defects. We tackle this problem by use of time series of induced magnetic field caused by the defects. In the present study, we proposed a new digital analysis process to use the induced magnetic field waveform, and validated the effectiveness of the method using numerical simulations. First, we developed a high-speed electromagnetic simulator using a fictitious wave domain method to reproduce the conventional eddy current testing method for realistic sheet-piles seawater model. Then, we confirmed the features of the induced magnetic field waveforms by a few types of defects. Paying attention to the residuals of the induced magnetic field waveform, we developed a novel migration procedure for detecting accurate position of cracks or defects. Using our approach, we could obtain crack images without phase lag. For the evaluation of the crack position and wall thinning of the sheet piles, we also applied attribute analysis traditionally used in the field of seismic survey. Through the application of the digital signal processing using induced magnetic field waveform, we could successfully develop a processing scheme with a high degree of accuracy of the eddy current testing method.