Abstract
A novel inclined excitation method for eddy current thermography was proposed to eliminate the “fuzzy effect” together with the wavelet singularity-based image segmentation that effect adversely the crack detection level, especially for non-ferromagnetic materials. The efficiency of crack detection with parallel and inclined excitation was numerically investigated at different heating periods, crack depths and widths. The inclined excitation was shown to effectively enhance the detection effect and increase the heating period to 6 s that can reduce the impact of the “proximity effect” of the coil and make the detection results clear-cut. The inclined excitation method was adequate for cracks of different depths. The discontinuity point detection method was proposed for the quantitative identification of crack widths. Aluminum specimens with penetrating cracks were tested using the inclined excitation, and the detection results were processed based on the wavelet singularity detection method. Crack temperature variations under the inclined excitation are similar to those of numerical simulation, and the crack can be followed more closely and accurately, thus the combination of inclined excitation and wavelet singularity can effectively improve thermographic images.
Published Version
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