Defect Mapping Based on Signal Correlation for Ultrasonic NDE

This paper presents the application of a signal correlation technique to automatically classify ultrasonic A-scan signals for defect and non-defect regions in isotropic and anisotropic materials. First, a reference A-scan signal of a non-defect area was generated by autocorrelation and statistics. Next, the similarity between the reference signal and the signal of interest was analyzed based on their cross-correlation. The analyzed result was quantified using the correlation coefficient and the distance between the front and back echoes. After that, the defect mapping was defined based on these two criteria to locate the defect area on a 2D image. This method uses statistics rather than the prior knowledge of an inspector to generate a C-scan map, and has particular value in automated ultrasonic signal classification and characterization.

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