Spectral histogram and its application to flaw detection

The split-spectrum processing (SSP) minimization algorithm has been successfully used to enhance ultrasonic flaw detection. However, this technique is fairly sensitive to the processing parameters, especially the frequency region selected for processing. In the past, the optimal spectral region could be obtained only by trial and error. In the present work, the concept of the spectral histogram has been introduced to achieve the optimal region automatically. In addition, it has been shown that the spectral histogram for the SSP minimization algorithm can be used to approximate the frequency response of this nonlinear system in the statistical sense, which can be utilized for obtaining a linear filter analogous to the Wiener filter. Experimental data obtained by ultrasonic nondestructive testing show that the proposed technique yields performance comparable to that obtained by a trained operator using a trial and error approach, indicating its feasibility in the automation of the SSP minimization algorithm.<
>