Evaluation of ultrasonic C-scan attenuation image

Temporal averaging and homomorphic processing, which extract the local ultrasonic wavelet and estimate the attenuation coefficient, have been incorporated into C-scan imaging to generate and attenuation map. The variation of this map displays changes in the scattering cross section and in the absorption of materials. These processing schemes are implemented into an integrated software package designed to yield a high resolution C-scan attenuation image. Experimental results have shown that for a composite sample with fatigue damage caused by compression, the C-scan attenuation map provides an improved image of the damaged area over the conventional peak detection scheme. The benchmark of image quality (i.e., average pixel value of the damaged area over average pixel value of the nondamaged area) indicates that the C-scan attenuation map outperforms the peak-echo C-scan by a factor higher than two to one