Average difference imaging and its application to ultrasonic nondestructive evaluation of wind turbine blade

This paper describes a method of average difference imaging and applying it to ultrasonic nondestructive evaluation of wind turbine blade. Average difference image is made from the means of intensity difference among several images. The image demonstrates the difference between an interested image and the other images. In performance test of this method, we employ a specimen of wind turbine blade. This specimen has artificial damages. We acquire ultrasonic waveforms from scanning lines on specimen using an ultrasonic single probe. To extract the damage, we make average difference images for every line. In the images, we could successfully find the line image with damage portions, and we estimated depth of damage portions with high accuracy. Thus, average difference imaging effectively led the line image with the damages. We then found the depth of damage portions from the line image.