A digital image and sonagraph processing method to analyze the crack growth of a modified caustic is described. This novel device can operate automatically, precisely, and quickly. With two video cameras recording two sets of images of caustics during crack growth, the computers analyze the images and process them with a specified fringe counting algorithm to obtain the thickness variation rate and stress intensity factor. We develop a new algorithm to process the test sound in the PC-base digital signal processing system. According this method, we can analyze the fringes of caustics and sound of fracture, and successfully improve testing of fractures.
keyword¡Gsonagraph, caustic image, crack tip
