Algorithm of fatigue crack detection and determination of its tip position in optical images

Abstract

An algorithm of fatigue crack detection in optical images taken in fatigue tests of materials is proposed and tested. The algorithm is designed for automation of measurements of the crack propagation parameter and tracing the crack tip position in the course of cyclic loading for the purpose of shifting the optical system with respect to the examined sample surface to the “region of interest.” It is found that the coordinates of the image fragment containing the crack can be determined with a mean error of 1.93% of the total size of the raster. Testing of the algorithm on model images shows that the mean error of determining the crack tip position is smaller than 56 pixels.