Texture Analysis for Crack Detection in Fracture Mechanics

In the context of the metal-mechanic industry, there is a strong demand for material behavior measuring methods in the presence of cracks under stress conditions. This behavior is usually quantified by means of fracture toughness tests using parameters such as the stress intensity factor K, the CTOD, or the J integral. Regardless of the parameters used to quantify fracture toughness, all tests require knowledge of the correct length of the existing fatigue pre-crack in the sample that generated the failure. Hence, most laboratories have adopted visual measurement methods using a stereoscopic magnifying glass or a profile projector. Additional techniques, such as the use of heat tinting, help users and researchers to visualize the stable crack growth front. With the improvement in image processing and computer vision techniques, the present paper proposes the application of a new method for border detection by texture analysis, in order to get the corresponding contour of the crack front in postmortem analyses of SE(B) samples with high precision. The results suggest that the proposed method could be applied with high precision to images of fracture toughness tests for crack length measurement, having achieved a discrimination rate of 98%. The results also suggest that the method can be applied to samples that have not undergone heat tinting.