An autonomous surface discontinuity detection and quantification methodby digital image correlation and phase congruency

• Published in: Optics and lasers in engineering Vol. 96; p. 94
• Main Authors: Cinar, Ahmet, Barhli, Selim, Hollis, Dave, Flansbjer, Mathias, Tomlinson, Rachel, Marrow, James, Mostafavi, Mahmoud
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: Crack; Digital image correlation; Fracture mechanics; Phase congruency; Segmentation
• ISSN: 1873-0302; 0143-8166
• DOI: 10.1016/j.optlaseng.2017.04.010

Digital image correlation has been routinelyused to measure full-field displacements in many areas of solid mechanics,including fracture mechanics. Accurate segmentation of the crack path is neededto study its interaction with the microstructure and stress fields, and studiesof crack behaviour, such as the effect of closure or residual stress infatigue, require data on its opening displacement. Such information can beobtained from any digital image correlation analysis of cracked components, butit collection by manual methods is quite onerous, particularly for massiveamounts of data. We introduce the novel application of Phase Congruency to detectand quantify cracks and their opening. Unlike other crack detection techniques,Phase Congruency does not rely on adjustable threshold values that require userinteraction, and so allows large datasets to be treated autonomously. Theaccuracy of the Phase Congruency based algorithm in detecting cracks isevaluated and compared with conventional methods such as Heaviside function fitting.As Phase Congruency is a displacementbased method, it does not suffer from thenoise intensification to which gradient-based methods (e.g. strain thresholding)are susceptible. Its application is demonstrated to experimental data forcracks in quasi-brittle (Granitic rock) and ductile (Aluminium alloy)materials.