PSI - Issue 39

O.N. Belova et al. / Procedia Structural Integrity 39 (2022) 761–769 Author name / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 3 Interference pictures of isodromes in the cracked plate. Digital image processing such as fringe tracking and fringe order assignment has become the central topic of current research in digital photoelasticity (Ramesh and Sasikumar (2020), Ramesh (2021), Ramesh (2000), Ganesan and Mullick (2008)). The skeleton of the fringe is identified first to accurately collect the experimental data from the fringes. The programming tool is specially developed for the interpretation and processing of experimental data from the holographic interferometry measurement experiments. The developed and approved tool allows us to find points that belong to interference fringes with minimal light intensity. Data 1 2 ( , , , ) m m r θ are collected from the stored digital image. The analysis of the experimental data uses a Java application programmed for the advanced determination of the fracture mechanics characteristics: coefficients of the Williams series expansion for the stress field ahead of the crack tip. The programming tool allows us to collect experimental points from the holographic interferometry tests on the cracked specimens. The skeleton of isodrome fringes is shown in figs. 4 and 5. It is worth noting that, as it is revealed in the process of the experimental data processing, in order to produce theoretically the isodrome fringe shown in fig. 3 it is indispensable to keep at least fifteen terms in the Williams series expansion (3).