PSI - Issue 57

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Mathilde Renault et al. / Procedia Structural Integrity 57 (2024) 22–31 Mathilde RENAULT/ Structural Integrity Procedia 00 (2019) 000 – 000

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The images are then thresholded, with the threshold being chosen to correspond to the length of the crack obtained at the time of thermal marking. This technique allows for the measurement of the crack size as a function of the number of cycles.

Figure7 a) Crack detection results based on differential measure binarization for = 130MPa b) fractography of a thermally marked specimen used for the choice of binarization parameters These measurements allow for the estimation of the crack-propagation phase duration (represented by the ratio of the number of cycles until the crack is detected and the number of test stop cycles on a cylinder displacement criterion), as well as the crack growth rate, as shown in the illustration Figure8.

Figure8 a) Ratio of the number of cycles to crack detection over total fatigue life for longitudinal and transversal directions (longitudinal results are from (Bercelli et al,2020))

b) Crack growth rate(estimated between 2 and 8mm) for longitudinal and transversal directions (longitudinal results are from (Bercelli et al,2020))