PSI - Issue 66

Slobodanka Boljanović et al. / Procedia Structural Integrity 66 (2024) 535– 542 S. Boljanovi ć and A. Carpinteri/ Structural Integrity Procedia 00 (2025) 000–000

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Fig. 5. Fatigue degradation analysis: (a) a vs. N and (b) b vs. N (1 – R = 0.1, 2 – R = 0.2, 3 – R = 0.3, calculated curves are the present research results). Fatigue resistance evaluations in terms of the number of loading cycles, as functions of crack length in depth and surface direction, for three values of thicknesses is plotted in Fig.6a and b. From relevant comparisons, it can be concluded that, if thickness increases from 6 mm to 7.8 mm, it leads to an increase in the number of loading cycles by about 25 % for fatigue-critical damaged pipe.

Fig. 6. Fatigue degradation analysis ( R = 0.1): (a) a vs. N and (b) b vs. N (1 – t = 6 mm, 2 – t = 7.8 mm, 3 – t = 10.14 mm, calculated curves are the present research results). 5. Conclusions The fast-growing aerospace and maritime sectors face the challenge of reducing operation and maintenance (O&M) costs for large systems. Predictive maintenance is essential to improve system reliability and prolong operation time, thereby reducing the relevant mentioned costs for systems exposed to dynamic loads such as aircrafts, platforms and wind power plants. The current study proposes a computational design strategy to predict the fatigue performances of systems with semi-elliptical flaws. In this context, through linking relevant damage tolerance-based concepts, theories of structural analysis and appropriate mathematical tools, this research work provides descriptions of stress intensities in safety-critical zones and cyclic load environment. They have been then used as input data for failure strength estimations. With the output description of fatigue life and crack paths, successfully verified by experiments, they enable reliable design, risk analysis, and maintenance controls and inspections during exploitation for both pipe and plate-type configurations with part-through flaws.