PSI - Issue 79

Andrea Avanzini et al. / Procedia Structural Integrity 79 (2026) 88–96

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N curves reported in Fig. 5b with Risitano's method, they were found to provide an acceptable approximation of the real fatigue curves (not shown in the present work) only for high loads. For the low load testing condition, a sudden decrease in the predicted fatigue curve slope is instead observed, which is however the consequence of uncertainties in the acquired data in presence of very limited heating. For this reason, the estimated energy is probably affected by an intrinsic error due to the quality of the data. In fact, this behavior is quite marked in the DA specimen, that also exhibited higher measurement error. Of course, fatigue behavior is inherently statistical, especially when using additive materials for which microstructure is highly dependent on the manufacturing process. Because of that, it is particularly advisable to use more than one specimen to obtain more robust results. Due to production constraints and previous testing campaigns, only one sample per HT type was available, which is an inherent limitation of our work but was deemed acceptable considering the comparative nature of the present study. 4. Conclusions Rapid fatigue assessment of additively manufactured IN625 was conducted using an infrared thermographic (IRT) approach. Several indexes, such as energy-based (Q-parameter from cooling curve and Φ parameter) and temperature based (initial rise slope dT/dt and steady temperature  T Steady ), are analyzed in a comparative perspective, as well as different fitting strategies derived from the literature. A reasonable correlation between conventional tests and IRT fatigue predictions was observed. The fatigue stress limits that were estimated were approximately in accordance with the actual lives of the specimens between 1E6 and 2E6 cycles. Beyond this life range, in conventional fatigue experiments conducted up to 2E7 cycles, failures occurred also at stress levels lower than predicted fatigue limit. Defects in AM materials are likely to be the cause, as they may increase the probability of fracture initiation and propagation. In summary, the potential of IRT method' as screening tools for AM materials was confirmed by the sensitivity to variations in the fatigue limits as a function of HT. The accuracy of IR thermography when applied to AM materials may be influenced by the presence of defects, more relevant when considering high cycle fatigue. Acknowledgements The Authors would like to acknowledge funding for the use of IR thermal camera by Departmental Grant AAD2022 of University of Brescia – Dept. Mechanical and Industrial Engineering. References Balit, Y., Joly, L. R., Szmytka, F., Durbecq, S., Charkaluk, E., & Constantinescu, A. (2020). 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