PSI - Issue 42

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Pedro R. da Costa et al. / Procedia Structural Integrity 42 (2022) 1560–1566 Pedro R. da Costa/ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. SEM fatigue fracture surfaces with fatigue crack initiation and other fatigue crack morphologies identified: (A, B) tension-compression; (C, D) pure torsion; (E, F) multiaxial Tension/Torsion.

4. Conclusions A complete fatigue behaviour comparison in the VHCF region was conducted for an AISI P20 steel. Three different stress states were applied using the same fatigue method technology, the ultrasonic piezoelectric transducer fatigue machines. A complete comparison between numerical results, analytical computed calculations and conducted measurements was first made showing a good correlation. Afterwards, ultrasonic fatigue testing to failure was conducted. All individual fatigue fracture results were compared between the three ultrasonic methods and the ultrasonic scientific community published results. The made fracture morphology comparison consolidated the experimental measurements. There was a clear distinction between the two uniaxial fracture fatigue surfaces and a combination of the two was present in the multiaxial tension-torsion. Therefore, all methods proved to induce fatigue in the desired stress state cycle combined with an improved measuring methodology that allows for stress determination and fatigue testing execution for the VHCF study. Acknowledgements The author thanks FCT, Fundação para a Ciência e Tecnologia, which through several research projects in the last 20 years has supported financially the development of these technologies of multiaxial very high cycle fatigue and namely through LAETA/IDMEC, project UID//50022/2020, Project PTDC/EMS-PRO/5760/2014, and the authors PhD scholarship 2020.06550.BD. This work is also co-financed by the project PTDC/EME-EME/7678/2020, Giga Cycle Fatigue Behaviour of Engineering Metallic Alloys. References Bathias, Claude and Paul C. Paris. 2005. Gigacycle Fatigue in Mechanical Practice . edited by Marcel Dekker. da Costa, Pedro R., Luís Reis, Diogo Montalvão, and Manuel Freitas. 2021. “A New Method for Ultrasonic Fatigue Testing of Equibiaxial and Pure Shear Cruciform Specimens.” International Journal of Fatigue 152(June). da Costa, Pedro R., Manuel Sardinha, Luís Reis, Manuel Freitas, and Manuel Fonte. 2021. “Ultrasonic Fatigue Testing in As -Built and Polished