PSI - Issue 68

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 68 (2025) 405–408

European Conference on Fracture 2024 Stress ratio effect on the functional behavior of the pseudoelastic SMA N. Bykiv a *, S. Yankovyi a , V. Iasnii a a Ternopil Ivan Puluj National Technical University, Ternopil, Ukraine Abstract The effect of stress ratio on the functional properties of a nickel-titanium shape memory alloy was studied. Cylindrical specimens with a diameter of 4 mm were tested under uniaxial tensile cyclic loading in stress-controlled mode. The stress ratios were 0.1 and 0.5, with a frequency of 0.5 Hz in both cases. The experimental results determined the dissipated energy W dis for both stress ratios 0.1 and 0.5. The dissipated energy increases exponentially up to 7 times with a decrease in the stress ratio under the same load. This result is explained by increased hysteresis loop area at a higher load amplitude. However, the fatigue life of specimens under a stress ratio equal to 0.5 is approximately three times higher than under a stress ratio equal to 0.1 at the same stress range. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Shape memory alloy, stress ratio, functional behavior, dissipated energy, hysteresis degradation. 1. Main text Shape memory alloys, in particular pseudoelastic alloys, are widely used in various engineering fields due to their ability to change shape in response to temperature or mechanical loading (Bykiv and Iasnii, 2022). However, for the safe operation of structural elements, active or passive control devices based on SMAs, it is necessary to carry out comprehensive experimental and computational studies of the changes in the mechanical and functional properties of such materials under cyclic loading, considering the stress ratios and loading amplitude. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

* Corresponding author. Tel.: +380-982-384-310. E-mail address: nazarii_bykiv@tntu.edu.ua

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.073