PSI - Issue 64

Mao Ye et al. / Procedia Structural Integrity 64 (2024) 1824–1831 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Conclusions This experimental study investigated the influence of the prestrain level and activation temperature to the stress recovery behavior of a NiTiNb-SMA plate. Re-activation scenarios were investigated. The following conclusions could be drawn: 1) During loading, stress plateau and transformation bands may form, suggesting the existence of strain localization. Unloading had a negligible influence on strain localization, while residual strain accumulated after unloading. 2) A subsequent re-activation to the same temperature could not substantially increase the recovery stress. 3) 8% and 10% of prestrain level generally led to a higher recovery stress. When prestrained by 8% and activated at 180 ℃ , the largest recovery stress reached 448.6 MPa, which could be the optimal thermal activation strategy for this NiTiNb-SMA plate to exert the best recovery behavior. The capacity of this material to generate ample recovery stress through moderate thermal activation is very promising. Since a conservatively lower activation temperature is favorable for the adhesive bond, if utilized for application of bonded prestressed strengthening of structures, this NiTiNb-SMA plate exhibits significant potential. Acknowledgements This project was supported by the National Natural Science Foundation of China (Grant No. 51978509) and Top Discipline Plan of Shanghai Universities-Class I. The authors also acknowledge the support from Beijing Gee SMA Technology Co., Ltd., China, for the supply and manufacture of the NiTiNb-SMA plate specimens for this study. References Chen, Z. Y., Gu, X. L., Zhao, X. L., Ghafoori, E., & Yu, Q. Q. (2023). Fatigue tests on Fe-SMA strengthened steel plates considering thermal effects. Journal of Structural Engineering, 149(3), 04022255. Fritsch, E., Izadi, M., & Ghafoori, E. (2019). Development of nail-anchor strengthening system with iron-based shape memory alloy (Fe-SMA) strips. Construction and Building Materials, 229, 117042. Gu, X. L., Chen, Z. Y., Yu, Q. Q., & Ghafoori, E. (2021). Stress recovery behavior of an Fe-Mn-Si shape memory alloy. Engineering Structures, 243, 112710. Izadi, M. R., Ghafoori, E., Shahverdi, M., Motavalli, M., & Maalek, S. (2018). Development of an iron-based shape memory alloy (Fe-SMA) strengthening system for steel plates. Engineering Structures, 174, 433-446. Izadi, M., Hosseini, A., Michels, J., Motavalli, M., & Ghafoori, E. (2019). Thermally activated iron-based shape memory alloy for strengthening metallic girders. Thin-Walled Structures, 141, 389-401. Jiang, S., Liang, Y., Zhang, Y., Zhao, Y., & Zhao, C. (2016). Influence of addition of Nb on phase transformation, microstructure and mechanical properties of equiatomic NiTi SMA. Journal of Materials Engineering and Performance, 25, 4341-4351. Lee, W. J., Weber, B., Feltrin, G., Czaderski, C., Motavalli, M., & Leinenbach, C. (2013). Stress recovery behaviour of an Fe – Mn – Si – Cr – Ni – VC shape memory alloy used for prestressing. Smart Materials and Structures, 22(12), 125037. Li, L., Chatzi, E., Czaderski, C., & Ghafoori, E. (2023). Influence of activation temperature and prestress on behavior of Fe-SMA bonded joints. Construction and Building Materials, 409, 134070. Li, L., Wang, W., Chatzi, E., & Ghafoori, E. (2023). Experimental investigation on debonding behavior of Fe-SMA-to-steel joints. Construction and Building Materials, 364, 129857. Suhail, R., Amato, G., & McCrum, D. (2020). Heat-activated prestressing of NiTiNb shape memory alloy wires. Engineering Structures, 206, 110128. Tan, G., Liu, Y., Sittner, P., & Saunders, M. (2004). Lüders-like deformation associated with stress-induced martensitic transformation in NiTi. Scripta Materialia, 50(2), 193-198. Vůjtěch, J., Ryjáček, P., Matos, J. C., & Ghafoori, E. (2021). Iron -Based shape memory alloy for strengthening of 113-Year bridge. Engineering Structures, 248, 113231. Wang, S., Li, L., Su, Q., Jiang, X., & Ghafoori, E. (2023). Strengthening of steel beams with adhesively bonded memory-steel strips. Thin-Walled Structures, 189, 110901. Wang, W., Li, L., Hosseini, A., & Ghafoori, E. (2021). Novel fatigue strengthening solution for metallic structures using adhesively bonded Fe SMA strips: A proof of concept study. International Journal of Fatigue, 148, 106237. Yang, C., Liu, T., Zhong, M., Wu, Z., Deng, J., & Du, Y. L. (2023). Enhancement of recovery stress by annealing and prestraining of NiTiNb wires. Journal of Intelligent Material Systems and Structures, 34(17), 2047-2060. Zhang, X., Feng, P., He, Y., Yu, T., & Sun, Q. (2010). Experimental study on rate dependence of macroscopic domain and stress hysteresis in NiTi shape memory alloy strips. International Journal of Mechanical Sciences, 52(12), 1660-1670.