PSI - Issue 64

Ali Jafarabadi et al. / Procedia Structural Integrity 64 (2024) 2059–2066 A. Jafarabadi et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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around 34% solely as a result of heat-treatment. Furthermore, the superior SME in the heat-treated sample is evident in the earlier onset of activation. This trend is also observed in free recovery behavior, where the heat-treated sample outperforms the as-received one, achieving a recovery ratio of 8.5% compared to 5.6% in the as-received case, as

shown in Fig. 3. 4. Conclusions

This paper explores the behavior of Fe-SMA tubes subjected to biaxial pre-straining, followed by activation, focusing on the contact pressure development in the joint as a result of SME. Through pre-straining process of the Fe SMA tubes the cross-section experiences a fully inelastic state with a non-uniform strain distribution. Thus, a non uniform biaxial pre-straining forms throughout the cross-section. That is, stress-induced marternsite forms in both radial and circumferential directions. However, it is feasible to interpret the overall SME performance through tracking of the resultant pressure that the Fe-SMA tube applies on the steel tube, restricting its free recovery. For this purpose, through experimental setups involving Fe-SMA and steel tubes, the contact pressure at the interface is quantified. This enables differentiating the SME performance for Fe-SMA tubes with different geometrical and implementation parameters. In particular, the effects of heat-treatment on the interface contact pressure and free recovery were investigated. Moreover, the evolution of the induced principal strains on the substance subjected to Fe- SMA’s pressure and the contact pressure at the interface was quantified throughout the course of activation up to 200°C for each sample. The results highlight the effect of heat-treatment for an enhanced gripping capacity in Fe-SMA tubes. Moreover, similar improvement is reported for the free recovery behavior. Acknowledgements The authors acknowledge the Innosuisse Swiss Innovation Agency for funding this research project (project number 56959.1 IP-ENG). The financial and technical support from the project partners, namely Hilti AG, Schaan, Liechtenstein and re-fer AG, Switzerland are highly appreciated. Any opinion and findings in this paper are those of the authors and do not necessarily reflect the view of the sponsors. References Cao, B. & Iwamoto, T. 2023. A strength prediction of joints by Fe-Mn-Si-Cr shape memory alloy through strain monitoring during pre-processes including diameter expansion and tightening by heating. Engineering Fracture Mechanics, 284. Cao, B., Sun, Q. & Iwamoto, T. 2022. Effect of deformation rate on the axial joint strength made of Fe-SMA. Journal of Constructional Steel Research, 191. Chakrabarty, J. 2012. Theory of plasticity , Elsevier. Cladera, A., Weber, B., Leinenbach, C., Czaderski, C., Shahverdi, M. & Motavalli, M. 2014. Iron-based shape memory alloys for civil engineering structures: An overview. Construction and building materials, 63 , 281-293. Ferretto, I., Kim, D., Della Ventura, N. M., Shahverdi, M., Lee, W. & Leinenbach, C. 2021. Laser powder bed fusion of a Fe – Mn – Si shape memory alloy. Additive Manufacturing, 46. Hosseini, E., Ghafoori, E., Leinenbach, C., Motavalli, M. & Holdsworth, S. R. 2018. Stress recovery and cyclic behaviour of an Fe – Mn – Si shape memory alloy after multiple thermal activation. Smart Materials and Structures, 27 , 025009. Jafarabadi, A., Ferretto, I., Mohri, M., Leinenbach, C. & Ghafoori, E. 2023. 4D printing of recoverable buckling-induced architected iron-based shape memory alloys. Materials & Design, 233 , 112216. Janke, L., Czaderski, C., Motavalli, M. & Ruth, J. 2005. Applications of shape memory alloys in civil engineering structures — Overview, limits and new ideas. Materials and Structures, 38 , 578-592. Khodaverdi, H., Mohri, M., Ghorabaei, A. S., Ghafoori, E. & Nili-Ahmadabadi, M. 2023. Effect of low-temperature precipitates on microstructure and pseudoelasticity of an Fe – Mn – Si-based shape memory alloy. Materials Characterization, 195 , 112486. Lee, W. J., Weber, B. & Leinenbach, C. 2015. Recovery stress formation in a restrained Fe – Mn – Si-based shape memory alloy used for prestressing or mechanical joining. Construction and Building Materials, 95 , 600-610. Leinenbach, C., Kramer, H., Bernhard, C. & Eifler, D. 2012. Thermo-Mechanical Properties of an Fe-Mn-Si-Cr-Ni-VC Shape Memory Alloy with Low Transformation Temperature. Advanced Engineering Materials, 14 , 62-67. Li, J., Zhao, M. & Jiang, Q. 2002. Comparison of shape memory effect between casting and forged alloys of Fe14Mn6Si9Cr5Ni. Journal of materials engineering and performance, 11 , 313-316. Liu, D., Liu, W. & Gong, F. 1995. Engineering application of Fe-based shape memory alloy on connecting pipe line. Journal de Physique IV, 5 , C8-1241-C8-1246. Maruyama, T. & Kubo, H. 2011. Ferrous (Fe-based) shape memory alloys (SMAs): properties, processing and applications. Shape Memory and