PSI - Issue 64

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Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 64 (2024) 2059–2066

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Contact Pressure Evolution in Heat-Treated Iron-Based Shape Memory Joints Ali Jafarabadi a,b,* , Christoph Czaderski a , Maryam Mohri a , Christian Leinenbach a,c , Elyas Ghafoori d , Eleni Chatzi b , Masoud Motavalli a a Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland, b Institute of Structural Engineering, Swiss Federal Institute of Technology Zürich (ETH-Zürich), 8093 Zürich, Switzemrland, c Laboratory for Photonic Materials and Characterization, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, d Institute for Steel Construction, Faculty of Civil Engineering and Geodetic Science, Leiübniz University Hannover, 30167 Hannover, Germany Abstract This paper presents an experimental investigation into the behavior of open-ended Fe-based Shape Memory Alloy (Fe-SMA) tubes under biaxial pre-straining conditions, focusing on development of interface contact pressure as a result of the shape memory effect (SME). During the pre-straining process of Fe-SMA tubes, the cross-section undergoes complete inelastic deformation with a non uniform distribution. Consequently, non-uniform biaxial pre-strain emerges across the cross-section, leading to the formation of stress-induced martensite in both the radial and circumferential directions. This results in the alteration of the SME due to the direction and interaction of biaxial martensite. Consequently, the material experiences a complex pre-strain state, posing challenges in assessing the SME in Fe-SMA tubes. Nevertheless, it is possible to interpret the complex overall SME performance on the basis of measurements of the resultant pressure exerted by the Fe-SMA tube on a substance, thereby limiting its free recovery. This study explores the development of the interface contact pressure highlighting the impact of heat-treatment on the gripping capacity in Fe-SMA tubes. Via coupling of analytical models with results extracted from an experimental campaign, the resultant pressure at the interface throughout the course of activation is quantified aiding to assess the SME performance. The experimental setup involves Fe-SMA and steel tubes enabling the quantification of interface contact pressure through principal strain measurements at the inner diameter of the steel tube, allowing for differentiation of SME performance under as-received and heat-treated conditions. © 2024 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 SMAR 2024 Organizers Keywords: Iron-based shape memory alloy, Bi-axial Shape memory effect, Contact pressure quantification SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Contact Pressure Evolution in Heat-Treated Iron-Based Shape Memory Joints Ali Jafarabadi a,b,* , Christoph Czaderski a , Maryam Mohri a , Christian Leinenbach a,c , Elyas Ghafoori d , Eleni Chatzi b , Masoud Motavalli a a Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland, b Institute of Structural Engineering, Swiss Federal Institute of Technology Zürich (ETH-Zürich), 8093 Zürich, Switzemrland, c Laboratory for Photonic Materials and Characterization, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, d Institute for Steel Construction, Faculty of Civil Engineering and Geodetic Science, Leiübniz University Hannover, 30167 Hannover, Germany Abstract This paper presents an experimental investigation into the behavior of open-ended Fe-based Shape Memory Alloy (Fe-SMA) tubes under biaxial pre-straining conditions, focusing on development of interface contact pressure as a result of the shape memory effect (SME). During the pre-straining process of Fe-SMA tubes, the cross-section undergoes complete inelastic deformation with a non uniform distribution. Consequently, non-uniform biaxial pre-strain emerges across the cross-section, leading to the formation of stress-induced martensite in both the radial and circumferential directions. This results in the alteration of the SME due to the direction and interaction of biaxial martensite. Consequently, the material experiences a complex pre-strain state, posing challenges in assessing the SME in Fe-SMA tubes. Nevertheless, it is possible to interpret the complex overall SME performance on the basis of measurements of the resultant pressure exerted by the Fe-SMA tube on a substance, thereby limiting its free recovery. This study explores the development of the interface contact pressure highlighting the impact of heat-treatment on the gripping capacity in Fe-SMA tubes. Via coupling of analytical models with results extracted from an experimental campaign, the resultant pressure at the interface throughout the course of activation is quantified aiding to assess the SME performance. The experimental setup involves Fe-SMA and steel tubes enabling the quantification of interface contact pressure through principal strain measurements at the inner diameter of the steel tube, allowing for differentiation of SME performance under as-received and heat-treated conditions. © 2024 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 SMAR 2024 Organizers Keywords: Iron-based shape memory alloy, Bi-axial Shape memory effect, Contact pressure quantification © 2024 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 SMAR 2024 Organizers

* Corresponding author. Tel.: +41-587-654-055 E-mail address : ali.jafarabadi@empa.ch * Corresponding author. Tel.: +41-587-654-055 E-mail address : ali.jafarabadi@empa.ch

2452-3216 © 2024 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 SMAR 2024 Organizers 2452-3216 © 2024 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 SMAR 2024 Organizers

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