PSI - Issue 66

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 66 (2024) 265–281

8th International Conference on Crack Paths Crack Formation and Pathways in Nitinol Biomedical Devices A.R. Pelton a †, M.E. Launey a , W.S. LePage b , M.R. Mitchell c , J. Ulmer d a G.RAU Inc., 5617 Scotts Valley Dr., Suite 100, Scotts Valley, CA 95066 USA b Department of Mechanical Engineering, University of Tulsa, 800 S. Tucker Drive, Tulsa, OK 74104 USA c Mechanics & Materials Consulting, LLC 4447 Acrete Ln., Flagstaff, AZ 86004 USA d Euroflex GmbH, Kaiser-Friedrich-Str. 7, 75172 Pforzheim DE

Abstract Nitinol is a near equiatomic intermetallic that is increasingly being used in medical devices due to its unique shape memory behaviors of both superelasticity and shape memory effect, as well as its ability to be heat set into complex shapes. The metallurgical characteristics and properties rely on a diffusionless solid-state phase transformation between cubic Austenite and monoclinic Martensite. Such implanted Nitinol devices may experience millions to billions of in vivo cyclic deformations; these cycles may result in microstructural damage accumulation with the result of functional fatigue (e.g., change in strain recovery, transformation temperature, displacements and/or forces) and/or structural fatigue ( e.g ., cracks and fractures). Consequently, lifetime predictions of components are critical for the design and optimization of devices manufactured from Nitinol. Although most medical device companies conduct total life fatigue tests on their devices, damage-tolerant fatigue assessment is also important in order to understand safe-use conditions. This paper reviews the literature on investigations of crack formation and propagation in Nitinol materials under a variety of conditions. © 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 CP 2024 Organizers © 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 CP 2024 Organizers

* Corresponding author.. E-mail address: alan.pelton@g-rau.com

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 CP 2024 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 CP 2024 Organizers 10.1016/j.prostr.2024.11.076