PSI - Issue 68

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

www.elsevier.com/locate/procedia

Procedia Structural Integrity 68 (2025) 439–445

European Conference on Fracture 2024 High Temperature Fracture Toughness Tests on P91 Steel for Fusion Applications A.F Perez a *, T.F. Calvet a , Y. Wang b , C.M. Davies a a Imperial College London, Department of Mechanical Engineering, South Kensington Campus, London, SW7 2AZ, UK b UK Atomic Energy Authority, Culham Science Centre, Abingdon, OX14 3DB, UK Abstract Steels used in fusion reactors must maintain structural integrity and safety under extreme conditions, including high temperatures and 14MeV neutron irradiation. Fracture toughness is influenced by geometry, temperature, and loading conditions. Due to the limited availability of irradiated materials, using small-scale samples is desirable. In this work, fracture toughness tests were performed on three compact tension samples (50 mm wide and 25 mm thick) made from Grade P91 steel, a material similar to EUROFER97, at 600°C. Crack length was monitored using Direct Current Potential Drop method, while surface strains were measured via Digital Image Correlation. The average !" value was found to be equal to 321 kPa·m, though significant plastic deformation around the crack tip was observed. This deformation, combined with the non-rectilinear crack propagation, led to questioning the predictions of the standards, with a final !" value of 800 kPa·m based on physical crack extension measurements. The influence of sample size was also explored, revealing that larger specimens are more likely to achieve plane strain conditions, while miniature ones tend to exhibit plane stress dominance at the crack tip, leading to lower toughness values. © 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: Fracture toughness tests ; J-R curves ; Direct Current Potential Drop method ; Digital Image Correlation ; Tunnelling effect 1. Introduction Two main approaches to achieving nuclear fusion exist: inertial fusion utilized by the National Ignition Facility (NIF), and magnetic confinement employed by the International Thermonuclear Experimental Reactor (ITER) project. © 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.: +33 6 76 66 80 15. E-mail address: arthur.perez@gadz.org

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.2025.06.079 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