PSI - Issue 68

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 68 (2025) 1081–1090

European Conference on Fracture 2024 Hollow specimen method for mechanical testing in gaseous hydrogen Robert Sundström a,b, * a Department of Engineering Science, University West, SE-461 86 Trollhättan, Sweden b Production Technology Department, Swerim AB, SE-164 07 Kista, Sweden Abstract Hydrogen embrittlement remains a problem in many applications. Rocket engines that use hydrogen as a propellant have small margins, operating in harsh conditions with weight-minimizing design requirements, and additive manufacturing is increasingly used to meet these goals. Rapid, inexpensive testing methods for assessing mechanical properties in gaseous hydrogen are needed to characterize additively manufactured alloys. A hollow specimen geometry has been used for evaluating these properties, and a standard was published in 2024. Research using autoclaves indicates that surface condition can influence results. The hollow specimen has an inner surface that is difficult to polish. Studies show that this geometry gives higher relative reductions of area in slow strain rate testing compared to solid specimens in hydrogen. This paper provides an overview of the benefits, drawbacks, status, and future developments of this method. Based on a literature review, it discusses the history, its use in other fields, manufacturing methods, surface condition, gas purity, and comparisons with solid specimens. The method requires attention to inner surface condition as it can influence results when ranking materials based on embrittlement indicators. Current research indicates it is potentially suitable for quasi-static tensile testing, providing a hydrogen embrittlement index based on ductility. Further work is needed to refine testing parameters, investigate reproducibility, and assess its suitability for fatigue testing in gaseous hydrogen. © 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: hollow; tubular; review; ISO 7039; hydrogen embrittlement; rocket engine; additive manufacturing © 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.: +46-722-356-714 E-mail address: robert.sundstrom@hv.se

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

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.2025.06.173