PSI - Issue 59

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Procedia Structural Integrity 00 (2024) 000 – 000

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ScienceDirect

Procedia Structural Integrity 59 (2024) 198–205

VII International Conference “In -service Damage of Materials: Diagnostics and Prediction ” (DMDP 2023) Role of hydrostatic stress in hydrogen diffusion and embrittlement

of pearlitic steel in the presence of notches In the Name of Johann Sebastian Bach Jesús Toribio * Fracture & Structural Integrity Research Group (FSIRG), University of Salamanca (USAL) E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain

© 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 DMDP 2023 Organizers Abstract The relevant role of hydrostatic stress in hydrogen diffusion and embrittlement of pearlitic steel in the vicinity of notches is outlined. The theoretical statement is based on hydrogen diffusion equations where hydrogen flux density depends not only on the concentration gradient, but also on the hydrostatic stress distribution in the sample ( stress-assisted hydrogen diffusion ). The experimental programme consisted of slow strain rate tests (SSRT) on axisymmetric notched samples at different strain rates under simultaneous hydrogen charging by cathodic polarization. The use of different notched geometries allows a study of the influence on hydrogen diffusion of the hydrostatic stress state in the vicinity of the notch tip. A specific microscopic mode of fracture different from classical cleavage was found, associated with hydrogen effects: the tearing topography surface (TTS). In the quasi-instantaneous tests , the value of hydrostatic stress at the sample boundary (just the notch tip) at the failure instant is relevant from the fracture point of view. Concerning the quasi-static tests , the TTS depth equals that of the maximum hydrostatic stress point, and the maximum value of the stress triaxiality in each geometry (ratio of the hydrostatic to the equivalent stress, almost constant during the tests) seems to govern the diffusion process. These facts emphasize the relevant role of hydrostatic stress in the vicinity of the notch in hydrogen diffusion and embrittlement of pearlitic steel. © 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 DMDP 2023 Organizers

* Corresponding author. Tel.: +34-677566723; fax: +34-980545002. E-mail address: toribio@usal.es

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 DMDP 2023 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 DMDP 2023 Organizers 10.1016/j.prostr.2024.04.029