PSI - Issue 75

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia (2025) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia (2025) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 75 (2025) 450–456

www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia

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 the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper 10.1016/j.prostr.2025.11.045 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 the scientific committee of the Fatigue Design 2025 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 the scientific committee of the Fatigue Design 2025 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 the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper All specimens exhibited cyclic softening; the evolutions of stress amplitudes with the current number of cycles merged into a single curve until damage development. Prior tensile deformation reduced fatigue lifetime by approximately 10%, without altering the Manson-Coffin exponent, and the cumulative plastic strain at fracture also decreased. These effects were consistent regardless of prior deformation conditions. In a given specimen, several fatigue cracks initiated from persistent slip bands and propagated independently, extending toward the specimen axis up to 25% of the specimen radius. Comparison between cold-formed and tensile prestrained specimens showed that prior tensile plastic deformation proved effective in assessing the residual low cycle fatigue strength of cold deformed high strength martensitic steel. Keywords: High strength martensitic steels; low cycle fatigue; fatigue lifetime; predeformation 1. Introduction Exploration and production of oil and gas involves using a full range of seamless steel tubes including casing, tubing and accessories. Connections between tubes such as VAM® premium connections provided by Vallourec All specimens exhibited cyclic softening; the evolutions of stress amplitudes with the current number of cycles merged into a single curve until damage development. Prior tensile deformation reduced fatigue lifetime by approximately 10%, without altering the Manson-Coffin exponent, and the cumulative plastic strain at fracture also decreased. These effects were consistent regardless of prior deformation conditions. In a given specimen, several fatigue cracks initiated from persistent slip bands and propagated independently, extending toward the specimen axis up to 25% of the specimen radius. Comparison between cold-formed and tensile prestrained specimens showed that prior tensile plastic deformation proved effective in assessing the residual low cycle fatigue strength of cold deformed high strength martensitic steel. Keywords: High strength martensitic steels; low cycle fatigue; fatigue lifetime; predeformation 1. Introduction Exploration and production of oil and gas involves using a full range of seamless steel tubes including casing, tubing and accessories. Connections between tubes such as VAM® premium connections provided by Vallourec Fatigue Design 2025 (FatDes 2025) Effect of prior plastic deformation on the fatigue behavior of a high strength martensitic steel D. Tousse Tchamassi a , H. Nouri b , O. Cazier b , M Piette b , Y. Madi a , A.-F. Gourgues Lorenzon a * a Mines Paris – PSL, CMAT – Centre des Matériaux, UMR CNRS 7633, BP 87, 91003 Evry Cedex, France b Vallourec ONE R&D, 60 Route de Leval, 59620 Aulnoye-Aymeries, France Abstract This study investigates the impact of prior plastic strain deformation on the residual fatigue lifetime and crack mechanisms of a high-strength martensitic steel. Polished low-cycle fatigue specimens were tested with and without prior tensile deformation up to 4%. Additional specimens were cut from components that underwent cold forming and stress relieving. Manson-Coffin curves were determined, and damage mechanisms were analyzed using 2D and 3D techniques. Fatigue Design 2025 (FatDes 2025) Effect of prior plastic deformation on the fatigue behavior of a high strength martensitic steel D. Tousse Tchamassi a , H. Nouri b , O. Cazier b , M Piette b , Y. Madi a , A.-F. Gourgues Lorenzon a * a Mines Paris – PSL, CMAT – Centre des Matériaux, UMR CNRS 7633, BP 87, 91003 Evry Cedex, France b Vallourec ONE R&D, 60 Route de Leval, 59620 Aulnoye-Aymeries, France Abstract This study investigates the impact of prior plastic strain deformation on the residual fatigue lifetime and crack mechanisms of a high-strength martensitic steel. Polished low-cycle fatigue specimens were tested with and without prior tensile deformation up to 4%. Additional specimens were cut from components that underwent cold forming and stress relieving. Manson-Coffin curves were determined, and damage mechanisms were analyzed using 2D and 3D techniques. * Corresponding author. Tel.: +33-171416350, no fax currently available. E-mail address: anne-francoise.gourgues-lorenzon@minesparis.psl.eu * Corresponding author. Tel.: +33-171416350, no fax currently available. E-mail address: anne-francoise.gourgues-lorenzon@minesparis.psl.eu