PSI - Issue 75

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ScienceDirect

Procedia Structural Integrity 75 (2025) 419–425 Structural Integrity Procedia 00 (2025) 000–000 Structural Integrity Procedia 00 (2025) 000–000

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Fatigue Design 2025 (FatDes 2025) Modelling of the Test Frequency Discrepancy in USF Testing of Structural Steels Lewis Milne a , Yevgen Gorash a, ∗ , Tugrul Comlekci a , Donald MacKenzie a , Carl Walker b Fatigue Design 2025 (FatDes 2025) Modelling of the Test Frequency Discrepancy in USF Testing of Structural Steels Lewis Milne a , Yevgen Gorash a, ∗ , Tugrul Comlekci a , Donald MacKenzie a , Carl Walker b

a Weir Advanced Research Centre, University of Strathclyde, Glasgow, Scotland, UK b Weir Minerals Australia, Divisional Technology, 1 Marden Street, Artarmon, Australia a Weir Advanced Research Centre, University of Strathclyde, Glasgow, Scotland, UK b Weir Minerals Australia, Divisional Technology, 1 Marden Street, Artarmon, Australia

© 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 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers. Keywords: Structural steel; Very High Cycle Fatigue; Ultrasonic Testing; High strain rate testing; Frequency e ff ect Abstract This research addresses the discrepancy in fatigue resistance between the test data for conventional test frequency and accelerated frequency for common structural steels. As the most commonly attributed factor for the di ff erence is the increase in strain rate at elevated test frequencies, high strain rate tensile tests were carried out to evaluate the influence of strain rate on material strength. The tested steels exhibited an increase in yield strength of 28-48% at strain rates corresponding to 20kHz. Normalising the SN curves by the dynamic yield strength was not su ffi cient to account for the discrepancy in fatigue resistance, however, pointing to the existence of some other factor influencing the frequency sensitivity. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers. Keywords: Structural steel; Very High Cycle Fatigue; Ultrasonic Testing; High strain rate testing; Frequency e ff ect Abstract This research addresses the discrepancy in fatigue resistance between the test data for conventional test frequency and accelerated frequency for common structural steels. As the most commonly attributed factor for the di ff erence is the increase in strain rate at elevated test frequencies, high strain rate tensile tests were carried out to evaluate the influence of strain rate on material strength. The tested steels exhibited an increase in yield strength of 28-48% at strain rates corresponding to 20kHz. Normalising the SN curves by the dynamic yield strength was not su ffi cient to account for the discrepancy in fatigue resistance, however, pointing to the existence of some other factor influencing the frequency sensitivity. Unalloyed low-carbon steel grades S355JR, Q355B, S275JR, S275J2, according to EN 10025-2 (2019), are com mon structural materials for the heavy machinery in minerals, sand-&-aggregate applications. A medium carbon steel C45, according to EN 10083-1 (2006), o ff ers exceptional tensile strength, a key feature for components that must withstand intense forces, with a good machinability similar to that of mild steels, however reduced weldability. Steel 080A15, according to EN 10277-1 (2018), is a mild steel for general engineering use with weldability characteristics, but poor hardenability, therefore suitable for the production of low-stressed components such as shafts, gears and threaded bars. Currently, heavy machinery components are designed with high safety factors against SN curves with an assumed asymptotic fatigue limit above > 10 7 load cycles. Nevertheless, fatigue cracks are seen even at the high number of cycles ( > 10 8 ), producing a noticeable scatter of the fatigue data (over an order of magnitude) as the stress reduces. While high-cycle fatigue (HCF) failure occurs at the surface, fatigue cracks at the very high number of cycles ( > 10 8 ) may initiate at oxides or intermetallic inclusions below the surface (or slag and flux inclusions for welds) typ- Unalloyed low-carbon steel grades S355JR, Q355B, S275JR, S275J2, according to EN 10025-2 (2019), are com mon structural materials for the heavy machinery in minerals, sand-&-aggregate applications. A medium carbon steel C45, according to EN 10083-1 (2006), o ff ers exceptional tensile strength, a key feature for components that must withstand intense forces, with a good machinability similar to that of mild steels, however reduced weldability. Steel 080A15, according to EN 10277-1 (2018), is a mild steel for general engineering use with weldability characteristics, but poor hardenability, therefore suitable for the production of low-stressed components such as shafts, gears and threaded bars. Currently, heavy machinery components are designed with high safety factors against SN curves with an assumed asymptotic fatigue limit above > 10 7 load cycles. Nevertheless, fatigue cracks are seen even at the high number of cycles ( > 10 8 ), producing a noticeable scatter of the fatigue data (over an order of magnitude) as the stress reduces. While high-cycle fatigue (HCF) failure occurs at the surface, fatigue cracks at the very high number of cycles ( > 10 8 ) may initiate at oxides or intermetallic inclusions below the surface (or slag and flux inclusions for welds) typ- 1. Introduction and motivation 1. Introduction and motivation

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.2025.11.041 ∗ Corresponding author. Mob.: + 44-790-9780901; Tel.: + 44-141-4447969. E-mail address: yevgen.gorash@strath.ac.uk 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers. ∗ Corresponding author. Mob.: + 44-790-9780901; Tel.: + 44-141-4447969. E-mail address: yevgen.gorash@strath.ac.uk 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers.