PSI - Issue 47

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 47 (2023) 608–616

27th International Conference on Fracture and Structural Integrity (IGF27) Influence of fracture toughness and defect size on vibration characteristics and resulting stress amplitude of AISI 52100 and AISI 4140 during ultrasonic fatigue testing Jan Patrick Sippel*, Eberhard Kerscher Materials Testing (AWP), RPTU Kaiserslautern-Landau, D-67663 Kaiserslautern, Germany Abstract The fatigue failure beyond the traditional fatigue limit of 10 7 cycles, the so called very high cycle fatigue (VHCF) is constantly gaining attention due to the demand for long service life of highly stressed components to reach a better sustainability. To realize these long lifetimes economically, ultrasonic test benches are commonly used for VHCF testing. In contrast to conventional testing using servo-hydraulic test setups, force control cannot be realized while testing with ultrasonic test setups. The loading of the specimen is realized by means of excitation with natural frequency of the oscillating system and the resulting standing longitudinal wave. For high-strength steels, most of the fatigue life in VHCF regime is accounted for by the crack initiation phase, during which the natural frequency of the specimen is nearly constant. However, as the fatigue crack grows, the natural frequency of the specimen and therefore that of the test setup drops. Depending on the fracture toughness of the tested material, a frequency drop and an associated stress drop are observed at the end of the test. Therefore, a resulting discontinuous residual stress fracture surface is observed in case of AISI 4140, but not in case of AISI 52100. In this publication, the different effects of the natural frequency of the system and the indirectly affected stress amplitudes during fatigue testing of AISI 52100 and AISI 4140, as well as the resulting fracture surface topographies, are discussed. In addition, the relationship between the roughness of the different fracture surface areas is compared with the fracture surface morphology to draw conclusions about the crack propagation behavior.

* Corresponding author. Tel.: +49-631-205-5453; E-mail address: j.sippel@rptu.de

2452-3216 © 2023 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 IGF27 chairpersons

2452-3216 © 2023 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 IGF27 chairpersons 10.1016/j.prostr.2023.07.062