PSI - Issue 68

ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 68 (2025) 1173–1180

European Conference on Fracture 2024 Computational framework for fatigue analysis of metals with nonconstant cyclic stress-strain curve Robert Szlosarek a *, Chinmay Salvi a , Pia Nitzsche b , Sebastian Henkel b , Horst Biermann b , Matthias Kröger a a Technische Universität Bergakademie Freiberg, Institute for Machine Elements, Design and Manufacturing, Agricolastraße 1, 09599 Freiberg, Germany b Technische Universität Bergakademie Freiberg, Institute of Materials Engineering, Gustav-Zeuner-Straße 5, 09599 Freiberg, Germany Abstract The cyclic stress-strain behavior is often modelled using the Ramberg-Osgood equation assuming that the material-related parameters are constant. However, nonconstant cyclic deformation curves are observed due to hardening or softening of the material. Fatigue tests of an experimental X2CrNiCuN17-6-4 steel were analyzed to determine the parameters in several intervals with the result that they were nonconstant. The parameters were fitted by a polynomial function to calculate the increase of damage for each cycle individually. Repeating this procedure up to the damage sum of one delivers the lifetime. The study shows the increase of computation accuracy from the approach of constant parameters to the approach of calculating the damage per cycle with transient material parameters. © 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: cyclic stress-strain curve; hardening, transient material parameters, Ramber-Osgood model, PSWT damage model 1. Introduction The cyclic stress-strain curve of metals is usually modelled using the Ramberg-Osgood equation, Ramberg and Osgood (1943). This relation is often used to perform a strain-based fatigue analysis out of the results of a linear elastic finite element analysis. Therefore, the Ramberg-Osgood equation helps to transform the quasi-static stresses European Conference on Fracture 2024 Computational framework for fatigue analysis of metals with nonconstant cyclic stress-strain curve Robert Szlosarek a *, Chinmay Salvi a , Pia Nitzsche b , Sebastian Henkel b , Horst Biermann b , Matthias Kröger a a Technische Universität Bergakademie Freiberg, Institute for Machine Elements, Design and Manufacturing, Agricolastraße 1, 09599 Freiberg, Germany b Technische Universität Bergakademie Freiberg, Institute of Materials Engineering, Gustav-Zeuner-Straße 5, 09599 Freiberg, Germany Abstract The cyclic stress-strain behavior is often modelled using the Ramberg-Osgood equation assuming that the material-related parameters are constant. However, nonconstant cyclic deformation curves are observed due to hardening or softening of the material. Fatigue tests of an experimental X2CrNiCuN17-6-4 steel were analyzed to determine the parameters in several intervals with the result that they were nonconstant. The parameters were fitted by a polynomial function to calculate the increase of damage for each cycle individually. Repeating this procedure up to the damage sum of one delivers the lifetime. The study shows the increase of computation accuracy from the approach of constant parameters to the approach of calculating the damage per cycle with transient material parameters. © 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: cyclic stress-strain curve; hardening, transient material parameters, Ramber-Osgood model, PSWT damage model 1. Introduction The cyclic stress-strain curve of metals is usually modelled using the Ramberg-Osgood equation, Ramberg and Osgood (1943). This relation is often used to perform a strain-based fatigue analysis out of the results of a linear elastic finite element analysis. Therefore, the Ramberg-Osgood equation helps to transform the quasi-static stresses © 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.: +49 3731 393653. E-mail address: robert.szlosarek@imkf.tu-freiberg.de * Corresponding author. Tel.: +49 3731 393653. E-mail address: robert.szlosarek@imkf.tu-freiberg.de

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

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.2025.06.184