PSI - Issue 75

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 75 (2025) 234–244

Fatigue Design 2025 (FatDes 2025) ‘Total - Life’ method: achieving accurate fatigue life predictions by combining strain-life and fracture mechanics Andrew Halfpenny a , Cristian Bagni a, *, Amaury Chabod b , Stephan Vervoort c a Hottinger Bruel & Kjaer UK Ltd, Advanced Manufacturing Park Technology Centre, Brunel Way, Rotherham, S60 5WG, United Kingdom b Hottinger Bruel & Kjaer France SAS, 2-4 rue Benjamin Franklin, 94370 Sucy-en-brie, France c Hottinger Bruel & Kjaer GmbH, Im Tiefen See 45, 64293 Darmstadt, Germany Abstract All components that fail through fatigue undergo a two- stage failure process: the first part of a component’s life is spent initiating one or more cracks (crack initiation stage), after this stage the crack(s) propagates to failure (crack propagation or crack growth stage). The proportion between crack initiation and crack growth depends on material, type of structure, application, etc. Traditionally, the two stages have been analysed using different physical models: generally, a strain-life (E-N) model for the crack initiation stage and a Linear Elastic Fracture Mechanics/Elastic-Plastic Fracture Mechanics (LEFM/EPFM) model for the crack propagation stage. Furthermore, common simulation methods focus either on the initiation or the propagation stage. However, this might produce inaccurate fatigue life predictions in situations where both stages are not negligible compared to the other. This is true for welded structures, lightweight jointed structures and lightweight cast components that are becoming increasingly popular and necessary to address the need for more sustainable methods of transportation. This paper presents a unified method for fatigue life estimation that combines both the initiation and the propagation stage. The proposed method, also called ‘Total - Life’, takes advantage of principles of both strain -life and fracture mechanics by combining them together and with a state-of-the-art multiaxial crack-tip plasticity model to account for mean-stress and overload retardation effects. The benefits of the ‘Total - Life’ method compared to traditional fatigue analysis methods are discussed. In order to exploit the potential of the presented method and allow its usage in a CAE environment, the ‘Total - life’ method has been implemented into a software package. The required inputs such as applied loading, finite element modelling techniques, material properties, residual stresses, etc. are also described. Finally, the ‘Total - Life’ method is applied to estimate the fatigue life of machined and welded specimens sharing the same complex shape. The results of the aforementioned analyses showed a good correlation with experimental results.

* Corresponding author. Tel.: +44-7768-091-654. E-mail address: cristian.bagni@hbkworld.com

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 the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper 10.1016/j.prostr.2025.11.025