PSI - Issue 76

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 76 (2026) 89–98

© 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 FDMD 2025 chairpersons Keywords: Fracture mechanics; Defect assessment; Fatigue resistence estimation This work advances the understanding of the essential structure of traditional S-N curves and the limitations they display in describing results. Proposed alternatives, as documented in the literature, are critically analyzed, and a new alternative is proposed, based on fracture mechanics methodologies that allow the entire propagation process to be quantified and the deficiencies of previous proposals to be explained. 1. Introduction When Wohler (1860) introduced the fatigue resistance Ds - N curve, the goal was to study basic fatigue behavior without explicitly considering the effects of material defects. The main focus was on determining fatigue endurance for a given life to enable safe designs. This approach remains common today, with Ds - N curves still widely used in fatigue design. Over time, various expressions were proposed to fit experimental Ds - N data and describe material fatigue resistance. Basquin (1910) first modeled s-N data with the exponential equation Ds = C 1 N C2 , which does not account for a fatigue limit or endurance. Later, several modified models were introduced (Stromeyer 1914, Palmgren 1924, Weibull 1949, D´Antuono 2020), but they primarily rely on curve-fitting procedures without considering the mechanical effects of cracks or defects. Additionally, these models do not address the physical or mechanistic factors 5th International Symposium on Fatigue Design and Material Defects FDMD 2025 Fracture mechanics approaches for material defect assessment and fatigue design Mirco Daniel Chapetti National University of Mar del Plata (UNMDP), National Research Council (CONICET), INTEMA, Av. Colón 10850 (7600) Mar del Plata, Argentina Abstract The increasing demand for reliability and safety in industrial mechanical components has heightened the focus on predictive methods in long-life fatigue analysis. Advances in fracture mechanics now enable accurate estimation of fatigue life and limits in components with small cracks or crack-like defects, often introduced during manufacturing. In processes like additive manufacturing, inherent defects may bypass the crack initiation phase, accelerating the fatigue process. Consequently, the damage mechanism primarily involves crack propagation from critical defects until component failure occurs. However, the statistical variation in the size of inherent defects in certain materials or components results in significant dispersion in fatigue life under similar stress levels, making it difficult to identify and quantify the intrinsic strengths involved, and particularly challenging to compare different configurations.

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 FDMD 2025 chairpersons 10.1016/j.prostr.2025.12.291