These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Fatigue is the predominant cause of structural failure under cyclic loading conditions. Fatigue failure typically involves two main stages: an initial phase where one or more cracks form (crack initiation stage), followed by a phase where these cracks, if subject to sufficiently high cyclic stress, grow until failure (crack propagation stage). The relative duration of these stages varies based on factors such as material properties, structural design, and application. Furthermore, in some cases, a crack may extend into a low-stress region, halting its progression and preventing failure. In such scenarios, the crack may be considered acceptable in-service, as it does not compromise the component's durability (damage tolerance approach). The term '˜fatigue crack growth'™ refers to the propagation (or not) of cracks under cyclic loading. Since the 1950s, extensive research has focused on understanding and characterizing crack propagation under cyclic loading. This includes defining threshold, propagation, and fast fracture regions from both experimental and numerical perspectives, as well as accounting for mean stress effects and crack retardation. Unfortunately, this research is dispersed across numerous scientific publications. Furthermore, common simulation methods often focus on either the initiation or propagation stage, which can lead to inaccurate fatigue life predictions when both stages are significant. This issue is particularly relevant for welded structures, lightweight jointed structures, and lightweight cast components, which are increasingly important for more environmentally sustainable transportation solutions. The aim of this work is to enable a more efficient review and comparison of available crack growth analysis tools to support informed decision-making, by collecting the most relevant fatigue crack growth laws and models into a single document. Additionally, this work introduces a unified fatigue life estimation approach, called the 'œTotal-Life' method, that integrates both the initiation and propagation stages, by combining principles from strain-life and fracture mechanics, and a state-of-the-art multiaxial crack-tip plasticity model to account for mean-stress and overload retardation effects.