Fracture mechanics models for short crack growth estimation and fatigue strength assessment

Modelos fractomecánicos para la estimación del crecimiento de fisuras cortas y la evaluación de la resistencia a la fatiga

ABSTRACT

The fatigue strength assessment of metallic components containing manufacturing defects is currently analysed by applying fracture mechanics-based methodologies. This work begins by dealing with the recently published paper entitled “Short crack propagation analysis and fatigue strength assessment of additively manufactured materials: an application to AISI 316L”, Int J Fatigue 151 (2021) 106396, by Bergant, Werner, Madia, Yawny and Zerbst, where IBESS approach and Chapetti´s short crack growth threshold models were implemented for assessing the fatigue strength of laser powder bed fusion processed AISI 316L stainless steels. The application of the Chapetti´s model is carried out here in the way its author thinks it should be made, and results show clear differences when comparing with the results of the referenced paper. Analyses of the sources of discrepancy are also carried out. Some discussions associated with other recent applications of the available fracture mechanics models and hypotheses, or their combinations, are added in order to optimize future analysis when using them for short crack growth threshold estimations. Later, several analyses are made by making general observations associated with the prediction models, their hypotheses, their combinations and their relationship to the Kitagawa-Takahashi diagram. Finally, it is shown that when applying the fracture mechanics models special attention is necessary when comparing intrinsic strengths of the analysed material and that of material-defect combinations, particularly when the defects used in the analysis are artificial and/or are relatively large comparing with the microstructural dimension.

Keywords
Fracture Mechanics; Microstructural Fatigue Threshold; Short cracks; Fatigue Strength Estimation; Small Defect Assessment