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MM: Fachverband Metall- und Materialphysik
MM 16: Mechanical Properties
MM 16.3: Vortrag
Dienstag, 6. September 2022, 14:30–14:45, H44
Influence of crack tip radius on fracture toughness: an atomistic study — •Tarakeshwar Lakshmipathy1 and Erik Bitzek1,2 — 1Department of Materials Science and Engineering, Institute I, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany — 2Department Computational Materials Design, Max-Planck-Institut für Eisenforschung, Germany
In fracture mechanics, initial cracks are typically assumed to be infinitely sharp, leading to a singularity in the crack tip stress field. However, on the atomic scale, crack tips have a radius of at least one atomic distance, which removes the singularity and leads to high, but finite stresses directly at the crack tip. Furthermore, cracks may blunt due to various reasons which leads to an increase in the macroscopic stress to reinitiate a sharp crack. Using harmonic "snapping spring" nearest-neighbor potentials which provide the closest match to linear elastic fracture mechanics (LEFM) on a discrete lattice, we show that the LEFM model for sharp cracks is insufficient to describe the boundary value problem (BVP) of blunted cracks at the atomic scale. We also show that the LEFM-based equations for blunted cracks are insufficient to describe the stress distribution ahead of atomically blunted cracks. We develop a semi-empirical scaling relation for blunted cracks using the LEFM-based equations for elliptical cracks by introducing a factor to account for the deviations. Furthermore, we identify a lower bound for the maximum crack tip radius at which this factor stops playing a role and a scaling model from the unmodified LEFM-based equations for elliptical cracks can be used.