SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 38: Topical Session: Fundamentals of Fracture – Fracture Experiments

MM 38.2: Vortrag

Donnerstag, 30. März 2023, 10:45–11:00, SCH A 215

Macro to micro in fracture - shorter is tougher — •Dov Sherman — School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel

Fracture of brittle solids is ultimately executed by atomistic-scale, discrete, and ultrafast bond-breaking mechanisms along the crack path. Here, we show new fracture behavior and properties of brittle materials not previously explored. It is based on macroscopic fracture cleavage experiments of brittle single-crystal silicon specimens, including cracks energy-speed relationships, and an atomistic-scale semi-empirical model for bond-breaking mechanisms in form of planer kinks along the (curved) crack front. As a result, we identified that the cleavage energy is not a constant but bounded by the Griffith Barrier and lattice-trapping barrier. Hence, a brittle material can be envisaged as having a pseudo-R-Curve behavior typical of metallic materials. A new and essential fracture mechanism was identified, which we termed *quasi-propagation*, occurring between initiation and propagation. During this mechanism, the sequence of the bond-breaking mechanisms is varying, causing an increase in the macroscale cleavage energy. The range of these changes is dictated by the energy release rate and its first derivative following initiation. The evaluated cleavage energy shows that *shorter is tougher* and hence the material is stronger than that predicted by the Griffith theory.