A MICROMECHANICAL VIEW OF THE FRACTURE TOUGHNESS OF ICE

Des essais de ténacité ont été réalisés avec de la glace d'eau douce en fonction de la taille de grains, de la température et de la vitesse de chargement. Les résultats montrent que la ténacité augmente avec la température et décroît avec la taille des grains. La ténacité est constante avec la vitesse de chargement ([MATH]) au dessus d'une vitesse critique [MATH]t qui dépend de la température. En dessous de [MATH]t la ténacité augmente lorsque [MATH] décroît. Les résultats sont interprétés à l'aide d'un modèle micromécanique.Fracture toughness tests have been performed on freshwater ice as a function of grain size, temperature, and loading rate. Results indicate that toughness increases as temperature and grain size decrease. Toughness is constant with loading rate ([MATH]) above a critical loading rate, [MATH]t, which is temperature dependent. Below [MATH]t the toughness increases as [MATH] decreases. The results are explained in terms of a micromechanical model

Coulombing faulting from the grain scale to the geophysical scale: Lessons from ice

International audienceCoulombic faulting, a concept formulated more than two centuries ago, still remains pertinent in describing the brittle compressive failure of various materials, including rocks and ice. Many questions remain, however, about the physical processes underlying this macroscopic phenomenology. This paper reviews the progress made in these directions during the past few years through the study of ice and its mechanical behaviour in both the laboratory and the field. Fault triggering is associated with the formation of specific features called comb-cracks and involves frictional sliding at the micro(grain)-scale. Similar mechanisms are observed at geophysical scales within the sea ice cover. This scale-independent physics is expressed by the same Coulombic phenomenology from laboratory to geophysical scales, with a very similar internal friction coefficient (μ ≈ 0.8). On the other hand, the cohesion strongly decreases with increasing spatial scale, reflecting the role of stress concentrators on fault initiation. Strong similarities also exist between ice and other brittle materials such as rocks and minerals and between faulting of the sea ice cover and Earth's crust, arguing for the ubiquitous nature of the underlying physics

The Ductility of Ni3Al and the accommodation of slip at grain boundaries

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