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Mécanismes de rupture dans le verre à l'échelle nanométrique

Abstract : The aim of this PhD. thesis is to identify the physical mechanisms involved in the fracture of glassy materials. An original experimental set-up – based on Atomic Force Microscopy - has been developed to follow in real time, at the nanometer scale, the very slow propagation of a crack in various glasses under stress corrosion. This has allowed us to show that the crack propagation occurs through growth and coalescence of damage cavities. Different glasses –from very complex ones to pure amorphous silica - have been investigated in order to understand the influence of the nanostructure. Same mechanisms of growth and coalescence of damage cavities were observed. This nano-ductile behaviour has macroscopic consequences: (i) the out-of-plane displacement field shows a departure from the one predicted by the Linear Elastic Fracture Mechanics (LEFM) in the vicinity of the crack tip; (ii) The macroscopic speed of the crack front is dominated by the accelerating phases corresponding to the coalescence events between the main crack tip and the cavity ahead. The morphology of the fracture surfaces and its variation with respect to the average crack growth velocity have also been investigated. All the fracture surfaces exhibit a self-affine regime characterized by a roughness exponent equal to 0.8 up to a correlation length xi. Variation of this length xi as a function of the average crack tip velocity is similar to the one presented by the extension of the non-linear elastic zone. Such observations on the post-mortem fracture surface allow to probe the fracture mechanisms within the bulk of the sample. They provide a rather strong argument as for the existence of damage cavities within the bulk of our specimen.
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https://tel.archives-ouvertes.fr/tel-00007499
Contributor : Silke Prades <>
Submitted on : Wednesday, November 24, 2004 - 12:01:46 PM
Last modification on : Friday, March 5, 2021 - 3:12:04 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:59:50 PM

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  • HAL Id : tel-00007499, version 1

Citation

Silke Prades. Mécanismes de rupture dans le verre à l'échelle nanométrique. Mécanique [physics.med-ph]. Université Pierre et Marie Curie - Paris VI, 2004. Français. ⟨tel-00007499⟩

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