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| Titel |
Up-scaling of the fracture energy in heterogeneous media during brittle creep experiments |
| VerfasserIn |
Olivier Lengliné, Jean Schmittbuhl, Jean Elkhoury, Jean-Paul Ampuero, Renaud Toussaint, Knut Jørgen Måløy |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054534
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| Zusammenfassung |
| The fracture energy (Gc) of an heterogeneous material is mainly controlled by the
fluctuations of its local strength. However relating these microscopic variations to a
global criterion defining the condition of crack propagation inside the material is not
straightforward. The front dynamics at large scale in the creep regime is shown to correspond
to a roughly constant value of G (energy release rate). It is also found to be well described by
an Arrhenius law. It is not yet clear how this evolution law is influenced by disorders over the
crack interface. Such influence has strong implications on many geological processes as the
brittle-ductile transition and the nucleation process of earthquakes. Here we present a series
of mode I experiments on two heterogeneous welded plexi-glass plates where we
measure Gc over a wide range of scales. Material heterogeneities are generated by
glass-beads blasting of the 2D surfaces prior to welding. Ruptures are confined to
the 2D interface between the two plates and propagation is initiated upon loading.
We track the progression of a slow rupture front line with optical imaging taking
advantage of the optical contrast between ruptured and un-ruptured parts of the
sample. We also continuously monitor the displacement and the applied force at the
loading point. This unique experimental setting provides the possibility to estimate
Gc during rupture under quasi-static rupture propagation conditions. We obtain
the large-scale estimate of G from the elastic energy flux due to the quasi-static
nature of the rupture propagation. Variation in the front position around its mean
provides an estimate of the heterogeneity in Gc at the smallest resolvable scale. We
show that the macroscopic estimates of fracture energy is not a simple average of
the microscopic fracture energy at local sites. The microscopic distributions of
fracture energy are systematically shifted to higher values compared to macroscopic
estimates. |
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