Viscous-Flow-to-Fracture Transition of linear Maxwell‐type vs. yield strength fluids by air injection–implications for magma fracturing and acoustic emission
| Quand ? |
Le 04/06/2024, de 11:00 à 12:00 |
|---|---|
| Où ? | Salle des thèses |
| S'adresser à | Valérie Vidal |
| Participants |
Claudia Sánchez |
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How flowing magma breaks like a solid is a fundamental problem that has been investigated for decades. This talk introduces a study on the flow and fracture of complex fluids, consisting of experimental approaches. In volcanology, the glass transition is considered to appear at high strain rates and control the brittle fracture of magma. In physics, on the other hand, the glass transition is more frequently associated with the appearance of yield strength at low strain rates. The present study investigates bubble growth and fracture by air injection in Maxwell-type and Bingham-type fluids, both having similar elasticity. We demonstrate that brittle fracture occurs in the Maxwell fluid at high air flux but never in the Bingham fluid. Detailed observations of the deformation until brittle fracture reveals a stress increase and strain rate decrease. The fracture onset is not determined by the critical strain rate, contrary to conventional brittle fragmentation criteria widely used in volcanology. Furthermore, I will show the acoustic wave generation induced by bubble growth and bursting in two distinct fluids. The waveform and frequency of the acoustic signals generated by these fluids display pronounced variations, contingent upon factors such as flux and also the depth of air injection.