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Physics of the H2O-weakening effect in deformation of quartz
Pongrac, Petar ; Jeřábek, Petr (advisor) ; Stipp, Michael (referee) ; Peč, Matěj (referee) ; Kronenberg, Andreas (referee)
In order to investigate the influence of H2O on relationships between mechanical behavior, microstructural properties, deformation mechanisms and H2O distribution in natural quartz aggregates, the Tana-quartzite samples were deformed with various quantities of added H2O. The samples were deformed in axial shortening setup (1) with constant conditions of 900 řC, 1 GPa and strain rate of ∼10−6 s−1 , (2) in strain rate stepping in interval ∼10−5 to ∼10−7 s−1 , and (3) in temperature stepping in interval 750 řC to 950 řC. The constant conditions experiments were carried out with added H2O in a range from 0 (as-is) to 0.5 wt%, while the strain rate and temperature stepping experiments were carried out using only as-is and 0.1 wt% H2O-added samples. With respect to their mechanical behavior, the samples after con- stant conditions experiments are grouped into low-H2O (0-0.2 wt% added H2O) and high-H2O (0.3-0.5 wt% added H2O). The low-H2O samples show relatively similar mechanical behavior, with 0.1 and 0.2 wt% H2O-added samples showing slightly lower strength compared to the as-is ones. Behavior of the high-H2O samples is more erratic and less systematic, dividing samples to the weaker ones and the stronger ones. Most of the strain in the weaker samples is localized in the vicinity of the thermocouple...
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