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| Titel |
Evolution of kink-band microstructures and rheology during torsion deformation of muscovite |
| VerfasserIn |
Santanu Misra, Jean-Pierre Burg |
| 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 |
250046299
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| Zusammenfassung |
| Kink-band formation is one of the frequent types of deformation-driven instabilities
commonly observed in layer- and fiber-composites. Natural kink-bands are reported from
strongly anisotropic, layered and/or foliated rocks principally deformed under compression
and shearing. Yet, there is a lack of detailed experimental investigations on the rheology,
deformation mechanism and evolution of kink microstructures during shear deformation of
rocks. Therefore, we investigated the development of kink bands in synthetic muscovite
aggregates during layer (001)-parallel torsion experiments with emphasis on microstructure
and rheology at different temperatures (400-600oC), pressures (100-300 MPa) and finite
shear strains (γ = 0.2-5). The kink-instabilities developed during elastic to plastic
transition (yield) at finite shear strain < 0.2. The shear stress required to form the
instabilities is a function of pressure and temperature and can range from 30 to 120
MPa within the experimental conditions. Scanning Electron Microscopy of the
deformed samples on both longitudinal and transverse sections revealed that the kink
bands are strongly asymmetric and spaced at shear strain γg < g.5. The samples
showed gentle work hardening at strains >2. . With progressive shearing the bands
were packed and became narrowly spaced either by widening of early-formed kink
bands or nucleation of new kink bands. The orientation of the kink band axes with
respect to the shear direction asymptotically decreases from ~ 60o to ~45o with
increasing strain. The rate of rotation of the kink band axes is more sensitive to
confining pressure than to temperature. A two dimensional analytical model considering
elastic-plastic rheology, inter-layer friction, confining pressure and bending energy of a
transverse anisotropic body is proposed to justify the experimental observation. |
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