Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions
We performed high-strain torsion experiments on aggregates of Fo 50 olivine to test the influence of imposed boundary conditions on localizing deformation. We deformed both solid and thin-walled cylinders of Fo 50 either at constant strain rate or at constant stress. Samples deformed in constant-str...
| Main Authors: | , , , |
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| Format: | Journal article |
| Language: | English |
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2012
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| _version_ | 1826292109218414592 |
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| author | Hansen, L Zimmerman, M Dillman, A Kohlstedt, D |
| author_facet | Hansen, L Zimmerman, M Dillman, A Kohlstedt, D |
| author_sort | Hansen, L |
| collection | OXFORD |
| description | We performed high-strain torsion experiments on aggregates of Fo 50 olivine to test the influence of imposed boundary conditions on localizing deformation. We deformed both solid and thin-walled cylinders of Fo 50 either at constant strain rate or at constant stress. Samples deformed in constant-strain-rate experiments reached a peak stress followed by weakening at a continually decreasing weakening rate. In contrast, samples deformed in constant-stress experiments weakened at an accelerating weakening rate. Localization is manifested in samples deformed at constant stress as irregularities along strain markers, S-C foliations, and torsional buckling of thin-walled cylinders. In contrast, samples deformed at constant strain rate deformed homogeneously. Grain-boundary maps created with electron-backscatter-diffraction data indicate that high-strain regions in constant-stress samples correlate with finer grain sizes and stronger crystallographic fabrics. Since the dominant deformation mechanism is grain-size sensitive, heterogeneous recrystallization leads to strain localization in finer-grained regions. However, variations in strength are not large enough to initiate localization in constant-strain-rate experiments. The magnitude of grain-size heterogeneity remains relatively constant with increasing strain, implying that shear zones are maintained throughout the experiments even as non-localizing regions recrystallize. Based on our results, we propose that deformation driven at constant stress in Earth's lithosphere will easily localize even if structural heterogeneities are not initially present. © 2012 Elsevier B.V. |
| first_indexed | 2024-03-07T03:09:37Z |
| format | Journal article |
| id | oxford-uuid:b3bd013f-3dbf-4547-936d-5c4061b0185a |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T03:09:37Z |
| publishDate | 2012 |
| record_format | dspace |
| spelling | oxford-uuid:b3bd013f-3dbf-4547-936d-5c4061b0185a2022-03-27T04:21:22ZStrain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditionsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:b3bd013f-3dbf-4547-936d-5c4061b0185aEnglishSymplectic Elements at Oxford2012Hansen, LZimmerman, MDillman, AKohlstedt, DWe performed high-strain torsion experiments on aggregates of Fo 50 olivine to test the influence of imposed boundary conditions on localizing deformation. We deformed both solid and thin-walled cylinders of Fo 50 either at constant strain rate or at constant stress. Samples deformed in constant-strain-rate experiments reached a peak stress followed by weakening at a continually decreasing weakening rate. In contrast, samples deformed in constant-stress experiments weakened at an accelerating weakening rate. Localization is manifested in samples deformed at constant stress as irregularities along strain markers, S-C foliations, and torsional buckling of thin-walled cylinders. In contrast, samples deformed at constant strain rate deformed homogeneously. Grain-boundary maps created with electron-backscatter-diffraction data indicate that high-strain regions in constant-stress samples correlate with finer grain sizes and stronger crystallographic fabrics. Since the dominant deformation mechanism is grain-size sensitive, heterogeneous recrystallization leads to strain localization in finer-grained regions. However, variations in strength are not large enough to initiate localization in constant-strain-rate experiments. The magnitude of grain-size heterogeneity remains relatively constant with increasing strain, implying that shear zones are maintained throughout the experiments even as non-localizing regions recrystallize. Based on our results, we propose that deformation driven at constant stress in Earth's lithosphere will easily localize even if structural heterogeneities are not initially present. © 2012 Elsevier B.V. |
| spellingShingle | Hansen, L Zimmerman, M Dillman, A Kohlstedt, D Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title | Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title_full | Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title_fullStr | Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title_full_unstemmed | Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title_short | Strain localization in olivine aggregates at high temperature: A laboratory comparison of constant-strain-rate and constant-stress boundary conditions |
| title_sort | strain localization in olivine aggregates at high temperature a laboratory comparison of constant strain rate and constant stress boundary conditions |
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