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Numerical simulation coupled with in-situ annealing experiments: A new model for recovery
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A new, deterministic model for recovery integrated with the microstructural modelling platform Elle is presented here. Experimental data collected from 2D in-situ annealing experiments were used to develop and verify the simulation. The model is based on the change of strain energy related to misorientation when a virtual rotation is applied to a crystallite (i.e. physical data point). Boundary energies are calculated using the Read-Shockley relationship. The axes of rotation were selected based on the deformation geometry and potentially activated slip systems. Crystallographic rotation was applied in the case where largest reduction of energy was observed. The effect of parameters such as rotation mobility, neighbourhood size, critical misorientation and specific energy calculation method were systematically investigated. Simulations reproduced many aspects of the experiments and showed that processes were highly dependent on dislocation type and increase of long-range effects with temperature. The results suggest that dislocations remain independent entities for longer than expected, even in an organised subgrain boundary. The model could not, however, retain higher angle boundaries and always resulted in a general shift of boundary distributions towards lower angles. We suggest that the classic interpretation of boundary energies does not entirely work for misorientations that lie in the less defined part of the Read-Shockley relationship.

Research subject
URN: urn:nbn:se:su:diva-45687OAI: diva2:369339
Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2010-11-12Bibliographically approved
In thesis
1. Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
Open this publication in new window or tab >>Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Substructure dynamics incorporate all features occurring on a subgrain-scale. The substructure governs the rheology of a rock, which in turn determines how it will respond to different processes during tectonic changes. This project details an in-depth study of substructural dynamics during post-deformational annealing, using single-crystal halite as an analogue for silicate materials. The study combines three different techniques; in-situ annealing experiments conducted inside the scanning electron microscope and coupled with electron backscatter diffraction, 3D X-ray diffraction coupled with in-situ heating conducted at the European Radiation Synchrotron Facility and numerical simulation using the microstructural modelling platform Elle. The main outcome of the project is a significantly refined model for recovery at annealing temperatures below that of deformation preceding annealing. Behaviour is highly dependent on the temperature of annealing, particularly related to the activation temperature of climb and is also strongly reliant on short versus long range dislocation effects. Subgrain boundaries were categorised with regard to their behaviour during annealing, orientation and morphology and it was found that different types of boundaries have different behaviour and must be treated as such. Numerical simulation of the recovery process supported these findings, with much of the subgrain boundary behaviour reproduced with small variation to the mobilities on different rotation axes and increase of the size of the calculation area to imitate long-range dislocation effects. Dislocations were found to remain independent to much higher misorientation angles than previously thought, with simulation results indicating that change in boundary response occurs at ~7º for halite. Comparison of 2D experiments to 3D indicated that general boundary behaviour was similar within the volume and was not significantly influenced by effects from the free surface. Boundary migration, however, occurred more extensively in the 3D experiment. This difference is interpreted to be related to boundary drag on thermal grooves on the 2D experimental surface. While relative boundary mobilities will be similar, absolute values must therefore be treated with some care when using a 2D analysis.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University, 2010. 23 p.
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 342
halite, in-situ, X-ray diffraction, EBSD, annealing, substructure, modelling
National Category
Earth and Related Environmental Sciences
Research subject
urn:nbn:se:su:diva-45811 (URN)978-91-7447-187-8 (ISBN)
Public defence
2010-12-20, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:30 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-11-28 Created: 2010-11-11 Last updated: 2010-12-03Bibliographically approved

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Borthwick, VerityPiazolo, Sandra
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