Suchergebnisse

Creep due to ice flow is generally thought to be the main cause for the formation of crystallographic preferred orientations (CPOs) in polycrystalline anisotropic ice. However, linking the development of CPOs to the ice flow history requires a proper understanding of the ice aggregate's microstructural response to flow transitions. In this contribution the influence of ice deformation history on the CPO development is investigated by means of full-field numerical simulations at the microscale. We simulate the CPO evolution of polycrystalline ice under combinations of two consecutive deformation events up to high strain, using the code VPFFT (visco-plastic fast Fourier transform algorithm) within ELLE. A volume of ice is first deformed under coaxial boundary conditions, which results in a CPO. The sample is then subjected to different boundary conditions (coaxial or non-coaxial) in order to observe how the deformation regime switch impacts the CPO. The model results indicate that the second flow event tends to destroy the first, inherited fabric with a range of transitional fabrics. However, the transition is slow when crystallographic axes are critically oriented with respect to the second imposed regime. Therefore, interpretations of past deformation events from observed CPOs must be carried out with caution, particularly in areas with complex deformation histories. ; Maria-Gema Llorens was supported by a Juan de la Cierva-Incorporación fellowship (IJC2018-036826-I), funded by the MCIN/AEI/10.13039/501100011033. Enrique Gomez-Rivas was supported by the Ramón y Cajal fellowship (RYC2018-026335-I), funded by the MCIN/AEI/10.13039/501100011033 and the FSE. Ilka Weikusat received support from the HFG grant no. VH-NG-802. This work is part of the CSIC-PTI POLARCSIC activities, and it has been developed using the facilities of the Laboratory of Geodynamic Modelling of GEO3BCN and a computer cluster of the University of Tübingen. Funding was provided partly by GeoCAM (PGC2018-095154-B-100) of the Spanish Government. ...