Multiscale modeling of the effective viscoplastic behavior of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Mg</mml:mi> <mml:mn>2</mml:mn> </mml:msub><mml:msub><mml:mi mathvariant="normal">SiO</mml:mi> <mml:mn>4</mml:mn> </mml:msub></mml:mrow></mml:math> wadsleyite: bridging atomic and polycrystal scales

The viscoplastic behavior of polycrystalline Mg 2 SiO 4 wadsleyite aggregates, a major high pressure phase the mantle transition zone Earth (depth range: 410–520 km), is obtained by properly bridging several scale models. At very fine nanometric corresponding to dislocation core structure, thermally activated plastic slip modeled for strain-rates relevant laboratory experimental conditions, at and wide range temperatures, based on Peierls–Nabarro–Galerkin model. Corresponding single reference resolved shear stresses associated constitutive equations are deduced from Orowan’s equation in order describe average grain scale, easiest systems. These data have been implemented two grain-polycrystal models, mean-field one (the recent Fully-Optimized Second-Order Viscoplastic Self-Consistent scheme [1]) allowing rapid evaluation effective viscosity full-field (FFT [2, 3]) method investigating stress strain-rate localization typical microstructures heterogeneous activation systems within grains. Calculations performed temperatures in-situ conditions. Results good agreement with available mechanical tests conducted experiments.