Field distribution and overall stress-free strain of polycrystals with highly anisotropic grains

Within the framework of the LABCOM MISTRAL, Renald BRENNER will present a joint works with F. Willot (Mines ParisTech), H. Trumel (CEA Le Ripault), F. Onimus, L. Gélébart (CEA Saclay), R. Masson (CEA Cadarache)

In this talk, I will address the description of the local mechanical fields and the overall behaviour of linear (elastic or viscous) polycrystalline materials with a strong crystalline anisotropy.

In a first part, we study the elastic fields distribution within a polycrystalline energetic material with triamino-trinitro benzene (TATB) triclinic crystals. During its elaboration process, thermal loadings can give rise to microcracking. Full-field FFT computations have been performed on Johnson-Mehl polycrystalline microstructures for the sound material and including various crack populations. Comparisons are performed with self-consistent estimates by assuming a multivariate normal distributions at the phase scale (i.e crystalline orientation). A good agreement is obtained, especially for uncracked polycrystals.

In a second part, we tackle the issue of the macroscopic irradiation induced growth of linearly viscous (irradiation creep regime) zirconium polycrystals. Especially, we provide a detailed study of the role of the local anisotropic viscosity of the grains on the overall (axial) growth strain-rate. Analytical results with the Voigt model, for a simplified crystallographic fibre texture, allow to highlight characteristic features which are confirmed with more accurate self-consistent estimates and full-field numerical simulations. Besides, restrictions on the possible local anisotropy are discussed in connection with an assumption of linear dislocation glide for the single crystal deformation. It is shown that harder deformation mode of the single crystal along the axis is responsible for the macroscopic growth enhancement, with respect to the static model. Finally, numerical results are presented for polycrystalline microstructures with realistic crystallographic texture.

Le vendredi 15 novembre 2024 à 11h00 / Amphithéâtre François Canac, LMA

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