An ageing elasto-viscoplastic model for ceramics

Julian Soulacroix (1) , Bruno Michel (1) , Jean-Marie Gatt (1) , Régis Kubler (2) , Laurent Barrallier (2)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 MSMP - Mechanics surfaces and materials processing

A model reproducing strain softening behavior in ceramic materials is proposed, base on a critical treatment of previous mechanical experimental results on uranium dioxide. The main hypothesis is that the strain softening phenomenon is related to an ageing process, where some point defects move towards the dislocations and modify their velocity. This is different from most of models used up to now, as they were based on the hypothesis that only the initial lack of dislocations was responsible of the strain softening behavior. A model is first developed in a simple 1D framework. Evolution of the mechanical behavior with strain rate and temperature is well reproduced by this model. Then, the 1D model is extended to a 3D mechanical model, and mechanical compressive tests on UO2 pellets are simulated. The 3D model well reproduces the observed asymmetrical shape of the compressed pellet if one considers that the material is not initially perfectly homogeneous, which highlights the importance of accounting for spatial heteregeneity of materials in models.

Mots clés: Ceramics; Uranium dioxide; Strain softening; Mechanical behavior; Ageing

Domaines: Mécanique [physics.med-ph]; Matériaux et structures en mécanique [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Mécanique des structures [physics.class-ph]; Mécanique des structures [physics.class-ph]

Julian Soulacroix, Bruno Michel, Jean-Marie Gatt, Régis Kubler, Laurent Barrallier. An ageing elasto-viscoplastic model for ceramics. International Journal of Plasticity, 2014, pp.1-29. ⟨hal-01021798⟩