Overall viscoplastic behavior of non-irradiated porous nuclear ceramics

• Published in: Mechanics of materials 2006-07, Vol.38 (7), p.608-619
• Main Authors: Monerie, Yann, Gatt, Jean-Marie
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Creep; Engineering Sciences; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Nonlinear viscosity; Nuclear ceramics; Overall behavior; Physics; Porous materials; Solid mechanics; Structural and continuum mechanics
• ISSN: 0167-6636; 1872-7743
• DOI: 10.1016/j.mechmat.2005.11.004

This paper deals with the overall behavior of nonlinear viscous and porous nuclear ceramics. Bi-viscous isotropic porous materials are considered: the matrix is subjected to two power-law viscosities with different exponents related to two stationary temperature-activated creeping mechanisms (scattering-creep and dislocation-creep), and this matrix contains a low porosity volume fraction. The overall behavior of these types of composite materials is obtained with the help of quadratic strain-rate potentials combined with experimental-based coupling function depending on stress and temperature. For each creeping mechanism, the hollow sphere model of [Michel, J.-C., Suquet, P., 1992. The constitutive law of nonlinear viscous and porous materials. Journal of the Mechanics and Physics of Solids 40, 783–812] is used. Mechanical parameters of the resulting model are identified and validated in the particular case of non-irradiated uranium dioxide nuclear ceramics. This model predicts, under pure thermo-mechanical loading, a variation of the material volume and a variation of the porosity volume fraction (the so-called densification or swelling).