The thermo-order-mechanical behaviors of liquid crystal elastomers （LCEs） under biaxial loading are studied in this paper. Inverse method for nonlinear elastic problems is utilized by imposing biaxial stretching to thin rectangular samples. Neo-classical elastic energy is used together with the Landau-de Gennes nematic free energy. Under plane stress assumptions, the constitutive equations are derived. Due to the possible reorientations of the liquid crystal molecules induced by the imposed biaxial loading, the in-plane nonlinear stress-strain relations can have different expressions depending on which loading axis will have the largest effective principal strain. And the free energy is a multi-well non-convex potential function. As shown by some typical loading paths, the LCE samples will exhibit an anisotropic nonlinear elastic behavior, as long as the loading has not induced a reorientation of the liquid crystal molecules. When this did occur, jumps of stresses could take place for dead loadings due to the losing of stability.
Based on the commercial computational software, a three-dimensional finite ele- ment model to simulate the thermo-mechanical behaviors in a nuclear fuel rod is established; By taking into consideration irradiation-swelling of the pellet and the irradiation damage effects in the cladding together with the coupling effects between the temperature field and the mechanical field, the user subroutines to define the special material performance and boundary conditions have been developed independently and validated. Three-dimensional numerical simulation of the thermo-mechanical coupling behaviors in a nuclear fuel rod is carried out, and the evolution rules of the important thermal and mechanical variables are obtained and analyzed. The research re- sults indicate that： （i） the fuel pellets will be in contact with the cladding at high burnup, which will induce a strong mechanical interaction between them; （2） the irradiation creep effect plays an important role in the mechanical behavior evolution in the nuclear fuel rod.
Xin GongYijie JiangShurong DingYongzhong HuoCanglong WangLei Yang
