CYRANO 3 Code: implicit incremental formulation of a viscoplastic evolution problem derived by a partial duality technics

In the fuel rod, we want to get an estimation of the axial stresses σrz and σzz (Oz is the rod axis). As it is impossible with a classical axisymetric 1D displacement formulation, an 1D model was enriched by partial duality technics with a linear thermoelastic behavior law. We now want to generalize this model with a non-linear viscoelastic behavior law (as for the Zircaloy in the rod clad). It is proved that the viscoelastic implicit incremental problem can be transformed into a minimization, as in the elastic case. Then we can obtain the 1D viscoelastic enriched model exactly by the same process as in elasticity but on the incremental problem: writing the primal problem, partial dualizing approximating, obtaining a rough unidimensional problem. (author). 4 refs