r4.04.05 Elasto-viscous behavior model META_LEMA_ANI with metallurgy taken into account for fuel rod sheath tubes

Summary:

In order to carry out 3D calculations of the fuel sheath in an accidental situation of type APRP, the MMC department has formulated, for Zircaloy tubes, a model of elastoviscous behavior, without threshold, anisotropic and taking into account the effect of the transformation of the alpha beta phase on mechanical behavior.

This model, available in Code_Aster under the name META_LEMA_ANI, and its resolution algorithm are described here. It is available in 3D, plane deformation, axisymmetry.

The Hill anisotropy matrix can be filled in either in Cartesian coordinates, or in the cylindrical coordinate system associated with the tube. To date, it has been assumed that the axial axis \(z\) of the cylindrical coordinate system associated with the tube corresponds to that of the global coordinate system. So if several tubes have to be modelled or if the axis of the tube does not correspond to that of the global coordinate system, the model is not correct. Ultimately, this restriction should be lifted.

The speed equations are integrated numerically by an implicit Euler diagram. The system of equations obtained is solved by Newton’s method.

Table of Contents

• 1. background
• 2. Relationship META_LEMA_ANI in Code_Aster
  • 2.1. Generalities
  • 2.2. Restriction on the use of the model
  • 2.3. Use
  • 2.4. Internal variables
• 3. Notations
• 4. Presentation of the META_LEMA_ANI model
  • 4.1. Metallurgical phases
  • 4.2. Model equations
• 5. Model integration
• 6. Bibliography