r5.03.13 Viscoplastic behavior with damage to HAYHURST

Summary:

The visco-plastic model coupled with the so-called Hayhurst isotropic damage is particularly suitable for carrying out calculations of creep structures. The viscoplastic part of the model was proposed by Hayhurst et al in [bib1] while the damage law was proposed by Charles Pétry in [bib2]. This model allows a satisfactory prediction of the drop in ductility during creep via the application of limit criteria on deformation and damage. This model has so far been mainly used at EDF R&D/ MMC for creep life predictions on grade 92 steel. By identifying specific parameters and carrying out structural calculations, this model also makes it possible to satisfactorily predict the creep behavior and the lifetime of welded junctions [bib3].

This model is implemented in Code_Aster under the name of HAYHURST; the speed equations are integrated numerically by an explicit Runge-Kutta diagram of order 2 with automatic division into local sub-steps according to an estimate of the integration error (nested Runge-Kutta method, confer [R5.03.14]) or by an implicit Newton integration method.

Test SSNV225 validates the integration of this model and is presented in the validation document [V6.04.225] which also provides experimental references related to the test case.

• 1. Introduction
• 2. Formulation of the model
  • 2.1. Theoretical framework
  • 2.2. Model equations
• 3. Parameters of the law
• 4. Implementation in Code_Aster
  • 4.1. Explicit integration
  • 4.2. Implicit integration
• 5. Meaning of internal variables
• 6. Bibliography
• 7. Description of document versions