Validation of a creep and plasticity model for French and German RPV-steels


Validation of a creep and plasticity model for French and German RPV-steels

Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.

For pre- and post-test calculations of Lower Head Failure experiments like FOREVER or OLHF it is necessary to model creep and plasticity processes. Therefore a Finite Element Model is developed using a numerical approach which avoids the use of a single creep law employing constants derived from the data for a limited stress and temperature range. Instead of this a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. The CDB includes the primary, secondary and tertiary creep stage. A main task for this approach is the generation and validation of the CDB. The source for the CDB are uniaxial creep tests, like the REVISA-experiments.
For an evaluation of the failure times a damage model is necessary. The applied damage model accounts for the triaxiality of the mechanical stresses according to an approach of Lemaitre.
The validation of the numerical model is performed by the simulation of and comparison with experiments. This is done in 3 levels: starting with the simulation of single uniaxial creep tests, which is considered as a 1D-problem. In the next level so called “tube-failure-experiments” are modeled: the RUPTHER-14 and the “MPA-Meppen”-experiment. These experiments are considered as 2D-problems. The last level considers the application of the numerical model to scaled 3D-experiments, where the lower head of a PWR is represented in its hemispherical shape, like in the FOREVER-experiments.

Keywords: creep and plasticity; Finite Element Model; French and German RPV-steel

  • Lecture (Conference)
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136
  • Contribution to proceedings
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136

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Publ.-Id: 4439