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Thermo-Mechanical Modelling of Pebble Beds in Fusion Blankets and its Implementation by a Return-Mapping Algorithm

Published online by Cambridge University Press:  26 February 2011

Yixiang Gan  and
Marc Kamlah
Yixiang Gan
Affiliation:
yixiang.gan@imf.fzk.de, Forschungszentrum Karlsruhe, IMF II, Postfach 3640, Karlsruhe, D-76021, Germany, +49 (0)7247 82 3459, +49 (0)7247 82 2347
Marc Kamlah
Affiliation:
marc.kamlah@imf.fzk.de, Forschungszentrum Karlsruhe, IMF II, Postfach 3640, Karlsruhe, D-76021, Germany
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Abstract

In this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered.

Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importance with respect to the application of pebble beds in fusion blankets [1]. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis.

The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made.

Keywords

simulationthermal stressesceramic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 981: Symposium JJ – Structural and Refractory Materials for Fusion and Fission Technologies , 2006 , 0981-JJ04-04
Copyright
Copyright © Materials Research Society 2007

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References

REFERENCES

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