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This report describes the state of the art in constitutive modelling in the range of inelastic deformations, with particular consideration of the practical use of these models in the field of fast reactors. An outline is given of the constitutive equations for high-temperature reactor materials developed at the Oak Ridge National Laboratory. Two forms of equations are considered, a semi-classical treatment in terms of separate plasticity and creep and unified equations in which the classical plasticity does not occur explicitly. The fraction model originally proposed by Besseling is described. The basic concept of this model considers the material as subdivided into a number of parallel fractions, each with simple conventional properties. The more complicated behaviour of real material is thus approximated by choosing a number of parallel fractions with suitable models and model parameters. Three time-independent formulations of plasticity are considered and compared. Attention is focused on the kinematic hardening in the multi-yield surface theory of Mroz and the non-linear kinematic rule intensively used at Enset and Onera. Some connections are pointed out with the two-surface model of Dafalias and Popov.

Additional information

Authors: BRUHNS O T, Bochum University (DE)
Bibliographic Reference: EUR 11799 EN (1988)
Availability: (2)
ISBN: ISBN 92-825-8969-2;CD-NA-
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