On computational strategies for problems involving plasticity and creep

This paper discusses computational strategies for elastic-plastic-creep behaviour. These computational strategies, based on the tangent stiffness and initial strain techniques, include solution algorithms, modelling techniques and constitutive relations. A predictor-corrector iterative and non-iterative scheme is presented for combined plasticity and creep. This scheme has been incorporated into the three-dimensional, isoparametric element, module (HEX) of the Grumman PLANS finite element program for nonlinear analysis and used for the problems presented in this paper. The concept of modelling for inelastic behaviour is demonstrated by introducing a variable set of inelastic integration points within a finite element at which stresses and strains are monitored. In order to perform a meaningful analysis, one must understand and justify the employed constitutive relations. To this end, work at Oak Ridge National Laboratory in justifying constitutive relations for high-temperature nuclear reactor components is referred to. An analysis of a test model of a nuclear reactor inlet nozzle operating at high temperatures is presented to demonstrate some of the computational strategies discussed.

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