Abstract
An experimental programme of cyclic thermo-mechanical testing for a P91 power plant steel, under isothermal, and in-phase and out-of-phase thermo-mechanical, temperature-strain cycle conditions, has been implemented. Using the experimental data, an optimisation procedure has been developed for the accurate determination of the material constants under isothermal conditions, in which the Chaboche model is employed to describe material responses. The material was found to exhibit cyclic softening throughout the full life cycles, which is believed to be related to the evolution of microstructure and the propagation of micro-cracks. The model developed shows good predictive capability of cyclic stress–strain behaviour and cyclic softening.
Highlights
Increasing temperatures and pressures for increased efficiency and reduced CO2 emissions has become an ongoing trend for power generation plants
A material constitutive model for a P91 power plant steel under cyclic loading and high temperature conditions has been developed based on the experimental results
The material constants were determined by using an optimisation procedure
Summary
Increasing temperatures and pressures for increased efficiency and reduced CO2 emissions has become an ongoing trend for power generation plants. Due to the intermittent nature of renewable energy generation, conventional power generation plants are subjected to a higher frequency of thermo-mechanical cycling, demanded by flexible operation. This indicates that more attentions need to be given to the problem of thermo-mechanical fatigue in component life assessment and in the design of new plants. The introduction of more cyclic operation of power plant has introduced the possibility of fatigue problems. The present paper is concerned with the application of the Chaboche unified viscoplasticity model to characterising the isothermal and thermal–mechanical fatigue responses, and the preliminary study on the cyclic failure mechanisms of a P91 steel under such conditions
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