Thermomechanical analysis of a pressurized pipe under plant conditions

This paper is concerned with the development of a methodology for thermomechanical analysis of high temperature, steam-pressurized P91 pipes in electrical power generation plant under realistic (measured) temperature and pressure cycles. In particular, these data encompass key thermal events, such as "load-following" temperature variations and sudden, significant fluctuations in steam temperatures associated with attemperation events and "trips" (sudden plant shut-down), likely to induce thermomechanical fatigue damage. An anisothermal elastic-plastic-creep material model for cyclic behavior of P91 is employed in the transient finite element (FE) model to predict the stress-strain-temperature cycles and the associated strain-rates. The results permit characterization of the behavior of pressurized P91 pipes for identification of the thermomechanical loading histories relevant to such components, for realistic, customized testing. This type of capability is relevant to design and analysis with respect to the evolving nature of power plant operating cycles, e.g., associated with more flexible operation of fossil fuel plant.