Thermal-mechanical fatigue behaviour of 9–12Cr power plant steels and pipes

摘要

This paper is concerned with the thermal-mechanical fatigue (TMF) behaviour of 9–12%Cr steels (P91 and P92) and of steam pipes made from them. A unified visco-plasticity model has been used in material behaviour characterization (cyclic hardening and creep relaxation), using the data obtained from iso-thermal and anisothermal experimental testing. A method for determining the material properties has been developed. The cyclic uniaxial test results have shown the capability of the model, in representing the thermal-mechanical responses of the materials. The material model and the material properties obtained are then implemented into the FE package ABAQUS (and Z-mat code) to model a realistic main steam power plant pipe, using assumed plant thermal and mechanical loading histories. The detailed stresses and stress-strain loops within the pipe under the thermal-mechanical conditions are investigated. The results obtained will provide useful indication of possible crack initiation sites and could form a basis for the development of component lifing methodology under TMF conditions.