Local stress-strain behavior of a high-temperature steam valve under transient mechanical and thermal loading

The problem of determining stress-strain characteristics in a selected component operating in a power plant is discussed. Steam valve in transient working conditions during a power unit start-up is taken as an example. The aim of the paper is to prove the possibility to use measurements of steam temperature and the temperature of selected points of the investigated elements for defining boundary conditions of the heat transfer problem as well as to verify operative correctness of the elaborated computer models. The essential importance of time-variable and non-uniform temperature field for the course of local stress changes that results in metal fatigue processes is shown. The method of the computer model validation is discussed as the one of important problems which should be solved if we wanted to predict properly the variable temperature field. The problem of materials behavior under mechanical and thermal loading in the selected component has been discussed.