Model of the Deformation Process under Thermo-Mechanical Fatigue Conditions

Abstract

The paper focuses on the development of a mathematical representation of deformation characteristics under the conditions of an elevated changeable temperature and mechanical loads. The method proposed in the paper is based on the use of characteristics determined in low-cycle fatigue tests at constant temperatures. Hysteresis loops reflecting the behaviour of a material under the conditions of low-cycle loads at an elevated temperature were primarily used. The effect of relaxation on the course of the hysteresis loop was taken into account. The steady state of the material is referred to in the proposed representation. A calculation algorithm was developed to enable the determination of the stress value for subsequent increases of strain over time. The results obtained were compared with experimentally determined characteristics.

Effect of Flexible Operation on Residual Life of High-Temperature Components of Power Plants

“…However, these analyses were performed at a general load, and it was impossible to predict the change in the residual life of the plant component under flexible operating conditions. Several researchers [9][10][11][12][13] have studied the cumulative damage of each boiler component through a numerical approach. In addition, prior research focused on the thermal-structural fatigue life under specific loading conditions.…”

Thermo-Mechanical Fatigue of Thick-Walled Components of Power Devices

“…The evaluation of thermal stresses and mechanical strains in the elements of devices subject to mechanical and thermal strains requires the use of a methodology which combines a number of complementary test methods. These include tests performed under industrial conditions in order to determine mechanical and thermal loads, as well as computer modelling methods and experimental methods of determining material characteristics under conditions representing the course of the service process [2][3][4]. Of special importance in this case is an accurate specification of the conditions of heat exchange on the surface of the examined elements, which -to a large degree -determine the values of temperature gradients and stresses.…”