ABSTRACT
The paper presents the results of low-cycle fatigue tests on P91 steel specimens, carried out under constant strain and constant stress conditions, at three temperatures and several strain and stress amplitude levels. The experimental tests are performed to recognize different aspects of a material behavior. The analysis of the experimental data reveals the influence of fatigue testing conditions on the fatigue life predictions. In the next stage of the research the constitutive description of thermomechanical low cycle fatigue behavior of P91 steel is developed within the framework of thermodynamics of irreversible processes with internal state variables. The constitutive model describes different phases of cyclic softening, observed experimentally. The model is implemented into a numerical subroutine, and identified on the basis of the available experimental data.
