Identification and Verification of Material Functions of the Creep Model Under Thermal Radiation Effects for Austenitic Steel 1x18h10t

Abstract

In the present paper, on the basis of the information available in the scientific literature on the thermal creep rate of 1X18H10T austenitic steel under neutron irradiation conditions, the material functions of the thermal creep model implemented and verified in the framework of the certified software for numerical modeling of structural deformation under thermal and thermal radiation effects of UPAKS software are obtained and verified. The list of identifiable material functions of the thermal creep model includes: a function that characterizes the initial creep strain rate, referred to a unit stress level at a given temperature level and stress parameter; the radius of the creep surface, which is a function of temperature; the hardening function, characterizing the change in the initial creep rate from the hardening parameter at a given temperature; a function that takes into account the effect of a fast neutron flux on the creep rate at a given temperature. Using an analytical approximation of experimental data describing the rate of thermal creep of steels under neutron irradiation depending on the stresses, temperature, and flux of fast neutrons, we obtained relations for determining the values of all the functions of the thermal creep model. The value of the radius of the creep surface for a fixed temperature was determined from the condition that the creep deformation for a selected period of time and the neutron flux accumulated during this time will not exceed 0.2%. Using the UPAKS software, the creep model and the obtained material functions implemented in them, numerical simulation of the deformation of 1X18H10T steel under conditions of prolonged thermal load and neutron irradiation was performed. The results of numerical modeling are in good agreement with the analytical dependences that describe the creep of a given material under uniaxial SSS. A numerical creep simulation was also carried out under the assumption of the absence of neutron irradiation. As in the case of neutron irradiation, good agreement is obtained between the calculated and experimental data.