Simulation of fracture of heat-resistant alloys under creep and neutron irradiation conditions

Abstract

A numerical technique based on the finite element method of deformation processes and damage accumulation in structural elements made of heat-resistant alloys under high-temperature creep that accounts for the effect of neutron radiation is developed. The mechanical behavior of the material is described on the basis of previously developed general model of damaged material and creep model for unirradiated heat-resistant alloys, supplemented with taking into account the irradiation effect on creep rate and brittle fracture emerging in a given range of temperature and radiation intensity. The constitutive relations for creep model of irradiated material were obtained by modifying the creep model of the unirradiated material: a material function taking into account the effect of neutron flux on the strain rate of thermal creep is introduced; a material function taking into account the effect of neutron flux on creep surface radius is introduced; a material function taking into account the effect of neutron flux on the ultimate value of creep dissipation energy is introduced. To simulate the processes of brittle fracture during creep under neutron radiation, it is assumed that the destructive values of the effective normal stresses are the function of temperature, neutron flux and the current value of accumulated creep strain. To verify and illustrate the capabilities of the developed methodological and software tools, a number of problems on modeling the processes of high-temperature creep and fracture of structural elements made of heat-resistant alloy under consideration are solved.