Numerical Modeling of Hidden Damage Accumulation Due to Radiation Exposure and Hydrogen Embrittlement

Abstract

An approach that allows using the qualitative results of the analysis of the so-called "mechanism based" evolution equations, i.e. constructed using experiments at the micro- and meso-level, to determine the structure of the equation for another, similar in composition, material, is proposed. To determine damage due to irradiation influence, the classical method of Continuum Damage Mechanics was used. The proposed approach of qualitative reproduction of the effects of damage accumulation was used due to the lack of experimental data on the long-term behavior of the material under consideration (steel 08X18N9T) under the given conditions of temperature and radiation exposure. The previously studied influence of the effects of various processes on the hidden damage accumulation was used to reproduce it in the proposed equation. The influence of the type of stress state due to the invariants of the stress tensor and deviator is taken into account. The effect of hydrogen embrittlement is reflected using known data from experiments performed at the macro level, taking into account changes in the modulus of elasticity. The resulting function entered the evolution equation in an exponential form. The developed evolution equation for the damage parameter is added to the previously proven method and software for modeling structural elements exposed to thermal, force and irradiation fields. Examples of the analysis of problems of deformation, damage and fracture of specimens and a tube with a hole, in which the behavior of the corresponding zones of the reactor baffle is simulated, are provided. The performed numerical calculations showed the possibility of practical assessment of the deformed state and the level of acquired hidden damage.