Modeling of the Influence of Hydrogen on the Bearing Ability of Elements of the Power-Generating Equipment Under the Con
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MODELING OF THE INFLUENCE OF HYDROGEN ON THE BEARING ABILITY OF ELEMENTS OF THE POWER-GENERATING EQUIPMENT UNDER THE CONDITIONS OF TEMPERATURE CREEP F. Qin,1 O. V. Hembara,2, 3,4 and O. Ya. Chepil’2
UDC 620.197.5: 669.788
We perform the comparative analysis of the results of evaluation of the long-term strength according to the classical Kachanov–Rabotnov equations and within the energy approach. These results give satisfactory agreement with the experimental data. However, the errors of the time to fracture computed by using the energy approach are three times lower. Keywords: hydrogen concentration, creep, strain energy, damageability, long-term strength.
The reliability and safety of the thermomechanical equipment are guaranteed, especially in the course of long-term operation, both by the efficiency of the system of operative control over the metal and by the improvement of experimental-analytic methods used for the prediction of the residual service life of powergenerating equipment [1–3]. In the evaluation of durability, a significant role is played by the creep of materials accompanied by the accumulation of irreversible deformations and defects, which eventually leads to the initiation of cracks. The working medium in which the investigated structural elements are placed is also one of the crucial factors, which strongly affects the characteristics of creep and long-term strength. Hydrogen is regarded as one of the most aggressive media. Its intensifying influence on the creep of steel was studied in [4] . The results of experiments [5] demonstrate that the influence of the hydrogen-containing media on the metal manifest itself in the form of a decrease in its strength and plasticity on the macrolevel, as well as in the initiation, development, and accumulation of various defects (micropores, sub- and microdefects, microcracks) on the microlevel. The development of the indicated sources of hydrogen degradation is connected both with the directed diffusion of atomic hydrogen into the sites with maximum tensile stresses and with the interaction of diffusing hydrogen with hydrogen traps present in the bulk of the metal in the form of point, one-, two-, and three-dimensional defects of the crystal structure of the metal. Hence, the ambient medium affects the material through defects. Moreover, the development of the already available defects and the initiation of new defects sharply accelerate under the conditions of a triaxial stressed state. In what follows, we propose a method for the evaluation of the strength of structural elements under the conditions of creep with regard for the influence of hydrogen based on the energy approach. The developed method and software enable us to estimate the accumulation of defects and the appearance of cracks. In this case, the input data for calculations are the results of testing of smooth specimens (creep curves) well known for most materials at various temperatures. The accumulation of defects under the influence of hydrogen is 1 2 3 4
Yangtze University, Jingzhou, C
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