PSI - Issue 16

Yaroslav Ivanytskyi et al. / Procedia Structural Integrity 16 (2019) 126–133 Yaroslav Ivanytskyi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 8. Kinetics of damage accumulation in non-hydrogenated (1) and hydrogenated (2, 3, 4) specimens

Fig. 9. Hydrogen effect on time required to fracture of Bridgman specimen

5. Conclusions The introduction of the energy approach offered a method for estimating the strength and durability of structural elements, depending on the consideration of the influence of hydrogen. A comparative analysis of the results of the calculation of long-term durability by the classical equations of Kachanov-Rabotnov-Lokoschenko and the energy approach showed good convergence with experimental data. It was revealed that hydrogen reduced the durability of structural elements by 22 – 58%, depending on the level of hydrogen concentration in the material under creep conditions. References Babii, L. , Student, O., Zagórski , A., Markov, A. , 2007. Creep of degraded 2.25Cr-Mo steel in hydrogen. Materials science 43(5), 701 – 707. Chang Shu, Hembara, O., Chepil’ , O., 2018. Calculation of the lifetime of heat and power equipment under long-term static loading, high temperature, and the action of hydrogen. Materials science 54(1), 107 – 114. Hayhurst, D., Felce, I., 1986. Creep rupture under tri-axial tension. Engineering Fracture Mechanics 25, 645 – 664. Hembara, O., Chepil, O., Hembara, N., 2016. Influence of the parameters of discretization on the accuracy of numerical solution of the three dimensional problem of hydrogen diffusion. Materials Science 52(2), 280 – 286. Hyde, T., Xia, L., Becker, A., 1996. Prediction of creep failure in aeroengine materials under multi-axial stress states. International Journal of Mechanical Sciences 38, 385 – 403. Ivanyts ’ kyi Ya., Mol ’ kov Yu., Kun ’ P., Lenkovs ’ kyi T., W ó jtowicz M., 2014. Determination of the local strains near stress concentrators by the digital image correlation technique. Materials science 50 (4), 488 – 495. Ivanyts’kyi , Ya., Hembara, O., and Chepil’ , O., 2015. Determination of the durability of elements of power-generating equipment with regard for the influence of working media. Materials science 51 (1), 104 – 113. Kachanov, L., 1967. The theory of creep , Boston Spa, Yorks. Leckie, F., Hayhurst, D., 1974. Creep rupture of structures. Proceding of the Royal Society London A340, 323 – 347. Lemaitre, J. 1979. Application of damage concepts to predict creep-fatigue failures. Journal of Engineering Materials and Technology, ASME 101, 284 – 292. Lemaitre, J., 1984. How to use damage mechanics. Nuclear Engineering and Design 80, 233 – 245. Lemaitre, J., 1985. Continuum damage mechanics model for ductile fracture. Journal of Engineering Materials and Technology ASME 107, 83 – 89. Liu, Y., Murakami, S., 1998. Damage localisation of conventional creep damage models and proposition of a new creep damage analysis. JSME International Journal 41 , 57 – 65. Lokoshchenko, A., Fomin, L., 2015. Modelling the creep rupture of tensile rods in an aggressive medium with account of a variable diffusion coefficient. Mechanics of Composite Materials 50, No. 6, 739 – 746. Lokoshchenko, A., Fomin, L., 2018. Delayed fracture of plates under creep condition in unsteady complex stress state in the presence of aggressive medium. Applied Mathematical Modelling 60, 478 – 489. Murakami, S, Liu, Y, Mizuno, M., 2000. Computational methods for creep fracture analysis by damage mechanics. Computer Methods in Applied Mechanics and Engineering 183, 15 – 33. Murakami, S., Liu, Y., 1995. Mesh-dependence in local approach to creep fracture. International Journal of Damage Mechanics 4, 230 – 250. Qin, F., Hembara, O., Chepil’ , O., 2018. Modeling of the influence of hydrogen on the bearing ability of elements of the power-generating equipment under the conditions of temperature creep. Materials science 53(4), 532 – 540. Rabotnov, Yu., 1969. Creep Problems in Structural Members. Amsterdam, London. Student, O., Rusyn, B., Kysil’ , B., Kobasyar, M., Stakhiv, T., and Markov, A., 2003. Quantitative analysis of structural changes in steel caused by high-temperature holding in hydrogen, Materials Science 39(1), 17 – 24.