The energy approach to the evaluation of hydrogen effect on the damage accumulation

Ivanytskyi, Yaroslav; Kharchenko, Yevhen; Hembara, О. V.; Chepil, О. Ya.; Sapuzhak, Yaroslav; Hembara, N. Т.

doi:10.1016/j.prostr.2019.07.031

Cited by 9 publications

(3 citation statements)

References 16 publications

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“…When the energy reaches a critical value in the local volume of the material, a microcrack of critical size appears, which results in a sharp localization of strain and fracture. Thus, the fracture criterion is the condition for reaching the critical value of the specific strain energy, i.e., the specific fracture energy [ 49 ], as follows:

where W is the strain energy of the local volume of the element, calculated using the FEM;

is the pressure, temperature, and hydrogen concentration, at which the strain energy becomes critical; and

is the characteristic fracture resistance of a material under given conditions of loading, temperature, and working environment, which is determined experimentally using the ODIC method.…”

Section: Numerical Simulationsmentioning

confidence: 99%

A New Energy Approach to Predicting Fracture Resistance in Metals

et al. 2023

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To ensure the reliability and durability of structural elements, modern approaches require data characterizing the local stress-strain state of the material in risk zones. In order to predict the fracture resistance of structural elements, a theoretical-experimental method based on the damage accumulation model using the energy approach is proposed. One of the unique characteristics of the proposed approach is that it uses local parameters of the stress-strain state, which are determined using a highly accurate and easy-to-use noncontact method of optical–digital image correlation (ODIC). This can be used both in laboratory conditions and for structural elements under real operating conditions. The proposed method of plotting stress–strain curves makes it possible to determine the true stresses near the concentrators in structural elements under a complex load. Using these diagrams in calculations and the finite element method (FEM), a study of local strain not only of the surface, but also of the internal volumes of the material was carried out. The damage parameter is introduced as the ratio of the elastoplastic strain energy of the local volume to its critical value. It is confirmed that the damage of the sample material starts from its centre. It was established that the damage parameter in the centre of the sample is 25–35% higher than its value on the surface of the sample.

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where W is the strain energy of the local volume of the element, calculated using the FEM;

is the pressure, temperature, and hydrogen concentration, at which the strain energy becomes critical; and

is the characteristic fracture resistance of a material under given conditions of loading, temperature, and working environment, which is determined experimentally using the ODIC method.…”

Section: Numerical Simulationsmentioning

confidence: 99%

A New Energy Approach to Predicting Fracture Resistance in Metals

et al. 2023

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“…To describe the accumulation of defects in a local volume according to the energy approach, we introduce a measure of damage ω(t) that characterizes the ratio of the energy of elastoplastic deformation of a local volume to its critical value in hydrogen W C [4,5,[10][11][12][13][14][15]:…”

Section: Energy Approach To the Evaluation Of The Residual Service Life Of Structural Elementsmentioning

confidence: 99%

Computer Modeling of the Influence of Hydrogenation on the Durability of Pipe Elements

2021

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We construct a mathematical model for the evaluation of the influence of hydrogen saturation and stress corrosion cracking on the durability of structural elements. By using the developed computer programs, we reproduce the processes of hydrogenation and deformation of structural elements. We also determined the service life of straight sections of heat-exchange pipes of steam generators of nuclear power plants under operating conditions.

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“…Long-term operation of elements of structures of nuclear and thermal power plants in conditions of elevated temperatures and interactions with hydrogen-containing and corrosive environments requires researchers to use approaches that take into account changes in the physical and mechanical characteristics of metal when reassigning the period of operation or extending the service life. It was established that changes can manifest in local volumes in the form of internal and surface damage [ 21 , 22 , 23 , 24 ]. For a reliable assessment of the strength and deformability of metal after long-term operation, it is necessary to use criteria that would take into account changes in the characteristics of the metal in the local volume.…”

Section: Introductionmentioning

confidence: 99%

Influence of Hydrogen on the Fracture Resistance of Pre-Strained Steam Generator Steel 22K

et al. 2022

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In the paper, experimental studies of the hydrogen and pre-strained effect on fracture resistance of steam generator steel 22K were carried out. Special cylindrical samples were loaded up to fracture under a uniaxial tensile test with different pre-strained degrees and hydrogen charged times of the material. Stress-strain curves «Si–ei» were plotted. The true strain «ei» in the local volume was determined using the method of optical-digital image correlation (ODIC). The results showed that the hydrogen influence is practically absent in the elastic area of strain. The fracture energy of steel 22K decreases under the hydrogen influence and pre-strain in all investigated cases. It is shown that during six months of air exposure, with the 0% pre-strained samples release almost all hydrogen. In pre-strained samples, the hydrogen concentration decreased by 1–3% compared to the initial values. This indicates that they have trapped hydrogen that cannot escape on its own. Hydrogen embrittlement (HE) indexes for 0% pre-strained samples at different levels of hydrogen-charging calculated by the strain and energy approaches are equal to each other. There is a difference in the values of the HE index depending on the hydrogen-charge time for pre-strained samples. This indicates that both strain and strength characteristics of the material, which are integrally taken into account in the energy approach, are sensitive to HE.

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The energy approach to the evaluation of hydrogen effect on the damage accumulation

Cited by 9 publications

References 16 publications

A New Energy Approach to Predicting Fracture Resistance in Metals

A New Energy Approach to Predicting Fracture Resistance in Metals

Computer Modeling of the Influence of Hydrogenation on the Durability of Pipe Elements

Influence of Hydrogen on the Fracture Resistance of Pre-Strained Steam Generator Steel 22K

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