Flow Controllability of Hydrogen Diffusion Driven by Local Stress Field for Steel under Cyclic Loading Condition

Ohmi, Toshihito; Yokobori, A. Toshimitsu; Takei, K.

doi:10.4028/www.scientific.net/ddf.326-328.626

Cited by 5 publications

(7 citation statements)

References 9 publications

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“…Furthermore, authors have proposed the FEM–FDM method, in which stress analysis is conducted by the finite element method (FEM) and hydrogen diffusion analysis is conducted by the finite difference method (FDM), which are suitable for each analysis. 14 , 37 )…”

Section: Quantitative Characterization Of the Sensitivity Of Hydrogenmentioning

confidence: 99%

“…Furthermore, authors have proposed the FEM-FDM method, in which stress analysis is conducted by the finite element method (FEM) and hydrogen diffusion analysis is conducted by the finite difference method (FDM), which are suitable for each analysis. 14), 37) Based on these methods, the theoretical equation for predicting the site of hydrogen concentration and the sensitivity of hydrogen embrittlement in engineering structures was proposed for the first time, which is a meso and macroscale analysis. 14),36), 37) Other studies on the analysis of hydrogen diffusion were mainly concerned with the clarification Relationship of thermally activated process for aluminum alloy Fig.…”

Section: Introductionmentioning

confidence: 99%

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Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications

Yokobori

2020

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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In this work, the mesoscale mechanics of metals, which links their microscopic physics and macroscopic mechanics, was established. For practical applications, the laws for quantitatively predicting life of cycle and time-dependent fracture behavior such as fatigue, hydrogen embrittlement, and high-temperature creep were derived using particle transport phenomena theories such as dislocation group dynamics, hydrogen diffusion, and vacancy diffusion. Furthermore, these concepts were also applied for estimating the degree of viscoelastic deterioration of blood vessel walls, which is dominated by a time-dependent mechanism, and for the diagnosis of aneurysm accompanied by the viscoelastic deterioration of the blood vessel wall. In these theories, new mechanical indexes were derived as dominant factors for predicting the life of fatigue crack growth and the time-dependent fracture of notched specimens of materials such as hydrogen embrittlement and high-temperature creep. Furthermore, as an example of a practical application, these theories were applied to estimate the degree of viscoelastic deterioration and chaotic motions of blood vessel walls, which are closely related to blood vessel diseases such as atherosclerosis and aneurysm. Moreover, new indexes to diagnose them were also proposed for clinical applications.

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Section: Quantitative Characterization Of the Sensitivity Of Hydrogenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications

Yokobori

2020

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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“…Validity of our proposed interpolating method was assured in this research and in our previous literatures. 21,22,36)…”

Section: Analyses Of Hydrogen Flow Based On the Coupled Analysis Of Hmentioning

confidence: 99%

“…Detailed descriptions of interpolation method were written in previous studies which carried out similar analytical method. 21,22,36) 3. Results of Analysis with increase in time, at first, the maximum hydrogen concentration increases from C + = 3.0 (0 step) to 3.39 (5 step) and after that, it decreases to C + = 2.60 (1000 step).…”

Section: Thermal Stress Induced Hydrogen Diffusion Analysismentioning

confidence: 99%

“…Furthermore, for the application of engineering structure, the FEM-FDM (Finite element methodFinite difference method) analytical method was proposed. 21,22) In this method, stress analysis is conducted by FEM and diffusion analysis is conducted by FDM, respectively, since FEM and FDM are suitable for stress and fluid analysis respectively. Furthermore, this proposed analysis enables us to obtain more reasonable numerical solutions for such time sequential behaviors of hydrogen diffusion.…”

Section: Introductionmentioning

confidence: 99%

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Dominating Driven Factors of Hydrogen Diffusion and Concentration for the Weld Joint–Coupled Analysis of Heat Transfer Induced Thermal Stress Driven Hydrogen Diffusion–

et al. 2019

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Hydrogen embrittlement cracking caused at a weld joint is considered to be dominated by hydrogen diffusion and concentration driven by thermal stress induced by heat transfer during cooling process. The gradient of hydrostatic stress component is considered to be a driven force of hydrogen transportation. However, this problem concerns the occurrence phenomenon during cooling process. Therefore, diffusion coefficient, yield stress and Young's modulus are changed corresponding with temperature change. Especially, diffusion coefficient shows the space gradient corresponding with space gradient of temperature caused by heat transfer. This affects the diffusion equation of hydrogen as a driven force of hydrogen diffusion. Under these backgrounds, to clarify not only the effect of local thermal stress but also that of space gradient of diffusion coefficient on hydrogen release and trap, the hydrogen diffusion analysis based on our proposed ¡ multiplication and FEM-FDM methods was conducted by introducing the terms of gradients of diffusion coefficient and temperature into the diffusion equation. The following results were obtained. The space gradient of diffusion coefficient was found to contribute the release of hydrogen from the site of stress concentration when the gradient of local hydrogen concentration takes the same sign as that of diffusion coefficient. Concerning the prevention of hydrogen embrittlement cracking at weld joint, these results show that not only Pre-Heat Treatment (PHT) which is a mechanical factor, but also the space gradient of diffusion coefficient which is a factor of material science was found to be one of effective factor of release of hydrogen from a site of stress concentration.

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The characteristics of load frequency of corrosion fatigue crack growth rate for Ti–6Al–4V alloys

Yokobori

Nunokawa

Ohmi

et al. 2016

SFC

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Flow Controllability of Hydrogen Diffusion Driven by Local Stress Field for Steel under Cyclic Loading Condition

Cited by 5 publications

References 9 publications

Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications

Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications

Dominating Driven Factors of Hydrogen Diffusion and Concentration for the Weld Joint–Coupled Analysis of Heat Transfer Induced Thermal Stress Driven Hydrogen Diffusion–

The characteristics of load frequency of corrosion fatigue crack growth rate for Ti–6Al–4V alloys

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