Journal ArticleDOI
Numerical analysis of hydrogen transport near a blunting crack tip
TLDR
In this paper, Oriani's equilibrium theory is used to relate the hydrogen in traps (micro-structural defects) to concentration in normal interstitial lattice sites (NILS), and the resulting non-linear transient hydrogen diffusion equations are integrated using a modified backward Euler method.Abstract:
T he hydrogen transport problem is studied in conjunction with large deformation elastic—plastic behavior of a material. Oriani's equilibrium theory is used to relate the hydrogen in traps (micro-structural defects) to concentration in normal interstitial lattice sites (NILS). The resulting non-linear transient hydrogen diffusion equations are integrated using a modified backward Euler method. Coupled diffusion and plastic straining is analysed with this numerical procedure in the area around a blunting crack tip. A uniform NILS concentration as dictated by Sievert's law at the pressure and temperature of interest is used as initial condition throughout the body. The crack is initially blunted by plane strain mode I (tensile) loading. The finite element results show that hydrogen residing at NILS is generally very small in comparison with the population that develops in trapping sites near the crack surface. That is, lattice diffusion delivers the hydrogen but it is predominantly the trapping that determines its distribution at temperatures of interest. The predominance of trapped hydrogen over lattice concentration prevails even in the case when hydrogen migrates under steady state conditions. Hence, the hydrostatic stress effect is less important than traps created by plastic straining as far as the creation of high total hydrogen concentration is concerned. The trapping site locations and the temperature determine the amounts and locations of high hydrogen concentrations. Consequently, ahead of a blunting crack tip, the total hydrogen concentration and plastic strain diminish with distance from the crack tip whereas the hydrostatic stress rises. This would seem to have significant consequences for fractures induced by the presence of hydrogen.read more
Citations
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Journal ArticleDOI
Identification of microstructure factors affecting hydrogen embrittlement of a 2205 duplex stainless steel
TL;DR: In this article , the authors investigated H-assisted cracking of duplex stainless steel (DSS) with different microstructure based on the initiation and evolution of microcracks during deformation.
Journal ArticleDOI
Modeling hydrogen dragging by mobile dislocations in finite element simulations
TL;DR: In this article , an extension of this model is proposed where hydrogen dragging by mobile traps is modeled by reaction-diffusion equations, involving trapping and detrapping kinetic, and is applied for evolving trap density with plastic strain.
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A novel approach for quantifying hydrogen embrittlement using side-grooved CT samples
TL;DR: In this article , the authors developed a novel method to measure the stress intensity threshold for hydrogen embrittlement (K t h ) in industrial plating conditions, which consists in plating side-grooved CT samples and measuring K t h with an incremental step loading methodology.
Journal ArticleDOI
Effect of transient trapping on hydrogen transport near a blunting crack tip
TL;DR: In this paper, the authors revisited the way transient trapping is introduced in the literature based on the Sofronis and McMeeking model of hydrogen transport and showed that the direct use of the improved formulation made by Krom et al. (1999) for transient trapping may lead to non-physical results of hydrogen concentration in case of an insulated system.
Journal ArticleDOI
Hydrogen Diffusion Simulation in Dual Phase Microstructure Considering the Difference in Diffusion Constants
TL;DR: In this paper, a numerical simulation using a two-dimensional dual-phase model was performed to evaluate the effect of the microstructure on hydrogen diffusion behavior, and the results indicated that the hydrogen does not diffuse through the higher coefficient phase on a preferential basis; instead, the diffusion occurs with the same time dependency in both phases.
References
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Book
The finite element method
TL;DR: In this article, the methodes are numeriques and the fonction de forme reference record created on 2005-11-18, modified on 2016-08-08.
Journal ArticleDOI
A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks
TL;DR: In this paper, an integral is exhibited which has the same value for all paths surrounding a class of notches in two-dimensional deformation fields of linear or non-linear elastic materials.
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Effects of hydrogen on the properties of iron and steel
TL;DR: In this paper, the effects of hydrogen on the physical and mechanical properties of iron and steel are reviewed and a new mechanism for the cold work peak for hydrogen in iron is considered.
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The diffusion and trapping of hydrogen in steel
TL;DR: In this paper, the mobility of dissolved hydrogen in an iron lattice having a population of extraordinary, or trapping, sites for hydrogen is analyzed under the assumption of local equilibrium between the mobile and the trapped populations.