Characterization of the Effect of Notch Bluntness on Hydrogen Embrittlement and Fracture Behavior Using FE Analyses

2015 ◽  
Author(s):  
Jun-Young Jeon ◽  
Nicolas O. Larrosa ◽  
Young-Ryun Oh ◽  
Yun-Jae Kim ◽  
Robert A. Ainsworth
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Concentration ◽  
Fracture Behavior ◽  
Hydrogen Diffusion ◽  
High Strength ◽  
Ductile Damage ◽  
Diffusion Analysis ◽  
As Stress ◽  
Damage Simulation

This paper introduces a method to characterize the effect of notch bluntness on hydrogen embrittlement for high strength structural steel, FeE 690T, C(T) specimens. Hydrogen concentration depending on notch radius is assessed via finite element (FE) hydrogen diffusion analysis already developed and validated by the authors. Reduction in fracture toughness, KIC or JIC, due to hydrogen embrittlement is evaluated by means of a coupled hydrogen diffusion-ductile damage analysis. The ductile damage simulation used in this study is based on the model known as ‘stress-modified fracture strain model’. Tensile properties and fracture strains are modified according to the level of hydrogen concentration in the simulation and its effect on the fracture behavior of the specimen is simulated for different notch radii.

scholarly journals Hydrogen Embrittlement and Diffusion in High Strength Low Alloyed Steels with Different Microstructures

2018 ◽  
Author(s):  
Marina Cabrini ◽  
Sergio Lorenzi ◽  
Diego Pesenti Bucella ◽  
Tommaso Pastore
Keyword(s):  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Hydrogen Diffusion ◽  
High Strength Steels ◽  
High Strength ◽  
Tempered Martensite ◽  
Hsla Steels ◽  
And Diffusion ◽  
Embrittlement Resistance ◽  
Hydrogen Embrittlement Resistance

<span lang="EN-US">The paper deals with the effect of microstructure on the hydrogen diffusion in traditional ferritic-pearlitic HSLA steels and new high strength steels, with tempered martensite microstructures or banded ferritic-bainitic-martensitic microstructures. Diffusivity was correlated to the hydrogen embrittlement resistance of steels, evaluated by means of slow strain rate tests.</span>

Diffusion of Hydrogen in Titanium-Vanadium Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 340-345 ◽  
Author(s):  
Hans Jürgen Christ ◽  
S. Schroers ◽  
F.H.S. dos Santos
Keyword(s):  
Diffusion Coefficient ◽  
Titanium Alloys ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
High Strength ◽  
Vanadium Concentration ◽  
Vanadium Alloys ◽  
High Hydrogen ◽  
Hydrogen Diffusion Coefficient ◽  
Diffusion Of Hydrogen

β–titanium alloys are very attractive materials for many applications because they combine low density, high strength and excellent corrosion resistance. The available data indicate a much higher hydrogen diffusion coefficient in β–titanium alloys as compared to α and α + β alloys. In order to predict the range of applicability of β–titanium alloys in environments, which release hydrogen, the hydrogen diffusion coefficient (DH) needs to be known quantitatively. In the framework of this study the value of DH was determinated on samples, which were electrochemically hydrogen charged. Long thin rods were used as samples and charged in such a way that high hydrogen concentrations were obtained in one half of the length of the specimens, while the other half was kept virtually unaffected. After charging, the rods were annealed enabling hydrogen to diffuse. Hydrogen concentration profiles were experimentally determined and evaluated on the basis of the Matano technique, in order to reveal any effect of concentration on DH. The experiments were carried out on β–titanium alloys of the binary Ti–V system. The concentration range of vanadium in the alloys studied was selected in such a way that it represents the compositions commonly found in commercial alloys. The results show that the effect of hydrogen concentration on DH is negligible and that DH increases with the vanadium concentration.

Studies of SCC and Hydrogen Embrittlement of High Strength Alloys Using Fracture Mechanics Methods

2005 ◽  
Vol 482 ◽  
pp. 11-16 ◽  
Author(s):  
Wolfgang Dietzel ◽  
Michael Pfuff ◽  
Guido G. Juilfs
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
High Strength Steels ◽  
High Strength ◽  
Constant Load ◽  
Rate Of Change ◽  
Extension Rate ◽  
Hydrogen Atoms

Fracture mechanics based test and evaluation techniques are used to gain insight into the phenomenon of stress corrosion cracking (SCC) and to develop guidance for avoiding or controlling SCC. Complementary to well known constant load and constant deflection test methods experiments that are based on rising load or rising displacement situations and are specified in the new ISO standard 7539 – Part 9 may be applied to achieve these goals. These are particularly suitable to study cases of SCC and hydrogen embrittlement of high strength steels, aluminium and titanium alloys and to characterise the susceptibility of these materials to environmentally assisted cracking. In addition, the data generated in such R-curve tests can be used to model the degradation of the material caused by the uptake of atomic hydrogen from the environment. This is shown for the case of a high strength structural steel (FeE 690T) where in fracture mechanics SCC tests on pre-cracked C(T) specimens a correlation between the rate of change in plastic deformation and the crack extension rate due to hydrogen embrittlement was established. The influence of plastic strain on the hydrogen diffusion was additionally studied by electrochemical permeation experiments. By modelling this diffusion based on the assumption that trapping of the hydrogen atoms takes place at trap sites which are generated by the plastic deformation, a good agreement was achieved between experimentally obtained data and model predictions.

The Analysis of Hydrogen Diffusion Behaviors Coupled With the Analysis of Heat Transfer Around the Heat Affected Zone of Welding

2014 ◽  
Author(s):  
Toshihito Ohmi ◽  
Toshimitsu Yokobori ◽  
Kenichi Takei ◽  
Yuki Konishi
Keyword(s):  
Heat Transfer ◽  
Heat Treatment ◽  
Residual Stress ◽  
Hydrogen Embrittlement ◽  
Stress Field ◽  
Hydrogen Concentration ◽  
Incubation Time ◽  
Hydrogen Diffusion ◽  
Local Stress ◽  
Weld Heat

Hydrogen penetrates into the metal and causes Hydrogen embrittlement due to the increase in hydrogen concentration. This is caused by the local stress fields such as residual stress field at the site of welding or local stress field around a crack tip. It accompanied with incubation time of several hours since the components were exposed to hydrogen atmospheric condition. This incubation time is time lag of hydrogen diffusion and concentration at the site where the hydrogen embrittlement occurs. Therefore, clarification of the hydrogen diffusion behavior is important to prevent from fracture of hydrogen embrittlement. In this paper, the numerical analyses of hydrogen diffusion around weld part including HAZ (Heat Affected Zone) under residual stress coupled with that of heat transfer during the cooling process before and after weld were conducted and the behaviors of hydrogen concentration were analyzed. On the basis of these analyses, the method of heat treatment to prevent from hydrogen concentration at the weld part was investigated. Results obtained by these analyses showed that pre weld heat treatment is effective in the prevention of hydrogen concentration and combined pre weld heat treatment with post weld heat treatment was found to be the most effective treatment.

Hydrogen Embrittlement Resistance of High Strength 9260 Bar Steel Heat Treated by Quenching and Partitioning

2021 ◽  
Author(s):  
E. Hoyt ◽  
E. De Moor ◽  
K.O. Findley
Keyword(s):  
Hydrogen Embrittlement ◽  
Carbon Content ◽  
Hydrogen Concentration ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Quenching And Partitioning ◽  
Quench Temperature ◽  
Embrittlement Resistance ◽  
Hydrogen Embrittlement Resistance

Abstract The influence of microstructure on hydrogen embrittlement of high strength steels for fastener applications is explored in this study. Space limiting applications in areas such as the automotive or agricultural industries provide a need for higher strength fasteners. Albeit, hydrogen embrittlement susceptibility typically increases with strength. Using a 9260 steel alloy, the influence of retained austenite volume fraction in a martensitic matrix was evaluated with microstructures generated via quenching and partitioning. X-ray diffraction and scanning electron microscopy were used to assess the influence of retained austenite in the matrix with different quenching parameters. The quench temperatures varied from 160 °C up to 220 °C, and a constant partitioning temperature of 290 °C was employed for all quench and partitioned conditions. The target hardness for all testing conditions was 52-54 HRC. Slow strain rate tensile testing was conducted with cathodic hydrogen pre-charging that introduced a hydrogen concentration of 1.0-1.5 ppm to evaluate hydrogen embrittlement susceptibility of these various microstructures. The retained austenite volume fraction and carbon content varied with the initial quench temperature. Additionally, the lowest initial quench temperature employed, which had the highest austenite carbon content, had the greatest hydrogen embrittlement resistance for a hydrogen concentration level of 1.0-1.5 ppm.

scholarly journals Hydrogen diffusion under the effect of stress and temperature gradients

2021 ◽  
Vol 2116 (1) ◽  
pp. 012037
Author(s):  
Zhichao Zhang ◽  
Can Ayas ◽  
Vera Popovich ◽  
Jurriaan Peeters
Keyword(s):  
Finite Element ◽  
Hydrogen Embrittlement ◽  
Circular Hole ◽  
Hydrogen Concentration ◽  
Gas Turbines ◽  
Hydrogen Diffusion ◽  
Solid Metal ◽  
Temperature Gradients ◽  
Fe Model ◽  
Concentration Gradients

Abstract In this paper, a finite element (FE) model is developed to investigate lattice hydrogen diffusion in a solid metal under the influence of stress and temperature gradients. This model is applied to a plate with a circular hole which is subjected to temperature and hydrogen concentration gradients. It is demonstrated that temperature gradients significantly influence hydrogen diffusion and hence susceptibility to hydrogen embrittlement when utilizing hydrogen for gas turbines.

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

2012 ◽  
Vol 326-328 ◽  
pp. 626-631 ◽  
Author(s):  
Toshihito Ohmi ◽  
A.Toshimitsu Yokobori Jr. ◽  
Kenichi Takei
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Hydrogen Embrittlement ◽  
Loading Condition ◽  
Hydrogen Diffusion ◽  
Local Stress ◽  
Cyclic Loading Condition ◽  
Diffusion Analysis ◽  
Concentration Behavior ◽  
Local Stress Field

The hydrogen diffuses and accumulates at the stress concentration area like a crack tip and it causes hydrogen embrittlement. To clarify the mechanism of hydrogen embrittlement, it is important to obtain the hydrogen concentration behavior. However, experimental detection is not feasible due to the high diffusivity of hydrogen and numerical analyses have been preceded. In this paper, by using a finite element and finite difference coupled method at which the diffusion analysis is performed by FDM coupled with the stress analysis by FEM, the analyses of hydrogen diffusion were conducted under cyclic loading conditions.

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