Journal ArticleDOI
Hydrogen-enhanced localized plasticity—a mechanism for hydrogen-related fracture
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TLDR
In this article, a theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined, which can account for the observed hydrogen-enhanced dislocation mobility.Abstract:
The mechanisms of hydrogen-related fracture are briefly reviewed and a few evaluative statements are made about the stress-induced hydride formation, decohesion, and hydrogen-enhanced localized plasticity mechanisms. A more complete discussion of the failure mechanism based on hydrogen-enhanced dislocation mobility is presented, and these observations are related to measurements of the macroscopic flow stress. The effects of hydrogen-induced slip localization on the measured flow stress is discussed. A theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined. It is shown that this shielding effect can account for the observed hydrogen-enhanced dislocation mobility.read more
Citations
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Journal ArticleDOI
Hydrogen effect on the mechanical behaviour and microstructural features of a Fe-Mn-C twinning induced plasticity steel
TL;DR: The influence of hydrogen on the mechanical properties and fracture behavior of Fe-22Mn-0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic analysis as mentioned in this paper.
Book ChapterDOI
Challenges Toward the Further Strengthening of Sheet Steel
TL;DR: In this paper, the authors reviewed the recent progress concerning sheet steel used in automobiles, taking into account history and technological problems, such as formability, fatigue properties, and hydrogen embrittlement.
Dissertation
Evaluation of Welded Clad Pipe - Properties and Simulations
Abstract: Pipelines are an essential part of the oil and gas offshore industry, for transporting unprocessed oil and gas from the seabed to the oil platform and to the mainland. The unprocessed oil and gas leaves a corrosive environment, which sets a demand for pipes with a corrosion resistant interior. Clad pipes meet this demand with a corrosion resistant, stainless steel interior and an outer carbon steel layer. There is of today no repair contingency for clad pipes. A knowledge basis needs to be established and the risk of hydrogen induced stress cracking (HISC) must be found. This thesis work has been divided into two parts; One part working on experimentally testing of the triple point in welded clad pipes. Focused on fracture resistance curves, fracture toughness and crack path, with and without hydrogen present. The second part was focused on modelling a FE-model that was able to simulate crack propagation in clad pipe interface samples, experimentally tested by Jemblie [1]. Both with and without hydrogen present during testing. Fracture mechanical testing of welded clad pipe C(T) samples have been successfully conducted, in air and under cathodic protection (CP). The samples with Ni-interlayer showed almost no reduction in fracture toughness from tests in air to tests under CP, with an average fracture toughness reduction of 0.13%. The small fracture toughness reduction may be explained by the crack path going into the Ni-interlayer which is not much susceptible to hydrogen embrittlement (HE). The samples without Ni-interlayer experienced a high decrease in fracture toughness tested under CP, with an average reduction in fracture toughness equal to 92%. The crack path in the samples without Ni-interlayer was examined in a light optical microscope (LOM). The test done in air showed a crack path shifting between the base material and the clad. The crack propagated mainly in the clad in the sample tested under CP. Not enough samples were tested to establish the fracture resistance curves for the samples without Ni-interlayer. A 2D FE-model with cohesive zone elements was successfully modelled. The FE-model was able to simulate crack propagation along the crack ligament, in a C(T) specimen, both with linear elastic and elastic-plastic materials. The FE-model was however not able to simulate the crack propagation observed in experimentally testing by Jemblie [1]. This was not possible due to numerical problems occurring after a few cohesive elements had failed, when using sufficiently high cohesive element parameter values. For further work should more tests in both air and under CP be done on welded samples, with and without a Ni-interlayer. To establish the fracture resistance curves for both sample types. The microstructure on the samples without Ni-interlayer needs to be checked, to be sure that the samples are representative for welded clad pipes. The fractography must be studied and the cross section on multiply samples must be examined, on the samples without Ni-interlayer. To establish a more solid basis to explain the crack path and the hydrogen susceptibility on welded clad pipes. A deep root-cause investigation should be done on the FE-simulation, to explain and come up with a possible solution on the numerical crack propagation problem.
Journal ArticleDOI
Hydrogen brittleness of austenitic steels
TL;DR: In this paper, the electronic concept for hydrogen embrittlement (HE) of austenitic steels is developed based on the hydrogen-caused increase of the concentration of free (i.e. conduction) electrons.
Molecular Dynamics Simulations Of Hydrogen Embrittlement: Preliminary Results
TL;DR: The XI Congreso Nacional de Materiales 2010, celebrated in Zaragoza (Espana) del 23 al 25 de junio de 2010 as mentioned in this paper, was the first edition of this workshop.
References
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Journal ArticleDOI
Embedded-atom method: Derivation and application to impurities, surfaces, and other defects in metals
Murray S. Daw,Michael I. Baskes +1 more
TL;DR: In this paper, the authors derived an expression for the total energy of a metal using the embedding energy from which they obtained several ground-state properties, such as the lattice constant, elastic constants, sublimation energy, and vacancy-formation energy.
Journal ArticleDOI
A new model for hydrogen-assisted cracking (hydrogen “embrittlement”)
TL;DR: A new model for hydrogen-assisted cracking is presented in this article, which explains the observations of decreasing microscopic plasticity and changes of fracture modes with decreasing stress intensities at crack tips during stress-corrosion cracking and HAC of quenched-and tempered steels.
Journal ArticleDOI
Equilibrium aspects of hydrogen-induced cracking of steels
R.A. Oriani,P.H. Josephic +1 more
TL;DR: In this paper, the threshold pressures, p ∗, of hydrogen and of deuterium gases necessary to cause crack propagation in AISI 4340 steel of 250 ksi yield strength, were determined as functions of plane-strain stress intensity factor K at room temperature.
Journal ArticleDOI
A theory of the fracture of metals
TL;DR: In this paper, a theory of the fracture of metals is presented, which is based on the theory of fracture theory of metal fracture, and it is proved that the theory is correct.
Journal ArticleDOI
Hydrogen embrittlement of α titanium: In situ tem studies
TL;DR: In this paper, the effect of hydrogen on fracture in the h.c.p. α Ti-4 wt % Al alloy and the role of titanium hydride in the fracture process have been studied by deforming samples in situ in a highvoltage electron microscope equipped with an environmental cell.