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Journal Articles International Journal of Hydrogen Energy Year : 2023

In situ measurement of plasticity accompanying Hydrogen induced cracking

Abstract

Single crack propagation is studied in a Hydrogen embrittled aluminum alloy. Hydrogen is introduced in the system by electrochemical reactions in an acid aqueous medium. After Hydrogen charging, tensile tests are performed in air, on notched samples, with a micro-tensile machine. An optical microscope is used to follow single crack initiation and propagation at a high magnification. Digital Image Correlation gives the displacement field on the surface with a spatial resolution of about 1 micron. It enables the determination of the position of the crack tip and the local velocity at a sub-grain scale. The equivalent Von Mises strain is calculated and gives a precise measure of the local plastic field which accompanies crack propagation. In addition to the primary plasticity which is emitted from the crack tip or its immediate neighborhood in the form of two intense slip bands, it is systematically found a secondary plastic zone which spreads over several microns ahead of the tip. The characteristics of the plastic zone are measured, together with the velocity and the applied stress intensity factor. In addition, different fracture mechanisms are found on the fracture surface. In particular there are transitions in the fracture mode from intergranular smooth to transgranular parallel to the grain boundary plane. The local fracture mechanisms, in the vicinity of the surface, are linked to the local velocities and plastic deformations. Surprisingly no strong velocity/plasticity correlations are found while the velocities are scattered over a wide range.
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Dates and versions

hal-03410735 , version 1 (01-11-2021)

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L. Stermann, G. Simon, L. Vanel, D. Tanguy. In situ measurement of plasticity accompanying Hydrogen induced cracking. International Journal of Hydrogen Energy, 2023, 48 (73), pp.28567-28582. ⟨10.1016/j.ijhydene.2023.03.384⟩. ⟨hal-03410735⟩
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