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Hydrogen-Enhanced Fatigue Crack Growth in a Single-Edge Notched Tensile Specimen Under In-Situ Hydrogen Charging Inside an Environmental Scanning Electron Microscope

25 Pages Posted: 14 Dec 2018 Last revised: 4 Jan 2019 Publication Status: Under Review

See all articles by Di Wan

Di Wan

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Yun Deng

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Jan Inge Hammer Meling

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Antonio Alvaro

SINTEF Energy Research

Afrooz Barnoush

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Abstract

Fatigue crack growth (FCG) test was done on a pre-cracked single-edge notched tensile (SENT) specimen with oligocrystalline ferritic structure. Innovative in-situ hydrogen (H)- charging by plasma inside an environmental scanning electron microscope (ESEM) was adopted to directly observe the H influence on the FCG behavior of this material. Diverse in-situ and post-mortem characterization methods including secondary electron imaging, backscatter electron imaging, electron backscatter diffraction (EBSD) and scanning probe microscopy (SPM) were used to investigate the material's behavior. It was observed that the crack growth rate was enhanced by about one magnitude when H was charged, in comparison with the reference test in vacuum (Vac). The FCG procedure was concluded as strongly associated with the plasticity evolution in the vicinity of the crack-tip. A simple model based on the restricted plasticity was proposed for the H-enhanced FCG behavior. A peculiar frequency dependency of the H-enhanced FCG behavior was observed at low loading frequencies (0.015 Hz ~ 0.15 Hz): under the same in-situ H-charging condition, a lower frequency gave a slower crack growth rate and vice versa. This behavior was explained by the thermally activated dislocation motion correlated with the plasticity shielding effect during crack growth.

Keywords: fatigue crack growth (FCG); hydrogen embrittlement; SENT specimen; EBSD; SEM

Suggested Citation

Wan, Di and Deng, Yun and Meling, Jan Inge Hammer and Alvaro, Antonio and Barnoush, Afrooz, Hydrogen-Enhanced Fatigue Crack Growth in a Single-Edge Notched Tensile Specimen Under In-Situ Hydrogen Charging Inside an Environmental Scanning Electron Microscope. Available at SSRN: https://ssrn.com/abstract=3301332 or http://dx.doi.org/10.2139/ssrn.3301332

Di Wan (Contact Author)

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering ( email )

Trondheim NO-7491
Norway

Yun Deng

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Trondheim NO-7491
Norway

Jan Inge Hammer Meling

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering

Trondheim NO-7491
Norway

Antonio Alvaro

SINTEF Energy Research

Kolbjørn Hejes vei 1A
Trondheim, NO-7034
Norway

Afrooz Barnoush

Norwegian University of Science and Technology (NTNU) - Department of Mechanical and Industrial Engineering ( email )

Trondheim NO-7491
Norway

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