Fundamental criterion Ktrans for failure analysis of hydrogen-assisted cracks in notched specimens of pure Ni

Tingshu Chen, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi

Research output: Contribution to journalArticle

Abstract

The effects of short notches on crack initiation and extension were studied under electrochemical hydrogen charging in pure nickel. In the hydrogen-charged smooth specimen, multiple cracks were initiated on grain boundaries after significant plastic deformation and were subsequently arrested by crack blunting in the interior of neighboring grains. With the assistance of sub-cracks on specimen surface, quasi-cleavage crack propagation occurred soon after, causing the final failure. The introduction of a notch did not change the crack initiation site (grain boundary). However, crack propagation exhibited significant initial notch-length dependence. A 2.5 mm notch caused quasi-cleavage crack propagation without sub-critical cracks (intergranular cracks) initiation and growth, because the notch root acted as a strongly preferential site for crack extension. However, with a smaller notch, sub-critical cracks initiation and growth were necessary to extend intergranular fracture depth and reach a critical crack length to supply adequate plasticity. This plasticity could not be met in the initial stage from the notch root with hydrogen charging. The relation between maximum remote stress and critical crack length among different notch lengths was shown to be a geometry-independent parameter of pure nickel, which can predict tensile strength under various notch configurations.

Original languageEnglish
Article number102556
JournalTheoretical and Applied Fracture Mechanics
Volume107
DOIs
Publication statusPublished - Jun 2020

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering
  • Applied Mathematics

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