Free energy formulation of fatigue crack initiation along persistent slip bands: calculation of SN curves and crack depths

G. Venkataraman*, Y. W. Chung, Y. Nakasone, T. Mura

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Scopus citations

Abstract

A theory of fatigue crack initiation along PSBs based on free energy considerations has been developed. The PSB is modelled as an accumulation of vacancy dipoles. The total free energy of the system increases with fatigue cycle number due to the increase in elastic strain energy. It is shown that there exists a critical fatigue cycle number above which the initial state of dislocation accumulation along the slip band becomes energetically unstable, leading to the initiation of a microcrack within the PSB. SN curves for initiation can be calculated and the resulting crack depths determined. The theory correctly predicts several observed phenomena of fatigue crack initiation: (i) crack initiation is easier in air than in vacuum; (ii) crack initiation is easier at room temperature than at cryogenic temperatures; (iii) just-initiated cracks are shallow.

Original languageEnglish (US)
Pages (from-to)31-40
Number of pages10
JournalActa Metallurgica Et Materialia
Volume38
Issue number1
DOIs
StatePublished - Jan 1990

ASJC Scopus subject areas

  • Engineering(all)

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