Synergy of crack closure, near-tip residual stress and crack-tip blunting in crack growth under periodic overloads – A fractographic study

R. Sunder, A. Biakov, A. Eremin, S. Panin

Research output: Contribution to journalArticle

11 Citations (Scopus)


Fatigue crack growth tests were performed on an Al-Cu alloy under specially designed load sequences with a periodic overload cycle. These overloads were either immediately followed by or preceded by underloads of controlled magnitude. Baseline loading magnitude was designed to induce near-threshold conditions well below the Paris Regime. The fatigue fracture surfaces obtained from the tests were subject to fractographic analysis. The study shows that irrespective of their magnitude, underloads preceding tensile overloads do not affect crack growth rate after the overload. However, if the underload follows an overload, it carries a deleterious effect on retardation, whose magnitude is determined by the extent to which the underload drops below baseline cycling level. In either case, observed effects do not seem to have anything to with crack closure, but rather, are attributable to the effect of underloads on near-tip residual stress during baseline cycling that in turn controls threshold stress intensity range. Post-overload crack closure is reduced by crack-tip blunting, but rapidly recovers.

Original languageEnglish
Pages (from-to)18-29
Number of pages12
JournalInternational Journal of Fatigue
Publication statusPublished - 1 Dec 2016



  • Crack closure
  • Crack-tip blunting/re-sharpening
  • Near threshold fatigue
  • Near-tip residual stress
  • Variable-amplitude loading

ASJC Scopus subject areas

  • Modelling and Simulation
  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering

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