In-situ experimental study on the fatigue crack propagation behavior of 7075-T6 and 2024-T3 aluminium alloys under variable amplitude loading and retardation model modification

Liang Cai, Wei Li*, Zhenglin Mo, Ping Wang, Muhammad Imran Lashari, Usama Hamid, Xiaoming Ding, Tatsuo Sakai, Tianyi Hu, Yucheng Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Fatigue crack propagation behavior of Al7075-T6 and Al2024-T3 under four typical variable amplitude loading (VAL) patterns are investigated by using in-situ testing. The near-tip strain fields and crack opening level are measured combining in-situ optical microscopy testing and digital image correlation (DIC) technique. The crack tip deformation process is directly observed by in-situ scanning electron microscope (SEM). The results show that both the crack propagation behaviors and the crack-tip strain distributions are greatly influenced by the VAL patterns. The shape effect of the overload-induced plastic zone may prolong the crack growth retardation. The crack-front plasticity plays a dominant role in controlling fatigue crack growth. The crack-front plasticity supplies a link between crack closure and crack growth. The crack tip resharpening caused by the underload applied immediately after the overload may reduce the retardation extent. Finally, a modified retardation model is proposed and gives reasonable prediction results of the crack growth rate under VAL.

Original languageEnglish
Article number103372
JournalTheoretical and Applied Fracture Mechanics
Volume119
DOIs
Publication statusPublished - Jun 2022

Keywords

  • Crack closure
  • Crack growth prediction
  • In-situ
  • Plasticity
  • Variable amplitude loading

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