Crack growth behavior of Al alloy 7075-T6 under ultrasonic fatigue

Norio Kawagoishi, Masahiro Oki, Masahiro Goto, Qiang Chen, Qingyuan Wang

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T 6, in ambient air and in N2 gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3×10-9 m/cycle. The relation between an applied stress σa and a crack depth at the transition of crack growth direction bT was expressed by σanbT=constant. These results were explained from the time dependent environmental effect and texture of microstructure.

Original languageEnglish
Pages (from-to)1356-1363
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
Issue number9
Publication statusPublished - Sept 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Mechanics of Materials
  • Mechanical Engineering


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