Biaxial tension–tension fatigue crack growth behavior of 2024-T3 under ambient air and salt water environments

• Three biaxiality stress ratios (λ = 0.5, 1 and 1.5) were investigated.
• Biaxial fatigue crack growth data were developed for salt water and air environments.
• Biaxiality affected crack growth rates which depended upon biaxiality stress ratio.
• The effect of biaxiality was greater in the salt environment compared to air.
• For λ = 1.5 with higher mode II, brittle striations were observed.

Uniaxial and biaxial fatigue crack growth behavior of aluminum alloy, 2024-T3 was characterized under air and salt water environments using cruciform specimen with a horizontal pre-crack in L–T orientation. Crack propagated coplanar to the pre-crack under biaxial fatigue with biaxiality ratios of 0.5 and 1 and non-coplanar to the pre-crack with biaxiality ratio of 1.5. Fatigue crack growth versus crack driving force relationships showed two regions. The crack growth rates and damage mechanisms were different depending upon biaxiality ratio in these two regions as well as in two test environments. These were also compared with counterparts from uniaxial fatigue.