Influence of complex defect on cast AS7G06-T6 under multiaxial fatigue loading

•The fatigue limits under multiaxial fatigue loadings are identified.•Crossland criterion gives reasonable equivalent stress under multiaxial loadings.•A new definition of the equivalent defect size for complex defect is proposed.•The competition between single and complex defects in fatigue failure is explained.

AS7G06-T6 cast aluminum alloy is tested under tension, torsion and tension–torsion fatigue loading for two load ratios. Basquin’s law and step loading method are used to obtain the fatigue limit under multiaxial loading. Crossland criterion and principal stress criterion considering Goodman idea are compared to evaluate the multiaxial behavior. The influence of complex defects on fatigue limit is analyzed under multiaxial loadings. Several artificial defects are machined on fatigue specimen with different distance between edges. A new definition of the equivalent defect size considering the distance between defect edges is proposed. For both tension and tension–torsion fatigue, the competition between single natural defect and complex artificial defects is observed and analyzed.