Effects of the Non-Proportional Loading Path on the Fatigue Crack Path

Fatigue crack path prediction and crack arrest are very important forstructural safety. In real engineering structures, there are many factors influencing thefatigue crack paths, such as the material type (microstructure), structural geometry andloading path, etc. This paper studies the effects of loading path on the crack path.Experiments were conducted on a biaxial testing machine, on the specimen made ofsteel 42CrMo4, with six different biaxial loading paths. Fractographical analyses of theplane of crack initiation and propagation were carried out. Theoretical predictions ofthe damage plane were conducted using the Findley, the Fatemi-Socie, the SWT and theLiu s criteria. Comparisons of the predicted orientation of the damage plane with theexperimental observations show that the shear-based multiaxial fatigue models givevery good predictions.