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Fatigue behaviour of casting materials or generally flawed materials is mainly
governed by defects. Critical defects are located either at the surface or within the
bulk. Different approaches considering the defect as a crack or notch exist.
However the approaches are often based on 2D description which are limited to
simple axial loading and do not allow to predict fatigue limit evolution under
multi-axial conditions. Furthermore, approaches often use elastic stresses as input
parameter for the fatigue analysis, this can lead to wrong fatigue estimation
because plastic strain at the tip of the defect is not taken into account. To describe
the influence of surface defect geometry on fatigue behaviour, a stress based
multi-axial fatigue criterion has been proposed by Nadot and Billaudeau [1, 2].
This model uses a multiaxial fatigue criterion and the size of the defect is taken
into account through Murakami’s parameter area and the spatial gradient of
stresses.