Non-local area approach to fatigue life evaluation under combined reversed bending and torsion

The paper presents a new non-local approach to reduction of non-uniform distribution of shear and normal stresses on the critical plane to the uniform ones. Different influence of shear and normal stress gradients on the fatigue life were taken into account in the reduction process. The reduced stress histories were introduced to the algorithm of fatigue life calculation. The proposed non-local area approach was verified by fatigue tests on the hour-glass shaped specimens subjected to the combined proportional or non-proportional bending and torsion. The verification was carried out on the basis of the experimental and calculated fatigue lives with use of two multiaxial fatigue failure criteria.