The effects of mean stress and stress concentration on fatigue under combined bending and twisting

The Gough test data on fatigue of alloy steel under combined bending and twisting with superimposed mean bending and torsion stresses with and without stress raisers has been re-investigated in terms of the stresses acting on the plane of max. range of shear stress. It has been shown that the allowable amplitude of shear stress on this plane can be predicted from an equation of the form tau sub a = (t--c sub 1 (K sub t x sigma sub a ) exp 1.5 --c sub 2 sigma exp 2 sub m )/K sub t where sigma sub a and sigma sub m are the normal stress amplitude and mean normal stress, respectively, on the plane of max. range of shear stress, c sub 1 and c sub 2 are defined material constants and K sub t is the theoretical stress concentration factor. 4 ref.--AA