Published online by Cambridge University Press: 04 July 2016
The ability to design components such as drive shafts, propellers and rotor blades to carry combined bending and torsion alternating stresses, which may be out-of-phase is a common requirement in industry. The test data of Nishihara showed that fatigue limits for ductile materials are apparently higher for combined bending and torsion with phase difference than for the conventional in-phase cyclic stressing case. This is true when the out-of-phase fatigue data are stated in terms of the maximum in-phase shear stress amplitudes. However, Little showed that this apparent increase in fatigue strength is very misleading, as when the fatigue limit data are expressed in terms of the true shear stress amplitudes it becomes clear that the fatigue limit actually decreases as the phase difference increases.