On Fatigue Strength Under Out-of-Phase Sinusoidal Loadings

Let us focus our attention on predicting the influence of phase shifts between sinusoidal stress components of equal frequencies upon the safety factor and the number of cycles-to-failure in fatigue design of structural members made from structural steels. The general state of stress is considered and analyzed by means of the stress-based calculation procedure developed for the case of in-phase stress components. The basic variable space is divided into the safe region and the failure region. In the failure region the subregion of high-cycle fatigue is determined. Functionals of safety are defined, the minimum values of which can be taken as measures of safety in the safe region and in the failure subregion. lt is shown when the phase shift between normal and tangential stress components is most advantageous.