Fatigue strength assessment of beams under variable combined periodic stress

Abstract

The paper deals with the fatigue life prediction of beams under variable periodic stress due to combined bending moment, torsional moment and axial force. It is assumed that the envisaged service life can be considered as a set of states and that the stress components in each state are given in the form of Fourier series. The equivalent state of stress with in-phase constant-amplitude components are determined on the basis of Cempel’s theory of energy transforming systems. It enables to estimate the time to fatigue failure without application of any cycle counting method and hypothesis of fatigue damage cumulation.