Effective fatigue damage summation

The cumulative fatigue damage caused by uniaxial variable stress is considered. To facilitate the lifetime prediction at complex stress patterns, has been defined an effective stress of constant parameters, claimed to be equivalent to the sequence of original stresses in terms of fatigue life of material. The equivalence conditions are based on the theory of energy transformation systems. To the effective stress the Palmgren-Miner rule is applied. Thereby the cycle counting is not required.