A non-linear fatigue damage rule with an exponent based on a crack growth boundary condition

For the life prediction of cyclic loaded specimens several damage accumulation theories exist. Some use a power law rule to convert the damage from one load level to another. The difference between these rules is the calculation of the exponent. In this article, a new exponent is proposed based on a crack growth boundary condition. In order to improve life prediction accuracy, the variation of the crack growth speed with the load level is needed. The new theory is compared with experimental data from the literature and the results are presented. Further developments of the theory are proposed.