Fatigue Life Extension in a Structural Steel

Single tensile overload cycles were applied to evaluate the influence of the overloading ratio on the fatigue crack retardation. The results indicated that the extended fatigue life increases with increasing the magnitude of overloading and in the presence of higher compressive residual stress fields. The effect of two equal and consecutive overloads, with the second one applied at different intervals of crack propagation from the first, was also considered. The residual life after overloading was found to increase after some crack propagation between the two overloads. Larger intervals of crack propagation lead to higher fatigue resistance.