Fatigue Life Prediction Using Frequency Response Functions

Abstract

This paper presents a method for fatigue life prediction of engineering components subjected to dynamic loads. It is based on the determination of the nominal stress at the crack position using frequency response functions and this in turn enables the prediction of dynamic fatigue life under forced vibration. The main advantage of this approach lies in the fact that stresses used for fatigue life prediction are determined via a vibration analysis and hence not only elastic but also inertia and damping forces are included in the model. The implementation of the technique is discussed in the case of a bladed-disc assembly where single-blade mistuning is caused by a fatigue crack. It is believed that the proposed method has promising implications for safer designs and also for the prediction of inspection intervals, especially in rotating machinery applications where such considerations are of paramount importance.