Transient Dynamic Fatigue Analysis using Inertia Relief Approach with Modal Resonance Augmentation

Inertia relief approach is often used to predict fatigue life of automotive structures. This approach, which completely ignores resonance effects, can provide reliable results, if the natural frequencies of the system are higher than loading frequencies by more than four times. In this paper, a method is proposed to augment the inertia relief results by including modal resonance effects. This new method has the same accuracy as that of the direct transient dynamic analysis with the efficiency of inertia relief approach. Here, inertia relief and normal mode results are obtained using commercial finite element codes and the modal resonance parameters are calculated in a manner suitable to handle long time histories of proving ground loads.