Structural damage in mechanical components is frequently caused by high-cycle vibration fatigue. The non-linearities, frequently observed in real structures at increased excitation levels, significantly influence the damage accumulation. As the modal analysis bases on linear theory, the non-linearities are hard to include. Based on a new experimental identification of the non-linearities, this research proposes the corrected linear damage-accumulation estimation. With the proposed correction, the linear modal analysis is used for damage estimation of structures with non-linearities.
The proposed approach is applied to a real-life case of steel-sheet attached with rivets. Several samples are exposed to an accelerated vibration-fatigue test with increasing and also decreasing excitation levels. It is shown that with the experimentally identified non-linearity correction, the numerical fatigue life-time was within the 10% of the experimentally identified life-time. Experimentally, it was shown that rivets same by design, but produced by different manufacturers, have a significant difference in the fatigue life-time; this difference was clearly identified with the proposed correction to the linear damage-accumulation estimation.
Further, the frequency response function based identification of the non-linearity can be identified before the structure is exposed to fatigue loads resulting in new possibilities of vibration-fatigue analysis of non-linear systems.