Abstract: A method of improving lifetime prediction for resonant fatigue using strain modal test results is presented. The difference between the resonant fatigue and forced fatigue is discussed. The principle of using strain modals to locate the position of maxium strain point in the structure and to determine the maxium strain time history based on other measured data is described. Furthermore, the technique by means of structure dynamic modification to reduce strain response is discussed. Strain modal test and fatigue test are carried out for a cantilever beam. Fatigue life prediction is performed using the proposed method.

Key words: Fatigue, Lifetime, Modal analysis, Resonant, Strain