The effect of overloading sequences on landing gear fatigue damage

In service, landing gear can be subject to unexpected hard landing load, which is beyond the design domain. The consequences due to overload can affect the design life of a landing gear to some extent. In this paper, the effect of overload and different loading sequences in random spectra on fatigue damage are investigated, using strain–life based fatigue analysis methods. The discussions are emphasised on the effect of loading sequences on residual stress and mean stress, especially the effect of overload on the fatigue damage of subsequent cycles. In addition, different fatigue analysis techniques in commercial fatigue analysis packages are reviewed and compared. The analysis indicates that the overload effect is stress state dependent and dominated by local residual and mean stress. A ‘Begin’ overload in a load spectrum would cause more damage in the local compressive yield area and an ‘End’ overload within a spectrum will worsen the tensile yielding area. It is suggested that the load sequence effect should be considered in common fatigue analysis if local yielding would exist before or after overloading.