Reliability modelling for fatigue life prediction: with application to components in dynamic systems of rotorcraft

A mechanical component can break due to repeated load cycling, even if these loads remain well below the component’s regular static strength. In a simplified fashion, a component’s fatigue life depends on the loads that it has to endure during its service life, as well as its fatigue strength to resist the formation of cracks. Since both of these factors can be considered as random variables, the time until a fatigue-induced rupture occurs can be considered as a random variable as well. Airworthiness regulations require that aircraft manufacturers show by numerical analysis that the probability that a fatigue failure occurs during a critical part’s maximum allowable service life does not exceed a specified probability.