Damage tolerance analysis of a helicopter component

Fatigue critical helicopter components are, in general, subjected to complex high frequency dynamic loading. Due to these high frequencies small flaws can propagate to failure in a short period of time. Consequently, the demonstration of damage tolerance for those components must include the analysis of near-threshold crack propagation, i.e. growth in the low-to-mid stress intensity factor range (ΔK) regime. To this end this paper presents a fatigue crack growth analysis of a helicopter airframe component, that was used as part of a round-robin study into helicopter fatigue, performed using a non-similitude based crack growth law, termed the Generalised Frost–Dugdale law. The resultant computed crack growth history is in excellent agreement with the measured crack length histories.