Foundation of damage tolerance principles in-service for the RRJ-95 aircraft structural components

Fatigue cracks initiated from holes in several zones and structural components of the RRJ-95 aircraft frames were investigated. Using the method of quantitative fractography, the crack growth duration in the wing panels during full-scale bench tests and in the brackets of the in-service airframe was estimated by measuring the spacing of meso-beach-marks (MBM) and fatigue striations. The applied program of bench test consisted of blocks of variable loads that were equivalent to the wing loading in flight and reproducing schematized flight-cycle. It was shown that the duration of fatigue crack propagation in several structural components of the RRJ-95 aircraft frames was approximately the same as for the crack nucleation duration. The total lifetime is sufficiently long for cracks in the structural components to be detected and reliably monitored with a large operating time interval between adjacent inspections.

Automated summary

Fatigue cracks initiated from holes in several zones and structural components of the RRJ-95 aircraft frames were investigated. The study estimated the crack growth duration by measuring the spacing of meso-beach-marks and fatigue striations, showing that it was approximately the same as for the crack nucleation duration. The total lifetime of cracks in the structural components is long enough to be detected and monitored with a large operating time interval between adjacent inspections.