This paper contains the in-service fatigue fracture analysis for the first stage low-pressure compressor disk of the aircraft engines D30KU-154. Based on the results of the fractographic investigation on collapsed compressor disks the fatigue crack initiation and propagation mechanisms were established. It is shown that the crack initiation in the rim part of the compressor disk is due to a high frequency loading that leads to very high cycle fatigue fracture. The total fatigue life of the compressor disk is determined by simultaneous action of low amplitude loading due to blades vibration, and high amplitude loading due to flight cycle (centrifugal forces). To study the in-service fracture of the compressor disk the numerical simulation of the stress state in the damaged zone under corresponding loading conditions was evaluated. The estimation of fatigue life and crack path predictions were performed based on the multi-regime fatigue fracture model proposed by the authors.

The process of fatigue spalling in the rings of ball bearings at durability exceeding 10 8 cycles under in-service loading conditions is analyzed on the basis of fractography and the slices prepared in radial planes of rings. The cracks are shown to originate at subsurface from carbides inherent in the bearing steel or inclusions permissible by sizes for the material. Subsequently, the development of cracks perpendicular to the ring raceway surface takes place similarly as in the VHCF regime with the elliptical “fish-eye” formation. The subsequent crack growth was demonstrated step-by-step up to the ring material fragment separation. The total crack path by alternating stops of propagation and new crack nucleation under conditions of mixed-mode I+II+III mechanisms with the crack branching was discussed. In the final stage, the crack grows towards the ring raceway and either appears on the raceway surface or coalesce with a similar adjacent crack followed by fatigue spalling formation.

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 brackets of the in-service airframe and in the wing panels during full-scale bench tests was estimated 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.