PSI - Issue 39

Andrey Shanyavskiy et al. / Procedia Structural Integrity 39 (2022) 327–332 Author name / Structural Integrity Procedia 00 (2019) 000–000

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phase (α + β) titanium alloys and their pronounced sensitivity to dwell -time under load as it was demonstrated by Howard (1986), Shanyavskiy et al. (1998), Wanhill and Oldersma (1999). Cracks can originate in both the rim (as shown by Shanyavskiy and Stepanov (1995)) and the hub part of the disks (as demonstrated by Shanyavskiy et al. (1998), Shanyavskiy and Losev (1999), McEvily (2004)). Therefore, the fracture of disks is mainly determined not by the presence of material defects but by the sensitivity of the titanium alloys to operating conditions (long dwell-time under load) or the appearance of an anomalous high-stress state.

Nomenclature δ

fatigue striation spacing

σ 0.2 σ el σ eq σ max

yield stress elastic limit

equivalent stress

maximum cyclic stress

calc max σ calculated maximum cyclic stress a

fatigue crack length in a depth direction for semi-elliptical crack

durability in terms of the number of cycles equivalent stress intensity factor

N p K eq

Below the results of the investigation on the in-service fatigue fracture of the fan titanium disk of D-18T gas-turbine engine of the aircraft An-124 are discussed. 2. Information on the incident with the fan disk After take-off to flight, the aircraft An-124 experienced a shutdown of engine No. 2. The crew decided to return to the departure airport. After landing, the aircraft passed through the runway out of a distance of about 300 meters from the runway end. As a result, the aircraft was damaged. A survey of engine No. 2 has shown that the fan disk does not exist in the engine. Therefore, the engine shutdown was resulted from the fracture of the fan disk. Parts of the failed engine were scattered for 3.5 km along the take-off course. A fragment of the engine fan disk comprising 15 slots for blades fell on one of the warehouses of the store, breaking through the roof of the building. Only this disk part is analyzed, and the results are discussed below. The disk fragment under investigation is shown in Fig. 1.

Fig. 1. The fragment of fractured fan disk with parts of blades.