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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Engine D-18T released on 04.06.1992 had operated for 18,400 hours (3732 flight cycles) since the new, including 2308 hours (458 cycles) after the last overhaul. 3. Fan disk material and methods used The fan disk was manufactured by forging from the two-phase VT3-1 titanium alloy (Ti–6Al–3Mo–2Cr alloy). The material state of the disk was evaluated using the following methods:

• chemical composition estimation; • measuring of the material hardness; • metallography; • fractography.

It was established that the chemical composition and Brinell hardness of the disk material correspond to those as stated in the technical documentation regulating the fan disk manufacturing procedure. The metallographic analysis confirmed the correspondence of the disk material to a two- phase (α + β) titanium alloy with a mixed type of globular and lamellar structure as shown in Fig. 2.

a

b

Fig. 2. The microstructure of the two- phase (α + β) titanium alloy with a mixed type of globular and lamellar structure : (a) optical and (b) SEM images at different magnifications.

The analysis of the fracture surface had shown that the fatigue crack with the semi-elliptical shape of its front (Fig. 3) was propagated in the direction from the disk rim to its hub. The crack originated in the bottom part of the slot for a blade. The maximum crack length along the slot surface and in a depth direction was 200 mm and 48 mm, respectively.

Fig. 3. Fracture surface of the disk with the region of fatigue crack growth (dark grey area).