PSI - Issue 60

V. Venkatesh et al. / Procedia Structural Integrity 60 (2024) 372–381 V Venkatesh et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3.4. Fillet surface on the unbroken side of bearing housing

In view of initiation of cracks along machining marks on fillet surface leading to fracture in the bearing housing, the fillet surface on the unbroken side of the bearing housing was examined. Examination revealed presence of incipient cracks at the trough of at least three deep circular machining marks (refer Fig. 9).

Fig. 9. (a) Fractured bearing housing of the control rod, (b) close-up view of the fillet surface indicated by an arrow in (a), (c) SE image of the region marked in (b) and regions marked 'A' through 'C' in showing incipient cracks along the trough of the machining marks, and (d) magnified view of one of the incipient cracks.

3.5. Damages on the inner surface of bearing housing

Figure 10(a-b) shows SE images of a typical damaged region on the inner surface of the bearing housing. Examination revealed loss of material from the damaged regions by fretting wear. Figure 10(c) shows an energy dispersive X-ray spectroscopy (EDX) spectrum recorded on the damaged regions of the bearing housing. The spectrum shows the presence of bearing race elements such as iron (Fe), chromium (Cr), and nickel (Ni) on the inner surface of the titanium alloy rod's bearing housing. The presence of bearing race elements on the rod's bearing housing further confirms that the damage was caused by fretting. The material transfer occurred due to the small oscillatory movements between the bearing outer race and housing. This indicates the deficiency in the bearing's interference fit or press fit at the swash plate end.