Digital Repository, ICF12, Ottawa 2009

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Failure Investigations of Cracked Spherical Bearings in Aircraft
X. Wu, A. Bourgeois

Last modified: 2013-05-03


During aircraft overhaul, six spherical bearings were found cracked in bearing
balls made of 440C stainless steel. The cracked bearings were used for different
aircraft joints and came from different suppliers. Investigations revealed that all
the cracks originated from the ball surface and extended in the axial direction of
the bearing. Intergranular fracture was the common characteristic found in most
of the cracked balls.
Detailed fractographic analyses of the bearing balls provided additional evidences
that allowed differentiating fracture mechanisms among bearings. All the cracks
were initiated from surface discontinuities, such as plating defects, micropitting
resulted from contact fatigue, etc. Hydrogen presented in service environment
contributed to crack extension, but was not the root cause of the failure.

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