Failure Analysis of a Squirrel Cage Bearing of a Gas Turbine Engine
- 762 Downloads
Premature failure of a squirrel cage bearing of a developmental aero-engine was encountered during its structural test. Four ribs (out of 12) in the cage were fractured from both ends, and the rear flange was completely separated from the cage. One of the support bearings was also found fractured, and the other was damaged to a lesser extent. There were secondary damages to the other components in the test assembly. Fractographic analysis established fatigue failure of the ribs. Two crack fronts were originated from the diagonally opposite corners of the ribs indicating failure of the bearing cage under reverse bending fatigue loading condition. No metallurgical anomalies were present at the crack origin. The rear flange was separated from the bearing cage in shear mode of failure, whereas the support bearing outer race failure was by instantaneous overloads. Design modifications were introduced after thorough stress analysis of the component. Subsequently, no such failure incidents were encountered, and the modified design has been put into service.
KeywordsGas turbine engine Bearings Fatigue Beach marks Striations Dimples
The authors express their gratitude to DRDO and Director, GTRE, for supporting the work and granting permission to publish the data. The support and guidance provided by the Technical and Associate Directors and the help extended by the Structural Mechanics Group and NDT-Quality Assurance Group in completing the analysis also gratefully acknowledged.
- 2.T. Nishikawa, N. Hayashi, A. Hayakawa, Technical trend of aircraft bearings. NTN Tech. Rev. 82, 83–87 (2014)Google Scholar
- 3.Bearing Failure: Causes and Cures, Technical Brochure, Barden Precision Bearings (2007) pp. 1–15Google Scholar
- 4.Ball & Roller Bearings: Failures, Causes and Countermeasures, CAT. NO. B300 1 E (2009) pp. 1–20Google Scholar
- 5.ASM Handbook, Properties and Selection: Irons, Steels, and High Performance Alloys, vol. 1 (2005)Google Scholar
- 6.Aircraft Turbine Engine Reliability and Inspection Investigations, AD-A274 860, DOT/FAA/CT-92/29 (U.S. Department of Transportation, Federal Aviation Administration, 1993)Google Scholar
- 7.ASM Handbook, Failure Analysis and Prevention, vol. 11 (2002)Google Scholar
- 8.ASM Handbook, Fractography, vol. 12 (1987)Google Scholar
- 9.ASM Handbook, Fatigue and Fracture, vol. 19 (1996)Google Scholar
- 10.P.P. Milella, Fatigue and Corrosion in Metals (Springer-Verlag Italia, 2013). doi: https://doi.org/10.1007/978-88-470-2336-9_2