Failure Analysis of Bearings of Aero-Engine
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TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis of Bearings of Aero-Engine Manish Roy
Submitted: 12 April 2019 / in revised form: 28 August 2019 ASM International 2019
Abstract Failed bearings of various aero-engines were subjected to investigations. The bearing of cooling turbine of aircraft designated as B-1 was found to fail due primarily to misalignment and overloading. Bulk fatigue and permanent dimensional changes also accelerated the failure. The center main bearing of another aero-engine designated as CMB-1 was found nonfunctional because of ‘Brinelling’ action. Lack of lubrication caused over heat and deformation of rollers by metal to metal contact, and this resulted in formation of untempered martensite, leading to failure of center main bearings referred as CMB-2 of another helicopter engine. Stationary race and rotating race of thrust bearing of positive displacement reciprocating hydraulic pump bearing denoted as EDP-1 failed by abrasive action of foreign particles and oxidized metallic particles. In contrast, balls of the same bearing failed because of abrasive action of oxidized metal debris and rolling contact fatigue. Keywords Contact fatigue Brinelling Misalignment Over heating
Introduction Bearings are extensively used components in any engineering assembly with diverse applications ranging from domestic (fans, turn tables, etc.) to aerospace. Depending on area of applications, bearings are subjected to radial loading or thrust loading or combination of both types of M. Roy (&) Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058, India e-mail: [email protected]
loading. Based on operating condition, these bearings are subjected to mechanical or chemical degradation. Bearings are used in various parts of the aero-engines. Bearings can fail due to several reasons such as contact fatigue, denting, wear, corrosion, misalignment, contamination, etc. [1–4]. A large number of literatures on failures of bearings are available [5–8]. Mishra et al. [5] analyzed the failure of an inter-shaft bearing in an aero gas turbine engine. They attributed the failure to insufficient clearance due to differential expansion of inner ring and contraction of outer ring due to heating and cooling, leading to progressive fatigue as a result of overload. Analysis due to Ejaz et al. [6] indicated that an aero-engine failed due to the misalignment of the ball bearing fitted on the main shaft of the engine. As reported by Bhat et al. [7], ball bearing belonging to jet engine of a military aircraft failed due to eccentricity caused by improper mounting of the bearing onto the shaft of the bevel gear. According to Yu and Yang [8] interaction between dry friction and impact both led outer ring of a cylindrical roller bearing within an air blower motor. Failures of several bearings of aeroengine have been investigated in author’s laboratory over past few years. Results of such investigation have been compiled in this work.
Background The present article is concerned with failure of sever
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