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Current Status and Development Trends of Research on Condition Monitoring of Aeroengine Spindle Bearings (1)

Release time:

2023-01-13

Source:

Journal of Aerodynamics

The Dn value (product of inner diameter D and rotational speed n) of the aviation engine main shaft bearing (hereinafter referred to as the main shaft bearing) can reach 3 × Above 106mm • r/min, contact stress can reach over 2 GPa, and temperature can reach over 220 ℃. Compared with ordinary bearings, spindle bearings have high rotational speed, large load, severe cage impact, high friction heat generation, high working environment temperature, difficulty in ensuring good lubrication, large range of operating conditions changes in a short period of time, and severe slipping in some cases.

The service process of spindle bearings is actually the friction behavior of two rough surfaces. Vakis et al. [1] discussed the friction behavior of two rough surfaces under complex influences such as physical, chemical, and mechanical loads, and believed that in the tribological model, complementary nonlinear effects such as plasticity, adhesion, friction, wear, lubrication, and surface chemistry still need to be further studied.

Friction between rough surfaces may lead to bearing fatigue, wear, and other failures. There are significant differences in the bearing structures and failure behaviors of various support points in aviation engines. The service state of bearings is the result of the combined action of multiple factors. Internal factors include materials, surface properties, etc., while external factors include lubrication status, load, speed influence, etc. Fatigue limits the final life of spindle bearings, but early abnormal failures still account for the majority.

The bearing material is continuously improved to meet the requirements of excellent aviation engine spindle bearings. For bearing materials and combinations containing different elements and ratios, their wear resistance and failure mechanism will change [3 ⁃ 4]; Wakiru et al. [5] believe that lubrication status monitoring can serve as a fault warning for mechanical equipment, and the lubrication status monitoring of spindle bearings is of great significance for fault prevention; The rotational speed and load of the main shaft bearing are the main factors affecting failure, which have an impact on the number of rolling elements carried by the bearing, the relative position of the inner and outer rings, contact stress, slip rate, contact zone temperature, etc. [6].

The main parameters detected to determine the service status of spindle bearings include vibration [7 ⁃ 9], sound [8], acoustic emission [10], lubricating oil [11 ⁃ 12], temperature [13 ⁃ 14], etc. High end equipment usually installs multiple sensors, and through the combination of multi-sensor information and information fusion algorithms, a comprehensive and complete description of its status can be obtained.

Main failure modes of spindle bearings

The spindle bearing operates under harsh working conditions and complex environmental conditions, with complex failure forms and the possibility of multiple failures coexisting. The main failure modes of spindle bearings include fatigue, wear, thermal damage, slipping and scratching, and cage failure [15].

1.1 Fatigue

Fatigue is divided into surface induced fatigue and subsurface induced fatigue. Surface induced fatigue refers to the occurrence of fatigue on the surface under cyclic pressure exceeding the fatigue strength or under the attack of hydrogen ions; Fatigue originating from the subsurface layer, which is related to the maximum orthogonal shear stress. The L ⁃ P (Lundberg ⁃ Palmgren) theory [19] can estimate the fatigue life of bearings, and on this basis, the basic formula of the I ⁃ H (Ioannides ⁃ Harris) life theory applicable to spindle bearings is applicable.

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