Non-Metallic Ring for Generator Bearing Corrosion
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Solution Overview
Problem
In electrical generators, particularly those used in aircraft, the differential thermal expansion between aluminum bearing liners and steel main bearings can lead to a loose fit, causing fretting corrosion and restricting axial motion due to operational vibrations.
Innovation Solution
A non-metallic ring, made from materials like graphite enhanced polyimide, is interposed between the bearing liner and the main bearing to eliminate metal-to-metal contact, thereby preventing fretting corrosion and ensuring reliable axial motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a loose fit is used between the main bearing and bearing liner to accommodate thermal expansion, then the bearing can accommodate differential thermal expansion, but fretting corrosion occurs due to operational vibrations
Solution Approach 1:
A non-metallic ring is introduced as an intermediary component between the steel main bearing and the aluminum bearing liner. This ring acts as a mediator that eliminates direct metal-to-metal contact, thereby preventing fretting corrosion while still allowing the bearing assembly to accommodate differential thermal expansion between the steel and aluminum components.
Solution Approach 2:
The bearing assembly uses a composite structure combining steel (main bearing), aluminum (bearing liner), and a non-metallic material (intermediate ring). This composite approach leverages the advantages of each material: steel provides structural strength, aluminum provides thermal expansion characteristics, and the non-metallic ring provides corrosion resistance and eliminates galvanic corrosion between dissimilar metals.
2Reliability
If a tight fit is used between the main bearing and bearing liner to prevent vibration, then fretting corrosion is reduced, but axial motion of the main bearing is restricted
Solution Approach 1:
The non-metallic ring serves as a mediator that allows controlled axial motion of the main bearing while maintaining a secure radial fit. This intermediate layer enables the bearing to float axially for thermal expansion accommodation without the metal-to-metal contact that causes fretting corrosion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The non-metallic ring effectively inhibits fretting corrosion, enhancing the reliability and longevity of the bearing system by maintaining clearance and reducing wear, even at high operational temperatures.
Implementation Method 1
A non-metallic ring, made from materials like graphite enhanced polyimide, is interposed between the bearing liner and the main bearing to eliminate metal-to-metal contact, thereby preventing fretting corrosion
Implementation Method 2
Because the bearing liner is made from aluminum and the outer ring of the main bearing is made from steel, clearances increase at operational temperatures
Data Source
AI summary
A bearing assembly for an electrical generator includes a frame, a bearing liner, a bearing and a non-metallic ring. The frame is configured to connect with a housing of the electrical generator. The bearing liner is connected with the frame. The bearing is received in the bearing liner. The non-metallic ring is interposed between the bearing liner and the bearing.