Split Key Foil Bearing Anti-Rotation Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thin foil, hydrostatic journal bearings in rotating machinery experience fatigue failure due to non-synchronous high-cycle loads, particularly at the tight radius of the formed key, leading to cracking and material degradation.
Innovation Solution
A thin foil, hydrodynamic gas bearing with a split key configuration, featuring a trailing edge key or a split key design that replaces the single anti-rotation tab with two separate tabs, each with a large radius, reducing stress risers and eliminating the 180° bend, thereby enhancing material fatigue strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single anti-rotation tab with tight radius is used, then the key provides effective anti-rotation support, but stress risers cause fatigue cracking and material degradation
Solution Approach 1:
The single anti-rotation tab is divided into two separate tabs (first anti-rotation tab and second anti-rotation tab) positioned at different locations on the foil. This segmentation eliminates the tight radius geometry that causes stress risers, as each tab can be formed with a large radius. The two tabs collectively provide the necessary anti-rotation support while individually avoiding the fatigue cracking problem associated with tight radii.
Solution Approach 2:
The foil structure is modified to have different geometric properties at different locations. The anti-rotation tabs are specifically designed with large radii at their attachment points, creating localized regions of reduced stress concentration. This local quality change (large radius at tab locations) prevents fatigue cracking in the critical anti-rotation regions while maintaining the overall structural integrity of the foil.
2Shape
If a 180° bend is formed to create the anti-rotation tab, then the key geometry is achieved, but the foil exceeds ultimate elongation and develops orange peel condition
Solution Approach 1:
The geometry parameters of the anti-rotation tabs are changed from tight radius to large radius. This parameter change allows the foil to be formed without exceeding its ultimate elongation limit. The large radius geometry reduces the forming strain, preventing the orange peel condition and associated degradation in material fatigue strength, while still achieving the required anti-rotation key geometry.
3Ease of operation
If tight radius geometry is used at the key location, then the anti-rotation tab fits within the key way, but stress risers initiate cracking under high-cycle loading
Solution Approach 1:
By segmenting the anti-rotation support into two separately positioned tabs, each tab can be designed with large radius geometry that fits within the key way without creating stress risers. The segmentation allows the tabs to be positioned where they can engage the key way effectively while maintaining generous radius values that prevent fatigue cracking under high-cycle loading conditions.
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 solution significantly reduces or eliminates fatigue failure under non-synchronous loading conditions, achieving a high load capacity and tolerance for environments with high external vibrations or intermittent reverse rotation.
Implementation Method 1
thin foil, hydrodynamic gas bearing
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A gas bearing within a cylinder (110) is provided. The gas bearing comprises an anti-rotation tab comprising a first side and a second side, the anti-rotation tab sitting within a key way of the cylinder. Further, the gas bearing also comprises a first foil (420) extending in a first direction from a first end (420A) to the first side of the anti-rotation tab and a second foil (430) extending in a second direction from a second end to the second side of the anti-rotation tab.