Non-Circular CMC Attachment Pin for Lower Hole Edge Stress
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Solution Overview
Problem
Existing attachment pins for ceramic matrix composite (CMC) components in gas turbine engines concentrate loads on the edge of the CMC hole, leading to increased bending moments and potential fracture due to differences in curvature between the CMC component and the pin, resulting in high contact stresses.
Innovation Solution
The use of non-circular attachment pins with matched radii of curvature, such as D-shaped or elliptical cross-sections, which provide a larger contact area while minimizing pin height, reducing radial stiffness and contact stresses, and accommodating thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If circular attachment pins are used for CMC components, then the pin structure is simple and easy to manufacture, but the load is concentrated on the edge of the CMC hole causing high bending moments and contact stresses
Solution Approach 1:
The patent applies asymmetry by changing the pin cross-section from circular to non-circular shapes (D-shaped, elliptical, or rectangular). This asymmetric geometry allows the pin to better match the curvature of the CMC hole, distributing the load more evenly across the contact surface and reducing stress concentration at the hole edge, thereby improving fracture resistance while maintaining manufacturability.
Solution Approach 2:
The patent applies curvature matching by designing the pin's cross-sectional shape to have a radius of curvature that matches the CMC hole's radius of curvature. This curvature compatibility ensures optimal contact between the pin and hole, distributing contact stresses uniformly and preventing edge loading that would lead to bending moments and potential fracture.
2Stress or pressure
If pins with larger contact area are used, then contact stresses are reduced, but the pin height increases consuming more radial space
Solution Approach 1:
The non-circular cross-section (D-shaped, elliptical, or rectangular) allows the pin to achieve a larger effective contact area with the CMC hole while maintaining a compact overall height. The asymmetric geometry optimizes the contact surface distribution, increasing the load-bearing area without proportionally increasing the pin's radial dimension.
Solution Approach 2:
The patent transitions from a circular cross-section to non-circular cross-sections that better utilize the available space in different dimensions. This dimensional optimization allows the pin to maximize contact area within the constrained radial space by distributing the contact interface more effectively across the pin's cross-sectional geometry.
3Device complexity
If the pin radius of curvature differs from the CMC hole radius of curvature, then the pin design is simpler, but bending moments increase due to curvature mismatch
Solution Approach 1:
The patent applies curvature matching by designing the pin's cross-sectional shape to have a radius of curvature that matches the CMC hole's radius of curvature. This curvature compatibility ensures optimal contact between the pin and hole, distributing contact stresses uniformly and preventing edge loading that would lead to bending moments and potential fracture.
Data Source
AI summary
A component assembly includes a first component that has a first hole. The first hole has a non-circular cross section. A first portion of the first hole has a first radius of curvature and a second component. A pin extends from the second component and through the first hole. The pin has a non-circular cross section. A second portion of the pin has a second radius of curvature. The first radius of curvature and the second radius of curvature are substantially the same.