Gas Turbine Shaft Spline Geometry for Damage-Tolerant Assembly
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Solution Overview
Problem
Conventional spline designs in gas turbine engines suffer from impact damage, surface cracks, and misalignment during assembly due to sharp edges and high stress concentrations, leading to foreign object debris and undesirable wear.
Innovation Solution
The design incorporates splines with axial faces that taper to a spline top surface, featuring a curved chamfered surface with radii and compound curvature, eliminating acute or obtuse angle transitions, and axial segmentation to reduce damage and ensure proper alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional splines with sharp edges are used for coupling rotating components, then the spline structure is simple and easy to manufacture, but impact damage, surface cracks, and metal chipping occur during assembly due to high stress concentration
Solution Approach 1:
The patent applies curvature by replacing sharp edges with rounded fillets and curved surfaces on the spline geometry. Specifically, the spline features rounded leading edges, curved transition surfaces between the spline face and top surface, and filleted root radii. This curvature eliminates stress concentration points that cause impact damage and crack propagation, directly resolving the contradiction between reliability and geometric complexity.
Solution Approach 2:
The patent changes geometric parameters of the spline including the introduction of specific radius values (R1, R2, R3) at critical locations, modification of the spline face angle, and adjustment of the top surface curvature. These parameter changes optimize the stress distribution and reduce impact damage while maintaining manufacturability through defined geometric constraints.
2Object-affected harmful factors
If conventional splines with acute angle transitions are used, then the manufacturing process is simple, but foreign object debris is generated due to metal chipping at contact points
Solution Approach 1:
The patent eliminates acute angle transitions by introducing curved surfaces and rounded edges throughout the spline geometry. The curved transition surfaces replace sharp corners, and the rounded leading edges prevent metal chipping during assembly. This directly reduces foreign object debris generation while the curvature radii are specified to maintain manufacturability.
3Manufacturing precision
If conventional splines are aligned through hunting and pecking process, then the alignment method is simple, but misalignment and undesirable wear occur due to impact damage
Solution Approach 1:
The curved leading edges and rounded surfaces of the spline allow for smoother engagement during the hunting and pecking alignment process. The curvature enables the splines to glide into alignment more easily, reducing impact damage and improving alignment precision while maintaining the simplicity of the assembly process.
4Duration of action of stationary object
If splines with high stress concentration locations are used, then the spline structure is compact, but crack propagation and damage occur leading to reduced component longevity
Solution Approach 1:
The patent systematically applies curvature at all potential stress concentration locations including the leading edges, root radii, and transition surfaces. This eliminates crack initiation sites and prevents crack propagation, directly extending component longevity. The geometric complexity is controlled through defined radius values and standard manufacturing practices.
Data Source
AI summary
Aspects of the disclosure are directed to a gas turbine engine shaft, having an outer circumferential surface that circumscribes a central axis. The gas turbine engine shaft may comprise a plurality of splines extending along a portion of the outer circumferential surface, where each of the plurality of splines comprises an axial face that tapers from the outer circumferential surface to a spline top surface and includes a curved chamfered surface at a radially distal end of the axial face. The plurality of splines may further comprise a first sidewall and a second sidewall separated by a first spline width distance along the outer circumferential surface, where the first and second sidewalls taper inwardly from the outer circumferential surface to a second spline width along the spline top surface where the second spline width distance is less than the first spline width distance.