Aircraft Engine Rotor Crack Mitigator Design
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Solution Overview
Problem
Aircraft engine rotor discs experience low cycle fatigue leading to crack formation due to centrifugal and thermal loads, with cracks potentially propagating radially and undesirably towards the bore, posing safety risks.
Innovation Solution
Incorporation of crack mitigators such as grooves and bumps on the rotor disc surfaces, strategically located and designed to redirect crack propagation towards the gaspath-facing surface, thereby minimizing the risk of cracks reaching the bore by introducing stress concentration factors and increasing radial contribution to crack growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crack mitigators are added to redirect crack propagation, then crack propagation control is improved, but device complexity increases
Solution Approach 1:
The crack mitigator is segmented into multiple discrete features (grooves and bumps) distributed around the circumferential direction. Each groove or bump acts as an independent stress concentration element that can individually influence crack propagation, allowing the system to control crack paths through multiple localized interventions rather than a single complex structure
Solution Approach 2:
The crack mitigators (grooves and bumps) serve as intermediary structures between the crack source and the bore. These intermediaries create controlled stress concentration zones that mediate the crack propagation process, forcing cracks to follow predetermined safe paths away from critical areas without requiring fundamental changes to the rotor design
2Reliability
If crack mitigators are strategically located to redirect cracks, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
The grooves and bumps are pre-formed during the manufacturing process before the rotor enters service. Their locations, depths, and dimensions are precisely determined in advance based on stress analysis and crack propagation modeling, allowing manufacturers to prepare the crack mitigator features as part of the initial rotor fabrication rather than adding them later as corrective measures
Solution Approach 2:
The crack mitigators utilize controlled variations in geometric parameters (groove depth, bump height, spacing between features) to achieve the desired stress concentration effects. By adjusting these parameters within optimized ranges, the design achieves effective crack redirection while maintaining compatibility with standard manufacturing processes and material properties
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 crack mitigators effectively redirect and slow down crack propagation, ensuring that cracks grow towards the gaspath-facing surface instead of the bore, enhancing safety and maintaining the rotor's minimum life expectancy.
Implementation Method 1
strategically located and designed to redirect crack propagation towards the gaspath-facing surface, thereby minimizing the risk of cracks reaching the bore by introducing stress concentration factors and increasing radial contribution to crack growth
Data Source
AI summary
A rotor for an aircraft engine, has: a hub extending circumferentially about a central axis, the hub having a bore, a gaspath-facing surface located radially outwardly of the bore relative to the central axis, a first face extending from the bore to the gaspath-facing surface, and a second face opposite the first face and extending from the bore to the gaspath-facing surface; blades circumferentially distributed about the central axis, the blades protruding away from the gaspath-facing surface of the hub; and a crack mitigator located on the first face, the crack mitigator extending circumferentially relative to the central axis, the crack mitigator extending axially from a baseline surface of the first face.