Fan Casing Ovalization Correction via Isostatic Pressure
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Solution Overview
Problem
Existing methods for fabricating fan casings, such as resin transfer molding, often result in deformation and ovalization due to residual stresses, which are exacerbated by machining and adhesive-bonding operations, leading to insufficient control over the final shape and mechanical integrity.
Innovation Solution
A method involving a shaping tooling with inflatable bladders that apply isostatic pressure to correct the ovalization by imparting a cylindrical profile to the fan casing's inside surface, either during fabrication or repair, using a stoving process that combines heat and pressure to stabilize the shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If resin transfer molding is used to fabricate fan casings, then weight is reduced and mechanical strength is maintained or improved, but deformation and ovalization occur due to residual stresses
Solution Approach 1:
The patent applies preliminary counter-deformation to the mold cavity shape before fabrication. The mold cavity is intentionally designed with a pre-distorted shape that anticipates the ovalization deformation. When the casing is fabricated and then extracted from the mold, the residual stresses cause the casing to deform into the correct cylindrical shape, compensating for the expected distortion.
Solution Approach 2:
The patent introduces preliminary anti-action by applying counter-forces during fabrication to offset subsequent harmful deformations. The mold cavity is designed with opposite distortion to the expected deformation, and additional counter-deformation measures are taken to balance the residual stresses that will cause ovalization during extraction and machining.
2Ease of manufacture
If machining operations and adhesive bonding are performed on the fan casing, then functional requirements are met, but residual stresses are released and ovalization is exacerbated
Solution Approach 1:
The patent performs preliminary shaping operations before machining and adhesive bonding to establish the correct cylindrical profile. By pre-distorting the mold cavity and applying counter-deformation, the casing is fabricated with anticipated compensation for future deformations, ensuring that subsequent machining and bonding operations do not significantly alter the cylindrical shape.
3Manufacturing precision
If the mold cavity shape is adjusted to compensate for extraction deformation, then ovalization on leaving the mold is reduced, but ovalization during machining and bonding operations is not addressed
Solution Approach 1:
The patent applies preliminary counter-deformation not only to compensate for extraction deformation but also to anticipate and offset deformations from subsequent machining and bonding operations. The mold cavity is designed with comprehensive pre-distortion that accounts for the entire fabrication sequence, ensuring the casing maintains its cylindrical profile throughout all manufacturing stages.
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
This approach allows for the correction of ovalization at any stage of the fan casing's life cycle, reducing fabrication and repair time, improving shape accuracy, and enhancing the mechanical robustness and repeatability of the parts produced.
Implementation Method 1
applying isostatic pressure via the at least one bladder so as to impart a cylindrical profile to the portion of the inside surface of the casing facing the at least one bladder
Implementation Method 2
stoving the assembly comprising the casing, the tooling, and the at least one bladder at a predetermined temperature
Implementation Method 3
at least one bladder that is inflatable under the action of a fluid under pressure
Data Source
AI summary
A method of shaping the profile of a fan casing having an inside surface, the method including placing the casing around a surface of revolution of a drum of shaping tooling; interposing at least one bladder that is inflatable under the action of a fluid under pressure between a portion of the inside surface of the casing and the drum, the bladder extending over all or part of the surface of revolution of the drum; stoving the assembly including the casing, the tooling, and the at least one bladder at a predetermined temperature; and during the stoving, applying isostatic pressure via the at least one bladder so as to impart a cylindrical profile to the portion of the inside surface of the casing facing the at least one bladder.