Creep Age Forming Sequence for Complex Aircraft Panels
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Solution Overview
Problem
Conventional creep age forming (CAF) techniques face challenges in producing aircraft components with complex shapes, such as integrally stiffened skin panels, due to material springback issues and limitations in creating components with low bending stiffness, thin stiffeners, surface pads, large openings, and large radii of curvature.
Innovation Solution
The process involves subjecting a flat metal plate to CAF to produce a curved preform, followed by machining to create the final component, allowing for the production of complex shapes by approximating the final shape in the forming tool and then removing material to form integral features like stiffeners and openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional CAF techniques are used to produce complex shaped aircraft components, then integral structural members can be formed, but springback causes dimensional inaccuracies and limits the types of components that can be produced
Solution Approach 1:
The patent applies preliminary action by performing machining operations on the flat plate before CAF forming. Integral structural members such as stiffeners, pads, and openings are machined into the flat plate prior to forming, so that after the plate springs back during CAF, the final component achieves the desired dimensional accuracy and complex shape without being constrained by springback limitations
Solution Approach 2:
The patent inverts the conventional CAF sequence by reversing the order of operations: instead of forming then machining, the process machines the flat plate first to create integral features, then forms the plate using CAF. This inversion allows the machined features to serve as a precursor geometry that guides the final formed shape, overcoming springback issues
2Manufacturing precision
If forming tools are designed to account for springback in CAF processes, then dimensional accuracy can be improved, but tooling complexity increases significantly
Solution Approach 1:
The patent simplifies tooling by applying preliminary machining actions to the flat plate before forming. The machined integral structural members provide a pre-defined geometry that reduces the complexity of the forming tool surface, as the tool only needs to form the remaining curvature rather than compensating for complex springback behavior of fully formed features
Solution Approach 2:
The patent applies local quality by machining specific integral structural members (stiffeners, pads, openings) at localized positions on the flat plate before forming. This allows different regions of the component to have different geometries prepared in advance, simplifying the overall forming tool design while maintaining dimensional accuracy in critical areas
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 reduces springback, tooling complexity, and residual stresses, enabling the production of a broader range of aircraft components with improved dimensional repeatability and reduced material volume, making it economically advantageous and flexible.
Implementation Method 1
subjecting the flat plate on the forming tool to creep age forming in an autoclave
Implementation Method 2
subjected to elevated temperature and pressure conditions for a specified period of time to relax induced stresses in the machined panel
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
Aircraft components are produced by creep age forming (CAF) processes whereby a flat plate (10) is initially subjected to CAF processing to produce a curved product preform which is thereafter machined to remove material therefrom so as to produce the final aircraft component.