Superplastic Forming and Diffusion Bonding With Multi-Gas Pressure Control
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Solution Overview
Problem
Current superplastic forming/diffusion bonding processes face challenges in achieving uniform gas pressure distribution and preventing gas entrapment between sheets, which can lead to reduced diffusion bond strength and mechanical properties, particularly in complex aerospace structures.
Innovation Solution
The process involves injecting different gases between the core and skin sheets to control pressure and utilize venting grooves in the sheets to manage gas flow, ensuring uniform bonding and minimizing gas entrapment, with specific gas pressures and injection points optimizing the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas is injected between skin sheet and core sheet to form cavity and urge skin sheet against mould, then superplastic forming is achieved, but gas entrapment between sheets occurs reducing diffusion bond strength
Solution Approach 1:
The gas injection system is segmented into multiple independent injection points and channels. Different gases can be injected at different locations (between skin-core, between core-mould, at flange regions) to create controlled pressure zones that prevent gas entrapment while maintaining forming accuracy and bond strength
Solution Approach 2:
A third gas is introduced as an intermediary medium between the skin sheet and the mould. This third gas acts as a mediator to control pressure distribution and prevent gas entrapment at the skin-core interface, thereby improving diffusion bond strength while maintaining forming quality
2Strength
If gas pressure is maintained on core sheet to form diffusion bond, then bonding strength improves, but gas pockets may form reducing bond quality
Solution Approach 1:
Different gas pressures and compositions are applied to different regions of the structure. The gas injection system provides localized pressure control at skin-core interfaces, core-mould interfaces, and flange regions, ensuring uniform bonding quality throughout the structure without gas pocket formation
Solution Approach 2:
The gas injection system incorporates pressure regulation and control mechanisms that monitor and adjust gas pressure in real-time during the bonding process. This feedback control ensures consistent diffusion bond quality by preventing gas pocket formation while maintaining optimal bonding pressure
3Device complexity
If single gas injection system is used, then process complexity is reduced, but uniform pressure distribution and gas entrapment prevention become difficult
Solution Approach 1:
The gas injection system is divided into multiple independent injection circuits with separate control mechanisms. Each injection point can be independently regulated to achieve uniform pressure distribution across the entire structure, preventing gas entrapment while maintaining manageable process complexity through modular design
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 enhances the strength and fatigue properties of the diffusion bonds by ensuring intimate contact between sheets and reducing the likelihood of gas pockets, leading to improved mechanical performance in aerospace components.
Implementation Method 1
injecting a third gas on the side of the skin sheet remote from the core sheet, between the skin sheet and the mould, to force the skin sheet against the core sheet
Implementation Method 2
heating the pack to a temperature at which the sheets are capable of superplastic deformation
Implementation Method 3
maintaining gas pressure on the said side of the core sheet remote from the skin sheet, thereby forming a diffusion bond between the skin sheet and the core sheet
Data Source
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AI summary
A process and apparatus for forming a structure comprising: a) forming a pack (200) from a skin sheet (16, 18) and a core sheet (10, 12), b) placing the pack (200) in a mould (20) and heating the pack (200); c) injecting a first gas between the core and skin sheets to urge the skin sheet (16, 18) against the mould (20); d) injecting a second gas on the side of the core sheet (10, 12) remote from the skin sheet (16, 18) to urge the core sheet (10, 12) against the skin sheet (16, 18); e) maintaining gas pressure of the second gas thereby diffusion bonding the sheets; and f) injecting a third gas between the skin sheet (16, 18) and the mould (20), to force the skin sheet (16, 18) against the core sheet (10, 12).