Cold Drawing Aluminium Alloy Pressure Vessel Liners
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Solution Overview
Problem
Existing manufacturing methods for seamless aluminium alloy pressure vessel liners are limited in their ability to process a range of aluminium alloys, particularly the stronger AA7xxx series, resulting in liners that are heavier and less efficient than necessary, due to uniform thickness constraints and material excess.
Innovation Solution
A method involving cold drawing of a cup-shaped shell with a transition zone, followed by shaping and threading, allows for the effective processing of both softer and harder aluminium alloys, including AA7060, by thinning and strengthening the material while maintaining sufficient thickness for pressure resistance and threading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If uniform thickness is used throughout the vessel tube to ensure sufficient material at the neck for threading, then the neck can support threading for attachment of fittings, but the drum region ends up thicker than necessary, resulting in excess material and increased weight
Solution Approach 1:
The patent applies local quality by creating a non-uniform thickness distribution in the liner tube, with the drum region being thinner (first thickness) and the end region being thicker (second thickness greater than first thickness). This allows the neck to have sufficient material for threading while the drum region uses minimal material, resolving the contradiction between neck strength and overall weight.
2Weight of moving object
If stronger aluminium alloys (AA7xxx series) are used to reduce liner weight and material usage, then the liner becomes lighter and more efficient, but the material becomes harder to process with traditional manufacturing methods
Solution Approach 1:
The patent applies preliminary action by performing cold drawing on the liner tube before forming the neck region. This preliminary cold working strengthens the material and prepares it for subsequent neck formation, enabling the use of stronger AA7xxx series alloys that would be difficult to process with traditional methods. The cold drawing is performed on the entire tube first, then the end region is selectively formed to create the thickness variation.
3Ease of manufacture
If traditional extrusion and drawing methods are used to manufacture the liner, then the manufacturing process is well-established, but the process cannot effectively handle stronger aluminium alloys and results in uniform thickness that cannot optimize material usage
Solution Approach 1:
The patent applies parameter changes by modifying the manufacturing process to include cold drawing at controlled temperatures and selective forming of the end region. These parameter changes enable the process to handle stronger aluminium alloys (AA7xxx series) that cannot be processed by traditional methods, while still maintaining a practical manufacturing approach. The cold drawing temperature and the selective forming parameters are adjusted to achieve both processability and optimal thickness distribution.
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 method enables the production of lighter, more portable liners with improved strength and reduced material usage, suitable for high-pressure applications, by applying cold working techniques effectively across a broader range of aluminium alloys.
Implementation Method 1
cold drawing of a cup-shaped shell with a transition zone, followed by shaping and threading, allows for the effective processing of both softer and harder aluminium alloys, including AA7060, by thinning and strengthening the material
Implementation Method 2
cold drawing of a cup-shaped shell... by thinning and strengthening the material while maintaining sufficient thickness for pressure resistance and threading
Data Source
AI summary
A method of manufacturing a liner for use in a pressure vessel includes a cold drawing process that shapes a transition zone (20b) part of an aluminium alloy liner shell (10). The transition zone (20b) links a thinner walled drum part (18) and a thicker walled end region (20a), which is at an open top of the shell. The transition zone (20b) may be shaped by the cold drawing process such that it reduces susceptibility of the shell to fracture during removal from a cold drawing press and also redistributes shell material in preparation for a subsequent process in which a threaded neck is formed from the end region (20a). This process is particularly suited to processing harder aluminium alloy materials such as AA7060 or AA7032.