Composite Rod Fitting Assembly Using Radial Expansion Retention
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Solution Overview
Problem
Attaching fittings to composite material rods is challenging due to difficulties in forming screw threads or drilling holes, which can lead to damage during storage and handling, and may not accommodate thermal expansion, limiting application range.
Innovation Solution
A method involving radial expansion of the rod end using a tool, followed by insertion of a retainer and fitting, with a curable resin to secure the fitting, allowing for compression and thermal expansion accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rod end is pre-split to allow fitting insertion, then the fitting can be attached to the rod, but the split rod is vulnerable to damage during storage and handling
Solution Approach 1:
The rod end is expanded before fitting insertion using an expansion tool that is inserted into the rod and actuates expansion elements to radially expand the rod end, creating the necessary clearance for fitting insertion without pre-splitting the rod. This preliminary expansion action eliminates the need for damaging pre-splitting while still enabling fitting attachment.
2Ease of manufacture
If the rod is expanded to fit the ferrule, then the fitting can be secured to the rod, but thermal expansion of the ferrule may cause the connection to loosen
Solution Approach 1:
The rod end expansion is made adjustable and controllable through the expansion tool, allowing the rod end diameter to be precisely matched to the fitting inner diameter. This dynamic adjustment capability enables proper initial interference fit while accounting for thermal expansion margins, ensuring the connection remains secure under varying temperature conditions.
Solution Approach 2:
The expansion degree of the rod end is controlled as a variable parameter, allowing optimization of the interference fit between rod and fitting. By adjusting the expansion parameter, the design accommodates thermal expansion of the fitting while maintaining secure connection, enhancing adaptability to temperature variations.
3Ease of manufacture
If a tapered insert is used to expand the rod, then the ferrule can be held captive on the rod, but the rod expansion degree is limited by the ferrule presence
Solution Approach 1:
An expansion tool acts as an intermediary device between the operator and the rod end expansion process. This tool contains expansion elements that can be actuated to provide controlled radial expansion of the rod end, enabling greater expansion range than would be possible with direct ferrule engagement alone, while still achieving secure ferrule retention.
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 avoids the need for pre-split rods, enhances handling and storage, and maintains secure connections despite thermal expansion, ensuring the assembly remains intact under varying conditions.
Implementation Method 1
inserting a tool into the bore to cause radial expansion of the end part of the rod
Implementation Method 2
the retainer serving to retain the end part of the rod in an expanded condition
Implementation Method 3
a curable resin material is introduced into the bore to fill the bore and voids between the bore and the retainer
Data Source
AI summary
A method for securing a fitting 14 to a composite material rod 12, the method comprising forming a bore 20 in an end part of the rod 12, inserting a tool 26 into the bore 20 to cause radial expansion of the end part of the rod 12, inserting a retainer 22 into the expanded end part of the rod 12, and withdrawing the tool 26 from the end part of the rod 12, the retainer 22 serving to retain the end part of the rod 12 in an expanded condition. An assembly of a fitting 14 and composite material rod 12 is also described.