Friction Bit Joining High Melting Point Materials
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Solution Overview
Problem
Current joining methods for metal workpieces, such as welding and mechanical fastening, face limitations with high melting temperature materials, leading to defects, residual stresses, and loss of base material properties, while friction stir welding is not efficient for all materials due to the hole left by the pin and cumbersome equipment requirements.
Innovation Solution
A friction bit joining method using a partially consumable tool with a cutting edge that cuts through workpieces and forms a solid-state bond at varying speeds, allowing for efficient joining of high melting temperature materials without the need for predrilled holes and with reduced equipment complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction stir welding is used to join high melting temperature materials, then solid state bonding is achieved without fusion defects, but a hole is left behind by the pin and equipment complexity increases
Solution Approach 1:
The tool is segmented into two functional parts: a consumable cutting bit that penetrates and stirs the material, and a non-consumable shoulder that provides forging pressure and contains the stirred material. This segmentation allows each part to be optimized for its specific function, eliminating the need for complex through-pin designs while achieving reliable solid state bonding.
Solution Approach 2:
The cutting bit is designed as a consumable component that is replaced after a certain number of uses or when worn. This disposable approach simplifies the overall tool design and eliminates the need for complex mechanisms to retrieve and remove through-pins, reducing equipment complexity while maintaining joint strength through consistent fresh cutting edges.
2Productivity
If traditional welding methods are used on high melting temperature materials, then joining is achieved, but defects, residual stresses, and loss of base material properties occur
Solution Approach 1:
The process changes the thermal parameters by controlling the temperature to remain below the melting point of the base material throughout the joining process. The rotating bit generates friction heat that softens the material for plastic deformation and bonding, while the shoulder applies pressure to forge the bond, achieving high-strength joints without fusion defects or residual stresses from phase transformation.
3Strength
If mechanical fastening methods are used, then joining is achieved, but load carrying capability is limited and space is required for fasteners
Solution Approach 1:
The process merges the functions of cutting, stirring, heating, and bonding into a single integrated tool and operation. The rotating bit cuts through the material, stirs it into a plasticized state, generates friction heat, and facilitates solid state bonding all in one continuous motion, eliminating the need for separate fasteners and reducing the space required for joining.
4Manufacturing precision
If friction stir welding is used, then solid state bonding is achieved, but predrilled holes are required and equipment complexity increases
Solution Approach 1:
The cutting bit performs preliminary action by penetrating and cutting through the material before the bonding occurs. This pre-cutting and stirring action creates the necessary plasticized material state and geometry for subsequent solid state bonding, eliminating the need for predrilled holes and simplifying the overall process equipment requirements.
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
Enables rapid, economical, and defect-free joining of high melting temperature materials with reduced residual stresses and no hole left behind, improving joint strength and energy absorption capabilities.
Implementation Method 1
the rotational speed of the tool may be changed to cause plasticization of the bit itself, as well as the first workpiece material that is being joined to a second workpiece material. After sufficient heating of the first and second workpiece materials and the bit by the friction stir tool
Implementation Method 2
cause plasticization of the bit itself, as well as the first workpiece material
Data Source
AI summary
A system and method of joining at least two workpieces together using a friction rivet and a friction rivet cap that are friction stirred together after a cutting tip or cutting feature on the friction rivet cuts through workpieces and is then bonded to the friction rivet cap, and wherein the friction rivet cap may be excluded if the friction rivet includes a hollow in the cutting tip, the hollow being flared after the friction rivets cuts through the workpieces to thereby create an integral rivet cap in the end of the friction rivet.