Friction Stir Spot-Welding Tool for Stacked Metal Foils
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Solution Overview
Problem
Conventional methods for spot-joining stacked metal foils, such as friction stir welding, often result in low joint strength and risk of delamination due to tool holes left after welding, and require additional steps like bonding agents to prevent displacement, increasing workload and cost.
Innovation Solution
A double-acting type rotary tool with a hollow member and pin member, where the clamp member holds the outer annular part of the stack, allowing the hollow and pin members to move in and out to fill the tool hole with the generated metal mass, preventing tool holes and enhancing joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction stir welding is performed with a fixed type rotary tool, then the metal foils can be joined, but tool holes are formed and left in the weld, deteriorating the joint strength
Solution Approach 1:
The rotary tool is designed with movable hollow member and pin member that can independently move in the axial direction, transforming the fixed tool structure into a dynamic one. This allows the pin member to be retracted and the hollow member to fill the resulting space with metal mass, eliminating tool holes while maintaining joint strength
Solution Approach 2:
The rotary tool is divided into separate functional components: a hollow member and a pin member, which can move independently. This segmentation allows the pin member to create the friction stir welding effect while the hollow member subsequently fills the space to prevent tool hole formation, resolving the contradiction between achieving weld penetration and avoiding tool holes
2Object-generated harmful factors
If linear-joining operation is performed instead of spot-joining, then tool holes are avoided, but the stacked metal foils may be displaced relative to each other during welding
Solution Approach 1:
The dynamic structure with independently movable hollow member and pin member allows the tool to maintain a compact spot-joining configuration. The pin member can be inserted to create friction stir welding while the hollow member remains positioned to fill the space, preventing foil displacement that would occur with linear-joining tool movement
Solution Approach 2:
The hollow member acts as an intermediary that fills the space created by pin member insertion. This intermediary structure prevents the metal foils from being displaced during the welding process, while still allowing the pin member to perform the friction stir welding function
3Stability of the object's composition
If bonding agent is used to fix metal foils together, then foil displacement is prevented, but workload and cost increase
Solution Approach 1:
The friction stir welding process itself, through the controlled insertion and retraction of the pin member followed by hollow member filling, provides the fixation function that would otherwise require bonding agents. The metal mass generated during welding automatically fills and secures the foils in place, eliminating the need for additional bonding steps
Solution Approach 2:
The fixation function is extracted from the separate bonding agent process and integrated into the friction stir welding process itself. The hollow member and pin member mechanism directly provides the securing action during welding, removing the need for external bonding agents and simplifying the overall process
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
The process achieves a sound state of electrical and mechanical joining without tool holes, improving joint strength and preventing foil displacement, thus ensuring a stable weld without additional workload or cost.
Implementation Method 1
a friction stir welding operation is performed by using a rotary tool (10) rotated about its axis
Implementation Method 2
a metal mass is generated by insertion of the one of the hollow member and the pin member into the portion to be friction-stirred, and is accommodated within the space
Data Source
AI summary
Friction stir spot-welding is performed to join together a stack of a plurality of metal foils and a metal sheet by using a double-acting type rotary tool including a hollow member and a pin member which are movable independently of each other in their axial directions, and a clamp member which is fitted on an outer circumferential surface of the hollow member and which is movable in its axial direction. While an outer annular part of a portion to be friction-stirred is pressed with the clamp member, the pin member is inserted into the above-described portion and the hollow member is retracted, whereby a metal mass is accommodated within a space formed between the above-described portion and the hollow member. Then, the hollow member is advanced to press the metal mass into a hole formed by retraction of the pin member, whereby the hole is filled with the metal mass.