Friction Stir Joining Pin Geometry to Prevent Butt-Section Flow
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Solution Overview
Problem
Conventional joining methods using friction stir welding apply high loads on metal members, risking plastic fluid material flow and requiring thicker metal plates to withstand the pressure, which increases weight and complexity.
Innovation Solution
A joining method that uses a rotary tool with a stirring pin, featuring a flat surface and protruding section, where only the stirring pin contacts the metal members, reducing load and preventing fluid flow by inserting the pin deep beyond the lap section, and using a flat surface to inhibit material stirring and oxide film shattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shoulder section is pressed into the surfaces of the metal members to apply large load, then the joining strength is improved, but the plastic fluid material may flow out of the butt section into the hollow section
Solution Approach 1:
The invention divides the tool into two separate functional parts: a stirring pin for material mixing and a shoulder section for applying pressing load. This segmentation allows the stirring pin to be inserted deep into the butt section to prevent material flow, while the shoulder section independently provides the necessary pressing force, resolving the contradiction between achieving high joining strength and preventing harmful material flow.
Solution Approach 2:
The stirring pin acts as an intermediary element that is inserted deep into the butt section to physically block and control the plastic fluid material, preventing it from flowing out into the hollow section. This intermediary structure mediates between the pressing force from the shoulder section and the material behavior, ensuring controlled material flow while maintaining joining strength.
2Strength
If the shoulder section is pressed into the surfaces of the metal members, then the joining strength is improved, but the plate thickness needs to be large enough to withstand the pressing load
Solution Approach 1:
By segmenting the tool into a stirring pin and a shoulder section, the invention allows the stirring pin to be inserted deep into the butt section to provide mechanical interlocking and joining strength, while the shoulder section applies distributed pressing load. This eliminates the need for increased plate thickness to withstand concentrated pressing forces, as the load is distributed and the joining strength comes from the deep insertion of the stirring pin rather than plate thickness.
3Strength
If the stirring pin is inserted deep beyond the lap section, then the material flow is prevented and joining strength is enhanced, but the complexity of the preparation step increases
Solution Approach 1:
The invention performs preliminary actions by forming specific geometric features (first and second steps) on the metal members before the friction stir welding process. These pre-formed steps create defined butt sections and lap sections that guide the insertion depth of the stirring pin, making the deep insertion process more manageable and reducing the operational complexity despite the enhanced joining strength achieved.
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 securely joins metal members with reduced thickness and weight, preventing fluid flow and enhancing joining strength while minimizing material stirring and oxide film issues.
Implementation Method 1
a friction stirring step of welding the front-side butt section and the lap section by inserting the stirring pin, as rotating, from the front-side butt section, and by relatively moving the rotary tool along the front-side butt section
Data Source
AI summary
Provided is a joining method that can prevent a plastic flowing material from flowing out from a butt section and that can reduce the thickness and weight of metal members. The joining method is for joining a first metal member and a second metal member by using a rotary tool comprising a stirring pin, and is characterized in that: the stirring pin comprises a flat surface perpendicular to the rotation axis of the rotary tool and comprises a protruding section protruding from the flat face; and in a friction stirring step, the flat surface is brought into contact with the first metal member and the second metal member, and a front end face of the protruding section is inserted deeper than an upper overlapping section to join an upper front butt section and the upper overlapping section.