Friction Stir Joining Pin Geometry to Prevent Butt-Section Flowout
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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, while securely welding the lap sections by inserting the protruding section deep beyond the lap section.
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 welding force is sufficient, but the plastic fluid material may flow out of the butt section into the hollow section
Solution Approach 1:
The invention divides the contact interface into two separate sections: the shoulder section contacts only the first metal member, and the stirring pin contacts both metal members. This segmentation prevents the shoulder from pressing into both surfaces simultaneously, eliminating the harmful material flow while maintaining sufficient welding force through the stirring pin's friction action.
Solution Approach 2:
The stirring pin acts as an intermediary element that performs the dual function of generating friction heat and preventing material flow. By positioning the stirring pin to contact both metal members at the butt section, it mediates the welding process without requiring the shoulder to press into both surfaces, thus preventing material from flowing into the hollow section.
2Strength
If the shoulder section is pressed into the surfaces of the metal members, then the welding process is effective, but the plate thickness needs to be large enough to withstand the pressing load
Solution Approach 1:
The contact load is segmented between different tool components: the shoulder contacts only the first metal member, and the stirring pin contacts both metal members. This segmentation distributes the mechanical stress, allowing thinner plates to be used without compromising welding effectiveness, as the stirring pin's friction-based welding requires less compressive load than traditional shoulder pressing.
Solution Approach 2:
The invention substitutes the traditional mechanical pressing system (shoulder pressing into both surfaces) with a friction-based system (stirring pin rotating and contacting both surfaces). This replacement reduces the required plate thickness because friction welding generates heat and bonding through rotational friction rather than high compressive pressure, enabling the use of thinner, lighter metal members.
3Temperature
If the shoulder section presses into the metal members with large load, then the friction heat is sufficient for welding, but the complexity of the structure increases
Solution Approach 1:
The heating function is segmented between the shoulder (contacting first metal member) and the stirring pin (contacting both metal members). This segmentation allows the stirring pin to generate friction heat through rotation without requiring the shoulder to press into both surfaces with large load, simplifying the overall structure while maintaining sufficient temperature for welding.
Solution Approach 2:
The invention introduces dynamic rotation of the stirring pin as the primary mechanism for generating friction heat, replacing the static pressing action of the shoulder. This dynamic approach generates heat through rotational friction between the stirring pin and both metal members, reducing the need for complex pressing mechanisms and large structural components to deliver high static loads.
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 effectively reduces the thickness and weight of metal members, prevents plastic fluid material flow, and securely joins the metal components by minimizing load on the members and inhibiting oxide film stirring.
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 with only the stirring pin put in contact with the first metal member and the second metal member
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.