Friction Stir Welding Tool Structure for Shaft Inclination Control
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Solution Overview
Problem
Conventional friction stir welding tools face durability issues due to resistance forces that cause bending of the stirring shaft, especially when working with thick double skin members, leading to reduced tool longevity and increased operational costs.
Innovation Solution
A friction stir welding tool and method featuring a stirring shaft with unrotatable shoulder portions and an inclination preventing portion to stabilize the shaft during welding, preventing inclination and bending by contacting the workpieces to absorb reaction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If friction stir welding is performed at two positions simultaneously using a bobbin tool with upper, lower, and intermediate shoulders arranged on a straight line, then productivity is improved by joining plates at both positions, but the stirring shaft is subjected to large resistance forces and rotational moments that cause bending and reduce durability
Solution Approach 1:
The shoulder structure is segmented into three separate shoulder portions (upper, intermediate, lower) that are not arranged on a straight line. The intermediate shoulder portion is positioned offset from the line connecting the upper and lower shoulders, creating a triangular configuration. This segmentation distributes the resistance forces more effectively and prevents concentrated loading on the stirring shaft, thereby improving tool durability while maintaining dual-position welding capability
Solution Approach 2:
The shoulder portions are arranged in a three-dimensional configuration rather than on a single straight line. The intermediate shoulder portion extends in a direction different from the upper-lower shoulder alignment, creating a spatial arrangement that provides structural stability and reduces bending moments on the stirring shaft during simultaneous dual-position welding operations
2Strength
If the thickness of the double skin member is increased, then the strength of the workpiece is improved, but the length between the upper and lower gaps increases, causing larger rotational moments that bend the stirring shaft and reduce tool durability
Solution Approach 1:
The welding process is divided into two separate welding regions (upper and lower) with the intermediate shoulder portion positioned between them. This segmentation allows the tool to handle thicker workpieces by distributing the welding loads across multiple zones, reducing the rotational moment on the stirring shaft while maintaining the ability to join thick double skin members
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 solution effectively enhances the durability of the friction stir welding tool by preventing shaft inclination and bending, allowing for longer tool life and reduced operational costs through improved resistance to movement forces.
Implementation Method 1
a third shoulder portion attached around the stirring shaft so as to be located at a position between the first shoulder portion and the second shoulder portion... The third shoulder portion includes an inclination preventing portion configured to prevent inclination of the stirring shaft during the friction stir welding by contacting the workpieces to receive reaction force from the workpieces
Data Source
AI summary
A friction stir welding tool and method, by which influence on durability of the tool is suppressed even when resistance force generated when the tool moves for joining acts on facing end portions of workpieces which are located close to an attachment side of the tool. The tool includes: a stirring shaft; a first shoulder portion provided to be unrotatable relative to the shaft and configured to rotate together with the shaft when it rotates; a second shoulder portion provided to be unrotatable relative to the shaft and configured to rotate together with the shaft when it rotates; and a third shoulder portion attached around the shaft located between the first and second shoulder portions, and includes an inclination preventing portion to prevent inclination of the shaft by contacting the workpieces to receive reaction force from the workpieces when the shaft is made to move along joining lines.