Fixed-Shoulder Friction Stir Welding for Defect-Free Fillet Surfaces
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Solution Overview
Problem
Friction stir welding with a fixed shoulder results in defects on the surface of the fillet formed at the corner portions of welded workpieces, particularly when long lengths are involved, due to material adherence and scratching by the fixed shoulder.
Innovation Solution
A friction stir welding device and method that maintains a gap between the fixed shoulder and the workpiece surfaces, supplying a filler material in excess of the geometrically calculated volume to form the fillet, ensuring the softened material flows into this gap, preventing adherence and surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a friction stir welding tool with a fixed shoulder is used to perform friction stir welding of corner portions, then the welding process can be completed, but defects such as roughness occur on the surface of the fillet due to material adherence and scratching by the fixed shoulder
Solution Approach 1:
The invention extracts the harmful function of the fixed shoulder by separating it from the welding tool. Instead of using a fixed shoulder that contacts and scratches the workpiece, the patent uses a shoulderless tool where the probe alone performs the stirring action, eliminating the source of surface defects while maintaining the welding process effectiveness
Solution Approach 2:
The invention introduces filler material as an intermediary substance between the probe and the workpiece corner portion. The filler material fills the corner portion and receives the stirring action, preventing direct contact between the probe and the workpiece surface that would cause scratching and defects, while still achieving proper material mixing and weld formation
2Shape
If filler material is added during friction stir welding to form a fillet at corner portions, then the fillet is formed, but defects occur on the fillet surface due to adherence of softened material to the fixed shoulder
Solution Approach 1:
The invention removes the fixed shoulder component that causes material adherence problems. By using a shoulderless tool design, the softened filler material and workpiece material are stirred without adhering to a fixed shoulder surface, eliminating the source of surface defects while still achieving proper fillet formation through probe stirring action
Solution Approach 2:
Instead of having the fixed shoulder contact the workpiece and filler material (conventional approach), the invention inverts the approach by using a shoulderless tool where only the rotating probe contacts and stirs the materials. This reversal eliminates the adherence problem associated with the fixed shoulder while maintaining effective material mixing
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
Inhibits the occurrence of defects on the fillet surface by maintaining a gap and controlling filler supply, ensuring smooth operation and high-quality welds.
Implementation Method 1
the probe 2 is rotated by a rotation driving device 10, thereby immersing an end portion of the probe 2 into a corner portion c between the workpieces W1 and W2, and thereby friction stir welding is performed on the corner portion c
Implementation Method 2
the materials of the workpieces W1 and W2 and the material of the filler 5 softened and stirred by the probe 2
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A friction stir welding device (8) includes a friction stir welding tool (1) equipped with a fixed shoulder (3) on an outer periphery of a probe (2) on a proximal end side, a main shaft positioning mechanism (11) which relatively moves the friction stir welding tool (1) with respect to a corner portion (c) between workpieces (W1, W2), a control device (12) thereof, and a filler supply unit (13, 13a, 13b) which supplies a filler (5) to a stirring region (s) in which the workpieces (W1, W2) are stirred by the probe (2) at the time of friction stir welding. When the probe (2) is immersed into the corner portion (c) to perform the friction stir welding, the fixed shoulder (3) is maintained at a position separated by a gap (4) from the surfaces of the workpieces (W1, W2) with the control device (12).