Friction Stir Welded Structure With Hooking Anchorage Against Peeling
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Solution Overview
Problem
Friction stir welding often results in 'hooking' where material from one workpiece is pulled along the outer periphery of the bonded area, reducing the bonding strength.
Innovation Solution
A welded structure with a hooking portion that has a base end embedded in one workpiece and a tip end extending into another workpiece, where the hooking portion extends radially outward and provides a favorable anchoring action to secure the workpieces together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction stir welding is performed with a conventional probe, then the welding process is simple, but the material forms hooking portions that reduce bonding strength
Solution Approach 1:
The probe shape is changed from conventional cylindrical to frustoconical (tapered) configuration. This geometric parameter change allows the probe to control material flow differently during welding, preventing hooking portions from forming while maintaining bonding strength. The tapered shape enables the probe to push material forward more effectively without allowing it to wrap around and create weak hooking structures.
2Strength
If a frustoconical probe is used to prevent hooking, then bonding strength is improved, but the device complexity increases and requires shape adjustment depending on workpiece thickness
Solution Approach 1:
Instead of changing the entire probe geometry to frustoconical shape, only the tip portion of the probe is modified with a localized tapered structure. This localized modification achieves the material control needed to prevent hooking while keeping the rest of the probe simple and universal. The localized quality change allows the same probe design to work across different workpiece thicknesses without requiring shape adjustments.
3Ease of manufacture
If hooking portions are formed during welding, then the welding process is straightforward, but the anchoring action is insufficient and workpieces can peel apart
Solution Approach 1:
The invention converts the natural tendency of material to wrap around the probe (which creates harmful hooking portions) into a beneficial forward-pushing flow. By using the frustoconical probe shape, the material that would otherwise form weak hooking structures is instead directed forward to create strong bonded material in the weld zone, providing both bonding strength and anchoring action to prevent peeling.
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 hooking portion enhances the mechanical anchoring between the workpieces, resisting peeling and improving the overall bonding strength of the welded structure.
Implementation Method 1
a rotating tool is pressed against a pair of mutually overlapping members so that the material of the members adjacent to the rotating tool is plastically stirred and displaced by frictional heat
Implementation Method 2
the hooking portion is enabled to provide a favorable anchoring action that mechanically secures the first workpiece to the second workpiece, and resists peeling of the two workpieces away from each other
Data Source
AI summary
A welded structure includes a first workpiece (11), a second workpiece (12), a bonded part (28) formed between the first workpiece and the second workpiece by plastically displaced materials of the first workpiece and the second workpiece, and a hooking portion (29) having a base end embedded in the second workpiece, and a tip end extending into the first workpiece, the hooking portion extending radially outwardly and upward along an outer periphery of the bonded part. A device for forming such a structure includes a clamp ring (18) which is provided with a central recess (25) in a part of a contact surface (24) thereof located around a through hole (19).