Bobbin Tool Friction Stir Welding for Thickness-Preserving Seam Finishing
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Solution Overview
Problem
Friction stir welding of aluminum alloys in aerospace applications faces challenges in removing characteristic welding marks without compromising material thickness, as conventional methods like milling or grinding can reduce the required thickness at the weld seam location.
Innovation Solution
Applying an additional axial force to the bobbin tool during the welding process to create a weld seam elevation that can be selectively removed, ensuring material balance and avoiding thickness reduction, using means such as hydraulic cylinders or electric linear drives to adjust the weld position and shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional machining methods (milling or grinding) are used to remove welding marks, then the surface finish is improved, but the material thickness at the weld seam location is reduced
Solution Approach 1:
The weld seam elevation is created during the friction stir welding process itself through controlled plastic deformation, before any subsequent machining. The additional axial force applied during welding pre-forms the material into an elevation that can be selectively removed without affecting the base material thickness
Solution Approach 2:
The additional axial force is applied locally at the weld seam location during the welding process, creating a localized weld seam elevation. This allows subsequent machining to be limited to only the elevation area, preserving the surrounding material thickness while still achieving the desired surface finish
2Quantity of substance
If additional axial force is applied to create weld seam elevation, then welding marks can be removed without thickness loss, but the device complexity increases
Solution Approach 1:
The function of applying additional axial force to create weld seam elevation is merged with the existing friction stir welding process. The bobbin tool's lower shoulder structure is designed to accommodate this additional force application, combining two functions (welding and elevation creation) into a single integrated process step
Solution Approach 2:
Hydraulic cylinders are employed to generate and apply the additional axial force to the bobbin tool during the welding process. This provides controlled, adjustable force application without requiring complex mechanical linkages or manual operation
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
Enables the removal of welding marks without reducing material thickness, improving the surface finish, fatigue strength, and aerodynamic properties of the aircraft fuselage by creating a controlled weld elevation that can be easily leveled, maintaining structural integrity.
Implementation Method 1
Due to the friction between the tool shoulder and the workpieces to be joined, the material under the shoulder heats up to just below the melting point
Implementation Method 2
the material under the shoulder heats up to just below the melting point
Implementation Method 3
subjecting the bobbin tool to an additional axial force Fx while it is moving along the joint gap in order to plastically deform the area of the weld seam produced
Data Source
Figure 1~4
AI summary
Friction agitation welding process for joining abutting plate-shaped workpieces comprising an aluminum alloy, comprises: moving a rotating bobbin tool (3) along a weld (9) between the two plate-shaped workpieces during a feed by exerting duplex pressing force; and subjecting the bobbin tool to an additional axial force during the movement along the weld to plastically deform the area of generated welding seam (10) such that welding seam is pressed towards one side of the plate-shaped workpieces while forming a welding seam elevation (13) protruding opposite to a workpiece surface (11). An independent claim is also included for a device for the joining of abutting plate-shaped workpieces, comprising a rotating bobbin tool configured for moving along weld between plate-shaped workpieces, and an apparatus for acting on the bobbin tool during the movement along the weld to exert additional axial force.