Friction Twist Welding Fuselage Joints with Removable Cover Plate
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Solution Overview
Problem
Conventional friction twist welding methods for connecting aircraft fuselage segments require tight dimensional tolerances and result in irregular surfaces, making it costly and difficult to achieve smooth outer skins, especially when dealing with large, curved components.
Innovation Solution
The method involves using a cover plate above the joint regions, which is milled smooth after welding, allowing for greater gap tolerances and enabling a smooth surface finish, while also reducing production outlay and potentially increasing strength and reducing weight by using a cover plate with a thickness greater than the tool diameter and repeating the machining process to fill gaps incrementally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional friction twist welding is used without a cover plate, then the welding process is simpler, but the gap tolerance requirement is very tight (approx. 1.3 mm) and the surface is irregular after welding
Solution Approach 1:
A cover plate is introduced as an intermediary element between the two fuselage segments being welded. The cover plate serves multiple functions: it fills the gap between segments, provides a smooth surface for welding, and acts as a material source that is pressed into the gap during the welding process. This intermediary component enables welding with significantly greater gap tolerances while maintaining weld quality and producing a smooth outer contour.
Solution Approach 2:
The cover plate is prepared in advance with a thickness greater than the diameter of the welding tool. This preliminary preparation ensures that sufficient material is available to be pressed into the gap between the fuselage segments during welding, allowing for greater gap tolerances without affecting weld quality. The cover plate is positioned and secured before the welding process begins.
2Manufacturing precision
If the cover plate thickness is increased to bridge larger gaps, then gap bridging capability improves, but more material remains to be removed after welding
Solution Approach 1:
The cover plate thickness is optimized to be greater than the diameter of the welding tool but not excessively thick. This parameter optimization ensures that sufficient material is available to bridge the gap and provide a smooth surface, while limiting the amount of material that needs to be removed during the subsequent milling process. The thickness is carefully selected to balance gap bridging capability with material efficiency.
3Shape
If a cover plate is used with thickness greater than tool diameter, then marginal strips remain to ensure smooth edges, but the milling process removes more material
Solution Approach 1:
The cover plate is designed with a thickness greater than the tool diameter, creating marginal strips on either side of the welding tool during the welding process. These marginal strips remain after welding and are subsequently milled out. The local presence of these strips ensures that no undesirable deformations form on the edges of the cover plate, resulting in a smooth contour after milling. The milling process selectively removes only these marginal strips and the weld seam region.
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 approach allows for significant reduction in dimensional tolerance requirements, achieving a smooth weld seam with increased gap bridging capabilities and improved strength properties, while maintaining weld quality and avoiding undesirable deformations.
Implementation Method 1
friction twist welding using a rotating tool (18)
Implementation Method 2
The welded interconnection of large components curved in one dimension (i.e. barrel-shaped) requires a tensioning process
Implementation Method 3
the region of the cover plate (20) being milled smooth after the friction twist welding
Data Source
Figure 1~3
AI summary
The present application relates to a process for connecting two aircraft fuselage segments (10a, 10b) and a reinforcing profile (14) arranged in the joint region (11) of the two aircraft fuselage segments (10a, 10b) by friction stir welding using a rotating tool (18), where in that a cover plate (20) is brought onto the aircraft fuselage segments (10a, 10b) to be connected above the joint regions (11) and after the friction stir welding the remainder of the cover plate (20) is milled off. This makes it possible to overcome significantly greater gap tolerances in the edges to be connected so that the dimension tolerance requirements for the aircraft fuselage segments (10a, 10b) can be reduced. Furthermore, a smooth surface can be achieved in the welding region.