Wingtip Torque Box Assembly Using Friction Stir Welded Clamshells
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Solution Overview
Problem
Conventional wingtip torque boxes in aircraft are complex, expensive to manufacture, and prone to issues like added weight, corrosion, and limited access during installation, repair, or replacement due to their multicomponent nature.
Innovation Solution
A wingtip torque box is formed by friction stir welding two monolithic clamshells along their spars, creating a single monolithic structure with internal and external stiffeners, which simplifies fabrication and provides a robust, accessible design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional torque box is constructed as a multicomponent assembly with spars, skins, ribs, and fasteners, then the structural strength can be achieved, but the device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent merges multiple discrete components (spars, skins, ribs, fasteners) into a single monolithic clamshell structure formed from one piece of material. This integration eliminates the need for assembly and reduces device complexity while maintaining structural strength through the continuous monolithic construction.
Solution Approach 2:
The torque box is divided into two monolithic clamshells that are friction stir welded together along their spars. This segmentation allows for simplified manufacturing of each half while achieving the required structural strength through the welding process that creates a continuous load path.
2Strength
If a conventional torque box uses multiple separate parts with fasteners, then the structural requirements can be met, but the weight increases
Solution Approach 1:
By combining multiple components into a single monolithic clamshell structure, the patent eliminates the weight of fasteners and reduction material required for multicomponent assemblies. The monolithic construction achieves structural strength without the additional weight penalties of conventional assembled structures.
3Strength
If a conventional torque box is assembled from multiple parts, then the structural integrity can be maintained, but the susceptibility to corrosion increases due to multiple part-to-part interfaces
Solution Approach 1:
The patent merges multiple parts into a monolithic clamshell structure that is then joined to its counterpart via friction stir welding along the spar. This creates minimal interfaces compared to conventional assemblies, significantly reducing the areas susceptible to corrosion while maintaining structural integrity through the continuous welded joints.
4Strength
If a conventional torque box uses a multicomponent assembly design, then the structural requirements can be satisfied, but the manufacturing cost increases
Solution Approach 1:
By merging multiple components into a single monolithic clamshell that is formed from one piece of material and then friction stir welded to its counterpart, the patent eliminates the need for complex assembly processes, fastener installation, and multiple manufacturing operations. This significantly reduces manufacturing cost while satisfying structural requirements through the continuous monolithic construction.
5Strength
If a conventional torque box is constructed with multiple separate components, then the structural strength can be achieved, but the access during installation, repair, or replacement is limited
Solution Approach 1:
The torque box is segmented into two monolithic clamshells that can be independently manufactured and then assembled via friction stir welding. This segmentation allows each clamshell to be produced separately using simplified processes and enables easier access during installation, repair, or replacement compared to conventional multicomponent assemblies.
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 monolithic design reduces weight, minimizes corrosion sites, lowers manufacturing costs, and enhances structural strength, allowing for easier maintenance and more frequent replacements while maintaining high safety levels.
Implementation Method 1
The upper front spar is friction stir welded to the lower front spar at a front friction stir welded joint. Likewise, the upper rear spar is friction stir welded to the lower rear spar at a rear friction stir welded joint.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Provided are a wingtip torque box and a method of fabricating such box using friction stir welding. Specifically, a wingtip torque box (200) may be formed by friction stir welding (304, 306) two monolithic clamshells (310a, 310b) along their respective spars (320a, 330a, 310b, 330b) thereby forming a new monolithic structure. Use of the friction stir welding (304, 306) and monolithic clamshells (310a, 310b) simplifies the overall fabrication process and yields a robust wingtip torque box (200) that can be bolted on or otherwise attached to an aircraft wing. The wingtip torque box (200) may include internal grid stiffeners (350a, 350b) and/or external stiffeners (360a, 360b) that may be also monolithic with other components of the box. For example, the stiffeners may be machined in spars or skin portions (340a, 340b) of the clamshells (310a, 310b) during fabrication of clamshells. The wingtip torque box (200) may have a continuous cavity (300) extending between the ends and preferably between spars of the box and providing access for performing various operations inside the box.