Bi-functional Extruded Stringer for Aircraft Structural Assembly
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Solution Overview
Problem
Current manufacturing processes for aircraft structural elements restrict alloy choices due to limitations in fusion welding, making it difficult to weld high mechanical property alloys with those of high damage tolerance, resulting in suboptimal structural performance and requiring costly riveting instead.
Innovation Solution
A process involving the extrusion of bi-functional structural elements using a composite hollow billet with a heat-treatable fusion weldable alloy for the body and a non-fusion weldable alloy for the base, allowing for fusion welding and subsequent heat treatment to enhance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high mechanical property aluminium alloys (2xxx or 7xxx series) are used for structural elements, then strength and mechanical properties are improved, but weldability deteriorates making fusion welding impossible
Solution Approach 1:
The structural element is divided into two distinct alloy regions: a base made of weldable aluminium alloy (5xxx or 6xxx series) and a body made of high mechanical property alloy (2xxx or 7xxx series). This segmentation allows each part to have optimized properties for its specific function while being manufactured as a monolithic extruded piece.
Solution Approach 2:
Different regions of the structural element have different material compositions tailored to their specific requirements. The base region uses weldable alloy for ease of assembly, while the body region uses high-strength alloy for mechanical performance. This local differentiation resolves the contradiction between overall strength and local weldability.
2Productivity
If fusion welding is used to assemble structural elements, then assembly is simplified and productivity is improved, but alloy selection is restricted to weldable alloys only
Solution Approach 1:
The structural element is segmented into a weldable base portion and a high-performance body portion, enabling the entire element to be joined by fusion welding while maintaining access to both weldable and non-weldable alloy types.
Solution Approach 2:
The base made of weldable alloy serves multiple functions: it provides a weldable surface for fusion welding operations and serves as the structural foundation. This multi-functionality allows fusion welding to be used universally for assembly while the body can still use high-strength non-weldable alloys.
3Reliability
If different alloys with optimized property balance are used for stringers and skin, then damage tolerance and mechanical properties are improved, but assembly complexity increases due to riveting requirements
Solution Approach 1:
The base and body of the structural element are merged into a single monolithic extruded component with two different alloys. This eliminates the need for separate assembly operations (riveting) between different alloy types, simplifying the overall assembly process while maintaining the ability to use optimized alloy combinations for damage tolerance.
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 creation of structural elements with improved mechanical and damage tolerance properties, simplifying aircraft assembly by allowing the use of high-strength alloys for stringers and high-damage-tolerant alloys for wing skins, while maintaining weldability, thus enhancing overall performance and reducing weight and cost.
Implementation Method 1
A process involving the extrusion of bi-functional structural elements using a composite hollow billet
Implementation Method 2
allowing for fusion welding and subsequent heat treatment to enhance properties
Data Source
AI summary
The invention relates to a bi-functional extruded structural element, particularly a stringer for aeronautical construction, comprising a base that can be fixed on a surface, and a body, wherein the base comprises a first aluminum-based alloy, and further wherein the body comprises a second heat treatable aluminum-based alloy, having properties that are different from the properties of the first aluminum based alloy.