Differential Work-Hardening for Aeronautical Structural Elements
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Solution Overview
Problem
The aeronautical industry faces challenges in manufacturing monolithic metallic structural elements with variable properties within the elements, as existing methods are costly, unreliable, or require artificial ageing, which limits their application to specific alloys and cannot achieve optimal property variations across different zones.
Innovation Solution
A process involving hot working followed by cold plastic deformation, where generalized average plastic deformations are imposed in at least two zones of the structural element, differing by at least 2-5%, to produce monolithic aluminium alloy structural elements with variable properties without the need for artificial ageing, allowing for the creation of multi-functional components with consistent geometric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If different heat treatments are applied between ends of structural element during artificial ageing, then variable properties within element are achieved, but process complexity and cost increase significantly
Solution Approach 1:
The patent applies parameter changes by varying the degree of cold plastic deformation (work-hardening) across different zones of the structural element rather than using complex thermal gradients. By controlling the amount of deformation in each zone during the rolling or forming process, the material develops different mechanical properties in different regions through work-hardening effects, eliminating the need for complex multi-zone ageing furnaces.
Solution Approach 2:
The patent implements preliminary action by creating the desired property distribution during the initial cold plastic deformation stage before final heat treatment. The differential work-hardening is applied during rolling or forming operations, and subsequent uniform heat treatment simply stabilizes the microstructure without needing to create property variations. This reverses the conventional approach of creating property variations during the final heat treatment stage.
2Strength
If monolithic structural elements with variable properties are manufactured using existing methods, then optimal property distribution is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent merges the property distribution creation step with the primary forming operation. By integrating differential work-hardening into the rolling or forming process itself, the patent combines what were previously separate operations (property tailoring and shaping) into a single manufacturing step, significantly simplifying the overall manufacturing process while achieving optimal property distribution.
Solution Approach 2:
The patent uses parameter changes in the deformation process (varying roll pressure, deformation rate, or pass schedule across different zones) to create property variations during standard forming operations. This allows existing manufacturing equipment to produce variable-property components without requiring additional specialized equipment or process steps.
3Strength
If artificial ageing is used to create variable properties, then property variation is achieved, but applicability is limited to heat-treatable alloys only
Solution Approach 1:
The patent replaces the thermal field (artificial ageing) with a mechanical field (differential cold plastic deformation) as the primary mechanism for creating property variations. By using work-hardening and dislocation density variations during cold forming to achieve property distribution, the method becomes applicable to all cold-formable metals including non-heat-treatable alloys like 5000 series aluminium alloys, thereby significantly expanding alloy family applicability.
4Strength
If mechanical assembly steps are used to achieve optimal properties in each zone, then property optimization is achieved, but manufacturing cost and time increase
Solution Approach 1:
The patent merges multiple separate manufacturing operations (creating variable properties and final shaping) into a single integrated cold plastic deformation process. By implementing differential work-hardening during the primary forming operation, the patent eliminates the need for subsequent mechanical assembly steps or additional processing to achieve zone-specific properties, thereby significantly improving manufacturing efficiency and productivity.
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 process enables the production of aluminium alloy structural elements with tailored mechanical properties across different zones, enhancing their functionality and efficiency while eliminating the need for costly assembly steps and artificial ageing, thus providing a cost-effective and reliable method for fabricating components with optimized properties.
Implementation Method 1
a hot working step
Implementation Method 2
at least one working step by cold plastic deformation after the hot working step, wherein generalized average plastic deformations are imposed in at least two zones
Data Source
AI summary
A process for fabricating a worked product or a monolithic multi-functional structural element comprising aluminium alloy includes a hot working step and at least one transformation step by cold plastic deformation after the hot transformation step. At least two zones of the structural element have imposed generalized average plastic deformations and the imposed deformations are different by at least 2%. Structural elements can be fabricated, particularly for aeronautical construction, with properties that are variable while their geometric characteristics are identical to those of existing components. The process is economic and controllable, and properties can be varied for parts not requiring any artificial ageing.