Multi-Probe Friction Stir Welding for Laminate Butt Seams
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Solution Overview
Problem
Existing methods for joining fibre metal laminates, such as those used in aircraft construction, are labor-intensive and inefficient, particularly when aiming to avoid material overlap in lap joints, and there is a need for a more efficient method to form high-quality butt weld seams in these materials.
Innovation Solution
A friction stir welding method and device using a probe assembly with at least two probe devices, each adapted to different material layers, allowing for simultaneous welding of metal and thermoplastic layers with varying thermal conductivity, enabling optimized welding by adjusting probe diameters and rotational velocities based on material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single probe is used for friction stir welding of laminates with different materials, then the device complexity is reduced, but the manufacturing precision and welding quality deteriorate due to inability to account for different material properties
Solution Approach 1:
The probe assembly is segmented into multiple probe devices (first probe device for metal layers, second probe device for thermoplastic layers), each optimized for specific material properties. This segmentation allows independent optimization of welding parameters for each material type, resolving the contradiction between device simplicity and welding precision.
Solution Approach 2:
Each probe device in the assembly has locally optimized properties (different diameters, rotational velocities, or material compositions) suited for the specific layer it contacts. The first probe device is configured for metal layers while the second is configured for thermoplastic layers, enabling precise control of welding quality for each material type.
2Productivity
If friction stir welding is applied to laminates with different thermal conductivity materials, then the productivity and weight reduction are improved, but the manufacturing precision deteriorates due to difficulty in controlling heat distribution
Solution Approach 1:
The probe assembly provides locally adapted welding action where the first probe device applies friction stir welding parameters optimized for high thermal conductivity metal layers, while the second probe device applies parameters optimized for low thermal conductivity thermoplastic layers. This local optimization maintains heat control accuracy despite processing materials with different thermal properties, enabling both high productivity and precision.
Solution Approach 2:
The system changes welding parameters (rotational velocity, feed rate, probe diameter) based on the material layer being welded. By adjusting these parameters according to the specific thermal conductivity of each layer, the system maintains precise heat control while achieving high welding speeds across heterogeneous laminate structures.
3Strength
If lap joint with material overlap is used to join laminate parts, then the joint strength is improved, but the weight increases and the ease of manufacture deteriorates
Solution Approach 1:
The invention replaces the mechanical lap joint system (requiring overlapping materials and fasteners) with a friction stir welding system that creates metallurgical bonds. This substitution eliminates the need for material overlap, reducing weight while maintaining or improving joint strength through direct bonding of the laminate layers.
4Weight of moving object
If friction stir welding is used to join laminate parts, then the weight is reduced and productivity is improved, but the device complexity increases due to need for multiple probe devices
Solution Approach 1:
Multiple probe devices with different configurations are merged into a single integrated probe assembly that operates simultaneously. This merging allows the system to handle multiple material layers in one welding pass, achieving weight reduction through butt joints while consolidating what would otherwise require multiple separate welding operations or complex interchangeable tooling systems.
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 enables efficient, rapid, and high-quality butt weld seam formation in fibre metal laminates, reducing weight and improving fatigue behavior, suitable for lightweight and resilient components like aircraft parts and cryogenic storage tanks.
Implementation Method 1
The material of the sheets is heated up using frictional heat generated by a rotating probe acting on the sheets at the location of the joint
Data Source
Figure 1(a)~2
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Figure 5~7
AI summary
The invention relates to a method for friction stir welding along a butt joint weld line (40). A welding device (70) comprises a probe assembly (90) including at least a first and second probe device (100a, 100b). A first and second part (31a, 31b) to be joined along the weld line (40) are provided, wherein the parts are each formed as a laminate (1; 1') comprising at least a first layer (2a, 2b) formed with a first material and a second layer (5a, 5b) formed with a second material. The first and second materials have different material properties. The method comprises friction stir welding of the parts using the welding device, wherein simultaneously, the first probe device acts on the first layers and the second probe device acts on the second layers. Moreover, the invention relates to a friction stir welding device and to a workpiece comprising a butt weld seam.