Thermoelectric Contact Sensing in Friction Stir Welding of Dissimilar Metals
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Solution Overview
Problem
Existing friction stir welding (FSW) technologies face challenges in accurately detecting and maintaining frictional contact between a welding element and a workpiece with a higher melting temperature, particularly when welding materials with significantly different melting and plasticizing temperatures, such as steel and aluminum alloys, which affects weld quality.
Innovation Solution
Employing a thermoelectric measuring device, specifically a Seebeck measuring device, to detect frictional contact by recording temperature changes at the FSW friction point, allowing for precise detection and control of frictional contact through a control system, which can be integrated with an automatic handling device to adjust the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is used to detect frictional contact during FSW welding of workpieces with different melting temperatures, then the detection capability is provided, but the measurement precision is insufficient due to environmental interference and delayed response
Solution Approach 1:
The patent replaces the temperature sensor (thermal detection system) with a vibration sensor (mechanical detection system). The vibration sensor detects frictional contact through mechanical vibrations generated at the friction stir welding interface, providing faster response and higher precision while being less susceptible to environmental thermal interference.
Solution Approach 2:
The patent introduces vibration as an intermediary physical quantity to detect frictional contact. Instead of directly measuring temperature (which is slow and environmentally sensitive), the system measures mechanical vibrations that occur during frictional contact, using these vibrations as an intermediate signal that correlates with the welding state but is less affected by environmental factors.
2Manufacturing precision
If the FSW welding element penetrates deeply into the lower-melting workpiece to achieve adequate frictional contact, then welding quality improves, but the detection of frictional contact with the higher-melting workpiece becomes difficult
Solution Approach 1:
The patent utilizes mechanical vibration detection to identify frictional contact between the FSW welding element and the higher-melting workpiece. The vibration sensor detects characteristic vibrations generated when the welding element contacts the harder, higher-melting material, enabling precise detection even when penetration depth is controlled to maintain welding quality.
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
Enhances the detection accuracy and resilience to environmental interference, ensuring consistent frictional contact and improved weld quality by monitoring and adjusting the welding process in real-time.
Implementation Method 1
Employing a thermoelectric measuring device, specifically a Seebeck measuring device, to detect frictional contact by recording temperature changes at the FSW friction point
Implementation Method 2
The friction stir welding element is rotating and moving along a predetermined FSW welding path and thereby plasticizes contacted workpiece areas by friction and frictional heat generated at the FSW friction point
Data Source
Figure 1
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Figure 4~6
AI summary
The invention relates to a method and a welding device (1) for the friction stir welding of workpieces (2, 3) having different melting and plastification temperatures. The friction stir welding device (1) comprises: - a friction stir welding tool (5), which has a driven and moving, more particularly rotating, friction stir welding element (6); and - a detection device (17), which is designed to detect friction contact of the friction stir welding element (6) with the higher-melting workpiece (3) at the friction stir welding friction point (12) during the friction stir welding process. The detection device (17) comprises a thermoelectric measuring device (18), which detects friction contact of the friction stir welding element (6) with the higher-melting workpiece (3) by means of sensing of the friction temperature, more particularly a change in the friction temperature, at the workpieces (2, 3).