Blind Flow Screw Joining Dissimilar Materials
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Solution Overview
Problem
Existing mechanical fastening methods struggle to securely join dissimilar materials like aluminum, magnesium alloys, and polymers, as they require high strength and adaptability to various material properties, and often involve complex processes that are not efficient for wide material ranges.
Innovation Solution
A two-part fastener system with a hollow, cylindrical or conical body and a mandrel, featuring external protuberances and a deformable end, which frictionally heats and penetrates workpieces to create a strong joint by collapsing the fastener body, allowing for secure attachment of layered workpieces with or without adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional mechanical fastening methods are used to join dissimilar materials, then the joint strength may be sufficient, but the process complexity increases and efficiency decreases
Solution Approach 1:
The patent applies parameter changes by utilizing frictional heating to raise the temperature of the workpiece materials, thereby changing their physical properties (reducing flow stress, increasing ductility). This thermal parameter change allows the fastener to penetrate and join dissimilar materials more easily, reducing process complexity while maintaining joint strength.
Solution Approach 2:
The patent replaces pure mechanical fastening with a combined thermal-mechanical process. Instead of relying solely on mechanical force to penetrate and join materials, the system uses frictional heating (thermal energy) to soften materials, making them more receptive to mechanical deformation and joining, thus simplifying the overall process.
2Force
If high force is applied to penetrate hard materials, then penetration is achieved, but the fastener body may deform or fail
Solution Approach 1:
The patent changes the physical state of the workpiece materials through frictional heating, reducing their flow stress and hardness. This parameter change allows penetration with lower forces, preventing fastener body deformation or failure while achieving effective material penetration and joint formation.
3Ease of manufacture
If frictional heating is applied to reduce material resistance, then penetration becomes easier, but energy consumption increases
Solution Approach 1:
The patent implements self-service by using the fastener's own rotation and advancement through the workpiece to generate frictional heating. The system does not require external heating equipment; instead, the mechanical energy of fastener insertion is converted into thermal energy at the joint interface, making the process self-contained and energy-efficient.
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 fastener system effectively secures multiple layers of diverse materials by reducing material resistance through frictional heating and deformation, enhancing joint strength and simplifying the joining process across a wide range of materials.
Implementation Method 1
The mandrel head may be adapted, when a rotating fastener is brought into contact with a workpiece, to frictionally engage and heat the workpiece
Implementation Method 2
the mandrel head interferes with the body end and deforms and collapses the body end until the mandrel shaft fractures
Data Source
AI summary
A two-part mechanical fastener comprising an elongated body with a bore slidably carrying a mandrel adapted to interferingly engage the body is described. The fastener body has one or more protuberances on its exterior surface. In an aspect, the protuberances form a thread. The fastener is adapted to form an opening in, and penetrate, a stack of two or more workpieces. To secure the workpieces in the workpiece stack and form a robust joint, the fastener body is deformed by the mandrel, expanding the body, so that a body end engages a surface of the workpiece stack and the one or more protuberances are brought into engagement with the walls of the opening. Methods of using such a fastener to secure non-ferrous or polymer-based sheet-like workpieces to one another are disclosed.