Blind Fastener Mandrel Geometry for Lower Installation Force
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Solution Overview
Problem
Existing fasteners in structural components often fail due to fatigue, overload, and geometric variations, making blind fastener installation challenging, especially in applications like vehicle frames and solar panel sub-structures.
Innovation Solution
A blind fastener design comprising a sleeve and a mandrel with a specific configuration, where the mandrel has an enlarged portion and a pull region of limited axial length, allowing for reduced installation force and enhanced corrosion resistance, and a method for installing the fastener using an installation tool to deform the sleeve and secure it onto the mandrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional fastener installation methods are used, then fasteners can be installed in structural components, but installation forces are high and mandrels may fracture during installation
Solution Approach 1:
The mandrel is segmented into distinct functional regions: a reduced-diameter shank region for deformation, an enlarged portion for positioning, and a pull region for tool engagement. This segmentation allows each region to perform its specific function optimally, reducing overall installation force requirements while preventing mandrel fracture during installation
Solution Approach 2:
Different regions of the mandrel have different diameters and properties tailored to their specific functions. The shank region has a smaller diameter optimized for deformation and swaging, while the enlarged portion provides positioning stability. This local differentiation of properties reduces the force needed for installation while maintaining reliability
2Reliability
If conventional blind fastener designs are used, then fasteners can be installed blind, but corrosion resistance is insufficient for structural applications
Solution Approach 1:
The fastener is constructed from corrosion-resistant materials suitable for structural applications. The mandrel and sleeve are designed to work together as a composite system where the mandrel provides structural integrity and the sleeve provides corrosion protection and deformation characteristics, achieving both corrosion resistance and functional performance
3Strength
If high installation forces are required, then fasteners can be securely installed, but tools become heavier and more complex
Solution Approach 1:
The segmented mandrel design with distinct functional regions enables secure fastening through controlled deformation of the shank region rather than requiring high overall installation forces. This reduces the force requirements, allowing for lighter and simpler installation tools while maintaining fastening security
Solution Approach 2:
The pull region acts as an intermediary element that allows the installation tool to engage and apply controlled forces to the mandrel. This intermediary design enables precise force application during installation, achieving secure fastening with reduced tool weight and complexity
4Productivity
If mandrels are designed to fracture during installation, then installation can be completed, but tool life is reduced and structural damage may occur
Solution Approach 1:
The segmented mandrel design with a reduced-diameter shank region is specifically engineered to deform and swage onto the sleeve during installation rather than fracture. This controlled deformation completes the installation process while preserving the mandrel and installation tool, extending tool life and preventing structural damage
Solution Approach 2:
Instead of relying on mandrel fracture to complete installation, the design converts the potential harm of high installation forces into a beneficial controlled deformation process. The reduced-diameter shank region deforms plastically to create the secure connection, eliminating the need for mandrel fracture and thereby extending tool life
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 design reduces installation forces, increases corrosion resistance, enables lighter weight tools, and enhances ergonomics by allowing for secure fastening without fracturing the mandrel, thus extending tool life and minimizing structural damage.
Implementation Method 1
the pull region is moved distal from the second sleeve end utilizing the collet of the installation tool
Implementation Method 2
The portion of the sleeve on a first side of the structure is deformed, and the second sleeve end is swaged onto the shank region of the mandrel
Implementation Method 3
the second sleeve end is swaged onto the shank region of the mandrel on an oppositely disposed second side of the structure
Data Source
AI summary
The present disclosure relates to a blind fastener and a method of installation thereof. The blind fastener comprises a sleeve and a mandrel. The sleeve comprises a first sleeve end, a second sleeve end, and a cavity extending from the first sleeve end to the second sleeve end. The mandrel is configured to be at least partially received by the cavity of the sleeve. The mandrel comprises a first mandrel end disposed adjacent to the first sleeve end and comprising an enlarged portion having a diameter greater than a diameter of the cavity, a second mandrel end comprising a pull region, and a shank region extending intermediate the first mandrel end and the second mandrel end. The pull region comprises an axial length no greater than four times a diameter of the shank region and is configured to be engaged by an installation tool.