Segmented Coated Fastener for Conductivity and Galling Control
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Solution Overview
Problem
Aerospace fasteners with insufficient connection between the conductive core and the material they secure experience high current density and heat generation due to inadequate conduction and lubrication, despite advancements in coating technologies.
Innovation Solution
Coated fasteners with a conductive core made of materials like stainless steel or titanium, featuring a dielectric coating on threaded portions and a conductive friction modifier material, such as graphite, on non-threaded portions to enhance lubricity and electromagnetic protection, applied using a specific coating method and apparatus that rotates the fastener during coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dielectric coating is applied to the entire fastener, then galvanic corrosion protection is improved, but electromagnetic conduction is worsened due to insufficient current flow through the conductive core
Solution Approach 1:
The patent applies different coating types to different portions of the fastener: dielectric coating on the threaded portion (first portion) for corrosion protection, and conductive friction modifier coating on the non-threaded shank portion (second portion) for maintaining electromagnetic conduction and reducing friction. This local differentiation resolves the contradiction by providing each coating type where it is most needed.
2Ease of operation
If a dielectric coating is applied to provide lubrication, then friction reduction is improved, but electromagnetic conduction is worsened due to high current density through the conductive core
Solution Approach 1:
The patent provides lubrication only where needed by applying the conductive friction modifier coating specifically to the non-threaded shank portion (second portion) that interfaces with the hole, while leaving the threaded portion (first portion) with dielectric coating for corrosion protection. This localized approach maintains electromagnetic conduction through the threaded portions while providing friction reduction where mechanical contact occurs.
3Strength
If the fastener material is changed to improve strength, then mechanical strength is improved, but heat generation is worsened due to high current density in less conductive materials
Solution Approach 1:
The patent creates a composite structure by coating the fastener with a conductive friction modifier material (such as graphite-based coatings) on the non-threaded portion. This coating layer provides enhanced electrical conductivity to reduce heat generation from current density, while the underlying fastener material (titanium, stainless steel, or nickel-based superalloy) provides the required mechanical strength. The composite approach allows both strength and conductivity requirements to be met simultaneously.
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 solution provides improved transition fit, reduced heat generation, and enhanced electromagnetic protection by lowering current density through the conductive core, while preventing galling and ensuring effective lubrication.
Implementation Method 1
The coating of dielectric material provides the fastener with lubrication properties
Implementation Method 2
a second coating comprising a conductive friction modifier material and disposed on the second portion of the core body to provide the fastener with a desired transition hold fit, improved lubricity, and improved electromagnetic effects protection
Data Source
Figure 1A~1C
Figure 2
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AI summary
A coated fastener includes a core body comprising conductive material and including a first portion and a second portion. The coated fastener also includes a first coating comprising dielectric material and disposed on the first portion of the core body. The coated fastener further includes a second coating comprising a conductive friction modifier material and disposed on the second portion of the core body to provide the fastener with a desired transition hold fit, improved lubricity, and improved electromagnetic effects protection.