Adhesive Disc Guides for Eddy Current Fastener Inspection
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Solution Overview
Problem
Current eddy current inspection tools for countersunk fasteners in aircrafts face issues with adaptation to curved surfaces, interference from assembly elements, and require multiple inspectors or increased inspection time due to template movement, potentially causing false crack indications.
Innovation Solution
A system comprising multiple adhesive discs with varying diameters, connected by a non-conductive wire, serves as guides for the inspection device, ensuring proper placement and reducing interference, allowing single inspector operation and minimizing false indications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a circle template is used for eddy current inspection around countersunk fasteners, then the probe can be guided to slide close to the hole edge for better detectability, but the template cannot be properly placed on curved surfaces and may move during inspection causing false indications
Solution Approach 1:
The template is divided into multiple separate discs (e.g., 6 discs for hexagonal fasteners) that can be independently placed on each flat surface of the countersunk fastener. This segmentation allows the template to adapt to curved surfaces while maintaining precise probe guidance on each individual surface.
Solution Approach 2:
The template uses multiple flat discs arranged to conform to the geometry of countersunk fasteners, which have conical surfaces. Each disc is adapted to fit on a specific flat surface of the fastener head, allowing the overall template structure to accommodate curved surfaces while providing stable guidance.
2Measurement precision
If a circle template is used to guide the probe around fasteners, then inspection coverage is improved, but assembly elements such as collars and clips prevent correct placement of the template
Solution Approach 1:
By segmenting the template into multiple small discs, each disc can be placed on available flat surfaces of the fastener head, avoiding interference from collars, clips, or other assembly elements. The inspector can select which discs to use based on the specific fastener configuration.
Solution Approach 2:
Each disc is designed to fit on specific local surfaces of the fastener head, allowing the template to adapt to different fastener configurations and assembly element arrangements. The local placement of individual discs ensures compatibility with various assembly elements while maintaining inspection coverage.
3Reliability
If a rigid circle template is used for inspection, then probe guidance is stable, but the inspector must hold the template in position and adjust controls manually requiring two inspectors or increased inspection time
Solution Approach 1:
The discs are pre-positioned on the fastener head surfaces before inspection begins. Once placed, they remain fixed during the sliding probe operation, eliminating the need for continuous manual holding and adjustment during the inspection process.
Solution Approach 2:
The template uses simple disc shapes that replicate the essential geometric features needed for probe guidance without the complexity of traditional circle templates. This simplification allows for faster placement and removal while maintaining the necessary guidance function.
4Measurement precision
If the probe slides close to the hole edge for better crack detection, then detectability improves, but the probe may lean against the template edge causing false crack indications
Solution Approach 1:
The template is segmented into multiple small discs rather than a single continuous circle. This creates gaps between the discs that prevent the probe from leaning against a continuous edge, eliminating the source of false indications while maintaining close proximity to the hole edge for detection.
Solution Approach 2:
The multiple separate discs act as intermediaries between the probe and the fastener head, providing guidance without creating a continuous edge that the probe can lean against. The gaps between discs serve as mediators that prevent harmful contact while maintaining proper probe positioning.
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 system improves adaptability to curved surfaces, reduces interference, and simplifies the inspection process, enabling faster and more accurate detection by maintaining disc position during the inspection.
Implementation Method 1
the, or each, disc comprises an adhesive on one of its surfaces, in particular, a detachable or weak adhesive that permits to fix the disc on a surface
Data Source
Figure 1
AI summary
The tool for eddy current inspection is intended to be used with an inspection device (1), comprising one or more guides, wherein the, or each, guide is a disc (2). Furthermore, the, or each, disc (2) comprises an adhesive on one of its surfaces, the adhesive being a detachable adhesive, i.e., it is a weak adhesive that allows its removal after inspection and to re-use it again at other fastener position. It is smaller than the currently known tools to improve the adaptability to curved parts and to avoid interference with near elements, it is easier in use, and it is kept fixed to the inspection surface to give the inspector more autonomy and preventing false indication.