Fastener Preload Indicator Layer for Consistent Joint Compression
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Solution Overview
Problem
Variations in frictional forces within fastener joints lead to inconsistent preloads, causing fatigue and reducing the structural life of fasteners in aircraft and other applications.
Innovation Solution
A fastening system that includes a layer disposed between the fastener assembly and the components, which provides an alert when a predetermined compressive load is reached, ensuring consistent preload application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a torque wrench is used to tighten the nut based on friction calculations, then the tightening process is simple and fast, but the preload varies due to frictional variations in the threads
Solution Approach 1:
The patent applies feedback by using a coating layer that provides visual indication (color change, cracking, or other detectable changes) when the fastener reaches the desired preload. This feedback mechanism allows the operator to stop tightening at the correct preload point, eliminating the variability caused by friction while maintaining simplicity and speed of the tightening process.
Solution Approach 2:
The coating layer acts as an intermediary between the fastener and the operator. It translates the internal mechanical state (preload) into an external observable signal, allowing precise control of preload without requiring complex measurement devices or calculations, thus maintaining simplicity while improving precision.
2Device complexity
If friction-based torque calculations are used, then the tightening process requires no additional components, but the preload accuracy is compromised due to frictional variations
Solution Approach 1:
The coating layer serves as a simple intermediary component that provides accurate preload indication without requiring complex measurement instruments. It is applied directly to the fastener surface and provides visual feedback when the desired preload is achieved, maintaining system simplicity while dramatically improving measurement accuracy.
Solution Approach 2:
The patent utilizes color changes in the coating layer as a visual indicator of preload achievement. The coating is formulated to change color, crack, or otherwise visually indicate when the fastener reaches the target preload, providing accurate measurement without adding mechanical or electronic complexity to the system.
3Ease of operation
If traditional torque tightening is used, then the fastening process is straightforward, but preload variations cause fatigue in the fastener over its life
Solution Approach 1:
The coating layer provides immediate visual feedback when the desired preload is reached, allowing operators to consistently achieve the correct preload without requiring complex procedures or training. This simple feedback mechanism eliminates preload variations that lead to fatigue, thereby extending fastener life while maintaining ease of operation.
Solution Approach 2:
The coating layer performs the function of preload indication automatically as the fastener is tightened. It self-regulates and provides information without requiring external measurement devices or complex procedures, making the process equally simple while ensuring consistent preload and improved reliability.
Data Source
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AI summary
A fastening system includes a first component and a second component. The fastening system includes a fastener assembly configured to attach together the first component and the second component. The fastening system also includes a layer disposed between the fastener assembly and the first component and/or the second component. The layer is configured to provide an alert when a predetermined compressive load has been reached in the first component and the second component which signals that a preload of the fastener assembly has been reached. A method of preloading a fastener assembly includes applying a torque to the fastener assembly until a predetermined compressive load has been reached in the first component and the second component. The alert of the layer is activated when the predetermined compressive load has been reached which signals that the preload of the fastener assembly has been reached.