Diffusion Bonded Fastener Assembly for Aircraft
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Solution Overview
Problem
Current aircraft fastener production is hindered by the unavailability of durable, reliable, and uniform fasteners due to limitations in machining and inspection processes, leading to variable clamp-up results, increased weight, and potential failure from vibration and shock, as traditional fasteners rely on surface contact and are prone to corrosion and fatigue.
Innovation Solution
A diffusion bonded fastener assembly using a bolt with a bondable portion made of amorphous metal, which is integrated with a collar through a diffusion bonding process, providing a strong, reliable, and consistent clamping force without the need for extensive machining, and capable of withstanding vibration and shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional threaded or swaged fasteners are used, then installation is straightforward, but clamp-up results are variable and reliability is reduced due to contamination, improper geometry, and vibration
Solution Approach 1:
The collar and bolt are merged into a single integral component through diffusion bonding, eliminating the interface between separate parts that causes contamination and variable clamp-up. The bonded interface creates a unified structure that maintains consistent clamping force without the problems of traditional assembled fasteners.
Solution Approach 2:
The fastener utilizes diffusion bonding to create a composite structure where the collar and bolt materials are metallurgically bonded at the molecular level. This composite approach provides both the structural integrity of solid fasteners and the consistency of controlled material properties, eliminating variability from traditional assembled connections.
2Reliability
If multiple machining and inspection steps are performed to control grain boundaries, then fastener durability is improved, but production throughput is reduced
Solution Approach 1:
The diffusion bonding process utilizes controlled temperature and pressure parameters to create optimal grain structure directly during manufacturing. By controlling the bonding parameters, the process achieves desirable grain boundaries without requiring subsequent machining and inspection steps, thereby maintaining both durability and production throughput.
Solution Approach 2:
The grain boundary control is performed preliminarily during the diffusion bonding manufacturing process itself, rather than as a separate post-processing step. The bonding process inherently creates the desired grain structure, eliminating the need for additional machining and inspection operations.
3Ease of manufacture
If revolved-shaped fasteners are used, then manufacturing is easier, but vibration and shock cause rotation and loosening
Solution Approach 1:
The collar is designed with an asymmetric non-revolved cross-sectional shape that prevents rotation under vibration and shock loads. This asymmetric geometry provides inherent anti-rotation characteristics while the diffusion bonding process maintains manufacturing feasibility, resolving the conflict between ease of manufacture and vibration resistance.
4Reliability
If larger and more fasteners are provided to compensate for variable clamp-up, then reliability is improved conservatively, but weight and cost increase
Solution Approach 1:
The diffusion bonding process enables precise control of material properties and interface strength, allowing fasteners to be designed with optimal rather than conservative dimensions. The controlled bonding parameters ensure consistent clamp-up, enabling the use of smaller, lighter fasteners that meet reliability requirements without excessive weight.
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 diffusion bonded fastener assembly achieves consistent clamping forces, reduces the number and size of fasteners required, and enhances durability by eliminating grain boundaries, thus improving the reliability and efficiency of aircraft assembly while minimizing production costs and weight.
Implementation Method 1
at least a portion of the bolt is heated close to the temperature of the collar, thus expanding the shaft body into an interference fit with the inner collar wall. The bondable material of both the shaft body and the inner collar wall is then heated to about 50-75% of the material melting temperature and placed under sufficient pressure to activate the diffusion bonding process
Data Source
Figure 1
Figure 2~3A
Figure 3B~3C
AI summary
A fastener assembly includes a bolt (102) having a shaft (104) and a head (106). The shaft has proximal and distal shaft ends and a shaft body, with the head at the proximal shaft end. At least a bondable portion (114) of the shaft body is at least partially made of a bondable material. At least one collar (218) has proximal and distal collar ends longitudinally separated by a collar body which includes a longitudinally oriented collar aperture extending through a thickness thereof between proximal and distal collar surfaces. The collar aperture (226) defines an inner collar wall (232) having a bondable portion (234) which is at least partially made of a bondable material. At least the bondable portion of the shaft body is located inside the collar aperture. The bondable material of both of the inner collar wall and the shaft body is activated to bond the shaft and the collar into an integral fastener assembly structure.