Thin-Walled Fastener Nut with Tapered Bell Flange
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Solution Overview
Problem
Conventional thin-walled fastener nuts used in aerospace applications are prone to cracking due to brittleness caused by high heat treatment, leading to failures such as hydrogen embrittlement, and often misused beyond their design limitations, resulting in mechanical property conflicts and safety issues.
Innovation Solution
A thin-walled nut design with a tapered bell flange and reduced Rockwell Hardness Scale (HRC) values between 38 HRC to 39 HRC, which reduces the likelihood of cracking and meets the mechanical requirements of NASM21042 and NAS1291 standards, while providing structural support and minimizing hydrogen embrittlement risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high heat treatment is applied to harden the nuts, then the tensile strength is improved, but the brittleness increases leading to hydrogen embrittlement and cracking
Solution Approach 1:
The patent changes the hardness parameter from conventional high HRC values (46-52 HRC) to a lower range (38-42 HRC). This parameter change resolves the contradiction by maintaining sufficient tensile strength while reducing brittleness and hydrogen embrittlement susceptibility, thereby improving cracking resistance and overall reliability
Solution Approach 2:
The patent employs a composite material system combining 7075-T6 aluminum alloy with a specific heat treatment process that achieves optimal mechanical properties at lower hardness levels. This composite approach allows the material to exhibit both high strength and improved ductility, resolving the strength-brittleness contradiction
2Weight of moving object
If the wall thickness is reduced to lighten the nut, then the weight is decreased, but the structural integrity and resistance to cracking are worsened
Solution Approach 1:
The patent optimizes the wall thickness parameter to a specific range that maintains structural integrity while minimizing weight. By combining this optimized geometry with the reduced hardness heat treatment, the nut achieves sufficient strength without requiring excessive material, thus resolving the weight-strength contradiction
Solution Approach 2:
The patent incorporates a bell flange with optimized curvature and geometry that distributes stress more effectively throughout the thin walls. This geometric optimization allows the thin-walled structure to maintain structural integrity and resistance to cracking while keeping the weight minimized
3Reliability
If self-locking nuts are used to prevent loosening, then the reliability is improved, but the applicability is restricted by NASM33588 limitations
Solution Approach 1:
The patent designs a universal nut configuration that can be used in both self-locking and non-self-locking applications. By optimizing the basic geometry and material properties, the same nut design achieves reliable performance across diverse aerospace applications, whether used with self-locking features or not, thus resolving the reliability-adaptability contradiction
Data Source
AI summary
A thin walled fastener nut of the present invention includes a tapered bell flange extending from one end towards the other. The tapered bell flange provides structural support to the nut when used in aerospace application. The thin walled fastener nut with the tapered bell flange meets the dimensional requirements of the National Aerospace Standard Specification MS21042 (NASM21042) and National Aerospace Standard Specification MS1291 (NAS1291).