Frangible Drive Fastener Assembly for Precise Torque Control
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Solution Overview
Problem
Existing fastener assemblies in aerospace applications face challenges with installation torque consistency and reliability due to 'jam nut effects' and material deformation, leading to premature screw failure and inconsistencies in load transfer under varying environmental conditions.
Innovation Solution
A fastener assembly with a non-deformable drive element and interlayer structure that fractures in torsional shear, preventing over-torquing and using materials like titanium and aluminum alloys for enhanced strength and reliability, and a brazing or soldering process for connecting the drive element to the bolt or nut member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a deformable drive element is used to facilitate installation, then ease of operation is improved, but material deformation occurs leading to jam nut effects and premature failure
Solution Approach 1:
The fastener system is divided into separate components: a drive element and a fastener body, connected through a frangible portion that can be cleanly separated. This segmentation allows the drive element to be optimized for installation while the fastener body maintains structural integrity, eliminating the jam nut effect caused by deformation in integrated designs.
Solution Approach 2:
The drive element is extracted as a separate removable component from the fastener body, connected only through a frangible portion. This extraction allows the drive element to perform its installation function without being permanently deformed, while the fastener body remains undamaged and reliable for sustained loading.
2Strength
If higher installation torque is applied to ensure secure fastening, then strength is improved, but over-torquing occurs causing premature screw failure
Solution Approach 1:
A frangible portion is pre-configured in the connection between the drive element and fastener body at a specific torque threshold. This preliminary design ensures that when installation torque reaches the predetermined level, the frangible portion will fracture, automatically preventing over-torquing and protecting the fastener from damage while ensuring adequate fastening strength.
3Device complexity
If traditional fastener designs are used to maintain simplicity, then device complexity is reduced, but inconsistencies in load transfer occur under varying environmental conditions
Solution Approach 1:
The frangible portion is designed using material selection and geometric configuration that enables controlled fracture at a predetermined torque. This composite approach combines materials with different mechanical properties to create a reliable fracture interface that ensures consistent load transfer across varying environmental conditions while maintaining overall structural integrity.
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 ensures precise torque application, eliminates 'jam nut effects, and enhances the reliability and consistency of fastener assemblies by preventing material deformation and ensuring controlled shear, thereby maintaining structural integrity and reducing the risk of premature failure.
Implementation Method 1
the interlayer structure adapted to fracture in torsional shear to separate the drive element from the bolt member or the nut member
Implementation Method 2
a brazing or soldering process for connecting the drive element to the bolt or nut member
Implementation Method 3
a brazing or soldering process for connecting the drive element to the bolt or nut member
Data Source
AI summary
Disclosed is a fastener assembly comprising at least one of a bolt member and a nut member; and a drive element adapted for engagement by an installation/driving tool, said drive element comprising a body. The body of the drive element is joined either to the bolt member or to the nut member by means of an interposed interlayer structure, the interlayer structure being adapted to fracture in torsional shear and/or tensile stress in response to a relative rotational and/or tensile force applied to the drive element with the installation/driving tool.