Stud Lockbolt Breakneck Design for Consistent Preload
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Solution Overview
Problem
Existing fastening systems, such as two-piece swaged fasteners, face challenges in securely attaching workpieces with consistent preload and efficient installation, particularly in applications like aerospace and satellite panels, where reliability and ease of use are critical.
Innovation Solution
A lockbolt fastening system comprising a pin member with a threaded portion, a lock portion, and a pull portion, along with a swage collar that is swaged into the lock grooves of the pin member, allowing for secure attachment and visual indication of installation through break-off of the pull portion at a breakneck groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional two-piece swaged fasteners are used, then installation is relatively simple, but preload consistency and reliability are insufficient
Solution Approach 1:
The fastener is divided into distinct functional segments: a pin member with threaded portion, smooth cylindrical shank portion, lock portion, and pull portion; and a separate swage collar. This segmentation allows each part to perform its specific function optimally while maintaining overall reliability.
Solution Approach 2:
The pin member is pre-configured with specific geometric features including lock grooves in the lock portion and pull grooves in the pull portion before installation. These pre-formed features enable consistent preload application and reliable locking without requiring complex installation procedures.
2Productivity
If traditional fastening methods are used, then installation procedures are lengthy, but ensuring adequate safety margins increases weight
Solution Approach 1:
The fastener system is designed to be self-indicating through the break-off of the pull portion at the breakneck groove. This visual indication automatically confirms proper installation and preload achievement, eliminating the need for additional inspection tools or procedures and reducing installation time.
Solution Approach 2:
The breakneck groove creates a distinct visual change when the pull portion breaks off, providing an immediate visual confirmation of proper installation. This visual indicator system replaces complex inspection procedures and reduces installation time.
3Measurement precision
If torque-tension acceptance methods are used, then installation is straightforward, but measurement precision and reliability are compromised
Solution Approach 1:
The system replaces torque-based installation with a mechanical break-off mechanism. The breakneck groove is designed to fail at a predetermined load, providing precise preload control through mechanical means rather than torque estimation, thereby improving measurement precision while maintaining ease of operation.
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 ensures accurate preload, reduces installation time, and allows for weight savings and reduced safety margins, eliminating the need for torque-tension acceptance, while providing a reliable and efficient method for securing workpieces in various applications.
Implementation Method 1
a swage collar adapted to be swaged into the at least one lock groove of the lock portion of the pin member
Data Source
AI summary
A fastener including a pin member having a shank portion, a threaded portion having a thread, a lock portion having at least one lock groove, and a pull portion located having at least one pull groove. The threaded portion is adapted to be engaged threadedly with a threaded hole of a workpiece to install the pin member therein. The fastener includes a swage collar adapted to be installed into the at least one lock groove of the lock portion to secure a plurality of workpieces. The pull portion is adapted to break off when the fastener is installed.