Modular Nut Plate Radial Expansion for Variable Opening Lengths
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Solution Overview
Problem
Conventional nut plates with fixed longitudinal lengths are not suitable for workpieces with varying opening lengths, requiring a variety of brackets to be stocked, which is inefficient and impractical.
Innovation Solution
A modular nut plate assembly with a multi-piece tubular section that includes an expandable bushing and tubular body, which can be radially expanded to fit different-sized workpiece openings, using a mandrel to form interference fits and induce compressive stresses for enhanced fatigue performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a one-piece expandable sleeve bracket is used, then the bracket can be installed in workpiece openings, but it has a fixed longitudinal length making it unsuitable for workpieces with significantly different opening lengths
Solution Approach 1:
The bracket is divided into multiple segments including a head portion and a tubular body portion that can be radially expanded. This segmentation allows the tubular body to expand radially to accommodate different opening lengths while maintaining a compact stored configuration, eliminating the need to stock multiple bracket sizes.
Solution Approach 2:
The bracket transitions from a static fixed-length design to a dynamic expandable design. The tubular body portion can be radially expanded during installation to adapt to different opening lengths, providing versatility without requiring multiple fixed-size brackets to be maintained in inventory.
2Ease of manufacture
If conventional fixed-length brackets are used, then manufacturing is simple, but a large variety of brackets must be kept in stock for different sized openings
Solution Approach 1:
The bracket design provides multi-functionality by enabling a single bracket type to accommodate multiple opening lengths through radial expansion of the tubular body. This universal design eliminates the need to manufacture and stock multiple specialized bracket sizes for different applications.
Solution Approach 2:
The bracket utilizes parameter changes by altering its radial dimension through expansion of the tubular body portion. This allows the same bracket to fit different opening lengths by changing its radial parameter during installation, reducing inventory requirements while maintaining manufacturing simplicity.
3Adaptability or versatility
If the tubular body is radially expanded to fit different openings, then adaptability improves, but compressive stresses and fatigue performance become critical considerations
Solution Approach 1:
The radial expansion of the tubular body is performed as a preliminary action during installation before the bracket enters service. This preliminary expansion creates the necessary interference fit and induces compressive stresses in advance, ensuring reliable fatigue resistance from the start of operation rather than developing later.
Solution Approach 2:
The radial expansion process, which initially creates harmful compressive stresses, is converted into a benefit by inducing beneficial compressive residual stresses in the tubular body. These compressive stresses improve fatigue resistance and reliability, transforming a potentially harmful effect into a protective mechanism.
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
Enables the installation of nut plates in a wide range of workpieces with varying sizes without the need for multiple bracket sizes, providing reliable clamp-up forces and improved fatigue resistance.
Implementation Method 1
using a mandrel to form interference fits and induce compressive stresses for enhanced fatigue performance
Implementation Method 2
induce compressive stresses for enhanced fatigue performance
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
A nut plate assembly includes a nut retainer and a bushing for expanding a tubular body of the retainer. The retainer assembly is used to cold work an opening of a workpiece in order to fix the nut retainer assembly relative to the workpiece. A nut can be snapped into the retainer. A method of installation includes passing a mandrel through the bushing to radially expand the bushing into a tubular body of the retainer. The tubular body is compressed between the workpiece and bushing as the bushing is displaced radially causing corresponding radial displacement of the tubular body. The expanded bushing applies pressure to the tubular body for a desired fit between the nut retainer and workpiece.