Deformable Flange Spacers for Impact Load Energy Absorption
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Solution Overview
Problem
Current deformable spacer designs in bolted joints are inefficient in absorbing energy and minimizing force transmission, leading to increased weight and cost in securing parts subjected to impact loads in applications like engines and aircraft.
Innovation Solution
The use of spacer assemblies with specific geometries and materials that absorb energy through plastic deformation, shear failure, or belt rupture, allowing for controlled energy absorption and reduced damage to flange bolts and flanges, including hollow cylindrical bodies with elongated slots, annular stiffeners, and annular shoulders, and annular belts that fail before the main body deforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of bolts and size of bolts are increased to withstand high-magnitude forces, then the strength and reliability of the bolted joint is improved, but the weight of the aircraft increases
Solution Approach 1:
A deformable spacer is introduced as an intermediary element between the bolt and the flange. This spacer absorbs impact energy through controlled deformation, reducing the force transmitted to the bolt and flange, thereby allowing for lighter bolt and flange designs while maintaining joint strength under impact conditions
Solution Approach 2:
The spacer is designed with specific material properties and geometric parameters (thickness, diameter, material yield strength) that enable it to deform plastically under impact loads. By controlling these parameters, the spacer can be optimized to absorb a predetermined amount of energy, allowing the bolted joint to withstand impact forces without requiring excessive bolt strength or flange thickness
2Reliability
If the thickness and size of flanges are increased to secure the inlet to the engine case, then the reliability of the connection is improved, but the weight and cost of the assembly increases
Solution Approach 1:
The deformable spacer acts as a mediator between the flange and the bolted connection. It absorbs the impact energy that would otherwise be transmitted to the flange, allowing the flange to be designed with reduced thickness and size while still maintaining reliable connection under impact conditions
Solution Approach 2:
The spacer is pre-installed in the flange bore before the bolt is inserted. This pre-positioned cushioning element is designed to deform under anticipated impact loads, providing beforehand protection to the flange and bolt from high-magnitude forces, thereby enabling lighter flange designs
3Loss of energy
If currently known deformable spacer designs are used, then some energy absorption is achieved, but the energy absorption efficiency is insufficient and force transmission to bolts and nuts is not minimized
Solution Approach 1:
The spacer design incorporates specific geometric parameters (length-to-diameter ratio, wall thickness) and material properties that are optimized to maximize energy absorption through plastic deformation. These parameter changes enable the spacer to absorb a predetermined amount of energy more efficiently, thereby providing better protection to the bolt and nut assembly
Solution Approach 2:
The spacer features localized geometric features such as circumferential grooves or varying wall thickness that create specific deformation zones. These local quality variations control where and how the spacer deforms under impact, maximizing energy absorption in controlled locations while minimizing force transmission to the fastener
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
These spacer assemblies effectively absorb impact loads, maintaining the integrity of flange bolts and flanges by distributing and managing energy, thereby reducing the weight and cost of securing components while preventing damage from high-magnitude forces.
Implementation Method 1
The annular shoulder is configured to fail in shear when a compressive axial load forcing the inner body and the outer body toward each other exceeds a predetermined shear failure load
Implementation Method 2
Deformable spacers and spacer assemblies absorb energy when flange bolts are subjected to compressive axial loads by plastically deforming
Implementation Method 3
an annular belt that fails before the main body deforms
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
Deformable spacers and spacer assemblies absorb energy when flange bolts are subjected to compressive axial loads by plastically deforming, failing in shear, rupturing or in a combination of failure modes so the flange bolts and the flanges connected thereby are not damaged. One deformable spacer may have a hollow cylindrical body with a plurality of elongated slots there through. Another deformable spacer may have an annular stiffener extending inwardly from an inner surface of a hollow cylindrical body. A spacer assembly may include an inner cylindrical body, and outer cylindrical body, and an annular shoulder extending from one of the bodies and engaged by the other body shears when a shear failure load is applied to the flange bolt. Another spacer assembly may include an annular belt around a cylindrical body so that the belt will rupture before the cylindrical body plastically deforms. (Fig. 3)