Elastomeric Isolator Radial Loading Stress Distribution
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Solution Overview
Problem
Existing automotive exhaust system isolators face challenges in providing a soft on-center rate while enduring spike durability loads, as they often suffer from poor tensile fatigue properties and unfavorable stress distributions due to tension and shear loading, leading to material failure and reduced durability.
Innovation Solution
The use of radial loading in elastomeric bushings with strategically designed voids to distribute stress evenly, independent of loading direction, which shifts the stress from concentrated areas to a more favorable compressive stress distribution, enhancing durability and maintaining a soft on-center rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional tension loading methods are used in elastomeric isolators, then the design is simple and cost-effective, but the material suffers from poor tensile fatigue properties and low tear strength leading to failure
Solution Approach 1:
The patent inverts the traditional loading approach by using compression loading instead of tension loading. The elastomeric isolator is designed with a rigid insert that compresses the elastomer vertically, transforming the harmful tensile stresses into beneficial compressive stresses that the elastomeric material can withstand without fatigue failure.
Solution Approach 2:
The patent changes the loading parameter from tensile to compressive. By designing the isolator geometry and rigid insert configuration to apply vertical compression, the elastomeric material experiences compressive stresses rather than tensile stresses, fundamentally altering the stress state to match the material's strength characteristics.
2Strength
If spoke design isolators are used to load elastomeric material in compression and tension, then the isolator can provide soft on-center rate, but the tensile loading makes the design vulnerable to fractures in overloaded conditions
Solution Approach 1:
The patent eliminates the tensile loading component entirely by inverting the loading mechanism. Instead of spokes experiencing both tension and compression, the rigid insert compresses the elastomer vertically, ensuring the elastomeric material only experiences compressive stresses even under overloaded conditions, thereby eliminating fracture vulnerability.
3Strength
If shear leg design is used with primary vertical loading, then the isolator can be designed desirably soft in the primary direction, but the secondary lateral loading direction inflicts tensile compressive stresses which are unfavorable for durability
Solution Approach 1:
The patent creates a universal loading solution where the rigid insert and elastomeric geometry work together to provide compression-only loading in all directions. The conical or frustoconical shape of the rigid insert ensures that lateral forces also generate compressive stresses in the elastomer, making the isolator durable under multi-directional loading conditions.
4Reliability
If the isolator is designed to provide a soft on-center rate, then vibration isolation is improved, but the isolator may bottom out or position in a groundout condition under spike durability loads
Solution Approach 1:
The patent changes the stress state parameter from tensile to compressive, and introduces a progressive stiffness characteristic through the rigid insert geometry. The elastomeric isolator maintains softness for vibration isolation while the rigid insert prevents bottoming out by maintaining compression contact, allowing the system to endure spike loads without groundout conditions.
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
This solution effectively provides a very soft on-center rate while improving the ability to withstand spike durability loads by distributing stress evenly across the elastomeric material, reducing the risk of material failure and enhancing the overall performance of the exhaust system isolators.
Implementation Method 1
The present invention provides the art with an elastomeric bushing which uses radial loading to avoid the tension stress loading of the elastomeric bushing. The radial loading cause shear stresses of the elastomeric bushing regardless of the direction of the loading.
Implementation Method 2
The radial loading cause shear stresses of the elastomeric bushing regardless of the direction of the loading.
Implementation Method 3
The preferred method to load the elastomeric material is in compression or shear.
Data Source
AI summary
An elastomeric isolator has an elastomeric body which defines a void extending into the elastomeric body from one side and a void extending into the elastomeric body from the opposite side. One member for attaching the elastomeric body to a component is located inside of the two voids and another member for attaching the elastomeric body to a component is located outside of the two voids. The two voids overlap a specified distance to determine the stresses and stiffness for the isolator.