Composite Leaf Spring for Vehicle Suspension Weight Stiffness Trade-off
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Solution Overview
Problem
Existing leaf tensioning springs face challenges in balancing high elasticity in specific areas with high stiffness in others, which is difficult to achieve simultaneously, especially in motor vehicle wheel suspensions, due to material limitations.
Innovation Solution
A leaf spring design combining a first spring part made of fibre reinforced plastic material with a second spring part made of steel, where the ratio of their lengths is greater than two, allowing for high stiffness in the steel part and low weight due to the fibre compound material, achieving a progressive spring characteristic and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a leaf spring is made entirely of fibre reinforced plastic material to reduce weight, then weight is reduced, but stiffness in certain areas becomes insufficient
Solution Approach 1:
The leaf spring combines fibre reinforced plastic material (for weight reduction and elasticity) with steel material (for stiffness and strength). This composite construction allows the spring to achieve both low weight and sufficient stiffness by using each material where its properties are most beneficial.
Solution Approach 2:
The leaf spring is divided into two distinct parts: a first spring part made of fibre reinforced plastic material and a second spring part made of steel material. The first part (longer, ratio > 2:1) provides elasticity and weight reduction, while the second part (shorter) provides stiffness and structural support.
2Stability of the object's composition
If the curved portion of the leaf spring is made highly deformable to introduce tensioning load, then elasticity is improved, but the spring rate becomes excessively progressive and too stiff
Solution Approach 1:
The curved portion combines fibre reinforced plastic material (providing high elasticity and deformability) with steel material (providing controlled stiffness). This composite construction allows the curved portion to be highly deformable while preventing excessive spring rate progression, achieving a balance between elasticity and controlled stiffness.
Solution Approach 2:
Different portions of the leaf spring have different material compositions tailored to their specific functional requirements. The curved portion uses a composite of fibre reinforced plastic and steel to achieve high deformability with controlled stiffness, while other portions may use different material ratios to optimize their specific functions.
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 design provides a progressive spring characteristic with sufficient stiffness, enhancing drive comfort and stability while maintaining a low weight and long service life, suitable for light utility vehicles and pick-ups.
Implementation Method 1
Leaf tensioning springs need to have a very high deformability in the area of the curved portion. This deformability is necessary in order to introduce a tensioning load into the curved portion, besides a bending load, upon increasing deflection.
Data Source
AI summary
A leaf spring for a wheel suspension of a motor vehicle, comprises a first spring part made from a fiber reinforced plastic material and a second spring part made from a steel material. The first spring part and the second spring part are connected to each other. The ratio of the length of the first spring part to the length of the second spring part is larger than two. A leaf spring assembly can include such a leaf spring and receiving devices.