Angled Fin Energy Absorber for Bumper Stiffness Trade-off
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Solution Overview
Problem
Vehicle bumper assemblies face a design challenge in balancing low-speed damageability and pedestrian impact protection, as existing standards often result in competing design requirements for stiffness and energy absorption.
Innovation Solution
A bumper assembly design featuring an energy absorber with fins angled between 60-65 degrees relative to the carrier, which transfers force without deformation at low speeds and deforms to absorb energy during high-speed impacts, incorporating a bumper beam and fascia that can maintain rigidity or deform based on impact conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bumper assembly is designed with high stiffness to prevent damage at low speeds, then low speed damageability is improved, but energy absorption capability during high speed pedestrian impact deteriorates
Solution Approach 1:
The bumper assembly employs a dynamic stiffness mechanism where the energy absorber with angled fins maintains rigidity at low speeds through geometric stability, but transitions to energy-absorbing deformation at high speeds. The fins at 60-65 degrees provide structural reinforcement during LSD tests while allowing controlled collapse during pedestrian impact tests, enabling the same structure to serve dual opposing functions based on impact severity
Solution Approach 2:
The design changes the effective stiffness parameter of the bumper assembly based on impact conditions. At low speeds, the angled fins create a rigid structure with high stiffness to prevent damage. At high speeds, the same fins undergo progressive deformation, reducing the effective stiffness to maximize energy absorption. This parameter change allows the bumper to adapt its mechanical properties according to the impact energy level
2Loss of energy
If the bumper assembly is designed with low stiffness to absorb energy during pedestrian impact, then pedestrian protection is improved, but low speed damageability deteriorates
Solution Approach 1:
The energy absorber with angled fins creates a dynamic stiffness system that appears rigid during low-speed impacts (preventing damage) but becomes compliant during high-speed pedestrian impacts (absorbing energy). The geometric configuration of fins at 60-65 degrees provides initial rigidity that progressively yields under higher impact loads, automatically adapting the stiffness level to the severity of the collision
3Force
If the fins are angled at 60-65 degrees relative to the carrier, then force transfer efficiency is improved, but structural complexity increases
Solution Approach 1:
The patent optimizes the fin angle parameter to 60-65 degrees relative to the carrier, which maximizes force transfer efficiency from the impactor through the fins to the carrier structure. This specific angular parameter creates optimal mechanical advantage for load distribution while maintaining manufacturing feasibility. The precise parameter selection balances performance optimization with practical manufacturing constraints
Data Source
AI summary
An energy absorbing system includes a carrier having a wall extending along a longitudinal axis. The energy absorber has a first leg and a second leg extending in a first direction away from the wall. A plurality of fins are fixed to and extend from the wall in the first direction, at approximately 60 to 65 degrees relative to the wall.