Cellular Foam Bumper Assembly for Pedestrian Impact and Low-Speed Damage
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Solution Overview
Problem
Existing vehicle bumper designs face a challenge in balancing low-speed damageability and pedestrian impact protection, as the desired stiffness for these conditions often conflicts.
Innovation Solution
A vehicle bumper design featuring a cell structure with varying crush strength and foam density along its length, where the first portion has a lower crush strength and open-cell foam for low-speed impacts, and the second portion has a higher crush strength and closed-cell foam for higher-speed impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bumper stiffness is increased to prevent damage at low speed, then low-speed damageability is improved, but pedestrian protection performance deteriorates
Solution Approach 1:
The bumper is divided into different zones with varying foam densities. The first portion (center region) contains high-density foam for stiffness and low-speed damage protection, while the second portion (side regions) contains low-density foam for pedestrian protection. This local differentiation allows each zone to optimize for its specific function.
Solution Approach 2:
The bumper foam structure is segmented into distinct portions with different material properties. The first portion and second portion are separated by a partition wall, creating independent compression zones that can be optimized for different impact scenarios without interfering with each other.
2Object-affected harmful factors
If the bumper stiffness is decreased to improve pedestrian protection, then pedestrian protection performance is improved, but low-speed damageability deteriorates
Solution Approach 1:
Different regions of the bumper are assigned different foam densities based on their functional requirements. The side regions use low-density foam to reduce impact forces on pedestrians, while the center region uses high-density foam to maintain structural stiffness for low-speed collision protection.
3Strength
If uniform high-density foam is used throughout the bumper, then low-speed damage protection is improved, but energy absorption during high-speed impact deteriorates
Solution Approach 1:
The foam density is optimized locally for each bumper region. High-density foam in the center provides stiffness for low-speed protection, while low-density foam in the sides enables greater energy absorption through deformation during high-speed pedestrian impacts.
Solution Approach 2:
The foam density parameter is varied across different portions of the bumper. By changing the density parameter from high in the center to low at the sides, the bumper achieves both stiffness where needed and energy absorption capacity where required.
4Object-affected harmful factors
If uniform low-density foam is used throughout the bumper, then pedestrian protection is improved, but low-speed damage protection deteriorates
Solution Approach 1:
The bumper structure incorporates spatially varying foam density to simultaneously achieve pedestrian protection and low-speed damage protection. Low-density foam is placed in regions that contact pedestrians, while high-density foam is placed in the center to maintain overall structural rigidity.
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 design effectively manages energy absorption during both low-speed and high-speed impacts, enhancing the bumper's ability to protect both the vehicle and pedestrians by optimizing stiffness and impact response.
Implementation Method 1
The bumper includes foam disposed in the cell chambers... effectively manages energy absorption during both low-speed and high-speed impacts
Implementation Method 2
A vehicle bumper design featuring a cell structure with varying crush strength and foam density along its length... optimizing stiffness and impact response
Data Source
AI summary
A vehicle includes a vehicle frame including a first frame rail and a second frame rail each elongated along a vehicle-longitudinal axis. The first frame rail is spaced from the second frame rail along a vehicle-lateral axis. The vehicle includes a bumper supported by the first frame rail and the second frame rail. The bumper includes a crossbeam elongated along the vehicle-lateral axis. The bumper includes a cell structure vehicle-forward of the crossbeam, the cell structure including cell walls that define cell chambers. The bumper includes foam disposed in the cell chambers.