Pellet-Based Energy Absorbing Device for Variable Stiffness
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Solution Overview
Problem
Vehicle bumpers require varying stiffness levels depending on vehicle speed to balance low-speed damageability and pedestrian protection, which existing design principles struggle to accommodate effectively.
Innovation Solution
An energy-absorbing device with a tube containing deformable first and second pellets, arranged in alternating layers, provides variable stiffness based on impact width and force magnitude, allowing for reduced deformation during low-speed impacts and increased deformation during pedestrian impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bumper stiffness is increased to prevent damage during low-speed impacts, then low-speed damageability is improved, but pedestrian protection is worsened due to higher impact forces on pedestrians
Solution Approach 1:
The bumper system transitions from a static stiffness design to a dynamic one by incorporating a variable stiffness mechanism. The mechanism includes a first element (rigid bumper portion) and a second element (energy absorption device with deformable pellets) that can change the overall stiffness based on impact conditions. During low-speed impacts, the system maintains high stiffness to prevent damage, while during high-speed pedestrian impacts, the stiffness reduces to absorb energy and protect pedestrians.
Solution Approach 2:
The invention changes the stiffness parameter of the bumper dynamically based on impact conditions. The energy absorption device contains deformable pellets that can change their deformation characteristics depending on the magnitude of the applied force. This allows the bumper to exhibit different stiffness values - higher for low-speed vehicle impacts and lower for high-speed pedestrian impacts - thereby resolving the contradiction between damage prevention and pedestrian protection.
2Object-affected harmful factors
If the bumper stiffness is decreased to absorb energy during pedestrian impacts, then pedestrian protection is improved, but low-speed damageability is worsened due to increased deformation
Solution Approach 1:
The bumper system uses a dynamic stiffness adjustment mechanism where the energy absorption device can transition between different deformation states. The deformable pellets in the second element are designed to remain relatively undeformed during low-speed impacts, maintaining high stiffness, but deform significantly during high-speed pedestrian impacts, reducing stiffness and absorbing energy to protect pedestrians.
Solution Approach 2:
The invention implements parameter changes by designing the energy absorption device with deformable elements that change their mechanical properties based on impact severity. The deformable pellets have a threshold behavior where they resist deformation at low force levels (maintaining stiffness for vehicle damage prevention) but yield at high force levels (reducing stiffness for pedestrian protection), thus resolving the contradiction.
3Device complexity
If a single stiffness value is used for the bumper, then device complexity is reduced, but the ability to meet both low-speed damageability and pedestrian protection requirements is worsened
Solution Approach 1:
The bumper is segmented into two functional elements: a first element (rigid bumper portion) that provides structural support and damage resistance, and a second element (energy absorption device with deformable pellets) that provides adaptive energy absorption. This segmentation allows each element to perform its specialized function while working together to achieve both low-speed damageability and pedestrian protection without requiring excessive overall complexity.
Solution Approach 2:
The bumper employs a composite structure combining a rigid material (for the first element) and a deformable material (for the second element's pellets). This composite approach allows the system to exhibit both rigid and flexible characteristics as needed - the rigid portion maintains structural integrity during low-speed impacts, while the deformable portion absorbs energy during pedestrian impacts, achieving adaptability without proportionally increasing complexity.
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 device achieves a balance in stiffness, reducing deformation in vehicle components during low-speed impacts while absorbing energy effectively during pedestrian impacts, resulting in a lower average impact force and customized energy absorption characteristics.
Implementation Method 1
The tube may be designed to deform the first pellets when the tube is deformed to decrease the volume of the tube
Implementation Method 2
The tube may be designed to deform the first pellets and move the second pellets toward the axial ends when the tube is deformed
Data Source
AI summary
An energy absorbing device includes a tube. A plurality of first pellets are disposed in the tube and a plurality of second pellets are disposed in the tube. The first pellets are deformable relative to the second pellets.