Impact Attenuation System Using a Passive Damper
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Date
2010-03-18
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Abstract
The goal of this work is to mitigate the degree of damage to passengers
caused by automobile collisions. Crash phenomena involving road
vehicles were investigated for the purpose of developing an impact
attenuation design that can withstand speeds higherthan the current
specified range of up to 4 km/h (for a bumper). Different impact
attenuation systems in the vehicle were studied with emphasis on the
bumper modeling, analysis and design.
A mathematical model for a bumper was developed. Simulation of
impact of the bumper against a fixed barrier was performed. A passive
friction element was introduced into the bumper system to improve on
the attenuation of the impact and kinetic energy absorption capacity. A
mathematical model of the bumper-damper system was formulated and
used to simulate impact phenomena for a 1900 kg mass moving at a
speed of 70 km/h (19.4 m/s), 17.5 times the speed of a typical design
specification.
The simulation revealed that the energy absorption capacity of the
bumper was improved with the addition of a frictionelement. Design
parameters for the friction damper were extracted from the results of the
simulation. The extracted design parameters includestiffness, k, and
coefficient of the damping, c, of the bumper. The use of the results from
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the simulation in the design of the bumper was pursued with success.
Friction damper designs were proposed. Two of thesedesigns were built
and used in experiments to verify their effectiveness and to validate the
simulation results. The experiments revealed that higher energy
absorption could be achieved with the addition of afriction element to
traditional bumpers.
From simulation, it was observed that a combinationof material stiffness
and damping factors could influence energy absorption ability of the
damper. It was observed that the addition of a friction element to an
ordinary bumper-damper system with the new design parameters can
improve its energy absorption capacity by 103.6 kJ,that is about 146 %.
Additionally, it was also observed that the addition of the friction element
to a traditional vehicle could increase the critical design speed from 4
km/h (1.11 m/s) to 14.9 km/h (4.1 m/s).
It was concluded that a passive friction damper system could be used to
attenuate road vehicle impact energy in collisions (of vehicles of mass
similar to that of a typical sedan car) at speeds 3times higher than the
speed for which current conventional bumpers are designed to attenuate
(i.e. 4 km/h).
Description
A thesis submitted to the Graduate School of Kwame Nkrumah University of Science and Technology in partial fulfilment of the Degree of Doctor of Philosophy.