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A crash-energy distribution technique for seats to improve neck protection in rear-end impacts
Last modified: 2024-08-08
Abstract
EuroNCAP subjects forward-facing seats to medium and high severity crash pulses with 16 and 24 km/h of delta-V respectively since a great majority of rear-end impacts happens at crash severities lower than 25 km/h of delta-V for the conventional seating plan involving forward-facing seats. In the first part of the study, a forward-facing seat utilising state-of-the-art occupant protection technology is presented which earns maximum points from EuroNCAP whiplash assessment criteria. This state-of-the-art seat has a passive head-restraint, an energy absorbing recliner and an energy absorbing device consisting of a nonlinear spring and damper underneath the seat-pan.
About 98% of rear-end impacts occur with delta-V's less than 35 km/h according to recent crash data reported in the NASS-CDS database in the United States. In order to provide further neck protection for rear-end crashes with 30 to 35 km/h of delta-V, the state-of-the-art seat is retrofitted with a pro-active head-restraint and an auxiliary damper at the recliner. Additionally, the damping constant of the energy absorbing device underneath the seat-pan is increased.
The retrofitted seat proposed in this study is designed by using a seat-occupant model. Virtual sled tests are performed by using a 50th percentile male human-body model which is successfully validated using volunteer and cadaver tests. The human-body model is able to mimic active muscle contraction. The virtual sled tests are performed in accordance with the EuroNCAP dynamic whiplash assessment protocol. The simulations are run using the multi-body dynamics software MSC VisualNastran.
The crash energy to be absorbed by the seat components are distributed to provide balanced protection for all crashes with delta-V's ranging from 9.4 to 35 km/h. For delta-V's less than 25 km/h, the energy absorbing device underneath the seat-pan is electromechanically locked with the aid of a solenoid hence the crash energy is directed to the recliner. For delta-V's higher than 25 km/h, both the recliner and the energy absorbing device underneath the seat-pan are operational. The estimation of delta-V of the crash can be performed online by measuring the closing velocity of the cars in the pre-crash phase, estimating the masses of the cars and the coefficient of restitution of the impact. If there is some uncertainty in delta-V estimation, both the recliner and the energy absorbing device underneath the seat-pan stay operational and the seat still performs well. Consequently, this proposed retrofitted seat earns maximum points from EuroNCAP whiplash assessment criteria even at the very high severity rear-end impact with a delta-V of 35 km/h. Therefore, this paper draws attention to designing seats that can both withstand very high severity rear-end impacts and provide sufficient neck protection to limit whiplash associated disorders considerably although such very high severity rear-end impacts are rare.
Keywords: whiplash, rear impact, seat design, high severity
About 98% of rear-end impacts occur with delta-V's less than 35 km/h according to recent crash data reported in the NASS-CDS database in the United States. In order to provide further neck protection for rear-end crashes with 30 to 35 km/h of delta-V, the state-of-the-art seat is retrofitted with a pro-active head-restraint and an auxiliary damper at the recliner. Additionally, the damping constant of the energy absorbing device underneath the seat-pan is increased.
The retrofitted seat proposed in this study is designed by using a seat-occupant model. Virtual sled tests are performed by using a 50th percentile male human-body model which is successfully validated using volunteer and cadaver tests. The human-body model is able to mimic active muscle contraction. The virtual sled tests are performed in accordance with the EuroNCAP dynamic whiplash assessment protocol. The simulations are run using the multi-body dynamics software MSC VisualNastran.
The crash energy to be absorbed by the seat components are distributed to provide balanced protection for all crashes with delta-V's ranging from 9.4 to 35 km/h. For delta-V's less than 25 km/h, the energy absorbing device underneath the seat-pan is electromechanically locked with the aid of a solenoid hence the crash energy is directed to the recliner. For delta-V's higher than 25 km/h, both the recliner and the energy absorbing device underneath the seat-pan are operational. The estimation of delta-V of the crash can be performed online by measuring the closing velocity of the cars in the pre-crash phase, estimating the masses of the cars and the coefficient of restitution of the impact. If there is some uncertainty in delta-V estimation, both the recliner and the energy absorbing device underneath the seat-pan stay operational and the seat still performs well. Consequently, this proposed retrofitted seat earns maximum points from EuroNCAP whiplash assessment criteria even at the very high severity rear-end impact with a delta-V of 35 km/h. Therefore, this paper draws attention to designing seats that can both withstand very high severity rear-end impacts and provide sufficient neck protection to limit whiplash associated disorders considerably although such very high severity rear-end impacts are rare.
Keywords: whiplash, rear impact, seat design, high severity
Keywords
Automotive Engineering; Crash Safety
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