Evaluation of a new visco-elastic foam for automotive applications
Tóm tắt
The geometry and mechanical characteristics of the automotive seat greatly influences the occupant kinematics in rear-end collisions. The head restraint is important particularly with respect to soft tissue neck injuries. While several studies analysed the effect of geometrical properties of head restraints, little is reported on the potential to reduce such injury by changing the material of the head restraint padding, i.e. the underlying foam. This study investigates whether the head restraint foam alone can be tailored to reduce whiplash injury. A newly developed visco-elastic (VE) foam was chosen, because advanced energy absorption properties are expected to produce beneficial effects on the occupant motion. The behaviour of the visco-elastic foam was evaluated by performing impact pendulum tests. The most important novel property of the foam thereby consists of its broad temperature range over which it keeps its advantageous visco-elastic deformation properties, while sustaining the ability to dissipate energy. The tests indicated in particular a broad glass transition temperature resulting in a stable impact behaviour over a temperature range of 5°C to 35°C. Applying this foam as a head restraint padding material, several sled tests using a standard car seat were performed. The tests were conducted to mimic rear-end collisions with a delta-v of 16 km/h. A BioRID dummy was used as a human surrogate. For the seat tested, the change of the foam resulted only in minor changes at room temperature, while the standard foam exhibited adequate performance. Additional changes of the head restraint geometry were shown to have a larger beneficial influence on the occupant kinematics.
Tài liệu tham khảo
BostrÖm, O, Svensson, M, Aldman, B, Hansson, H, HÅland, Y, LÖvsund, P, Seeman, T, Suneson, A, SÄljÖ A, Örtengren, T. (1996) A new neck injury criterion candidate based on injury findings in the cervical spinal ganglia after experimental neck extension trauma; Proc. IRCOBI Conf.; pp. 123–136.
Chapline, J, Ferguson, S, Lillis, R, Lund, A, Williams, A. (2000) Neck pain and head restraint position relative to the driver's head in rear-end collisions, Accident Analysis and Prevention, Vol. 32, pp. 287–297.
Davies, O, Mills, N. (1999) The rate dependence of confor polyurethane foams, Cellular Polymers, Vol. 18(2), pp. 117–136.
Dragan, A, Fehr, R, Kaeser, R. (2001) Pendulum impact test – a powerful and economical tool for testing materials and safety components, Proc. 7th Intern. Conf. on the role of experimentation in the automotive product development process, Florence, Italy, Paper No. 01A1021.
Eichberger, A, Geigl, B, Fachbach, B, Steffan, H, Hell, W, Langwieder, K. (1996) Comparison of different car seats regarding head-neck kinematics of volunteers during rear-end impact, Proc. IRCOBI Conf; pp. 153–164.
Farkas, P, Stanciu, R, Mendoza, L. (2001) Automotive moulded visco-elastic foams, Polyurethanes Expo 2001, Columbus, Ohio (USA).
Ferrari, R. (1999) The whiplash encyclopedia; Aspen Publishers Inc.; Gaithersburg
Gane and Pedder (2001) The effects of whiplash on insurance and insurance on whiplash, Proc. IIWPG/ IRCOBI Symposium, Isle of Man (UK).
Hell, W, Langwieder, K, Walz, F. (1998) Reported soft tissue neck injuries after rear-end car collision; Proc. IRCOBI Conf.; pp. 261–274.
Hofinger, M, Mayrhofer, E, Geigl, B, Moser, A, Steffan, H. (1999) Reduction of neck injuries by improving the occupant interaction with the seat back cushion, Proc. IRCOBI Conf., pp. 201–212.
Insurance Institute for Highway Safety (2001) Head restraints can protect your neck, Status Report, Vol. 36, No. 9.
Muser, M, Zellmer, H, Walz, F, Hell, W, Langwieder, K. (1999) Test procedure for the evaluation of the injury risk to the cervical spine in a low speed rear end impact, Proposal for the ISO/TC22 N 2071/ISO/TC22/SC10 (collision test procedures), http://www.biomed.ee.ethz.ch/ ~agu/.
Muser, M, Walz, F, Zellmer, H. (2000) Biomechanical significance of the rebound phase in low speed rear end impacts; Proc. IRCOBI Conf.; pp. 411–424.
Nusholtz, G, Bilkhu, S, Founas, M, Uduma, K. (1996) Impact response of foam: the effect of the state of stress, SAE Paper Nr. 962418.
Kuczynski, E, Farkas, P, Stanciu, R. (2001) Whiplash countermeasures: SafeGuard, Polyurethanes Expo 2001, Columbus, Ohio (USA).
Langwieder, K, Hell, W, Schick, S, Muser, M, Walz, F, Zellmer, Z. (2000) Evolution of a dynamic seat test standard proposal for a better protection after rear-end impact, Proc. IRCOBI Conf., pp. 393–409.
Schmitt, K-U, Muser, M, Walz, F, Niederer, P. (2002) Nkm – a proposal for a neck protection criterion for low speed rear-end impacts; Traffic Injury Prevention; Vol. 3(2), pp. 117–126.
Szabo, T, Voss, D, Welcher, J. (2002) Influence of seat foam and geometrical properties on BioRID P3 kinematic response to rear impacts; Proc. IRCOBI Conf.; pp. 87–101.
Temming, J, Zobel, R. (1998) Frequency and risk of cervical spine distortion injuries in passenger car accidents: significance of human factors data; Proc. IRCOBI Conf.; pp. 219–233
Viano, D, Davidsson, J. (2001) Neck displacements of volunteers, BioRID P3 and Hybrid III in rear impacts: implications to whiplash assessment by a neck displacement criterion (NDC), Proc. IIWPG/IRCOBI Symposium, Isle of Man.
Wiklund, C, Larsson, H. (1998) Saab active head restraint (SAHR) – seat design to reduce the risk of neck injuries in rear impacts; SAE paper 980297.
Woodbridge Group, Recticel Woodbridge Moulded Foam, Hessenring 32, 64546 Mörfelden, Germany.