FRONTAL VEHICLE-END OPTIMIZATION IN RELATION TO PEDESTRIAN–CAR IMPACT

Alberto L. Audenino (1), Elisabetta M Zanetti (2)

1. DIMEC, Politecnico di Torino, ITALY; 2. DII, University of Perugia, ITALY

Introduction

Pedestrian passive safety is receiving more and

more attention in automotive design: the growing

regulation demand both from CE and insurance

companies has leaded to the issue of CE 2003/102

by WG 17; this directive limits vehicle

aggressiveness towards a pedestrian, taking into

account human body injury threshold levels.

The development of a numerical model capable of

predicting lower-leg behaviour can be a useful tool

in order to optimize front-end designs or to test

varying pedestrian anthropometries. An attempt in

this sense was performed by Kerrigan et al. (2009)

who used a multibody code, whose parameters

(stiffness, inertia, damping) were evaluated on the

basis of a Finite Element code. Other authors make

use of finite element codes specialized in the

resolution of impact problems: Takahashi et al.

(2000) so created and validated a numerical model

of an H-dummy, Untaroiu et al. (2005) realised the

numerical model of a living human; here CE leg

impactor has been numerically simulated and

validated. This model can be used to support

vehicle design, evaluating how geometrical and

mechanical parameters influence vehicle-pedestrian

impact, as demonstrated in this work.

Methods

The numerical model was made of two elements:

the leg and the frontal side of the vehicle.

The leg geometry was taken from CE directive; it

was made of an inner solid cylinder, an outer

cylinder made of Confor CF-45, a superficial layer,

5 mm thick, made of Neoprene. The femur is

constrained to the tibia through a joint replicating

knee compliance. The leg model was realized in

Patran®, and was validated as required by CE

directive.

The impactor was simulated as a bumper

(chamfered C bar) and a spoiler (half a cylinder),

both elements were simulated as stiff shells; they

had only one degree of freedom that is the

translation towards the leg, modulated through a

linear spring.

The design of the frontal side of the vehicle was

parametrized in relation to geometrical and

mechanical properties: bumper and spoiler stiffness

(kb, ks), spoiler-bumper axial distance (Δx) and

bumper profile height (hb).

The model output were the physical quantities

which should be limited according to CE directive:

the absolute maximum tibial acceleration during the

impact (A); the maximum deflection angle of

femur-tibia complex (i.e of simulated knee joint,

D); the maximum shear strain in femur-tibia

complex (R).

Results

A factorial plane has been created, containing the

results of all performed simulations. These allowed

to estimate the influence of cited parameters and of

bumper stiffness-height interaction and spoiler

stiffness-position interaction.

The interpolating model allowed to estimate the

optimum frontal vehicle configuration,

interpolating data.

Min

kb

[kN/m]

hb

[mm]

ks

[kN/m]

Δx

[mm]

A [g] 102 40* 160* 60* 25*

S [mm] 0 43 124 109 25*

R [°] 0 120* 160* 61 25*

Table 1: Optimal frontal end configuration;

asterisks refer to values which coincide with

explored range limits

Discussion

Results concerning bumper stiffness and height are

in accordance with data in literature (Dunmore et

al, 2005); two more parameters are here considered

as well as bumper-spoiler interaction. Bumper-

spoiler design should comply with calculated

values.

References

Dunmore et al. Proc Inst Mech Engng H 220: 857-

69, 2006

Kerrigan JR et al, Traffic Inj Prev 10: 386-97, 2009

Takahashi et al, Stapp Car Crash J 44: 335-55,

2000.

Untariou et al, Stapp Car Crash J 49: 157-81, 2005.

S204 Presentation 1213 − Topic 18. Forensic biomechanics

Journal of Biomechanics 45(S1) ESB2012: 18th Congress of the European Society of Biomechanics