6 ï¼ neck right leaning 40Â°ï¼ is the posture with lowest neck injury riskï¼ Key wordsï¼ neck injuryï¼ side .... position for human neck is from C6ï¼ In this paperï¼the.
Journal of Beijing Institute of Technology，2010，Vol． 19，No． 3
Numerical Study on Neck Injury Under Different Postures in Vehicle Side Impact LI Zhi-gang（ 李志刚） ， ZHANG Jin-huan（ 张金换） ， MA Chun-sheng（ 马春生） ， LAI Qing-xin（ 赖庆鑫） （ State Key Laboratory of Automotive Safety and Energy，Tsinghua University，Beijing 100084，China） Abstract： Neck injury is a severe problem in traffic accidents． While most studies are focused on the neck injury in rear and front impacts，few are conducted in side impact． This study focuses on the difference of neck injury under different postures and the difference of 7 cervical vertebras under the same posture using the method of prescribed structure motion（ PSM） ． The analytical results show that the maximum changes of mean force and mean moment of 7 cervical vertebras under 8 different postures are 20% and 47% respectively． The variation of each cervical vertebra is different under different neck postures． Up cervical vertebras （ C1 － C4） and low cervical vertebras （ C5 － C7） suffer different forces and moments under the same neck posture． Generally speaking，No． 6 （ neck right leaning 40°） is the posture with lowest neck injury risk． Key words： neck injury； side impact； prescribed structure motion （ PSM） ； neck posture CLC number： U 461． 91
Document code： A
Article ID： 1004-0579（ 2010） 03-0318-06
Neck injury is a major issue in traffic accidents． It
the normal posture． Scarcely any literatures can be
accounts for about 50% in all of the traffic injuries and
searched on neck injury after changing neck posture．
［1］
Owning to the experimental limitation of human neck
this number is increasing
． Lots of studies of neck ［2 － 4］
since
injury in China and the development of computer simu-
such impact can cause severe neck injury． Frontal im-
lation technology，the neck injure difference under dif-
injury have been focusing on rear impact ［4 － 5］
pact has also been investigated
． However，studies
of neck injury in side impact are not sufficient． Studies on volunteers have defined a range of safe impact condition． Neck load of up to 794 N shear force or 56 N·m lateral bending moment are the tolerance of no inju［6 － 8］
ry
ferent postures in side impact has been analyzed by a numerical approach in this paper．
1 1． 1
Corpus experiment and sled test are the most com-
cadaver experiments and the injury thresholds value of 1 920 N shear force has been obtained
Prescribed Structure Motion （ PSM） Method in Side Impact
． More severe impacts have been conducted with ［9 － 10］
Methods
mon methods during the studies of human neck injury
．
Few data can be found to describe neck injury in
in vehicle crash． Besides，computer simulation is also
side impacts without head contacts． Statistics studies on
widely used because of its fast speed and low cost．
injury data of cadaver experiments have shown that the
Softwares of HYPERMESH，LSDYNA and MADYMO
average resultant head acceleration for AIS2 neck inju-
were used in this paper since one 50% human model is
ries was 112 g，resultant neck force was 4 925 N and
included in the database of MADYMO and strength a-
［4］
． However，all the relevant
nalysis can be easily processed via LSDYNA． The PSM
studies were based on the hypothesis that neck was in
method was adopted［11］． The full vehicle simulations
moment was 241 N·m
Received 2009-07-17 Sponsored by the National High Technology Research and Development Program of China（ “863”Program） （ 2006AA110102） Biographies LI Zhi-gang （ 1983 － ） ，doctoral student，li-zg08@ mails． tsinghua． edu． cn； ZHANG Jin-huan （ 1954 － ） ，researcher．
— 318 —
LI Zhi-gang（ 李志刚） et al． / Numerical Study on Neck Injury Under Different Postures in Vehicle Side Impact
were firstly conducted without human or dummy model．
simulation．
Then，the nodal displacement results of body in white
1． 2． 3
Human-Vehicle Model
（ BIW） and door parts were calculated using the file of
The whole model was integrated with PSM struc-
LSDYNA d3plot． This was the input of PSM parts in
tures，seat foam and inner trim panel． The influence of
MADYMO software． Finally，the restraint system，ma-
seatbelt in side impact was omitted． By adjusting the
terials and the relevant properties and human model
posture of the facet human model，the contacts between
were integrated． Contacts between human model and
human model and inner trim panel，human model and
restraint system and between human model and PSM
seat foam were defined． Because the contact between
parts were assigned． From the simulations，the injury
seat foam element and shell element couldn't be de-
values of human model were attained to assess human
fined directly，one null material shell elements were
injury and vehicle safety．
used to cover the surface composed by the seat foam el-
1． 2
ements． The simulation time step was 1E-6s and the
Modeling
1. 2. 1
Vehicle-Seat Model
termination time is set as 80 ms． The neck injury pa-
The vehicle-seat model included PSM structures and inner trim components as presented in Fig． 1． The
rameters of the facet human model to be put out were defined． The whole model is shown as Fig． 2．
PSM structures included vehicle parts and seat frame structure． The nodal displacements of PSM were extracted from full vehicle crash． The door window glass was pulled down in test． So we ignored the influence of glass on human injury． The inner trim structures and seat foam were respectively linked to the inner door mould and seat frame structure using keywords of SPOTWELD． NODE _ NODE，RIGID _ ELEMENT or ELEMETN． LINE3 in MADYMO．
Fig． 2
1． 2． 4
Whole human-vehicle model
Model Verification
To verify the model，we compared our results with Ref． ［4］ under similar crash condition． According to Ref． ［4 ］，the original model's vehicle structure was changed into a rigid wall as presented in Fig． 3． In Ref． ［4］，the cadaver sit in a relatively hard bench， so the seat foam elasticity modulus was changed into a
Fig． 1
1． 2． 2
big value． Other parts were same as the original mod-
Vehicle-seat model
el． In order to have similar impact condition，the ac-
Facet Human Model
human models of MADYMO have been developed and validated for impact simulation，comfort and other
celeration curve of the rigid wall （ RW） was approximately equivalent to a T-curve as shown in Fig． 4，
applications． The facet human model is one of them and has specific structure of spines． The outer surface of facet human model is described with meshes of shelltype massless contact elements． These facet surfaces are fully connected to rigid or flexible bodies． The human models have been validated extensively both on segment and full body level with volunteer and PMHS test data． Both static and dynamic tests have been used． The 50% facet human model was adopted in the — 319 —
Fig． 3
Verification human-vehicle model
Journal of Beijing Institute of Technology，2010，Vol． 19，No． 3
simulation and reference's conditions．
which is similar to the reference crash curve．
Tab． 1 subject value
1． 2． 5 Fig． 4
Human injury value obtained by simulation
maxa h / g 42． 1
maxα h-x / maxF n / maxM n / （ rad·s
－2
3 626． 1
RW a / pelvis a /
N
（ N·m）
g
g
1 935． 6
53． 6
15
222
）
Neck Injury Under Different Postures in Side Impact
T-curve acceleration waveform
After the simulation model was verified，the origi-
The facet human injury values from simulations were shown in Tab． 1 （ a h -head resultant acceleration， α h-x -head acceleration of x direction，F n -neck resultant force，M n -neck resultant moment） and compared with Ref． ［4］． Because of the difference of cadaver itself， the values of Ref． ［4］ existed in a large range． Most values in Tab． 1 are within this range or deviate a little from this range． Only the value of the maximum neck moment is less than Ref． ［4］． This may come from the definition difference of the model's neck between the
Fig． 5
nal model was adopted to study neck injury under different postures in side impact without head contact impact． 8 different neck postures were set—bending backward 30°，neck upright，bending forward 30°， bending forward 60°，left leaning 40°，right leaning 40°，left turning 40°and right turning 40°． These postures are referred as No． 1 － No． 8，as shown in Fig． 5． According to side impact C-NCAP，the sled test velocity was set as 50 km / h．
Eight different neck postures
Taking No． 2 as an example，when the simulation
the pelvis struck it． The force of neck and head were
was finished in 80 ms，the motion trace was shown in-
suffered from the inertia load of head． Owning to the
Fig． 6． From the motion trace，it can be seen that
effect of angular acceleration of the head，the neck ex-
when the PSM structures close to the human model，
hibits rotation characteristic when thorax and pelvis im-
the left thorax struck the vehicle door firstly and then
pact with inner trim panel．
Fig． 6
2 2． 1
Neck motion trace under No． 2 posture in side impact
to extract main injury parameters of head and neck
Results
（ Tab． 2） ． The linear acceleration of head was mainly
Simulation Data
caused by head inertia in z direction． So we only stud-
Simulations were conducted for each neck posture
ied head linear acceleration in z direction and resultant
— 320 —
LI Zhi-gang（ 李志刚） et al． / Numerical Study on Neck Injury Under Different Postures in Vehicle Side Impact
acceleration． Their values changes from 367. 7 m / s2 to 2
2
the data of force and moment of different vertebras in
2
436. 1 m / s and from 381. 2 m / s to 450. 52 m / s re-
different neck postures were compared． Since the C7
spectively when the posture changes from No． 1 to
directly links with thoracic spine，the major bending
No． 8． The angular acceleration of head has its own
position for human neck is from C6． In this paper，the
characteristic in different directions． From Tab． 2，it
position of C6 was taken as the initial position where
can be known that their values have a large difference
neck begins to bend． This will bring about the abnor-
both in different directions and different conditions． So
mal value of cervical moment． So the value of C6 was
we extracted the head angular acceleration in x，y and
ignored． Finally，each group of values was averaged
z direction and the resultant head angular acceleration．
from No． 1 to No． 8 and the resultant force and moment
The maximum changing rates are 127. 4% ，265. 3% ，
from C1 to C7 were also averaged for the convenience
715. 8% and 338. 7% respectively． The seven cervical
of comparison．
vertebras were abbreviated as C1 － C7． Meanwhile， Tab． 2
Main injury value of head and neck
max a h-z /
max a h /
max α h-x /
max α h-y /
max α h-z /
max α h /
（ m·s － 2 ）
（ m·s － 2 ）
（ rad·s － 2 ）
（ rad·s － 2 ）
（ rad·s － 2 ）
（ rad·s － 2 ）
1
367． 7
381． 2
2 256． 7
1 009． 2
1 458． 9
2
399． 8
410． 9
2 290． 8
826． 2
3
412． 7
424． 2
1 671． 3
4
389． 6
399． 3
5
416． 7
6
No．
C1
C2
maxF c1 /
maxM c1 /
maxF c2 /
maxM c2 /
N
（ N·m）
N
（ N·m）
2 441． 9
1 807． 5
38． 4
1 849． 6
40． 3
1 010． 8
2 527． 3
1 915． 3
28． 6
1 941． 8
31． 5
1 166． 0
1 731． 7
2 397． 3
1 995． 3
28． 4
1 997． 9
32． 9
1 343． 3
2 125． 2
6 658． 9
7 117． 7
1 880． 3
29． 2
1 876． 2
34． 2
421． 1
1 463． 2
1 025． 9
1 041． 9
1 622． 2
1 992． 0
22． 1
2 054． 3
21． 0
397． 7
402． 2
3 054． 6
581． 8
816． 2
3 212． 5
1 854． 9
39． 0
1 829． 5
41． 0
7
436． 1
450． 5
2 571． 1
634． 0
1 189． 1
2 887． 3
2 110． 8
29． 5
2 114． 7
34． 2
8
384． 0
392． 0
2 149． 9
1 119． 1
1 490． 1
2 438． 2
1 855． 3
37． 7
1 883． 8
37． 5
mean
400． 5
410． 1
2 100． 1
1 060． 9
1 924． 7
3 080． 6
1 926． 4
31． 6
1 943． 5
34． 1
C3
C4
C5
C6
C7
mean
mean max M c /
maxF c3 /
maxM c3 /
maxF c4 /
maxM c4 /
maxF c5 /
maxM c5 /
maxF c6 /
maxM c6 /
maxF c7 /
maxM c7 /
max F c /
N
（ N·m）
N
（ N·m）
N
（ N·m）
N
（ N·m）
N
（ N·m）
N
（ N·m）
1
1 885． 6
40． 46
1 914． 7
43． 3
1 938． 4
49． 7
1 957． 1
—
1 969． 4
73． 3
1 903． 2
47． 6
2
1 971． 6
32． 4
1 995． 2
35． 6
2 013． 1
42． 7
2 023． 9
—
2 026． 1
73． 8
1 983． 9
45． 5
3
2 005． 8
33． 7
2 016． 0
37． 5
2 022． 1
46． 0
2 020． 9
—
2 010． 7
75. 0
2 009． 8
46． 9
4
1 875． 8
38． 9
1 880． 1
46． 1
1 884． 3
55． 7
1 887． 3
—
1 881． 7
85． 3
1 880． 8
53． 5
5
2 114． 2
21． 2
2 166． 6
23． 8
2 214． 1
30． 4
2 258． 9
—
2 293． 3
68． 6
2 156． 2
36． 5
6
1 806． 0
37． 2
1 793． 8
38． 3
1 783． 0
47． 5
1 769． 1
—
1 756． 3
75． 6
1 798． 9
46． 4
7
2 124． 1
35． 7
2 133． 7
39． 3
2 138． 7
45． 4
2 136． 1
—
2 124． 5
70． 1
2 126． 1
42． 4
8
1 920． 1
35． 3
1 957． 1
35． 6
1 990． 6
39． 2
2 018． 6
—
2 036． 9
66． 4
1 951． 8
42． 0
mean
1 962． 9
34． 4
1 982． 2
37． 4
1 998． 0
44． 6
2 009． 0
—
2 012． 4
73． 5
—
—
No．
2． 2
Data Analysis of Neck Response
2． 2． 1
forces and moments of 7 cervical vertebras in different
Force and Moment Comparison of Different
postures． The variation is presented in Fig． 7． It can
Neck Postures
be known that the forces of No． 4 and No． 6 are smaller
The data in Tab． 2 show the maximum and mean
than other conditions while the forces of No． 5 and
— 321 —
Journal of Beijing Institute of Technology，2010，Vol． 19，No． 3
No． 7 are larger than other conditions． The moment of
moment） values are definitely larger than y-moment
cervical vertebra varies with force． The moments of
and z-moment （ flexion moment） values． So it is suit-
No． 5，No． 6，No． 7 and No． 8 are smaller than other
able to evaluate the cervical injury under inertia load in
conditions． In general，the neck posture of No． 6 is the
side impact by using z-force，y-force and x-moment．
best posture that suffered least injury under inertia load of head in side impact．
Fig． 9
2． 2． 3
Moment value of one cervical under 8 neck postures
Force and Moment of C1 － C7 Under Different Neck Postures
From the data in Fig． 10，cervical forces of No． 1， No． 2，No． 5 and No． 8 gradually increase from C1 to C7． It indicates that C7 is the most easily defective Fig． 7
2． 2． 2
cervical vertebra． The neck forces of No． 3，No． 4 and
Variation of moment and force under 8 conditions
Force and Moment Comparison in Different Directions of Neck
The neck forces in three directions under 8 different conditions are averaged as shown in Fig． 8． （ xforce and x-moment represent the maximum cervical force and the maximum moment in x direction，and so on． ） It can be seen that the value of z-force is much
No． 7 are at the same level． While the values of No． 6 condition gradually decrease from C1 to C7． Neck motion of No． 6 is different from other conditions，so the direction of cervical force is opposite with other conditions at beginning． Later the direction of cervical force changes into the same direction with other conditions， and the maximum value lags behind other conditions．
higher than that of x-force and y-force． The value of yforce is much higher than that of x-force for upper cervical vertebras （ C1 － C4 ） ，while for lower cervical vertebras（ C5 － C7） ，both of these values are similar． In general it can be known that cervical vertebras mainly suffer z direction axial force and y direction shear force．
Fig． 10
Force of 7 cervical vertebras under 8 conditions
The moment data of cervical vertebrasnot including C6 are shown in Fig． 11． The moments of No． 1 to Fig． 8
No． 4 and No． 7 gradually increase from C1 to C7． While the moments of No． 5，No． 6 and No． 8 condi-
Mean value of 8 postures of 7 cervical vertebras in three directions
The moment values of each cervical vertebra are approximately same． Fig． 9 shows the moment values of C5． It can be seen that the x-moment （ axial rotation
tions are different from former conditions． We can see that the moments of upper cervical spines （ C1 － C4） are at the same level，while lower cervical spines dramatically increase from C5 to C7．
— 322 —
LI Zhi-gang（ 李志刚） et al． / Numerical Study on Neck Injury Under Different Postures in Vehicle Side Impact ［2］ Linder A，Avery M，Kullgren A，et al． Real-world rear impacts reconstructed in sled tests［C］∥Proc of International Research Council on the Biomechanics of Impact （ IRCOBI） ． Graz，Australia： ［s． n． ］，2004： 233 － 244． ［3］ Sundararajan S， Prasad P， Demetropoulos C， et al． Effect of head-neck position on cervical facetstretch of post mortem human subjects during low speed rear end impacts［J］． Stapp Car Crash Journal，2004，48： 331 － 372． ［4］ McIntosh A S ，Kallieris D，Frechede B． Neck injury tolFig． 11
Moment data of 7 cervical vertebras
erance under inertial loads in side impacts［J］． Accident
ent postures in vehicle side impact was simulated with the facet human model from MADYMO database and u-
22． ［6］ Ewing C，Thomas D，Lustick L et al． Effect of initial po-
sing the method of PSM． The force and moment in
sition on the human head and neck response to + Y im-
each cervical vertebra were calculated． Compared with
pact acceleration［C］∥Proceedings of the 22nd Stapp Car
the results in Ref． ［4］，it can be seen that the forces
Crash Conference． Ann Arbor，USA： ［s． n． ］，1978： 103
of each spine have almost reached the injury tolerance． However，the moments of each cervical vertebra are
－ 138． ［7］ Patrick LM，Chou C． Response of the human neck in
underestimated． These forces and moments are differ-
flexion，extension and lateral flexion． Vehicle Research
ent under different neck postures． No． 6 is the best
Institute Report，No． VRI-7． 3［R］． Warrendale，PA，
condition that is less susceptible to suffer from injury under inertia load in side impact． Furthermore，differ-
USA： Society of Automotive Engineer，1976． ［8］ Wismans J，Spenny C． Performance requirements for mechanical necks in lateral flexion［C］∥Proceedings of the
ent forces and moments can be found at different cervi-
27th Stapp Car Crash Conference． New York： SAE，
cal spines even under the same neck posture．
1983： 137 － 149．
Although the adopted model was verified by litera-
［9］ Bendjellal F，Tarriere C，Gillet D，et al． Head and neck
ture，the modeling accuracy can be further improved．
responses under high G-level lateral deceleration［C］∥
More experiments are needed to further support the
Proceeding of the 31st Stapp Car Crash Conference． War-
man spine loads during trauma to mechanical investigations［C］∥ Proceedings of the IRCOBI Conference．
［1］ Kullgren A，Krafft M，Ydenius A，et al． Developments in car safety with respect to disability-injury distributions for car occupants in cars from the 80's and 90's［C］∥
Bron，France： ［s． n． ］，1996： 89 － 106． ［11］ Kim S． Side impact simulation using MADYMO FE and
Proc of International Research Council on the Biomechanics of Impact （ IRCOBI） ． Munich，Germany： ［s． n． ］， 2002： 145 － 154．
— 323 —
PSM［C］∥ The 4 th MADYMO China Users Meeting． Hainan，China： ［s． n． ］，2008．
