Chalmers University of Technology
Modelling of Whiplash TraumaParametric study of rear-end impacts using FEM and CFD
Andreu Oliver González
Mourya Vanama
Applied Mechanics
07 June 2010
Chalmers University of TechnologyApplied Mechanics
Outline
• Introduction
• Objective
• Methodology
• Results
• Conclusions
• Future Scope
2
Chalmers University of TechnologyApplied Mechanics
Introduction
3Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
4Introduction Objective Methodology Results Conclusions Future Scope
$4.5 billion/year€ 10 billion/year
Statistics – Whiplash Injuries
High cost to the society
Chalmers University of TechnologyApplied Mechanics
5Introduction Objective Methodology Results Conclusions Future Scope
Statistics – Whiplash Injuries
Chalmers University of Technology
Whiplash Injury
• Hyper extension of the neck
• Low speed rear-end impacts (16-24 km/h)
Applied Mechanics
6Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
Anatomy - Human Vertebral Column
7Introduction Objective Methodology Results Conclusions Future Scope
Ventral root
Spinal nerve
Dorsal root
Dura mater
Extradural (epidural) space
Arachnoid mater
Spinal ganglion mater
Subdural space
Pia mater
Subarachnoid space
Ramus communicans
Ventral primary ramus
Dorsal primary ramus
Chalmers University of Technology
Injury Mechanisms
Facet Joint Capsule Strain
• Impingement of the capsule
• Strain due to deformation
Applied Mechanics
8Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
9Introduction Objective Methodology Results Conclusions Future Scope
Injury Mechanisms
Pressure Gradients in Spinal Canal
Volume change
Pressure gradient
Chalmers University of TechnologyApplied Mechanics
10Introduction Objective Methodology Results Conclusions Future Scope
Injury Criterion
Neck Injury Criteria (NIC)
Calculated at maximum retraction phase
Critical limit of 15 m2/s2
211 )()·(2.0 dtHeadTHeadTNIC CgAccelAccelCgAccelAccel
Chalmers University of TechnologyApplied Mechanics
Objective
11Introduction Objective Methodology Results Conclusions Future Scope
Investigate the effect of different parameters on:
• Facet joint loadings and NIC FE simulations (LS-DYNA)
• Pressure gradients CFD simulations (OpenFOAM)
Chalmers University of TechnologyApplied Mechanics
Methodology
12Objective Results Conclusions Future ScopeIntroduction Methodology
Chalmers University of TechnologyApplied Mechanics
13Introduction Objective Methodology Results Conclusions Future Scope
Parametric Study FEM
Facet Joint Capsule Strain
NIC
Output
Output
InputCFD
Pressure
gradients
Procedure
Chalmers University of TechnologyApplied Mechanics
14Introduction Objective Methodology Results Conclusions Future Scope
Parametric Study
Chalmers University of TechnologyApplied Mechanics
15Introduction Objective Methodology Results Conclusions Future Scope
0 50 100 150 2000
2
4
6
8
Time (ms)
Acc
eler
atio
n (
g)
Square Crash Pulses at Delta V of 15 kmph
2.5g
5g
7.5g
Parametric Study
Crash pulses
Square Crash Pulses at delta-V of 15 km/h
Chalmers University of TechnologyApplied Mechanics
16Introduction Objective Methodology Results Conclusions Future Scope
FE modelling
Chalmers University of TechnologyApplied Mechanics
CFD
Theoretical model
17Introduction Objective Methodology Results Conclusions Future Scope
Whiplash
motion
Cervical spinal
canal length
change
Blood
transportation
Pressure
gradients
Model of the
spinal venous
plexus
Chalmers University of TechnologyApplied Mechanics
Geometrical model
Spinal venous plexus modelled with respect to the THUMS
18Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
Geometrical model
Different zone heights and top view
19Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
Geometrical model
The mesh
20Introduction Objective Methodology Results Conclusions Future Scope
C1_Occ
T1
Inner patch
Outer patch
Side pipe patch
Side pipe
extreme patch
Chalmers University of TechnologyApplied Mechanics
Kinematic model
21Introduction Objective Methodology Results Conclusions Future Scope
Representative
point
Inter-
polation
Input
data
Reading and saving
input data
Cylinder motion
Rigid
Deformable
Chalmers University of TechnologyApplied Mechanics
a) Rigid cylinders
Extrapolation of the motion
in two steps
b) Deformable cylinders
Interpolation of the
rigid cylinders
motion
22Introduction Objective Methodology Results Conclusions Future Scope
Upper rigid cylinder
Lower rigid cylinder
Deformable cylinder
Premotion Motion
Chalmers University of TechnologyApplied Mechanics
Fluid dynamic properties
• Blood
• Newtonian
• Laminar flow
Boundary conditions
• Extremes of side pipes and main pipe Inlet/Outlet
• The rest of the model Wall
Solver
• For incompressible fluid based on PISO and SIMPLE
23Introduction Objective Methodology Results Conclusions Future Scope
Properties Value
Density, [kg/m3] 1050
Dynamic viscosity, [kg/ms] 0.0035
Kinematic viscosity, [m2/s] 3.33·10-6
Chalmers University of TechnologyApplied Mechanics
Results
24Objective Methodology Conclusions Future ScopeIntroduction Results
Chalmers University of Technology
MotionWith head restraint
Without head restraint
Applied Mechanics
25Introduction Objective Methodology Results Conclusions Future Scope
2.5
g2
.5g
5g
5g
7.5
g7.5
g
Chalmers University of Technology
0 0.05 0.1 0.15 0.2 0.25-300
-250
-200
-150
-100
-50
0
50
100
150
200
Time [s]
Accele
ration [m
/s2]
C1
C2
C3
C4
C5
C6
C7
T1
Applied Mechanics
Motion
26Introduction Objective Methodology Results Conclusions Future Scope
Rotational displacement
around Y axis
Longitudinal acceleration
0 0.05 0.1 0.15 0.2 0.25-20
-10
0
10
20
30
40
50
Time [s]
Rota
tional D
ispla
cem
ent [d
eg]
C1
C2
C3
C4
C5
C6
C7
T1
Max. Extension at 0.115 s
Chalmers University of TechnologyApplied Mechanics
Motion verification
27Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
Motion verification
Longitudinal velocity
Vertical velocity
28Introduction Objective Methodology Results Conclusions Future Scope
0 0.05 0.1 0.15 0.20
2
4
6
8
10
Time [s]
Lo
ng
itu
din
al ve
locity [m
/s]
C1
C2
C3
C4
C5
C6
C7
T1
0 0.05 0.1 0.15 0.20
2
4
6
8
10
Time [s]
Ve
locity [m
/s]
C1
C2
C3
C4
C5
C6
C7
T1
0 0.05 0.1 0.15 0.2-1.5
-1
-0.5
0
0.5
1
Time [s]
Ve
locity [
m/s
]
C1
C2
C3
C4
C5
C6
C7
T1
0 0.05 0.1 0.15 0.2-1.5
-1
-0.5
0
0.5
1
Time [s]
Ve
locity [
m/s
]
C1
C2
C3
C4
C5
C6
C7
T1
C
F
D
F
E
M
0 0.05 0.1 0.15 0.2-1.5
-1
-0.5
0
0.5
1
Time [s]
Ve
locity [
m/s
]
C1
C2
C3
C4
C5
C6
C7
T1
Chalmers University of Technology
FE simulationsFacet Joint Strains
Applied Mechanics
29Introduction Objective Methodology Results Conclusions Future Scope
Acceleration
Pulses
Strains (With Head Restraint)
C2 - C3 C3 - C4 C4 - C5 C5 - C6 C6 - C7 C7 -T1
2.5g 0.0342 0.0368 0.1309 0.2062 0.1883 0.2151
5g 0.2265 0.2037 0.2759 0.2612 0.2076 0.2944
7.5g 0.2893 0.2633 0.3482 0.3290 0.2843 0.3763
Strains (Without Head Restraint)
2.5g 0.1715 0.1712 0.4301 0.7561 0.5989 0.5792
5g 0.4814 0.3383 0.5117 0.9172 0.6456 0.5791
7.5g 0.4029 0.3088 0.5132 0.9236 0.6067 0.9326
Chalmers University of Technology
Facet Joint Strains - 5g
Applied Mechanics
30Introduction Objective Methodology Results Conclusions Future Scope
With
he
ad
restr
ain
t
With
ou
t h
ea
d
restr
ain
t
0 50 100 150 200 2500
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Time [ms]
Str
ain
C2-C3
C3-C4
C4-C5
C5-C6
C6-C7
C7-T1
0 50 100 150 200 2500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time [ms]
Str
ain
C2-C3
C3-C4
C4-C5
C5-C6
C6-C7
C7-T1
Chalmers University of Technology
Neck Injury Criterion (NIC)
Applied Mechanics
31Introduction Objective Methodology Results Conclusions Future Scope
NIC
max
[m2/s
2]
Acceleration
0
5
10
15
20
25
30
35
40
45
2.5g 5g 7.5g
With Head Restraint
Without Head Restraint
Non-upright posture with head restraint
Chalmers University of TechnologyApplied Mechanics
CFD simulations
Convergence
- All time steps should fully converge
32Introduction Objective Methodology Results Conclusions Future Scope
10-3
10-2
10-1
25
30
35
40
45
50
Time [s]
Num
ber
of itera
tions
Chalmers University of TechnologyApplied Mechanics
Behaviour of Pressure
33Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
Behaviour of Pressure
34Introduction Objective Methodology Results Conclusions Future Scope
0 0.05 0.1 0.15 0.2-300
-200
-100
0
100
200
300
Time [s]
Mean p
ressure
[P
a]
Mean pressure of the different solid cylinders
C1
C2
C3
C4
C5
C6
C7
T1
Chalmers University of TechnologyApplied Mechanics
Behaviour of Velocity
35Introduction Objective Methodology Results Conclusions Future Scope
0 0.05 0.1 0.15 0.2-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
Time [s]
Vert
ical re
lative v
elo
city o
f th
e b
lood flo
w [m
/s]
Vertical relative velocity of the blood flow for the different solid cylinders
C1
C2
C3
C4
C5
C6
C7
T1
Chalmers University of TechnologyApplied Mechanics
Behaviour of Velocity
36Introduction Objective Methodology Results Conclusions Future Scope
t = 0.1897 s
t = 0.1209 s
Chalmers University of Technology
• Head restraint
• Ford Taurus Seat – Underperforms for 7.5g
• The CFD solver should be based on SIMPLE
algorithm
Applied Mechanics
Conclusions
37Introduction Objective Methodology Results Conclusions Future Scope
NIC
Facet joint strains
Chalmers University of TechnologyApplied Mechanics
Future Scope
• FEM simulations
• Broader parametric study
• Physiological factors for male and female
• Analysis of Nkm
• CFD simulations
• Consider blood compressibility and vein flexibility
• Use geometry without hole
• Include flow resistance when exiting the model
• Deformation in radial and axial direction
38Introduction Objective Methodology Results Conclusions Future Scope
Chalmers University of TechnologyApplied Mechanics
THANK YOU FOR YOUR ATTENTION
Questions?
39