EHTC 2008 in Strasbourg
2nd European HyperWorks Technology Conference
Strasbourg September 30th – October 1st, 2008
Mine explosion and blast effect on vehicleanalysis of the potential damages on passengers
Romuald FALLET
CONTEXTCONTEXT
All over the world, All over the world, guerrilla methods are more and more used. guerrilla methods are more and more used.
Today, terrorist attacks can affect both military and civilian vToday, terrorist attacks can affect both military and civilian vehiclesehicles
EHTC 2008 in Strasbourg2
For these specific applications, numerical simulations can be usFor these specific applications, numerical simulations can be useful to eful to
estimate damages created by a mine explosion, and to improve surestimate damages created by a mine explosion, and to improve survivability vivability
of occupants.of occupants.
Numerical Simulation of a mine Numerical Simulation of a mine
explosion under a civil vehicleexplosion under a civil vehicle
The RADIOSS model takes into account :
– Arbitrary Lagrange Euler (ALE) method for Fluid and Explosive [JWL] Modeling
– Fluid Structure Interaction (FSI) between
vehicle and blast wave (interface type 18)
– Deformable Structure of vehicle
– HYBRID III dummies to estimate damages
caused by the blast wave
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Explosion of a buried landmine of 6 Kg of TNT under the Explosion of a buried landmine of 6 Kg of TNT under the
front wheel of a civil pick upfront wheel of a civil pick up
Landmine 6kg of TNT
Problems raised by this kind of applicationsProblems raised by this kind of applications
Distortions and deletions of the structure during
exploding solicitation ���� Impossibility to manage a fluid
mesh coincident to the structure mesh.
Interest of the Fluid Structure Interaction (FSI) Interest of the Fluid Structure Interaction (FSI)
interface TYPE 18 :interface TYPE 18 :
• Lagrangian structure and Eulerian fluid meshes are not linked
Inherent difficulties due to the interface TYPE 18Inherent difficulties due to the interface TYPE 18
• Determination of the good stiffness of interface
• Required finely of fluid mesh to get a good precision in the FSI
Numerical Simulation of a mine Numerical Simulation of a mine
explosion under a civil vehicleexplosion under a civil vehicle
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Eulerian Mesh
Lagrangian mesh
Fluid / structure interfaceFluid / structure interface
Previous studies have showed that the relation below can be used to estimate
the interface stiffness.
EHTC 2008 in Strasbourg5
This equation permits:
– To be freed from an analysis of sensitivity at each new study
– To have a good evaluation of every studied cases
Gap
ScK
⋅⋅=
2ρ
ρ : Fluid density
C : wave celerity
S : Shell Section of the structure parts
Gap : interface gap
Air is modeled as a perfect gas by Mie Gruneisen hydrodynamic law,
where pressure is given by the equation of state :
With
γγγγ =1.4 :
C0 = 0
C1 = C2 = C3 = 0
C4 = C5 = (γγγγ – 1) = 0.4
E0 = 0.25
Fluids Meshing and ModelingFluids Meshing and Modeling
Explosive part and AIR volume around vehicle are meshed with Explosive part and AIR volume around vehicle are meshed with
BRICK elements. BRICK elements.
Fluid Parts are set up with Arbitrary Lagrange Euler (ALE) formuFluid Parts are set up with Arbitrary Lagrange Euler (ALE) formulationlation
EHTC 2008 in Strasbourg6
( )ECCCCCCP µµµµ 54321032 +++++=
10
−=ρ
ρµ
Mine ModelingMine Modeling
� The mine shape has been defined as described in the “AEP-55 NATO/PfP UNCLASSIFIED /
Procedures for evaluating the protection level of logistic and Procedures for evaluating the protection level of logistic and light armored vehicleslight armored vehicles”
� The mine is modeled by a cylinder with an equivalent
mass of TNT (6 Kg).
� The TNT behavior is managed by Jones Wilkins Lee material Law [JWL] in which the Equation Of State of Pressure is calculated by the following equation:
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H= 80 mmΦ Φ Φ Φ = 250 mm
TNTTNT
Air blast Parameters versus distance for Air blast Parameters versus distance for
TNT Hemispherical Surface BurstTNT Hemispherical Surface Burst
Pressure wave and celerity of the blast are Pressure wave and celerity of the blast are
correlated with TM 5 correlated with TM 5 –– 1300 1300 ““Structures to Structures to
resist the effects of accidental explosionsresist the effects of accidental explosions””
EHTC 2008 in Strasbourg8
Blast wave shape in free field Blast wave shape in free field
Calculation of the Reduce distance Calculation of the Reduce distance
R (m.kgR (m.kg--1/3)1/3)
Mine ModelingMine Modeling
Blast simulation of the mine in semi free fieldBlast simulation of the mine in semi free field
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Rigid groundRigid ground
MineMine
DummyDummy
An Hybrid III dummy is set on seat to simulate driver behavior aAn Hybrid III dummy is set on seat to simulate driver behavior and to nd to
estimate body damages.estimate body damages.
EHTC 2008 in Strasbourg10
The 50th percentile ATD represents the average male of populatioThe 50th percentile ATD represents the average male of population between 1970s n between 1970s
and 1980s with the following figures: and 1980s with the following figures:
�� length (standing position): 1.72 m length (standing position): 1.72 m
�� weight: 78 kg weight: 78 kg
�� erect sitting height: 0.88 m erect sitting height: 0.88 m
Mine explosion SimulationMine explosion Simulation
Damages caused by the mine explosion under front wheel Damages caused by the mine explosion under front wheel
EHTC 2008 in Strasbourg11
[6 Kg of TNT]
Mine explosion SimulationMine explosion Simulation
Blast effect on the front part of the car structure. Blast effect on the front part of the car structure.
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Mine explosion SimulationMine explosion Simulation
Blast effect on the front part of the car structure. Blast effect on the front part of the car structure.
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Mine explosion SimulationMine explosion Simulation
Damages caused by the mine explosion: a hole is created in the uDamages caused by the mine explosion: a hole is created in the under nder
structure parts by the blast structure parts by the blast �������� The blast penetrates in the vehicle The blast penetrates in the vehicle
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In the firsts millisecond of the explosion, Legs are broken
Important structural damages are noticed on the lower parts of the vehicle
Mine explosion SimulationMine explosion Simulation
To estimate damages on driver body, the AEPTo estimate damages on driver body, the AEP--55 NATO can be used.55 NATO can be used.
For examples, Pelvis acceleration or contact forces between feetFor examples, Pelvis acceleration or contact forces between feet and and
under structure can be plotted.under structure can be plotted.
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average vertical acceleration on driver [filtered at 500 Hz]
-30
-20
-10
0
10
20
30
40
50
60
0 5 10 15 20 25
Time in ms
Ac
ce
lera
tio
n in
g
Pelvis accelerationPelvis acceleration
Lower Tibia Load CellLower Tibia Load Cell
In this case tolerance value of 5.4 In this case tolerance value of 5.4 kNkN is is
reached at 3 ms.reached at 3 ms.
Mine explosion SimulationMine explosion Simulation
Pressure measured at the head level of dummyPressure measured at the head level of dummy
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Pressure time history in vehicle
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Time in ms
Pre
ss
ure
in
MP
a
Sound level above 140 dB
Pressure level MPa
Protection designProtection design
In case of important damages, simulation can be used to design In case of important damages, simulation can be used to design and and
test shield to reinforce vehicle structure test shield to reinforce vehicle structure �������� Armor plates can be added Armor plates can be added
under vehicle to avoid blast penetration in car.under vehicle to avoid blast penetration in car.
Here, a plane steel armor plate is tested :Here, a plane steel armor plate is tested :
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A quarter of FE Model is used for simulation
Rigid vehicle
Steel Armor plate
Cylindrical mine (6 Kg of TNT)
Protection designProtection design
Pressure level on steel armor plate. Pressure level on steel armor plate.
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armor plate
Rigid part on top
Air
Mine : 6 Kg of TNT
Blast absorber to limit accelerationBlast absorber to limit acceleration
In case of important acceleration level on passenger, energy In case of important acceleration level on passenger, energy
absorbers can be mounted under seat to limit acceleration peak.absorbers can be mounted under seat to limit acceleration peak.
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seat energy absorber
ConclusionsConclusions
� This methodology is adapted to study that kind of phenomena or This methodology is adapted to study that kind of phenomena or
cases where blast is generated by an explosion far from vehicle.cases where blast is generated by an explosion far from vehicle.
��Sensitivity studies can be easily performed to improve vehicle Sensitivity studies can be easily performed to improve vehicle
design or to prepare a tests campaigndesign or to prepare a tests campaign
�� This methodology can be applied to other explosion cases : This methodology can be applied to other explosion cases :
-- Explosion of hydrogen tank to evaluated damages on persons Explosion of hydrogen tank to evaluated damages on persons
around detonation pointaround detonation point
-- Luggage explosion in plane or trainLuggage explosion in plane or train
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