project 5report
TRANSCRIPT
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Venkata Sai Gopala Krishna vemuri [email protected]
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Project 5
Analysis of Dummy in Different Frontal Impacts
Venkata Sai Gopala Krishna Vemuri
Ft6503
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Problem:
Abstract: A finite element (FE) model based on a 2001 Ford Taurus passenger sedan
was developed through the process of reverse engineering at the National Crash
Analysis Center (NCAC) of The George Washington University (GWU) under an
FHWA contract. This model was initially validated by comparing the simulation of
the NCAP frontal wall impact with actual data from NHTSA tests for a comparable
vehicle. Acceptable results of the initial validation led to the release of the FE model.
Subsequently, the model was periodically updated and enhanced with the inclusions
of the interior elements. Additional validation efforts were undertaken using data
available from other crash tests, including full frontal wall, offset deformable barrier,
moving deformable barrier, and offset rigid pole impacts. Simulation results
compared well to data from these tests to determine the validity of the enhanced
model. The capabilities of the model were also checked by damage consistency
comparisons for rigid wall, offset deformable barrier, and centerline pole impacts at
varying speeds. The simulations executed without error in these runs and the results
reflected the expected responses and consistency with varying parameters.
A) Frontal Impact with Infinite Rigid Wall
B) Frontal Impact with 25% Rigid Wall
C) Frontal Impact with 40% Rigid Wall
D) Compare and Analyze impact on Dummy with airbag and seat belt
and without airbag and seat belt.
E) Compare the Plots of Vonmisses Stresses, Pressure and Plastic
Strain, and also total energy.
F) Improvise the structure and suggest the best way to save the
Dummy after the impact.
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Model given:
Note: The given model doesn’t have airbag, seat, Dummy and Rigid Wall.
Software’s used: LS-Prepost, Hypermesh (LS-Dyna).
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Project Tree:
Frontal Impact with
Infinite Rigidwall
• Plannar
Frontal Impact with finite wall
• 40% offset
Frontal Impact with
Finite rigidwall
• 25% offset
Improvement 1
• Seat belt incorporated for Dummy
Improvement 2• Use of
Composite materilas
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Solution Procedure:
Step 1: Incorporating Steering
Steering with airbag
Use rods to 1-d beams with Secbeam property and Matl1 Material. Give density and
elasticity values according to the units of Steering
Connect the beams as shown in
figure. In car we have a steering
part. Create a Spider to the
steering hole and attach the
spider to the steering node by a
beam resembling a steering shaft.
Use the same material and
Property.
Steering with beam elements connected to a node.
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Steering Set-up
Step 2: Seat Set-up
Create to surfaces according to the dimensions of the dummy in hypermesh
and import in to the car.
Use Matl34 fabric material for the seat.
Attach the seat to the floor of the car using the beams.
Make sure that the units of car, seat and steering are same. Units of car
steering and seat are tons, mm and sec.
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Step 3: Converting car, steering and Seat into Dummy Units.
Conversion file
Step 4: Importing Dummy
Never offset Dummy parts, it may give rise to Part out of Range error.
Open Dummy file into ls prepost and Import car setup.
Use limb-operations and h-point operations to adjust the dummy in the car.
Give Contacts between Dummy and Car floor, Dummy and Airbag,
Dummy and Seat, also between airbag and Car windshield.
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Step 5: Assign velocity for the complete car setup.
Velocity is 15.65 mm/ms
Create a Node-set id for the complete car set-up and assign it in the *Initial Keyword.
Velocity = 15.65 in X-direction
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Step 6: Creating a Rigid wall
Case 1: Infinite Rigid wall
Create a Planar rigid wall (Infinite) normal to Z-direction. Important note make sure the
Z-axis of the rigid wall face the car.
Create a base node for the rigid wall and adjust the rigid wall distance arbitrarily.
Select all the nodes of car as a slave nodes because Ls-Dyna takes rigid wall as master
by default. Without this contact car passes through the rigid wall without any impact.
Case 2: 40% offset Rigid Wall
Create a finite rigid wall similar to infinite case but in this case we give the rigid wall
some dimensions as shown in figure.
Similarly assign the Slave nodes as in the previous case.
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Length in X= 1500 and Length in Y= 1500
40% off set rigid wall
Case 3: 25% offset Rigid Wall
Construct similar wall as above but at 25% off set of car.
Give the slave node set for the car similarly.
Length X = 1500 and Length Y= 1500
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25% Offset rigid wall
Step 7: Control cards, Binary plots, Hourglass
Control Cards
Control termination for this model is 127 ms.
We use default hourglass viscosity type 5
Control time step is 0.001112
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Control cards
Binary Plots
Select GLSTAT, RWFORC, RCFORC, SWFORC etc., in ASCII_Option
which are used for plotting all the results.
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Step 8: Run each case separatly with 256000000 memory and 8 cpu as input using
Ls-Manager.
Use D3Plot to view the results.
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Results:
Case 1: Infinite Rigid Wall
@ 0 ms
Infinite Rigid Wall
At 0ms
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@ 40ms
Frontal impact @40ms
@ 90ms
Frontal impact @90ms
If we observe clearly as the material of the seat is fabric which has very
less stiffness it folds off after the impact and the dummy fall on to the
airbag.
The contacts between airbag and dummy prevents dummy to penetrate into
airbag.
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@ 127ms
Frontal impact @127ms
At this time step the dummy completely falls onto the front dash board due
to strong impact.
The frontal part of the car the bumper crushes completely and suddenly
comes to retardation which gives reaction to dummy and falls on to the
dash board.
The airbag prevents dummy coming out through windshield.
Vonmisses Stresses
Maximum Vonmisses stress is 7.626 GPa
Von-Misses Stress
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Pressure
Maximum pressure is 0.806061 units
Pressure
Total energy plot
The total energy increases from 0.175e6 to 0.21e6 with time increment
Total Energy
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Normal Force Plot
The normal force acting on the rigid wall is the maximum among all the
cases as the contact area of the car increases completely.
The maximum normal force is 800 units at 45ms.
Normal Force
Head Injury Criteria
Head Injury Criteria
In this case the Head Injury Criteria crosses the prescribed value 10 so the
dummy is out of control and is considered dead in this case.
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Case 2: Finite Rigid Wall with 40% offset
@ 0 ms
Finite Rigid Wall with 40% Offset
At 0ms
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@ 40ms
At 40ms
Only 40% of the front part of car impacts with the rigidwall.
@ 90ms
Frontal impact @90ms
The driver side of the car crushes completely on to the rigid wall and on
the other side, impact is less but in this phenomenon the dummy injury is
very high because the complete forces due to impact are transferred only
on one side that is driver side (dummy).
Also in this case the right roof rail and A-Pillar on right side deforms.
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@ 127ms
Frontal impact @127ms
The right side completely crushes on to the rigid wall. This is one of the
dangerous cases because of the impact and stress transfer are all taking
place on the side of the dummy.
The airbag prevents dummy coming out through windshield.
Vonmisses Stresses
Maximum Vonmisses stress is 1.5289 as the impact is on only one half.
Von-Misses Stress
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Pressure
Maximum pressure is 0.721158 units
Pressure
Total energy plot
The total energy increases from 0.175e6 to 0.182e6 with time increment
Total Energy
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Normal Force Plot
The normal force acting on the rigid wall is the maximum on only right
half rather than on the complete body. So the normal force increases to
1000 units which is more than the force acting on the infinite rigid wall.
The maximum normal force is 1000 units at 48ms.
Normal Force
Head Injury Criteria
Head Injury Criteria
In this case the Head Injury Criteria crosses the prescribed value 10 so the
dummy is out of control and is considered dead in this case. The impact is
very high in this case.
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Case 3: Finite Rigid Wall with 25% offset
@ 0 ms
Finite Rigid Wall with 25% off set
At 0ms
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@ 40ms
Frontal impact @40ms
@ 90ms
Frontal impact @90ms
The driver side of the car crushes completely due to the impact of rigid
wall and on the other side, impact is less but in this phenomenon the
dummy injury is very high because the complete forces due to impact are
transferred only on one side that is driver side (dummy).
Also in this case the right roof rail and A-Pillar on right side deforms
completely on the dummy.
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@ 127ms
Frontal impact @127ms
The most dangerous situation, the dummy completely packs in between the
crush. This is the most critical impact. Use of more composite materials on
the side of dummy and also seatbelt may prevent dummy dying.
Vonmisses Stresses
Maximum Vonmisses stress is 1.751 GPa
Von-Misses Stress
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Pressure
Maximum pressure is 0.936079 units
Pressure
Total energy plot
The total energy increases from 0.175E+6 to 0.181E+6 with time
increment
Total Energy
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Normal Force Plot
The Normal force is 400 units at 45ms. The force is less as the impact area
is less compared to the previous cases.
Normal Force
Head Injury Criteria
Head Injury Criteria
In this case the Head Injury Criteria crosses the prescribed value 10 so the
dummy is out of control and is considered dead in this case.
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Improvement 1: Incorporating Seat Belt for the Dummy in the
Infinite rigid wall case
In this case the termination time is 75ms only. Velocity is 8.99ms
@ 0 ms
At 0ms
The Dummy is incorporated with seat belt to prevent it falling forward due
to the impact.
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@ 40ms
Frontal impact @40ms
@ 75ms
Frontal impact @75ms
In this case the seat belt holds the dummy. The Retractor and Sensor act
alternatively in this case to hold the dummy.
As the holds to its seat the impact of frontal crash is less on it.
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Vonmisses Stresses
Maximum Vonmisses stress is 1.273 GPa
Von-Misses Stress
Pressure
Maximum pressure is 0.702252 units
Pressure
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Total energy plot
The total energy increases from 58.5e3 to 66e3 with time increment. The
energy is less because velocity is reduced to 8.99.
Total Energy
Normal Force Plot
The maximum normal force is 200units.
As velocity reduces the normal force impacting on the wall reduces
Normal Force
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Head Injury Criteria
Head Injury Criteria
In this case the Head Injury Criteria is less than the prescribed value 10 so
the dummy is out of danger.
The main reason for the dummy to resist the impact is due to
incorporating the seat belt and also reducing the velocity to 8.99. With
15.656 the program is ending up with out of range velocities.
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Improvement 2: Using Composite materials for front Bumper
and Left and right Fender
Front Bumper with left and right Fender
Matl58 is used for composite material and also each composite part have 5
composite layers.
The thickness of left and right fender composite layers is 2mm. Also the
thickness of bumper composite layers is 4mm.
Matl58 Composite Laminate Material
Left and Right Fender Part. B is layer angle Front Bumper Part
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@ 0 ms
At 0ms
@ 60ms
Frontal impact @60ms
The composite material takes maximum impact and does not transfer it to
the internal parts. So that is an advantage of using composite material.
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@ 65 ms
Frontal impact @65ms
In this phenomenon the stresses are not transferred to the internal parts.
Vonmisses Stresses
Maximum Vonmisses stress is 4.08405 GPa
Von-Misses Stress
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Pressure
Maximum pressure is 2.04913 units
Pressure
The pressure in this case is remarkable. Composite materials have the
maximum stresses compared to all other materials. These restrain the
energy and breaks into pieces without transferring the energy to the
internal parts.
Total energy plot
The total energy increases from 0.2e9 to 3.5e9 with time increment
Total Energy
The Composite materials have the maximum energy among all the above
iterations. They absorb more energy and breaks without transferring the
energy which in turn reduces the injury on dummy.
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Normal Force Plot
Similarly the Normal force is also high for composite materials. These
have 2000 units of normal force at the impact point which is maximum
among all the above cases.
Normal Force
Head Injury Criteria
Head Injury Criteria
In this case the Head Injury Criteria is below the prescribed value 10 so
the dummy is out of danger. Composite materials safe dummy from
injuries.
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Summary and Conclusion:
During the analysis I faced few errors regarding the seat belt
element not found. We get this error if the seat belt retractor
and sensor are disconnected from the floor. So we need to
connect the seatbelt elements to floor with beams. Also check
the velocity node set id.
25% off set causes more damage to the dummy and 40%
follows it. Using seat belt and composite materials at the area
of impact may reduce the damage.
Composite materials are best preferred in the concentrated
impact area. The main advantage of composite materials is
they absorb the energy rather than transferring it to the other
components. By this they gain maximum energy and also have
maximum normal force which breaks them into pieces rather
than impacting the internal parts and damaging the dummy.
Among all the iterations assigning Composite materials for
Bumper and fender has best results in saving the dummy from
impact followed by the seatbelt. So composites with seat belt
might be the best suggested product obtained by observing the
above results.
Note: Car, Airbag, Dummy models are separately taken from Class 8020
(Crashworthiness). Also Crashworthiness Project is also attached along with this
project. Each and every model is self-iterated and videos will be emailed. Can also
provide files of all the above iterations if necessary.