Project 5report

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


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


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


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


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


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


Pressure

Total energy plot


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




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


@ 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


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


Von-Misses Stress


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Pressure


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




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


@ 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


Von-Misses Stress

Pressure


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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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


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


In this phenomenon the stresses are not transferred to the internal parts.

Vonmisses Stresses


Von-Misses Stress


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Pressure


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


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



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.

Documents

Project 5report