Assignment 7

                                                             Side crash test on Dodge Neon with a rigid pole.

Objective:

To perform side crash of the given car model with the given conditions and study the BIW model after crash.

Conditions :

1. Check unit system and either follow [Mg mm s] or [Kg mm ms].
2. Create appropriate interface ,friction 0.2 and recommended parameters.
3. Make sure of no penetration and intersections.
4. Create rigid wall with friction 0.1 as per referance model.
5. Compare the model weight with the referance model and use added masses to reach target weight 700kg while getting CG about the required range.
6. Initial velocity as shown in picture.
7. Use model checker to ensure good quality.
8. Timestep :0.5 to 0.1 microseconds.
9. Run 80ms.

Introduction :

Side crashes are the second most common type of accident. They cause the highest number of critical injuries relative to the accident rate. One reason for this is the spatial proximity of the occupant to the deformation zone. There are different test standards for the side impact. These are the side crash according to ECE-R95 (European standard) and FMVSS-214 (US standard) as well as the tests given in the consumer protection programs. In addition to the actual side impact test, there is also a Pole Side Impact test according to Euro NCAP. 

Side-crash simulations on sled systems are carried out for the development of safety restraint systems. These tests begin in an early phase of the development of the whole vehicle. Prototype parts are not always available at this time and the price of these parts is very high.

Procedure :

1. Import the file:

• In the data we have two files 
•  neon_front_0000.rad (starter input file): Which has all data required for the solver such as model information, elements, nodes, loads, boundary condition etc.
•  neon_front_0001.rad (engine input file): Which has all data required for the radioss engine i.e speed , time step, run time, what all data we want as output.
• To import file,
•  change user profile to radioss Because we are using solver as Radioss

•  File>Import>Solver deck we can see the new tab where options available for browse file.
• Browse the file FIRST_RUN_0000.rad (starter input file),

•  

• Click on import so we can see imported file with required for the solver such as model information, elements, nodes, loads, boundary conation etc. 

2. Check the unit system followed:

•  Click on Cards>BEGIN CARD from model browser.
•  Check the entity editor in which unit system is used in this model.

•  Here we use the units kg-mass, mm-length, ms-time.

3.  Creating appropriate interfaces:

•  We create a type 7 interface on the car body to study self intersection.
•  Right click on Groups in model browser> click on create.
•  In card image choose Type 7
•  Choose the slave nodes in Grnod_Id(S) and master elements in Surf_id(M).
•  Give value of friction as 0.2
•  Then fill the parameters with recommended parameters

4. Check for penetrations and intersection :

•  Its is to check these in hypercrash so we can also open hypercrash.
•  Import the model in hypercrash.
•  Go to Quality > Check all solver contact interfaces

•  A quality tab appears and in that we can see that Intersection and penetration are zero.

5. COG and Mass balancing:

•  To see the COG point go to Mass > Balanceing .

• 

•  Click on the spectacle icon you can see the location of COG point now.
•  If it is not at the center, we need to shift it to the center.  Also the total mass should be 700kg. The masses should be divided to different areas so that it should never exceed 700kg.
•  We can change the COG by adding Masses.
•  For adding mass go to LoadCases > Added Mass.

•  Right click on the Added mass area> Create New> Select Type 1- Mass is distributed to each of node group.

• 

•  In title give a name.
•  In Added Mass give the mass to add.
•  In grnod_ID , pick the nodes to which the mass should be distributed.
•  Click on Save.
•  Like that add masses at different places of the car body and position the COG at center

6. Create rigid wall:

• Create Rigid wall by Solver > Create > Rwall > PCYL.
• Give sliding with friction of 0.1.

• 

•  XM, YM, ZM is the location where we need Rigid wall, axis is in Z direction.

• 

7. Give an Initial Velocity of 35mph (15.6464 m/s) :

•  In browser tab Right Click > Creat New > I-L > Initial velocity.

•  In the INVEL tab edit the values .
•  Type is translational because there is no rotation motion.
•  Only y velocity is given because there is only movement in the Y direction.
•  In Grnod_id select the whole nodes of the car. 

8. Check the model, eliminate errors and minimize warnings :

•  To check the quality go to Hypermesh and Tools > Model Checker > Radioss Block

•  Click on Run Checks, When the check is finished it will be show on the bottom.
•  If we have errors Click on Auto Correct, it will eliminate almost most of the errors.
•  Still errors persist we need to look manually and correct it.

9. Give Time step and Run time :

•  In Hypermesh from model browser choose Cards

• 

•  From cards open ENG_RUN
•  In that give the value of Tstop as 80.
•  To give the time step value open the ENG_DT card.

• 

•  In that give the value .0001 for Tmin.
• Give T scale 0.67

Output requests:

• Sectional force in the cross member.
• Intrusion at B pillar,hinge pillar and fuel tank region.Provide recommendation on what can help to reduce Fuel tank intrusion.
• Peak velocity of inner node of the door.

Procedure for creating Output requests :

a. Creating Cross sections for cross members :

•  For createing section we need to define skews so first we create skew.
•  Go to solver tab Right click> Create > Skew > MOV

•  Then we need to select the nodes to define the planes for getting direction of the skew.

•  First select the node to show origin, then choose an axis and select the nodes to define a plane.
•  Click on create.
•  Now we can create a section. Go to model tab Right click > Create > Cross section.

•  In the Entity editor Give the parameters correctly.

•  Give a Name to the crosection.
•  Select 3 nodes to define the x-axis and x-y plane.
•  In Frame_ID select the skew that we created.
•  In deltaT give .1 and for alpha give .67
•  In grshel_id select the set of elements. Where we want to see the section force.
•  Like this we need to create sections and skews in 2 Cross beams.

b. Intrusion at B pillar,hinge pillar and fuel tank region :

•  Intrution is measured using 3 springs from each node at B pillar, hinge pillar and fuel tank region.
•  For creating spring we go to 1D > springs > select the nodes between where we want to create the spring.

• 

c. Peak velocity of inner node of the door :

•  Peak velocity can be identifying by ploting TH for the inner node of the door.
•  Go to solver tab.
•  Right click on TH> NODE

• 

•  In entity editor select the node of which we need to see the peak velocity.
•  In NUM_VARIABLES select number of variables 
•  In Data:NODE  select which all forces you need to plot.

• 

d. For ploting graphs, add TH as required :

•  Go to solver tab.
•  Right click on TH, Select option as we needed.
•         INTER- Interfaces
•         ACCEL- Acceleration
•         SPRING- spring elongation
•         PART- For each parts forces
•         SECTIO- sectional forces
•  First we select SECTIO  for ploting forces.

• 

•  In Entity ID select the Cross sections of which we need to plot the graph.
•  In NUM_VARIABLES select number of variables .
•  In Data:SECTIO select which all forces you need to plot.
•  Like this create TH of SPRING, PART, INTER ... etc

Simulation analysis and plotting graphs:

Energy Error and Mass Errors:

• Energy error is 0 to -3.2 % and mass error is 0% this is due to energy is dissipated from the system.
• In case of under integrated elements, the Hourglass Energy can explain a negative Energy Error since it is not counted in the energy balance.
• If the enery error value negative and decreasing, also is less than 15% it is acceptable. 
• For Mass error, it should be less than 5% of the total model mass. 

Simulation:

• Here the side of the car is crashing towards a rigid pole.
• When the B Pillar hits the pole its movement is almost arrested but the front and back side will keep on moving  for a bit.
• Initially the car will be having a velocity of 15.6464m/s, then it will come to rest as it hit the pole.

Internal energy graph:

• For the car components, we used Ishell=24 QEPH formulation so only a small presence of the Hourglass energy is present,like 75.166J .
• The contact energy is formed only when there is penetration, at the begining there is no penetration.
• But at the end there is some penetration so some contact energy is created and that too 2521.89J which is soo small compare to other energies.
• Initially the K.E energy is high, which is 85634.9J and will reduce as the car moves and get crushed.
• The K.E energy is absorbed by the car and deformations occur.
• So the kinetic energy is converted to internal energy .
• That is why when we look at K.E and internal energy graphs we can see that the reduction in kinetic energy curve is just the opposite of increasing internal energy curve.
• The total energy is the sum of all energy so the curve is like a straight line.

Sectional force at the cross members:

•  Force which is coming from the Doors and its frame is received by Cross members.
• To find the this force we have sections defined. From the section forces graph,  
•  Force received Cross member 1 is 21.63KN @ 60.5 ms
•  Force received at Cross member 2 is 5.42KN @ 27.5 ms
• Here the 2 nd crossmember felt less force compared to 1st cross member because of having a support structure to 2 nd cross member.
• after that the section forces are produced because all parts touching to Rigid pole are deformed max amount, remaining forces are distributed again to the Cross members.

Intrusion at B pillar,hinge pillar and fuel tank region:

• Intrusions are one of the important parameter, while checking the passenger saftey in crash.
• To know the intrusions at fuel tank, B Pillar and Hinge Pillar we have placed a spring in these region.
• From the elongation of the spring we can understand how much intrusion is happend in these regions.
• Here in this graph we can see that the fuel tank have the maximum intrusion, then come the B piller and least intrusion is seen at the hinge pillar .
• So to reduce the fuel tank intrusion we should add one more cross member at the position of fuel tank. 
• Here at the B-Pillar, the spring set there is having an elongation 870.853mm
•  at the fuel tank, the spring set there is having an elongation 1011.984mm
• and at the hinge piller, the spring set there is having an elongation 268.716mm
• The B-pillar touches the rigid pole and the other side is crushed towards it, so its intrusion is  high.
• also becuause its a model without floor panel and missing of many parts the intrusion is so high.
• Here we have more Intrusions so it is not acceptable

Peak velocity of inner node of the door :

• To know the velocity of particular node so that we can study effect of sudden impact on velocity.
• Here because impact of the node 337773 is accelerated and increased velocity to 16.18 m/s at 4.00 ms.
• Here the velocity goes on decrease as crushing goes on.

Von Mises Animation :

Conclusion:

• The overall objective of the work was to simulate a Side Crash and validate the results of the simulations obtained from the crash-test.
• To know the saftey of the passengers of a car, side car crash test is very important
• Here we applied boundary condition to the cars parts and an initial velocity is given
• Then when we run the simulation we can see which all parts are affected in the crash, how much each part get deformed, Intrusion of part into the passenger cabin area and all.
• Due to limited number of nodes in student version some of the biw, engine blocks, suspension system etc are removed, so results are not as in real condition.
• It has been observed that there is Maximum deformation of the cabin and also there was Maximum intrusion at given nodes in driver compartment , its not acceptable. 
• After under standing these we will get to know what all things we should do on this car to make it more safe, example to decrease the amount of intrusion in the Fuel tank region we can introduce a cross member there.

Result:

side crash of the given car model with the given conditions is done.