Assignment 7-Side Pole Crash Simulation Challenge

Aim-

• To do deck set-up for side pole crash analysis and run the model.
• Post-processing of results in hyperview and hypergraph.

Objective-

• First to check the unit system.
• Create type-7 contact with friction value 0.2 with recomended parameters.
• To check for penetration and intersections ini the model if present.
• Check for rigid body if any, means make sure all component connected properly.
• Create Cylindrical rigid wall with 0.1 friction value.
• Add mass on given body to reach target of 700kg and make COG align approximately with seat rail.
• Give initial velocity of 35mph(mile per hour) which is 8.94m/s in x direction.
• Give time step of 0.0001 for Brick Noda and Inter.
• Give run time of 80 ms in run card.

Abstract:

Crash test is virtual reconstruction that replicates the same force and sped that would occurs if the vehicle was to be involved in an actual crash.Iin this type of testing, since nothing is physically impacting the body-in-white (BIW), no physical deformation or damage occurs to the body's structure, allowing multiple crashworthiness tets to conduct in succession.

• Frontal crash test.
• Side pole impact crash test.
• Roof crash test.

In this particular challenge we will discuss about the Side impact crash test

Since in side crash test, there are multiple standards use on which we have to focus.

FMVSS 214-

• This Final Regulatory Impact Analysis analyzes the potential impacts of new performance requirements and test procedures for head and thorax protection systems in side crashes.The rule requires a new 20 mph,75-degree oblique pole test run in two different
  configurations.
• Benifits-The agency estimates benefits for occupants in outboard seating positions in near-side crashes of 12-25 mph delta-V in vehicle-to-pole and vehicle-to-vehicle crashes.
• The agency has also found that the side air bags provide benefits to unbelted far-side occupants in side impacts and for belted drivers riding alone in the front seat.

Euro NCAP-

• In Euro NCAP’s test, a car is propelled sideways at 32 km/h against a rigid, narrow pole. The car is placed at right angles to the direction of motion, at a small angle away from the perpendicular.
• Where a vehicle is equipped with a centre airbag to protect against the front seat occupants hitting each other, two average male side impact dummies are placed in the front seats.Where there is no centre airbag, single dummy is placed on the driver’s seat.

• This is a very severe test of a car’s ability to protect the driver’s head. As the loading on the car is so localised, deformation can be very high and the pole can penetrate deeply into the passenger compartment.
• Some side impacts involve a vehicle travelling sideways into rigid roadside objects such as trees or poles. Often this is the result of a loss of control on the part of the driver, owing to speeding, misjudgement of a corner or because of a skid in slippery conditions.

side pole Crash in FE model-

Side pole crash on actual car-

Procedure:

1. Import the model in hypercrash.
2. Check for units both in Hypermehs and Hypercrash.
3. Perform mass balancing in hypercrash.
4. Export model in hypermesh.
5. Give time step for Brick,Noda and Inter as 0.0001 milisecons with respective scale factors.
6. Check for initial penetrarion and intersection.
7. Give initial velocity of 20mph(mile per hour) or 8.94 mps(meter per second).
8. Create type-7 interface contact with friction value as 0.2.
9. Create cylindrical rigid wall with friction 0.1.
10. Create intrusion spring on dasboard position to measure the deformation.
11. Create sections on Driver seat rail and middle rail.
12. Request for TH file as required for this challenge.
13. Find connectivity.
14. Perform model checker.
15. Run the simulation.
16. Post-processin

Abstract:

1.Check for units both in Hypermehs and Hypercrash:

Hypermesh

Go to Solver>cards>Begin card

Hypercarsh:

• In hypercrash while opening itself it will ask to select unit where we will choose as shown below.

2.Import the model in hypercrash.

• Go to File>import >Radioss>select the file from folder.
• Or, we can drag down(by shift+right click) the 0000.rad file and release on hypercrash GUI.

3.Perform mass balancing in hypercrash.

• For mass balancing first we will check the initial mass of the model for that,
• Go to Mass > Mass balancing , It will show the initial mass as shown below as 166.3 kg.

• So reach to mass value to 700kg we need to add 533.7 kg mass more.
• For mass addition we will use ADMAS option.

For Add mass

Go to Loadcase > Added mass

• We will use type-3 of mass addition.
• It will select the part and distribute the mass we will give for this selection.

• Means for driver seat rail we have given 100 kg so this total mass will be distributed over the nodes on that selected part.

• Now pick the part from graphics, and give right click it will get confirmed and changed into red colour.

• So in this way we will add the mass on different components to balance the mass.

• Now go for check the total mass and new COG.

• All yellow color parts,we had given mass on it.
• Now we can see that mass and COG we got as per required.

5.Give time step for Brick,Noda and Inter as 0.0001 milisecons with respective scale factors.

To give time step go to Model browser> cards > ENG_DT_BRICK

• Give CST type and add value for scale factor and time step.

• Simmilarly we will do for NODA.
• But here we wuill give scale factor 0.67

• Now we will give time step for interface and we will choose DEL here.
• DEL will activate delete element command if time step going below given time step.

6.Check for initial penetrarion and intersection.

• Here we will check for initial penetrtion in the model.

For that go to tool > Penetration check > Select group > Check

• After selecting components, hit on check it wil show the result below.

• Here we can see that 0 collision found.

7.Give initial velocity of 35mph(mile per hour) or 15.6464 mps(meter per second).

Create > Boundary condition > INVEL

Now create INIVEL card here,

• Select all component because we are going to give the initial velocity for whole BIW parts.
• After selecting component give velocity in Y- direction 0f 8.9408 m/s.

8.Create type-7 interface contact with friction value as 0.2.

Go to create > INTER > Type-7

• Name it as self contact for further reference.
• Set all the recomended parameter for type-7 contact.
• Delete remaing contacts card which is shown in below picture as INTER 24.

9.Create Infinite cylinderical rigid wall with friction 0.1.

Go to Create > RWall > CYL

Now create rigid wall card,

• Select a point on car body, co-ordinateds will get displyed.
• Normal value to define the z-axis of pole menas it will give normal of pole.
• Give sliding friction as 0.1 and Dsearch value as 2000 to caver hole car body.
• Since we can see that pole is intersecting so now we will change the co-ordinates to move it at some distance from there.

• Infinite cylinderical Rigid wall created now.

10.Intrusion at B pillar,hinge pillar and fuel tank region.Provide recommendation on what can help to reduce Fuel tank intrusion.

• Here we will deploy intrusion spring to measure the deformation.
• Means how much spring length will change, will tell length of BIW defomed in passenger compartment.

Go to Geometry > Temp node > select nodes > add.

• Here select opposite side node carefully, it should exact opposite with object symmetry.
• Now deploy spring connection between nodes,

Go to 1D > Spring >Spring2 > Select nodes

• Create different collector for this intrusion spring so that we can assign property for this spring.
• Now create property card for intrusion spring.

• Select as P4 spring and mass value as 1gm and stiffness 1N/mm.
• Also assign this property to the intrusion spring collector.

11.Create sections on Driver seat rail and middle rail.

• we are creating sections to analyze the amount of force is travelling from that region.

• Select nodes in a way that the frame z axis should come perpendicular to global co-ordinate system.

• Frame is created now.

Now affter frane we will create section,

• We can select the N1,N2 and N3 in the same way we selected the nodes for frame.
• Then we can see the red blu and green arrrow which is showing the section plane.
• Then in frame id select the frame which we have created erlier.
• Now select the elements in region where we are going to create section, for that right click on gshell_id and create and edit and select elements.
• Put the factors value of deltaT=0.001 and alpha=0.67.

• Hit on proceed and we can see the section is created successfully.
• Now we can review this section.
• Now simmilarly we will create frame and sections for right shotgun, for rails according to the node id given and for Apiller and for bumper as well.

12.Output Request:

a).TH for Sectional force in the cross member.

• Select all sections we had created.

b).Now request for TH file for intrusion spring at B pillar,hinge pillar and fuel tank region.

c).TH for Peak velocity of inner node of the door.

• After selecting the node, define the node type as default.

12.Find connectivity-

• select all component to find connectivity.
• Then check or run.

• Since it showing some free part.

• so we can isolate them indivisulay and work on it.

• Give connectivity.
• Give rigid type connection here which is RBody connection.
• Go to 1D>rigids>RBody> select nodes.

• Now run or check the model checker agian and it will show group of connected part only.

14.Perform model checker.

• Now run the model checker.

• It will some groups of warnings,Null and unused sets.

• We can delete unused sets from Tools>unused> select all unused sets>delete.
• Go for delete the unused sets again and again untill it will show no unused enetity found.

• Simmilarly go for deleting empty sets.

• Select all empty sets.

• Go for delete the empty sets again and again untill it will show no empty enetity found.

Now run model checker again,

warnings will show which we can ignore.

Run the simulation:

• To run the simulation go to Analysis > Radioss.

• After clicking Radioss click on input file and save it in new folder as Test-1 as shown below figure.
• Check the include connectors and option as -nt 4.
• N indicated the how many cores will involve to run the simulation.
• It will make simulation faster.

• After that click on Radioss it will start the simulation.
• And wait untill the new window popup and show as Radioss job completed.\
• After running the simulation we will get animation file, h3d file and also T01 file.
• Check for all the files.

• Now open 0001.out file and check all the details.
• Here we can see all variable in the out file about energy error and mass error also.
• So for checking the maximum loss check the last cycle details.

• Here in in last cycle of the simulation we have maximum energy losses where,

Energy error = -2.3 % Acceptable (Range is -15% to +5%)

Mass Error = 0 Acceptable (Range is 0 to 2%)

So the resultent energies are,

1. Internal Energy 7305
2. Kinetic Energy 0.1985E+5
3. External work -133.4
4. No of cycles 340400

Post processing-

• Review the simulation using Hyperview.
• Plot the graphs using Hypergraph-2D

1.Review the simulation using Hyperview.

Split the screen in two part-

• Now after splitting the sreen open hyperview after switching into in 2nd screen.

• In hypergraph window import the h3d file for simulation run.

Animation-

• Now after importing the h3d file on hyperview GUI go for contour activation.
• In contour it will show the simulation graphically and contour lines of load and other properties variation.
• To activate contour go to Tool bar > contour as shown below.
• Go to Contour > Displacement > apply contour.

• simillarly for Von-mises:

• According to simulation we can see that when car impact on pole then firstly force is coming to structural body is out pert of gate then b-pillar.And then it transfer continuously from inner rails to crossectional rails of BIW.
• As the force is transfering throught the body in y-dircetion the amount of force is going to decrease cause at every stage some amount of force going to absorb in every stage.
• From above simulation we can see that the stress distribution over the BIW is somewhat fine, very less area with stress concentration.
• Since this BIW body doesn't have any CCB assembly,engine assembly,chessis system ect. So the deformation will be different from actual car body.

Now check for intrusion-

• After running the simulation check for intrusion.
• Maximum intrusion allowed is 15 cm (150mm).
• Check intial length of the springs and final length means at the end cycle of simulation.

For Fuel tank intrusion-

• Initially magnitude was 1319.712 and final is 944.078,
• Which means intrusion is 1319.712-944.078=375.634 mm

For B-pillar intrusion-

• Initially magnitude was 1312.538 and final is 951.750.
• Which means intrusion is 1312.538-951.750=360.788mm.

For hing pillar intrusion-

• Initially magnitude was 1311.792 and final is 1189.765,
• Which means intrusion is 1311.792- 1189.765=122.07mm

2. Plot the graphs using Hypergraph-2D

• Now split the window in 3Part and open hypergraph-2D in new window.
• After opening the hypergraph windoe import the T01 file in Hypergraph.

First we will plot the graph which we have requested,

A).Section forces-

1.Seat rail-

• In the direction of velocity we have two main section rail.
• On those two we will draw graph of amount of force coming.

• In seat rail section force obtained is 11.3529 KN.

2.Mid rail-

• In mid rail sectional force obtained is 4.14KN.

B).Intrusion graphs-

• Here we will see lot of intrusion in spring deployed on different section.
• It is because of here in this model lot of structural parts are missing, mainly CCB assembly,seating system, chessis part and additional rails.

Graph For Fuel tank intrusion-

• Intrusion in spring at location of fuel tank obtained is 372.932mm.

Graph For B-pillar intrusion-

• Intrusion in spring at location of B-pillar obtained is 358.26mm.

Graph hinge pillar tank intrusion-

• Intrusion in spring at location of hinge pillar obtained is 120.22mm.

C).Peak velocity graph-

• In peak velocity graph we can see the velocity is about constant(8.94m/s) untill it impact to the pole.
• After the impact the velocity is decreases slightly due to folded deformation and then increaed little is because of inertia action of pole and car body.

D).Interface type-7 graph

• This graphis showing the force generated due to self contact with resepect to time.
• So the maximum amount of force generating due to sel contact is 23.0309KN.

E).Global Energies-

• Now we will study the energy variation throughout the simulation.
• Here is the cumulutive graphical variation of all type of energies involved in the simulation.

Internal Energy-

• At time t=0 internal energy will be zero, and as impact begins the amount of force causing the stress due to which starin start taking place and deformation happens.
• So due to deformation some internal energy will start storing whithin the body and keep increasing as defomartion increses in the body.

Kinetic Energy-

• Since we have given a initial velocity to the car body 0f 8.94m/s and car body itself having its mass so according to he kinetic energy formula.
• 1/2 mv^2 = 27973.26kJ(kilo joule)
• The value shown by graph below is less than calculated value is just because of energy error.

Contact Energy-

• Contact energy is due to self contact of FE elements of car body.
• So according to graph the maximum value of contact energy is 539.355KJ.

Hourglass Energy-

• Since we already used shell parametrs, inseat of thatwe observe some amount of hourglass energy.
• This hourgalss happenes in some region where goes below iven timestep of due to stress concentration in course mesh.
• For that we particularly work on that region to refine the the mesh.
• But here the value is 7.07489KJ less than 10% of the internal energy value(10% of 7277.67 is 727.767KJ).
• So this hourglass value is acceptable.

Total Energy-

• Total enrgy is combination of all energies present here,
• Maximum value of total energy is found 27926.9KJ.

Result-

• Mass balancing is done for the given BIW for final value of 700kg.
• Created Typ-7 Interface contact for BIW self contact.
• Created cylinderical rigid wall with friction value as given.
• Time step value is given for all type of elements and contacts.
• Initial velocity 8.94m/s is also given to the BIW body.
• Intrusion spring is created to measure the deformation of car in y-direction.
• All TH file requested for output and then run the model checker.
• Run the simulation and post-processed in hyperview and hypergraph.

Learning Outcome-

• In this challenege i came to know that how to balance mass in hypercrash.
• How to create cylinderical rigid wall for side pole crash.
• How to create interface contact and set all the required parameters.
• How to give initial velocity to car and time step values for brick shell and interface.
• How to request fo TH file which will be used in post-processing of the simulation.
• Learned how to create frame and section to determine sectional forces and its importance.
• Get to know what are standars use for crash analysis like FMVSS,Euro-Ncap etc.