Roof Crush Analysis on NEON Car Model

Aim-

• To perform the roof crash analysis on the Neon car model and study about deformation and stresses developed and energy distribution in the car components.

 

Objective -

• To translate the impactor to the desired location as per the question.
• To create a Type 7 contact interface between impactor and car.
• To create a boundary condition for the suspension shock tower and lock them in the Z direction.
• To create a moving SKEW to define the direction normal to the impactor.
• To create an impactor boundary condition.
• To apply an imposed displacement for the impactor.
• To create control cards.
• To set the termination time, nodal & element-time step.
• To request the output and run the simulation.
• To plot the graphs in the post-processing.

 

Theory-

• FMVSS 216, Roof Crush Resistance, establishes strength requirements for the passenger compartment roof of passenger cars, multipurpose passenger vehicles, trucks, and buses with a GVWR of 2722 kilograms or less.
• The purpose of the standard is to reduce deaths and injuries due to the crushing of the roof into the passenger compartment in rollover accidents.
• The prescribed static loading device is a rigid unyielding rectangular block 762 millimeters by 1,829 millimeters. It shall not move more than 127 millimeters to achieve the specified resistive load when applied to the forward edge of a vehicle’s roof.

 

 

 

 Procedure -

 

1. Import the model in hypermesh.

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

 

 

 

2. Check for units in Hypermeh:

Hypermesh

Go to Solver>cards>Begin card

 

3. Positioning Impactor over the Neon Car Properly

     (a)A 180° rotation about the global z-axis with the point opposite to C as base point 

 

              

 

                    

 

         (b) A 5° rotation about the axis through axis AB

                          

                   

 

        (c) A 25° rotation about the axis through axis AC

                   

 

                   

 

       (d) A translation to put point A at global ( -3500.00, 584.822, 1343.06)

                   

                   

                   

                   

                   

 

4. Check for initial penetration and intersection.

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

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

 

• After selecting, groups, hit on check it will show the result below.

• Here we can see that 0 collisions were found.

 

5. Create the Interfaces-

 A) Car and Impactor -

• Here for this model,TYPE 7 Contact Interface is created with the recommended parameters.To create interface,Right Click on Solver Browser >> Create >> Inter >> TYPE 7.
• First, we have to create Contact Interface for the Car and Impactor.

 

 

 

• Select the slave and master nodes by switching to the components and selecting all the car components for the slave. And for master nodes select all the components of Impactor.

 

 

 

B) Self Impact -

• The Type 7 Contact Interface for the Self Impact is created.

 

• Here for the self impact, Select the slave and master nodes by switching to the components and selecting all the car components for slave and master. 

 

 

 

 

6. Create Boundary Conditions for the Suspension -

• Here we have to create boundary conditions for the suspension shock tower.
• To create boundary conditions,Right Click on Solver Browser >> Create >> Boundary Conditions >> BCS

 

• Now we have to fix the Z-Direction [Constraint] for the suspension tower.
• To fix the Z-Direction of the suspension, We need to deploy a cluster of rigid connections on the suspension.
• To deploy a cluster rigid connections,Go to 1D Panel >> Rigids >> Create >> In Nodes 2-n option, Switch to Multiple Nodes >> In Primary Nodes Option,Switch to the Calculate Node >> Create.

 

• Constrain the Z-Direction of the suspension.

 

 

7. Create a BCS to Fix the Free End of the Spring -

 

• Here we have to create the boundary condition to fix the free end of the spring. 
• To create boundary conditions,Right Click on Solver Browser >> Create >> Boundary Conditions >> BCS

 

• Now select the free end of the spring.
• Now Constrain all the degree of freedom for the free end of the spring.

  

8. Create a Moving SKEW to Define the Direction Normal to the Impactor’s Face-

• Next, we have to create the boundary condition for the master node of the impactor.
• For that first, We want the impactor to move only in the perpendicular direction to the impactor.
• To give the boundary condition to the master node. We need to create a skew.
• To create a skew,Right Click on Solver Browser >> Create >> SKEW >> Mov.

 

 

 

 

• The skew created. 

 

 

9. Create a BCS to Guide the Master Node of the Impactor Rigid Body -

• Now we have to give the boundary condition to the master node of the impactor. 
• To give, we have to create a boundary condition and rename it as Impactor_Rigid_Master_Node.
• After creating the boundary condition, Select the master node of the impactor.

 

 

• Now constraint all the DOF apart from the Z-Axis.

• Next, select the skew in the skew ID.

 

10. Give the Imposed Displacement to the Impactor-

• To give the imposed displacement to the impactor. We have to create the boundary condition. 
• After creating the imposed displacement, we have to select the impactor master node.
• To select the impactor node,Below the Parameter Window >> Right Click on gmd_ID >> Create Edit >> Enitiy ID >> Select the Node >> Proceed

 

 

 

• Next, we have to create the curve to assign.
• So we want to impose the velocity of the impactor starting from 0 mm/s at t = 0 and the displacement of the impactor should be 200 mm at 200 ms.
• So we have to create a curve. To create the curve, Go to the Model Browser >> Create >> Curve.

 

 

 

 

 

• Now assign this curve to the imposed displacement,To aasign,Go to the fct_ID(T) >> Click on Curve >> A Window Will Pop Up >> Select the Curve >> Ok.

 

 

• Now Select the skew to move the impactor according to the skew.

 

11. Create Missing Control Cards-

 

 

• After creating the control cards, The Necessary control cards are shown below.

 

 

 12. Output Request-

• TH created for all the required files. 

 

13. Checks-

• Finally, After doing all the load case setup, We have to check for the errors, Whether every load case setup is fine or not.
• To check,Go to Tools >> Model Checker >> Radioss Block.

 

• Next, the model checker window will be open.
• There right-click on the browser and click run or hit on the green checkmark in the window, which will run and identify if the error exists in the model load case setup.

 

•  No errors Found.

 

Check for Connectivity-

• To check for the connectivity,Go to Tools >> Find Connectivity >> Window Pop-Up >> Below Parameter Window >> Select all Components >> Check.

 

 

• After checking connectivity for the model, The software will throw the free parts which are not connected.

 

• To connect the free parts,Go to 1D Panel >> Rigids >> Create >> In Nodes 2-n option, Switch to Multiple Nodes >> In Primary Nodes Option,Switch to the Calculate Node >> Create.

 

 

• Connected the free part with rigid connections.
• Similarly, connect all the free parts with rigid connections.

[Note: Don't connect free parts with cluster rbe2 elements, it will affect your energy error]

 

Run the simulation:

• To run the simulation go to Analysis > Radioss.

• After that click on Radioss, it will start the simulation.
• And wait until the new window popup and show as Radioss job completed.
• After running the simulation we will get the animation file, h3d file, and also the T01 file.
• Check for all the files.
• Now open 0001.out file and check all the details. 
• Here we can see all variables in the out file about energy error and mass error also.
• So for checking the maximum loss check the last cycle details.

 

 

 

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

Energy error  = -11.3 %     Acceptable     (Range is -15% to +5%)

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

So the resultant energies are,

1. Internal Energy       387.1
2. Kinetic Energy         53.05
3. External work          497
4. No of cycles             1126614

 

Result Plots-

• 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 screen open hyper view after switching into in 2nd screen.

• In Hyper View, the window import the h3d file for a simulation run.

 

 

 

 Animation-

 

 

• Now after importing the h3d file on hyper view 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 Toolbar > contour as shown below.
• Go to Contour > Displacement > apply contour.

 

 

• Here the contour plot gives the stress-induced at each node in the BIW model of the car.
• As the impactor hits the car roof, internal stress is developed in the model due to the material behavior.

 

 

 

 Similarly, the Plastic strain Simulation has shown below.

 

 

Plot the graphs using Hypergraph-2D

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

First, we will plot the graph which we have requested,

 

 

Interface Car and Impactor-

 

 

• Here the interfaces curve starts from origin and reaches peak due to collision.
• And it goes on increasing due to the contact within the car, When the roof comes and hits the car, it goes on increasing.

 

Interface Self Contact-

 

 

• Here the interfaces curve starts from origin and reaches peak due to collision.
• The maximum total resultant force obtained is 16.9145 KN.

 

Impactor Spring-

 

 

Global Energies-

• Now we will study the energy variation throughout the simulation.
• Here is the cumulative graphical variation of all types 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 strain starts taking place and deformation happens.
• So due to deformation some internal energy will start storing within the body and keep increasing as deformation increases in the body.

kinetic Energy- 

• The value shown by the graph below is less than the calculated value is just because of energy error. 

Contact Energy- 

• Contact energy is due to the self contact of FE elements of the car body.
• So according to the graph, the maximum value of contact energy is 54.3428KJ.

Hourglass Energy- 

• Since we already used shell parameters, instead of that we observe some amount of hourglass energy.
• This hourglass happens in some region where goes below the given timestep due to stress concentration in the coarse mesh.
• For that, we particularly work on that region to refine the mesh.
• But here the value is 0.1291KJ less than 10% of the internal energy value(10% of 386.635 is 38.66KJ).
• So this hourglass value is acceptable.

Total Energy- 

• The total energy is the combination of all energies present here,
• The maximum value of total energy is found at 439.63KJ.

 

 

 

Force vs Displacement -

• We have to plot the Force vs Displacement, To plot, First, we have to plot the displacement graph.
• To plot the displacement graph, Go to HyperView >> Build Plot.

 

 

• Check the FMVSS 216 target load of 47,000 N (= 3 * GVW) has been met.

 

 

• To convert it into the weight, We should consider the gravitational force. Therefore, the GVW value will be 1,715.2657 N.

        Load=3xGVW

        Load=3x1715.2657

        Load=1,715.2657N

• The target load given is 47000 N but the load attained here is 10% (1715.2657) of the target load. 

 

Result-

• Hence the Impactor has been positioned according to the given axis.
• Hence the two interfaces created for the self impact, car and impactor.
• Hence the Boundary Condition created and locked the two nodes of Z-Axis for the suspension tower.
• Hence the Boundary Condition was created to fix the free end of the spring.
• Hence the Boundary Condition was created to guide the master node of the impactor rigid body.
• Hence the Imposed Displacement is given to the Impactor.
• Hence all the necessary control cards were created.
• Hence the simulation was run successfully without any errors.

 

 Learning Outcome-

• Learned about the roof crash test.
• Learned to create boundary conditions.
• Learned to create imposed displacement.
• Learned to create cross plots.
• Learned about the FMVSS [Federal Motor Vehicle Saftey Standards]