Roof crush simulation

OBJECTIVE:

To perform roof crush analysis in the given BIW model. The following case setup has to be done.

1. To do a transformation given below.

• A 180° rotation about the global z-axis
• A 5° rotation about the axis through axis AB
• A 25° rotation about the axis through axis AC
• A translation to put point A at global ( -3500.00, 584.822, 1343.06)

2. To create a interface as per the criteria given below

• Create a Type 7 contact interface between the impactor and the car
• choose an appropriate stiffness definition
• choose an appropriate minimum gap
• change the coefficient of friction to 0.2
• choose the appropriate friction penalty formulation
• Save the data from the interface to the time history file.

3. The following boundary conditions for suspension shock tower nodes and impactor are given below.

• Keep the suspension shock tower nodes locked in Z.

• The impactor assembly contains a spring attached for stability. Create a BCS collector to fix the free end of the spring.
• Create a moving SKEW to define the direction normal to the impactor’s face.
• Create a BCS collector to guide the master node of the impactor rigid body so that it is free to translate normal to the face of the impactor, but is fixed in all other DOFs.

4. The following imposed displacement has to be defined for the impactor

• Impose the velocity of the impactor starting from 0 mm/s at t = 0. The displacement of the impactor should be 200 mm @ 200 ms.
• Avoid abrupt changes in the acceleration of the impactor.

5. To give the following parameters in the engine file

• Use a constant nodal time step
• Print time history every 0.0001 seconds
• Solve for 200 ms
• Create an animation file every 0.005 seconds

6. To include the selected output in animation files

• Elemental Energy
• Elemental equivalent plastic strain
• Elemental hourglass energy
• Elemental von Mises stress
• Nodal added mass
• Turn on parallel arithmetic

7. To include the following control cards

• /ANALY card
• /DEF_SHELL card,
• /DEF_SOLID card, and
• /IOFLAG card
• /SPMD card
• /TITLE card

8. The following output requests are to be given.

• Run the model
• Plot force vs. displacement. Check that the FMVSS 216 target load of
47,000 N (= 3 * GVW) has been met.
• Plot the energy vs. time curves

CASE SETUP AND EXECUTION:

1. Go to Hypermesh>>User Profile: Radioss>>Import Solver Deck>>Import the given 0000.rad model and the impactor model

2. Go to Tools>>Rotate>>Nodes>>Select the appropriate N1,N2 values based on the case setup given. Base point is the master node of the impactor>>Give the necessary angles>>Rotate.

3. Go to Tools>>Translate>>Select the appropriate N1,N2 values based on the case setup given. Base point is the master node of the impactor>>Give the necessary distance value>>Translate. The final position of the impactor is shown in the figures below.

4. Go to Model>>Groups>>Create a new interface with TYPE 7 contact interface. Delete the rest of the interfaces which are present in the model except the newly created interface. In this case two interfaces has to be created. The first one is all the components in the car should be selected as master and slave. The second one is the components of impactor should be given as master and components of car must be given as slave. This is shown in the figure below.

5. Go to Tools>>Penetration Check>>Selection: Groups>>Check. This is shown in the figure below.

6. To keep the suspension tower nodes locked in z-direction go to 1D>>rigids>>elem type = RBE2>>multiple nodes>>calculate nodes>>select nodes by path>>give the necessary dof (uncheck dof3 and dof6)>>create. The figures are shown below.                           

7. Go to Solver>>Create>>Boundary Condition>>BCS>>Select the free end of the spring element>>Select the DOF's which needs to be arrested. Similarly create BCS card for impactor master node and for all the rigid body nodes (arrest all DOF's).

8. Go to Solver>>Skew>>Moving Skew>>Create a skew in such a way that the z-axis of the impactor faces towards the car. This is shown in the figure below.

9. Go to Solver>>Boundary Conditions>>Imposed Displacement and enter the parameters given below. Select the skew axis defined in the earlier step.

10. Go to Tools>>Model Checker>>Radioss Block>>ERROR>>Right Click>>Run. Check for errors in the model. If found read the error ID and rectify the errors.

11. Go to Model>>Cards>>ENG_ANIM_DT>>T_freq: 5. By doing this timestep is changed to 5 ms

12. Go to Model>>Cards>>ENG_RUN>>Tstop: 200. By doing this run time is changed to 200 ms.

13. Check if all the control cards given in the objective are present in the model.                          

14. Go to Solver>>TH>>Create>>Inter>>Select the group in which impactor and car is present.

15. Run the model checker once again to ensure that the case setup is error free.

16. Go to Analysis>>Radioss>>Save the file with a proper name>>options -nt 4>>include connectors>>Radioss.

RESULTS:

1. The Von-Mises stress contour is shown in the figure below.

From the above contour the maximum stress value obtained is 0.24 GPa at node ID 100015

2. The displacement contour is shown in the figure below.

3. The various energy plot against time is shown in the figure below.

From the above plot, it is clear that the total energy and kinetic energy increases with time. The hourglass energy remains zero due to Qeph element formulation.

4. The force vs displacement is shown in the figure below.

From the graph the maximum force obtained is 5.26 kN for a displacement of 171.08 mm.

CONCLUSION:

1. The given case setup is done according to the objective.

2. The output requests are shown as plots. Energy plot and force vs displacement plot is shown with the peak force values.

3. The maximum force obtained in the simulation is 5.26 kN for a displacement of 171.08 mm.

The FMVSS 216 target load of 47000 N is not reached here in this model because this is a reduced model and some elemental masses are missing from the exact numbers. So, the exact load is not reached.