Side Crash Analysis in the given BIW model using Radioss

OBJECTIVE:

To perform side crash analysis in the given BIW model. The following parameters are to be done in the model.

• To check unit system and either follow [Mg mm s] or [Kg mm ms].
• To create appropriate interface ,friction 0.2 and recommended parameters.
• To check for penetration and intersections.
• to create a rigid wall with friction 0.1 as per reference model.
• To compare the model weight with the referance model and use added masses to reach target weight 700kg while getting CG about the required range.
• To given an initial velocity of 35 mph
• To use model checker to ensure good quality.
• To change the timestep within 0.5 to 0.1 microseconds.
• To run the simulaton for 80ms.

The output requests are as follows:

• 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.

CASE SETUP AND EXECUTION:

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

2. Go to Model>>Cards>>Begin_Card. Check the unit system. The unit system is Kg, mm and ms. This is shown in the figure below.

3. 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. This is shown in the figure below.

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

5. Go to Model>>Create>>Rigid Wall>>Friction: Sliding Friction: 0.1. The parameters are given as per the figure shown below.

6. To get the COG point the initial COG point is plotted using temp nodes. The coordinates of the COG point is obtained from the Tools>>Mass Details>>Mass, COG and Inertia. The mass to be added is calculated and after viewing in the Mass Details. Go to Model>>Solver Masses>>Create. The masses are to be added to obtain the COG position shown in the figures below.

7. Go to Solver>>Create>>INIVEL Card>>Convert the 35 mph to the given unit system which is  15.64 mm/ms

8. 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.

9. Go to Model>>Cards>>ENG_ANIM_DT>>T_freq: 0.5. By doing this timestep is changed to 0.5 microseconds.

10. Go to Model>>Cards>>ENG_RUN>>Tstop: 80. By doing this run time is changed to 80 ms.

11. Go to Model>>Create>>Cross-Section>>Give the values given below for create a section in cross-section.

12. For calculating intrusions, local skew is defined at the nodes opposite to the nodes given below. Go to Solver>>Create>>Skew>>Moving Skew.

For fuel tank = Node ID: 123561. Local Moving Skew Axis to be defined opposite to this node

For B Pillar = Node ID: 123475. Local Moving Skew Axis to be defined opposite to this node

For fuel tank = Node ID: 1240 . Local Moving Skew Axis to be defined opposite to this node

13. Go to Solver>>TH>>Node>>Enter the Node ID given above>>Select the corresponding skew axis. This is shown in the figure below.

14. Similarly create a TH card for Node ID 337773 and give the skew axis accordingly. This is done to calculate the peak velocity of the door.

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>>Radioss.

RESULTS:

1. The following results are obtained for Von-Mises Stress.

From the results it can be concluded that maximum stress is 0.3884 GPa is observed in the simulation runtime.

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

From the displacement contour, it is clear that maximum displacement obtained is 1542 mm at Node ID: 190233.

3. The energy plots are shown in the figures below.

Initially, the internal energy is zero and kinetic energy is at maximum values. After the start of the simulation, due to impact of car against the pole, the kinetic energy reduces due to resistance offered by the pole. Internal energy increases due to conservation of energy. (Crash energy is included)

From the above plot, it can be concluded that hourglass energy remains zero due to Qeph element formulation. The contact energy slightly increases during the run time. This is because due to deformation of elements there will be contact happening between the elements. This is captured in the plot.

3. The following intursions are obtained across various members.

From the above plots, the maximum displacement observed for hinge, B Pillar and Fuel tank is found to be 1055 mm, 215 mm, 189 mm at 79.5 ms respectively.

4. The peak velocity plot obtained for inner node of the door is given below.

From the above plot, it is clear that the peak velocity obtained is 16.85 mm/ms at 3 ms at the inner node of the door.

 5. The rigid wall force plot is shown below.

As shown above, the peak value of resultant normal force is 72.109 kN at 3 ms.

6. The sectional forces for various cross members is given below.

From the plot above, it can be deduced that during initial runtime the sectional forces considerably increases followed by steady plots. During the end there is a spike in the values which is due to self collision of elements. The maximum value of sectional forces obtained are 3.773 kN and 2.654 kN in cross member 1 and 2 respectively.

CONCLUSION:

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

2. The output requests are done according to the objective.

3. The energy error and mass error were found to be 

4. The Von-Mises stress contour is plotted and maximum stress obtained is 0.3884 GPa

5. The maximum displacement value is 1542 mm at node ID 190233

6. The cross sectional forces are plotted for the two cross members and maximum value of force is obtained as 3.773 kN in cross member 1 

7. The peak velocity of inner node of the door is found to be 16.85 mm/ms

8. The intrusions for Hinge, B-Pillar and fuel tank are plotted and maximum displacement was observed for hinge.

RECOMMENDATION TO REDUCE FUEL TANK INTRUSION:

1. By adding anti intrusion bars in the door strengthens the assembly, there causing less deformation during side crash.

2. By adding cross members near the fuel tank reduces the intrusions.

3. By changing the material of the fuel tank or B-Pillar helps us to get a lower intrusion value. For example, high quality steel with considerable strength avoids the problem but the drawback is that it increases the mass.

Drive Link: https://drive.google.com/file/d/1v1QQP-pOvMRuJnyuGPYCc9q-AlRZ_Z9U/view?usp=sharing