Frontal Crash Analysis in the given BIW model using Radioss

OBJECTIVE:

To perform frontal 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 at node 174247
• Axial force received on the rails from bumper
• Shotgun cross sectional forces.
• A pillar cross section.
• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
• Intrusions on the dash wall 66695,66244.

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.

13. Go to Solver>>TH>>Node>>Enter the Node ID 66695 >>Select the corresponding skew axis. This is shown in the figure below.

14. Similarly create a TH card for Node ID 66244 and give the skew axis accordingly. This is done to calculate the peak velocity of the door.

15. Similarly create a TH card for Node ID 174247 to compute the sectional forces.

16. Go to Model>>Create>>Accelerometer. The accelerometer positions are shown in the figure below.

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

18. 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 0.4057 GPa is observed in the simulation runtime.

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

From the displacement plots, it is clear that maximum displacement obtained is 1258 mm at Node ID: 79904.

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 wall, the kinetic energy reduces due to resistance offered by the wall. 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 acceleration curves obtained near the base of B-Pillar is given below.

From the above graph, it can be concluded that for left hand side of the pillar, the maximum acceleration corresponds to 3.589 mm/ms^2 at time 77.5 ms

From the above graph, it can be concluded that for left hand side of the pillar, the maximum acceleration corresponds to 8.512 mm/ms^2 at time 56 ms 

4. The intrusions obtained in the nodes 66695 and 66244 are shown below.

From the above plot it is clear that resultant displacement value for node 66695 is 839.96 mm

From the above plot it is clear that resultant displacement value for node 66244 is 826.16 mm. 

5. The sectional forces obtained on A pillar is shown in the plot below.

From the above plot it is clear that section force is maximum in right hand side A-Pillar with a maximum value of 5.68 kN at 26.5 ms. The maximum value of sectional froce obtained in left hand side A-Pillar is 4.09 kN at 68 ms.

6. The cross sectional force obtained in shotgun is given in the plot below.

The peak value of force is obtained in left hand side of the shotgun with a value of 16.16kN at 36.5 ms. The maximum force obtained on the right hand side of shotgun is 7.84 kN at 25 ms.

6. The sectional forces obtained on the rails is given below.

From the above plot, it is clear that right hand side rails has taken up a large force with a peak value of 20.11 kN at 10.5 ms. The peak value for left hand side rails is 10.58 kN at 66.5 ms.

7. The sectional forces obtained on the bumper is given in the plot below.

From the above plot it is clear that the force taken by the left hand side bumper is more with a peak value of 10.37 kN at 23.5 ms. The peak value of force on right hand side bumper is 2.9 kN at 32 ms.

8. The sectional forces obtained in the node ID 174247 is 10.58 kN at 66.5 ms. This is calculated using the sectional forces in the left hand side rails. This is because this node was included in that section.

ERRORS ENCOUNTERED:

The error shown in the image above was obtained during the initial run of the simulation. This error arised due to creation of a new component without defining the material and property for that component.

The error is rectified by deleting the unnecessary components in the model file.

CONCLUSION:

1. The case setup was done as per the given criteria.

2. The necessary output requests cards are created and plotted.

3. The energy error and mass error obtained in the simulation are -1.8% and 0.012% which are well within the accepted range.

4. The sectional forces obtained at bumper, rails, A-Pillar and Shotgun are plotted and peak values are determined.

5. The resultant acceleration values are plotted as obtained near the B-Pillar.

6. The sectional force at node ID 174247 is calculated along with the sectional forces in left hand side rails.

7. The von-mises energy and displacement contour are shown in the results.

In overall scheme, the left hand side of the car has faced a large deformation compared to the right hand side. This is because the sectional forces obtained are higher for the left hand side.

Drive Link: https://drive.google.com/file/d/1hYC0iq3HY43jUlOXPoCxdrs8YMtaI12S/view?usp=sharing