Side pole-crash analysis of a reduced BIW model of Neon car using RADIOSS Solver.

=============================================================================================

The instructions for this assignment were as follows:

1. Check the unit system and either follow [Mg mm s] or [Kg mm ms].
2. Create an appropriate interface, friction 0.2, and recommended parameters.
3. Make sure of no penetration and intersections.
4. Create a rigid wall with friction 0.1 as per the reference model.
5. Compare the model weight with the reference model and use added masses to reach target weight 700kg while getting CG about the required range.
6. Initial velocity as shown in the picture.
7. Use model checker to ensure good quality.
8. Timestep :0.5 to 0.1 microseconds.
9. Run 80ms.
10. Request for the following results:
    
    1. Sectional force in the cross member.
    2. The intrusion at B pillar, hinge pillar, and fuel tank region. Provide recommendations on what can help to reduce Fuel tank intrusion.
    3. Peak velocity of the inner node of the door.

=============================================================================================

OBJECTIVE: To set up the Rigid Pole-side crash simulation of a Neon car model, in the RADIOSS solver deck and analyze the results as per the instructions given.

PROCEDURE:

1. Solver deck set-up
   1. Import the .rad file provided. Kg mm ms kN is taken as the units for this model. The .rad file contains the solver deck set-up for a reduced model of the Neon car. The Model has been reduced to only some essential parts in order to make it possible for the students to edit the deck in Hyperworks student edition which has node limitations.

      Fig 1. The reduced Neon car model

   2. We need to set up the deck as per the instructions.
   3. Create an interface type 7 for the impact. Use the recommended values for the interface. Note: We need to make sure to enable the Time history option for the defined contacts to have the results recorded in the .T01 file during the simulation. We can either enable it while defining the contacts or by going into the Time History tab and adding the necessary requests separately.

      Fig 2. Interface type 7 defined for the whole model

   4. Now we need to apply an initial velocity of 15.64mps which is equal to 35mph. The initial velocity was applied to all the parts of the model in the Global Y direction.

      Fig 3. Initial velocity defined for the model

   5. A rigid pole with diameter = 254mm was created perpendicular to the Global X-Y plane for the crash simulation.

      Fig 4. Rigid barrier created

   6. Aditional mass was added to the model at necessary locations for bringing the COG to an acceptable location on the model.

      Fig 5. COG after Mass balancing

   7. Circular sections were created on the floor cross members.

      Fig 6. Sections created

   8. The Dtmin values were defined by going into the DT_eltype_keyword_flag present under the engine tab in the Control cards.

      Fig 7. DTmin values for the analysis

   9. The run time was set as 80ms by editing the RUN option under the engine tab in the Control cards.
   10. We need to find intrusions at three locations. The intrusion at B pillar, hinge pillar, and fuel tank region are to be found. For this, we will be recording the Time history for nodes 123408, 123254, and 123228 located in the respective regions. For getting the intrusion values, we have to measure the relative displacement of these nodes with respect to nodes that are free from deformation(124402, 124248, and 124222). Thus, the TH, for the nodes have to be recorded with respect to moving frames with origins at 124402, 124248, and 124222 respectively.
   11. We also need to measure the velocity at node 337773. This is also done using an approach similar to (x) but in this case, the global system is sufficient.
   12. Intersection and penetration checks were conducted. No intersections or penetrations were detected by the model checker.

       Fig 8. Intersection/ penetration check

2. Result requests
   1. Go to the Time history menu and create the required TH requests. Make sure to include the intrusion nodes, the Rpole, the Interfaces, and the Sections.

      Fig 9. TH requests created

   2. In order to request for contour animations, we have to go to the anim_vect option under the engine tab in the control cards.

      Fig 10. Contours requests created

3. Model checker
   
   1. Now that we have completed the solver deck set-up, we need to check the model for any error by using the model checker in Hypercrash.
   2. The connectivity of the model was checked to see if there are any free parts. Three free parts were detected. These parts were connected using springs and the connectivity issue was solved. In addition to these parts, there were some other components which were not completely connected. Those issues were also solved by using springs to form connections.

      Fig 11. Connectivity check

   3. The model checker came up with no errors but 5 warnings. Most of the warnings were created due to the presence of node groups, surface groups that are not being used. These were suppressed to remove those warnings. The completed model now shows a warning for possible hourglass elements. This can be ignored.

      Fig 12. Model checker

   4. Export the completed solver deck to the target folder and run the analysis using the engine starter file in the Radioss solver manager.
   5. The engine input file shows the engine parameters set.

      Fig 13. Engine input file(0001.rad file)

   6. The run completed successfully with no errors and 5 warnings as shown in the Starter listing file.

      Fig 14. Starter listing file(0000.out file)

   7. The energy error and mass errors need to be checked in the Engine out file. An energy error of -1.4% and a mass error of ~0.82% were found which are acceptable.

      Fig 15. Energy error(1.4%) and mass error(0.8%)

   8. The run seems acceptable as the errors are within limits. So we can move on to Post-processing the results. Open the Results in Hyperview and Hypergraph and generate the necessary contours and plots respectively.

RESULTS:

1. Crash animation: The deformation on the left side of the car is more than the right side. The window glass can be seen shattering as we have modeled the material as brittle using the material law 27.

   Fig 16. Crash animation

2. Energy plots: The plots show a decrease in KE and an Increase in internal station energy after the occurrence of the impact. The total energy has stayed nearly constant throughout the run. The choice of Hourglass free shell element formulations have helped in keeping the hourglass energy to a very negligible value. The contact energy can be seen to have increased across the run time with the increasing amount of deformations imparted on the model and the resulting increase in contact between different parts.

   Fig 17. Energy vs time plots

3. The intrusion of B pillar, hinge pillar, and fuel tank region into the occupant space: The intrusions are measured by taking a node on each of these regions. The intrusions are measured as relative displacement of these nodes(123408, 123254, and 123228) with respect to nodes(124402, 124248, and 12222 respectively). The plot is generated from the TH data for the nodes. The intrusion recorded for the hinge pillar and fuel tank were 633.47 mm and 636.4 mm respectively and an intrusion of 837.02 mm was noted for the node on the B-pillar region.

   Fig 18. Intrusions of nodes 66695 and 66244

4. Vonmisses stress contour: A maximum of 0.34Gpa was recorded during the run time.
   

   Fig 19. Vonmisses stress contour

5. Velocity measured on the node 337773: The plot shows the velocity values recorded by from in the TH for node 337773. Peak velocity of 16.58 m/s was observed. The velocity of the door has reduced to ~1.9 mps towards the end of the simulation.

   Fig 20. Velocity vs time plots for node 337773

6. Rigid wall forces: The rigid wall experienced a maximum force of 66.33kN at 2.5ms. The forces can be seen to have reduced with run time.

   Fig 21. Rwall forces(kN)

7. Sectional forces on the Cross members: The forces are high at the beginning of the impact and decreases as the run progresses. In the end, the forces can be seen to rise again, this might be due to self impact. A maximum of 5.67kN and 5.11kN was recorded during the run time for cross members 1 and 2 respectively.

   Fig 22. Sectional forces on the Cross members(kN)

CONCLUSION:

1. The solver deck was set-up as per the instructions.
2. All necessary output requests were placed.
3. The simulation was run successfully with acceptable amounts of energy error(1.4%) and mass error(0.8%).
4. The sectional forces were plotted for both the cross members. The more sectional force was recorded on the cross member 1 compared to 2 which shows that cross member 1 transfers the majority of the force.
5. Intrusions were measured using nodes in the respective regions. The intrusions were calculated as 837.02mm, 633.476mm, and 636.401mm for B pillar, hinge pillar, and fuel tank region, respectively. Velocity on node 337773 was also recorded.
6. Thus, for increasing occupant safety, the cross members need to be made more robust.

Find the simulation files and results here.