Assignment 7

SIDE CRASH ANALYSIS OF CHRYSLER NEON 2001 INTO A POLE

OBJECTIVES :

        To perform a side crash analysis of Chrysler Neon 2001 into a pole.

 Output Requests :

• 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.

PROCEDURE :

     1. Import the Chrysler Neon model into Hypermesh under Radioss profile. The unit system followed is Kg mm ms KN. Since the HyperCrash student version could not process more than 10K nodes,which has better user interface for crash applications, we follow the similar procedure in Radioss. 

         FIG 1 : REDUCED FE MODEL FOR STUDENTS VERSION (< 100K NODES)

    2.  As per recommended values, QEPH elements are used to avoid Hourglass errors and negligible contact error.The material used and properties are :

   3. Create a Type 7 contact interface for the entire structure. Since Hypercrash can handle only 10K nodes, it is impossible to run export the model. Hypercrash has better user interface for crash analysis. Create TH for interface.

    4. Create rigid wall with cylindrical pole of radius 254mm, friction 0.1. Create TH for rigidwall.

    5. Create Sections at cross rail members. Create TH for each sections.

    6. Create moving skews at B-pillar rockers on the right to create axis for intrusion points at  B pillar,hinge pillar and fuel tank region. Create TH for nodes at the B pillar,hinge pillar and fuel tank region and assign them their local skews.

    7. Create TH for a node(337773) on the inner side of Left Front door to find Peak velocity and Assign the local moving skew.

    8. Assign initial velocity 15.64mm/ms(35mph) for entire nodes in y-axis.

    9. Add Mass to the model to reach target 700kg using ADMAS card on solver browser while maintaining COG point at desired location.

    10. Run the Model Checker and correct the errors.

    11. Time-step :0.5 to 0.1 microseconds. Run 80 ms.

    12. Run the simulation Analysis > Radioss with -nt 4.

    13. The energy error is -1.3% and mass error is 0.5813E-02, so the simulation is acceptable. No. of cycles is 80001. Time taken is 2805.87 s. Also there is no sudden jump in values.

          INITIAL TIME STEP. . . . . . . . . . . . . . . . 0.000000
          MAXIMUM TIME STEP. . . . . . . . . . . . . . . . 0.1000000E+31 

    14. Open Hyperview and run .h3d file.

     15. Create contour with Von misses Stress.

     16. The Displacement contour.

      17. Switch to Hypergraph. Plot for Energies and Time.    

      The Total energy is 85000J and remains stable. When the car moves there is only Kinetic energy and decreases when it hits the rigid pole ,there would be sharp rise in internal energy. The Internal energy rises to 20000J for 80ms of simulation. Kinetic energy is at 60000J at end of 80ms. Some of the energy gets dissipated during the crash and transferred to rigid pole.

      Contact energy and Hourglass energy are negligible.

    18. Plot Total resultant force acting on body and check with simulation.

     19. Total Resultant force acting on Rigid wall.

     The peak resultant force acting on rigid wall is 68KN during 5ms of simulation.

     20. Plot the Total resultant forces acting on cross member 1 &2.

      The crossmembers play an important role in absorbing maximum crash from the side. It is evident that crossmember rail1 is more stiffer than crossmember rail2. Also the pole crashes linearly towards crossmember2 so more load is natually observed in it..

     21. Intrusions acting on B pillar(123255) ,hinge pillar(123475) and fuel tank region(123228). These regions are more important for passenger safety.

     The Displacement curves acting on 3 regions is taken into account seperately and their intrusion are measured.

    22. Peak velocity acting on inner node(337773) of the door.

     The velocity curve acting on the node is plotted. The Velocity of node attains peak value at 10ms and experience a sudden drop.

LINK FOR SIDE CRASH FILES :   https://drive.google.com/drive/folders/1E_ZQj21zB08AICqYK-WvfafphhK5FnnJ?usp=sharing

CONCLUSION :

     The initial velocity applied to the car body in Y-direction at 15.64mm/ms(35mph).

     No Errors throwed by Model Checker and recommended material property values are used to avoid hourglass error. 

     1. Maximum Sectional force in the rails at location of crossmember rail1 is 0.2 KN during 70-75ms of simulation.

     2. Maximum Sectional force in the rails at location of crossmember rail2 is 0.8 KN during 70-75ms of simulation.

     3. The intrusion at B-pillar as information obtained from graph,              1340 - 600 = 740 mm for 80ms of simulation.

     4. The intrusion at Hinge pillar as information obtained from graph,        1347 - 375 = 972 mm for 80ms of simulation.

     5. The intrusion at Fuel tank region as information obtained from graph, 1346 - 213 = 1133 mm for 80ms of simulation.

•     The Fuel Tank can be covered by an High Density material and cross members can be added to the left and right sides to reduce intrusions.

     6. Peak velocity acting on inner node(337773) of the door is 16 mm/ms at 10ms of simulation and decreases to 1mm/ms at the end of 80ms.