Frontal crash analysis of a BIW car using Hypermesh Hypercrash Radioss Hyperview and Hypergraph

Objective: To perform frontal crash analysis on the given model and obtain the required output requests.

Question:

Frontal crash-BIW:

  • Check unit system and either follow[Mg mm s] or [Kg mm ms].
  • Create appropriate interface ,friction 0.2 and recommended parameters.
  • Make sure of no penetrations and intersection.
  • Correct rigid bodies if any issues.
  • Create rigid wall with friction 0.1.
  • Compare the model weight with the full scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
  • Initial velocity 35 mph.
  • Use model checker to ensure good quality.
  • Timestep :0.5 to 0.1 microseconds.
  • Run 80ms.

Output requests:

  • Sectional force in the rails at location of indicated node 174247.
  • Axial force received on the rails from bumber.
  • Shotgun cross sectional foces.
  • 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 set up and Execution:

Procedure:

  • Open the given 'neon_front_0000.rad' file in Hypermesh and Hypercrash.
  • Keep the unit system as 'kN mm ms kg' in Hypercrash.
  • Run the model checker in Hypercrash and do the changes in Hypermesh and make sure that there are no penetrations and intersections.
  • Now delete all the previous interfaces and create 2 new Type 7 cards with the mentioned properties.

   

  • Now assign the slave nodes and master surface as shown below.

  • Create rigid wall with friction as 0.1, sliding as 2, and Dsearch as 1000.

  • Masses are added and we reach 678kg which is close to our target weight 700kg while getting CG about the line of the passenger which is in the required range.

  • The initial velocity of 35kmph is assigned which is 15.64 mm/ms.

  • Here we can see that the rigid wall and initial velocity are applied.

  • The timestep has been set to the following parameters and run time to 80 ms.

  • For finding the sectional forces, accelerations, and intrusions, nodes are added to the output block.

 

  • Below are the images showing acceleration sensors, rail cross-section, A-pillar cross-section, and shotgun cross-section.

  

  • Now we run the model by clicking on radioss analysis.
  • After a successful run check for errors where energy error is -2.7% and mass error is 0.0%. 
  • We also get the .h3d animation file in Hyperview and .T01 file for plotting graphs in Hypergraph 2D.

Output requests:

  • Sectional force in the rails at location of indicated node 174247.

  • In the above plot, we can observe that the max force is approx 22.5kN at 15ms.
  • In the below plot we see the resultant displacement and resultant velocity at node 174247.

  • Axial force received on the rails from bumper.
  • In the below plot peak force is approx 42kN at 15ms.

  • Shotgun cross sectional foces.
  • In below plot we see that initially right shotgun experiences high force then as time passes force on right shotgun decreases and force on left shotgun starts increasing.

  • A pillar cross section.
  • In below plot we can see that right pillar experiences more force than left pillar but the forces are very less when compared with the shotgun and bumper forces.
  • The result of less force maybe be because during crash first bumper hits the object where there is high force and then gradually decreases as the energy dissipates.

  • Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
  • In below graph we can see that initially on impact the acceleration is high but then gradually decreases after the impact.

  • Intrusions on the dash wall 66695,66244.
  • We can see that in (66695,121751) initially distance is 741mm and then it decreased to 573mm.
  • Similarly in (66244,122048) distance reduced from 782mm to 618mm.
  • Generally from a car safety point of view the lower the intrusion, the greater the safety. 

 

  • Energy curve plots.
  • We know that K.E. coverts to I.E. during the crash as elements get deformed and absorbs the energy.
  • If more energy is absorbed then fewer elements will get deformed which increases the safety of the car. 

  • Contact energy keeps on increasing.
  • Initially, there was an increase in hourglass energy but after few ms it became constant.

Result and Conclusion:

  • COG location and mass of the car are very important.
  • More forces are observed on the left side of the car.
  • Maximum forces are transferred to rails and shotgun components which implies that these components must be made robust.

Thus, all the points mentioned in the objective were successfully carried out using Hypermesh, Hypercrash, Radioss, Hyperview, and Hypergraph.


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