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

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

Question:

Neon side 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 penetration and intersections.
  • Create rigid wall with friction 0.1 as per referance model.
  • Compare the model weight with the referance model and use added masses to reach target weight 700kg while getting CG about the required range.
  • Initial velocity as shown in picture.
  • Use model checker to ensure good quality.
  • Timestep :0.5 to 0.1 microseconds.
  • Run 80ms.

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.

Case set up and Execution:

Procedure:

  • Open the given 'neon_side_reduced_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 new Type 7 card with the below mentioned properties.

   

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

  • Create rigid cylinder with friction as 0.1, sliding as 2, diameter as 254mm and D_search as 1000.

  • Masses are added and we reach 699kg which is very close to our target weight 700kg while getting CG in the required range.

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

  • Now delete all the previous sections and create 2 new cross-sections as shown below.

 

  • Here we can see that the rigid cylinder, cross-sections and initial velocity are applied.

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

  • Now we run the model by clicking on radioss analysis.
  • After a successful run check for errors where energy error is -2.5% and mass error is 0.73%. 
  • We also get the .h3d animation file in Hyperview and .T01 file for plotting graphs in Hypergraph 2D.

Output requests:

Sectional force in cross member:

  • Cabin-reinforcement is cross-section1 and Mid-rail is cross-section2.

  • For mid-rail, peak force is 17kN at 23ms.
  • For cabin-reinforcement, the peak force is 10kN at 70ms.
  • Forces are less in cabin-reinforcement when compared with the mid-rail forces.

Intrusion at B pillar,hinge pillar and fuel tank region:

  • We can see that in (123428,124489) initially distance is 1327mm and then it decreased to 447mm.
  • Similarly in (123413,124207) distance reduced from 1316mm to 483mm.
  • Also in (123320,124183) distance reduced from 1310mm to 825mm.
  • Generally from a car safety point of view the lower the intrusion, the greater the safety. 

  • In the above 3 displacement plots the intrusions are: a)123320-hinge pillar is 710mm b)123413-B pillar is 300mm c)123428-fuel tank is 275mm
  • To reduce the fuel tank intrusion material with high stiffness and high energy absorbing capacity can be used. We can also use some extra material with more mass at that location.

Peak velocity of inner node of the door:

  • Initially, the peak velocity is 16kN till 5ms then it is reduced 4kN at 11ms and then fluctuates between 6kN and 3kN till 80ms.

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 a slight increase in hourglass energy but after a few ms it became constant.

Result and Conclusion:

  • COG location and mass of the car are very important.
  • Impact forces are very high at the beginning and then reduces gradually.
  • We observed major deformation happening and the mid-section of the car, which means more robust components and materials must be used at these locations.

Thus, the side crash analysis of a BIW car is successfully carried out using Hypermesh, Hypercrash, Radioss, Hyperview, and Hypergraph.


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