Side Crash simulation of a Dummy car model using Radioss

OBJECTIVE

Perform a side crash simulation for the given model.

+

Follow the below instructions in setting up the case

• Check unit system and either follow [Mg mm s] or [Kg mm ms].
• Create an appropriate interface, friction 0.2, and recommended parameters.
• Make sure of no penetration and intersections.
• Create a rigid wall with friction 0.1 as per the reference model.
• Compare the model weight with the reference model and use added masses to reach the target weight of 700kg while getting CG about the required range.
• Initial velocity as shown in the picture.
• Use a model checker to ensure good quality.
• Timestep :0.5 to 0.1 microseconds.
• Run 80ms.

The outputs required from the simulation are as follows

• Sectional force in the cross member.
• The intrusion at B pillar, hinge pillar, and fuel tank region. Provide recommendations on what can help to reduce Fuel tank intrusion.
• Peak velocity of the inner node of the door.

PROCEDURE

Step 1 - Model Cleanup

• Since the model is a raw cut out from a larger model, there are few unwanted entities like joints, interfaces, surfaces, nodes, etc. The first step is to identify these elements and delete them if not required.
• Hypermesh -> Tools -> Empty -> select -> delete = to see the empty entities and select and delete.
• Hypermesh -> Tools -> Unused = unused entities in the model, select and delete
  
  

Step 2 - Interface deletion

• Since the model is a cutout from the larger model, the older interfaces are still defined. Which is not required for our current study, so delete these interfaces
• Hypermesh -> Solver -> Interface -> select all (6 interfaces are defined previously) -> delete
  
  

Step 3 - Define interface /contact

• Since we are targeting the frontal crash simulation against a rigid wall, we only have to define a self contact card.
• Type 7 contact card is defined with the recommended parameters from crash applications.
• Hypermesh -> Solver -> Interface -> Type 7
  
  

Step 4 - Mass addition

• Target mass = 700 kg and COG should be somewhere around the line of B-Pillar and bottom rail. Mass is added accordingly
• Hypermesh -> Solver -> Admas -> select the nodes and mass to be added.
  
  
  
  

Step 5 - Boundary condition

• the only boundary condition is initial velocity i.e. 35 mph or 15.6464 mm/ms
• Hypermesh -> Solver -> Boundary condition -> INIVEL -> define parameters.
  
  

Step 6 - Rigid Wall

• Here since we are replicating a side impact to the pole, we will use a cylindrical pole as a rigid wall.
• Hypermesh -> Solver -> RWall -> Cyl -> select base point and normal direction
  
  

Step 7 - Section Creation

• It is important to check the forces in the sections to determine if the simulation is correct or not. Few sections are created across the model on both the sides
• Hypermesh -> Solver -> Section -> select the reference nodes -> Create a local frame -> select 2 rows of elements
• A total of 2 sections were created as shown below
  
  

Step 8 - Output Blocks

• After creating all the sections, we require the output from these entities. For this purpose, output blocks are defined stating what all results are to be extracted.
• Hypermesh -> Model -> Output Blocks -> select cross sections -> assign necessary output requests

Step 9 - Intrusions

• A local skew was created on a center rail using Hypermesh -> Solver -> Skew -> Mov
• Hypermesh -> Model -> Output blocks -> select nodes -> assign necessary output requests (force, velocity, displacement).
• For the velocity nodes, two nodes on each door are selected. For intrusion, node on fuel tank, B-pillar and Hine pillar are selected
  
  
  

Step 10 - Model Checker

• Hypermesh -> Tools -> Model Checker -> Radioss Block or Hypercrash -> Quality -> Model Checker
  
  

Step 11 - Check Initial Penetration / Intersection

• Hypercrash -> Interface -> Run check
  
  

Step 12 - Run the simulation

• Hypermesh -> Analysis -> Radioss

Step 13 - Evaluate the results and verify them

• Evaluate the results using Hyperview or Hypergraph.
• Check energy and mass error in the simulation.
  
  

RESULTS

Based on the simulation performed, the following results are extracted

• Energy and Mass Error
  
  The error in energy and mass are withing acceptable limits which shows that there is no unwanted behavior taking place during the simulation
  
  
  
  
• Energy
  
  Total energy remains almost constant, whereas the decrease in kinetic energy is equal to the increase in internal energy depicting the correct transfer of energy.
  
  
  
  
• Stress
  
  
  
  
• Displacement
  
  
  
  
• Cross-Sectional Force (kN)
  
  
  
  
• Intrusion
  
  123388 - Front pillar node
  123409 - B-pillar node
  123362 - Fuel tank node
  
  
  
  
  In order to minimize the intrusions in fuel tank, proper reinforcement within the tank it around the tank maybe provide such that it doesn't add any additional complex design changes or extra cost. Alternatively proper cushion may also be provided in front of the tank to absorb majority of the crash load.
  
  
• Velocity
  
  338460 - front door node
  376192 - rear door node
  
  
  

CONCLUSION

The study helps us understand the typical process used in determining the side crash simulation. It helps us understand different outputs that need to be checked for an assessment of crash simulation results.