Side Pole Crash Simulation Challenge

Side Crash Simulation

Aim

To perform side crash analysis on the given Dodge neon Biw model using Hypermesh and Radioss solver.

Setup Request

• 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 reference model.
• Compare the model weight with the reference model and use added masses to reach the target weight 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.

Output requests:

• 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

• The units can be checked by opening the neon_Side_reduced_000.rad file on any text editor.

• Since the given units are in Kg,mm and ms,we will follow these units when adding values in hypermesh
• Import the file to hypermesh.
• First, we need to increase the weight of the model to 700Kg while making sure its centre of gravity is in the desired range.
• We can view the cog coordinates using the tools->mass details->mass,cog and inertia.
• 
• 

• You can create a node at the given coordinates to visualize the location of the cog.
• Enable the solver browser with view->browsers->hypermes->solver
• Create new mass using admas and use type 1 mass.

• Create a set of nodes to and assign them in gmd_id.

• After mass addition, we check for penetrations and intersections.
• Go to Tools->penetration check

• Select all the components and run the check manager

Since there are no penetrations or intersections,it is fine to go to the next step.

Rigid Wall

• We need to create a cylindrical rigid wall to the side of the door.
• In solver browser, create->rwall->cyl

• According to the fmvss standards, https://www.nhtsa.gov/sites/nhtsa.gov/files/tp214p-01.pdf
• The diameter of the cylinder needs to be 254mm.

Interface

• For this simulation, we will be creating a type 7 node to surface interface for self contact.

• The recommended values for type 7 contact are

1. Igap=2
2. Idel=2
3. Inacti=6
4. Istf=4
5. Gapmin=0.5mm
6. Iform=0
7. Stmin=1Kn/mm

Initial Velocity

• In solver browser, create->Boundary Conditions->Inivel

• Create a set consisting of all nodes and add it to gmd_id.

Sections

• We need to create 2 sections at the cross members.

• For each section, it is necessary to create a moving frame at the location.

• Choose the nodes such that the resultant is similar to the global axis.

• Create a set of around 3-4 rows of elements for each section.

Intrusions

• To measure the intrusions, we will be creating springs between the node and the opposite side of the model.

• The deflection experienced by the spring will indicate the amount of intrusion experienced.

• Create a property card for the spring with a mass of 0.001kg and stiffness of 0.001

Output Files

• In the solver browser go to th and create the following output and add the appropriate entities
• For node, the node id is 337773.

Model Checker

• Tools->Model Checker->Radioss Block

• Run the model checker.

• No errors,only warnings in the model checker

• With this, it is ok to run the model on the radioss solver.

Post Processing

• Open the _0001.out file in notepad , to check energy and mass error

• The energy error and mass error are within acceptable values for further analysis.

• It can be seen that the b pillar takes initial impact and then transmits the forces to the cross members

Energy Graphs

• The kinetic energy at the start is high due to the initial velocity of the model.
• As time passes,the kinetic energy gets converted to internal energy and will eventually reach 0.
• The total energy of the system is almost constant at 84595 kg*mm/ms2
• It decreases a bit due to the energy loss which we can see in energy error.

• There is some hourglass energy due to the use of reduced integrated QEPH elements.
• Contact energy is the energy applied by the system to resist penetration of elements
• As the time progresses,due to larger deformations there are more elements in contact with each other, hence more contact energy to resist penetrations.

Rigid wall

• The rigid wall forces are 0 till the car collides with thte rigid wall after which they spike to 68.90kN.
• After this spike the force decreases to around 40kN.
• After around 25ms,it starts increasing by a bit.This is because,due to larger deformations, more elements come in contact with the rigid wall thus leading to minor spikes in the rigid wall forces

Sectional Forces

• It can be seen that the force distribution from the b pillar to the cross members is uneven
• This can be because the centre of gravity slightly favours the b pillars cross member
• It can also be because it is closer to the b pillar in comparison to the other cross beam.
• This leads to it having a much higher peak force of 5.8kN in comparison to the 1.05kN of the driver cross beam.
• The cross members along with the b-pillar,doorbar and support and,door outer and rocker are majorly involved to control and reduce deformations

Peak Velocity at Node 337773

• The velocity peaks at 16.16mm/ms shortly after the crash.
• After this there is a huge drop in velocity,with minor spikes which may be due to the larger deformations that occur due to inertia
• It is important to know this , as during a crash the inner portion of the door might deform excessively and injure passengers

Intrusions

• The red line is the intrusion at the B pillar which peaks at 953 mm and continues to increase.
• The blue line is the intrusion at the fuel tank region which peaks at 150mm.This is the minimum intrusion that is experienced in comparison to the other 2 points
• The blue line is the intrusion at the hinge pillar which peaks at 581mm.
• These intrusions can be reduced by using a stronger material like composites so that the weight increase can be minimized
• An alternative will be to add another crossbeam but the increase to cost and weight can be significant.

Result and conclusion

• The given fe model was set up for side crash analysis and the desired output blocks were created
• The cross members play an important role in force absorption and distribution
• Using a stronger material for them or by adding more cross beams to reinforce the region, it can be possible to further decrease the intrusions at these points
• However it should be noted that such changes can make significant difference in the weight and cost of manufacturing the model.
• Another option is to strengthen the B pillar as it is the initial point of impact.