Side pole crash simulation of Dodge Neon BIW using RADIOSS

AIM: Car Sidecrash simulation of Dodge Neon BIW using RADIOSS.

OBJECTIVE: These are the following requirements for this project.

Setup Request:

• Check the 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 700kg while getting CG about the required range.
• The initial velocity of 35 mph.
• Use 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.

METHODOLOGY:

1. Import the model into Radioss/ Hypercrash.
2. Setup the boundary conditions as per given.
3. Remove all the unwanted and used components, property cards, sets, groups, joints, etc.
4. Check for penetration and intersections
5. Setup the output request and check the necessary card status eg. ANIM/DT, ENGINE_RUN, etc.
6. Run the model checker and debug the errors and warnings.
7. Generate the Radioss file for animation and time history plots.

INTRODUCTION:

In different parts of the world, there are several vehicle safety assessment programs that perform crash test in order to increase vehicle safety and ensure that vehicle has good occupant and pedestrians safety. These programs focus on improving the crashworthiness of motor passenger vehicles and reduce the number of injuries. In Europe, there is the New Car Assessment Program (NCAP), based on the program introduced in 1979 by the NHTSA (National Highway Traffic Safety Administration) in the USA. the Euro NCAP frontal crash test standards are followed in India.

Going through the FMVSS standards: https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/tp214p-01.pdf

Here in this simulation, we are going to take the angle of inclination as 90 degrees instead of 75 degrees and initial velocity as 35 mph as per the given requirements.

Load path for the side impact

PROCEDURE:

Import model

On importing the _0000.rad file into Hypercrash we get this partial reduced BIW model for performing side impact test. It contains 95 components, 94 material cards and 7 contact interfaces.

Setup the boundary conditions

1) Check the unit system and either follow [Mg mm s] or [Kg mm ms].

On opening the _0000.rad file we can see the unit system which is followed here is [kg mm ms]

2) Create an appropriate interface, friction 0.2, and recommended parameters.

Before we build the interface as required for this project we have to delete the redundant interface which were already present in the model.

After which we can setup self impact TYPE 7 interface over a full body by providing recommended parameter values as shown below

3) Make sure of no penetration and intersections.

Before moving to the next step we will make sure there are no intersection or penetration of elements. If any fix them by using the tools provided in Hypercarsh and HyperWorks. since there were no penetration or inetrsection during the check we can proceed furthur.

4) Create a rigid wall with friction 0.1 as per the reference model.

We are providing the cylindrical rigid pole with [fric] Friction value to be 0.1, search distance 300 and diameter as 254 mm as per FMVSS standards at a perpendicular distance away from the B-pillar.

5) 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.

On checking the mass balancing in the HyperCrash we see the total weight of the model is 166.3 kg and COG somewhere near the B-pillar cross member mid region.(as shown below)

so as to make the mass near to the 700kg we need to add mass so we added the 534 kg to the rocker cross beam so as to make the COG point over near to the rocker cross beam. As shown in the figure below.

6) The initial velocity of 35 mph.

we need to provide the initial velocity of 35 mph which equal to 15.64 mm/ms to the full vehicle body and in positive y direction towards the pole.

7) Cross-section setup for cross members.

To know the sectional force over the areas such as cross members we need to give section over the elements as shown below. The sections are provide using a moving frame.

8)Intrusion nodes

To know the intrusions over the area of crash impact we need to set the TH node for area as shown below.

9) Output TH request and Engine cards

Once we are done providing the setup request we have to request the TH output. such as accelerometer, sections, rigidwall, etc. After we are done with TH output we need to provide engine cards for animation and contour capturing eg. ANIM/DT,ANIM/VECT, ENG_RUN ETC.

10) Use model checker to ensure good quality.

Finally before generating the radioss simulation and file we need to do the final check i.e model check. On running the model check we see the it shown few errors and warnings so we need to check and fix them. Finally we got the debugging correct and manage to fix all errors.

POST PROCESSING

On opening the _0001.out file we can see the energy error to be -1.3% and mass error to be 0.01018 which is acceptable and can considered as good model with total no. of cycle as 80001 with time duration of 1:29:08 or 5248 sec.

ANIMATION FILE

1) Displacement contour plot

The maximum dispalcement achieved is the 1459mm at node 190233

2) Von-Mises stress plot (side view)

Here we can see the value of von-mises stress generated during the impact with side pole, the max value of 0.3524 Gpa generated at node 121527.

From the side view we can analyse the stress flow path during the impact absorbed by the B-pillar, sill beam and A-pillar

3)Von-Mises stress plot(top view)

In the top view, we can see the stress flow path over the cross members during a side pole crash,

TH plots

1) Energy plot

As we can see the kinetic energy at the start of the simulation is at 85KJ and reduces gradually with the impact into the rigid wall(velocity reduced). The Internal energy start at 0 and increases to a value of 20KJ at the end of simulation due to the deformation and conversion of K.E to I.E. The value of hourglass energy is zero throughout the simulation due to the use of recommended shell properties. and contact energy is insignificant.

2) Rigid pole forces

As we can see the plot below shows the total resultant force variation w.r.t simulation time. As it can be seen in the starting the pole force generated is zero till 12ms of simulation because of no contact but at the 15 ms there is peak rise in the wall forces to a value of 58KN and then at 20 ms. Then from 25 ms to 80 ms the value remains almost constant in between 30-40 KN value.

3) Section Force Rocker beam

The variation in section force at the Rocker beam is shown below. it starts with the value of 0 till 15ms and then shows amuch variation between 20 to 50ms with max value of 7.5 KN at 43ms.

4) Section Force cross member

The variation in section force at the B-pillar cross beam is shown below. it starts with the value of 0 till 14ms and then shows amuch variation between 17 to 50ms with max value of 3.75 KN at 27ms.

5) interface normal forces

The interface normal force generated due to self impact is shown below in the graph with sharp increase in the value of 53KN after 13 ms of simulation. Then at the near to the end of simulation the value reaches to 55 KN at 75ms.

6) Intrusion on nodes at different sections

The Intrusions are measured by taking the node under consideration at location 123362- fuel tank, 123341- B-pillar, 121297-hinge pillar, and the 337773 -inner door panel. so as to get the relative displacement(y-axis) we need to measure the just before the impact and at the end of the simulation therefore we get

• Node 123362: 362.958 - 234.523= 128.43mm(fuel tank)
• Node 123341: 623.466 - 234.523= 388.94mm(B-pillar)
• Node 121297: 990.056 - 234.523= 755.53mm(hinge pillar)

Frame just before the car body touches the pole.

The frame at the end of the 80ms simulation.

So to reduce the intrusion at the fuel tank area the cross members and the sill beam need to be more robust which can resist the deformation and play a major role in occupant safety.

7) Peak velocity of node at the inner door

The peak value of the inner door panel node(337773) velocity is 16.58 mm/ms at 16 ms of simulation then drops down after 22 ms at a value of 5 mm/ms. Between 25 to 80 ms the velocity value fluctuates between 6-10 mm/ms.

To make the glasses of the car window to show the shattering effect we need to change the material card to PLAS_BRIT type with properties of glass as shown below.

CONCLUSION:

After completing this project we can conclude that the maximum energy absorption is done by the cross members resisted by B-pillar. The results and plots obtained are relevant to the actual condition of crash analysis. All the boundary conditions are fulfilled as required and we get satisfactory results. so finally we can say for increasing the occupant safety the cross members are playing a major role thus they need to made robust.