Side Pole Impact Analysis of DODGE Neon BIW model using HyperMesh and RADIOSS

AIM :

To perform Side Pole Impact test on the given Dodge Neon BIW model as per FMVSS 214 Standards and to evaluate the side impact crashworthiness of the vehicle using RADIOSS solver in HyperWorks.

OBJECTIVES :

• 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.

TOOLS REQUIRED :

• HyperMesh
• RADIOSS
• HyperView
• HyperGraph 2D

THEORY :

Federal Motor Vehicle Safety Standards (FMVSS) 214 - Side Impact Protection

FMVSS 214, Side Impact Protection, specifies performance requirements for protection of occupants in side impact crashes. The purpose of this standard is to reduce the risk of serious and fatal injury to occupants of passenger cars by specifying strength requirements for side doors. This standard applies to all passenger cars as well as 90% of light truck type vehicles with a GVWR < 10,000 lbs, manufactured on and after September 1, 1993, to August 31, 1994. On and after September 1, 1994, all light truck type vehicles with a GVWR < 10,000 lbs will be required to meet the static requirements.

Side pole impact test setup

The given model for the analysis is a reduced model of Dodge Neon vehicle BIW structure.

Given BIW model

PROCEDURE :

• Import the given BIW model neon_side_reduced_0000.rad using the Import Solver Deck option in RADIOSS.

• The given model is checked for unit consistency. In this analysis, [kg mm ms] unit system is followed. For this, the given model file is opened in Notepad and checked as shown below.

• As the model is to crash into a rigid wall, appropriate contact interface have to be defined. TYPE7 self contact is defined with co-efficient of friction as 0.2 and other recommended parameters. The entire BIW structure is selected as master surface and the entire nodes as slave nodes as shown below.

/INTER card

TYPE7 self contact

• The given model is checked for proper connectivity between parts. To check connectivity, go to Tools (tab) -> Find connectivity and the entire BIW model is selected for connectivity check.

We can see that there are 3 free parts which are not connected to the structure. These free parts are connected to the adjacent parts using welds modelled using SPRING2N element. These spring elements are then given P13_SPR_BEAM property card to model these springs as welds.

After connecting the free parts, the model is again checked for connectivity.

We can see that the model has become a single group of connected parts.

• A cylindrical rigid wall is to be created for the car model to crash into. Rigid wall is created by specifying a base node and the axis direction of the cylinder. It is created with co-efficient of friction as 0.1. The diameter of the rigid wall cylinder is taken from the FMVSS 214 Standards which is 254 mm.

/RWALL card

Rigid wall creation

• As we are dealing with the reduced model of the BIW, the total mass of the structure is less than the mass of the complete BIW. Mass plays an important role in the analysis because it determines the kinetic energy of the model under analysis. So, mass have to be added to make the given model behave like the complete BIW model. Mass of the given model is 166 kg. The target mass is 700 kg. Also, mass have to be added in such a way that the centre of gravity (COG) of the model comes at the middle of the crossbeam.

Mass of the given model

Centre of gravity (COG) of the given model

Final mass after mass addition

Centre of Gravity (COG) after mass addition

• The entire BIW model is given an initial velocity as per the FMVSS 214 criteria , i.e., 31 kmph (8.611 mm/ms) in the transverse direction of the vehicle (in this case, along global Y-direction). It is done by creating INIVEL card and giving the velocity value in the Y-direction component and select the whole component.

/INIVEL card

• The BIW model is checked for any initial penetrations or intersections. To check this, go to Penetration Check in Tools tab. The self contact interface created is selected for penetration check.

• Set the time step to 0.5 microseconds in ENGINE_KEYWORDS -> DT -> DT/NODA.

/DT/NODA card

• Set the frequency of writing the animation files to 5 ms in ENGINE_KEYWORDS -> ANIM -> ANIM/DT.

/ANIM/DT card

• Also, set the simulation run time to 80 ms in ENGINE_KEYWORDS -> RUN -> ENG_RUN.

/RUN card

OUTPUT REQUESTS :

Sectional force in the cross members

• Create a local moving frame at the section where we want to create a section using Solver -> Create -> FRAME -> MOV tool.
• Create a set to store elements at the required section using Model -> Create -> Set tool.
• Now, create a section by calling the local frame and the element set created using Solver -> Create -> SECT tool.
• The above three steps are performed separately for both the cross-beams.

Cross-beam 1 /SECT card Cross-beam 2 /SECT card

• The local sectional force is requested in the Time History file using Solver -> Create -> TH -> /TH/SECTIO card.

Intrusions on the rocker at B pillar, hinge pillar and fuel tank region

• The nodes where the intrusions are to be found out are shown below.
• For finding the intrusions of these nodes, we need to create a local moving frame separately for each node on the opposite rocker and the intrusions (displacement) of the nodes is requested in the Time History file using Solver -> Create -> TH -> /TH/NODE card.

/TH/NODE card for Hinge pillar node /TH/NODE card for B-pillar node /TH/NODE card for Fueltank node

Peak velocity of inner node of the door

• The inner node of the door where the peak velocity is to be found out is shown below.
• To request the peak velocity of the node in the Time History, create a /TH/NODE card by Solver -> Create -> TH -> /TH/NODE and select the DEF variable output.

Finally the model is checked for any errors using Model Checker. For this, go to Tools tab and click on Model Checker.

Model Checker window

There are no errors, only some warnings are shown which can be neglected. Therefore, it is good to move forward with the analysis.

After setting up all the conditions and requesting the required outputs, the model is proceeded to analysis using Analysis -> Radioss option.

RESULTS :

The Side Pole Impact analysis is carried out and the following results are obtained.

Displacement contour plot

• This contour plot shows the displacement of each node of the BIW model in a graphical interface.
• Displacements are computed with respect to the global co-ordinate system.
• As the model crashes into the rigid pole, deformation occurs to each nodes and the nodes gets displaced from their initial position.
• During the analysis, maximum displacement occured at node 190233 and it got displaced by 828.8 mm.

Von-Mises stress contour plot

• This contour plot gives the stress induced at each node in the BIW model.
• As the model crashes, internal stress is developed in the model due to material behaviour.
• When the stress developed crosses the yield limit of the material assigned, it undergoes plastic deformation as we can observe from the plot.
• Maximum stress is developed at node 23242 and is equal to 0.3252 GPa.

Sectional force in the cross members

• We have defined sections at both the crossbeams along with a local frame of reference.
• Therefore, the force along the Z- direction of the local frame of reference gives the cross-sectional force in the crossbeams.
• The plot obtained is given below.

• From the plot, we can see that both the crossbeams are under compressive load..
• From this plot, we can conclude that the force propagation is not same through both the crossbeams. Crossbeam 1 takes more load than crossbeam 2 as is clear from the plot.
• We can see from the plot that both the plots are decreasing initially, i.e., force is increasing in the negative direction.
• The compressive sectional force increases in the cross beam 1 and reaches a maximum value of 10.5363 kN. After that, due to the deformation of the rocker, the crossbeam 1 start to bend in the XY plane. Due to this bending, the sectional force decreases as we observe in the plot.
• In the case of crossbeam 2, the sectional force increases during the initial phase of the crash. But this crossbeam undergoes heavy buckling due to its low cross sectional area and we can see that the compressive section force decreases as buckling proceeds.The maximum sectional force(compressive) experienced by this crossbeam is found to be 3.66152 kN.

Intrusions on the rocker at B pillar, hinge pillar and fuel tank region

• We have defined 3 local moving frame on the opposite rocker in order to find out the intrusions of the given nodes.
• The plot obtained is given below.

• For measuring intrusions, local moving frame should be used instead of skew.
• Frames give the relative displacement with respect to the moving frame.
• From the above plot, we can find that the hinge pillar reference node on the rocker has intruded 61.8361 mm from the position of the exact same node if there were no rigid wall, in the local Z-direction at the end of the crash simulation.
• Similarly. the B-Pillar reference node on the rocker has intruded 331.526 mm in the local Z-direction at the end of the simulation.
• Also, the Fuel tank reference node on the rocker has intruded 358.741 mm in the local Z-direction at the end of the simulation.

Peak velocity of inner node of the door

• The plot obtained is shown below.

• We can observe that the particular node on the front door attains the peak velocity at the moment when the car just hit the rigid pole. This is due to the sudden impact of the rigid pole and the peak velocity attained is 8.8706 mm/ms.

Energy plot

• The energy plot is given below.

• At the start of the simulation, the car model is possessing only kinetic energy due to the initial velocity boundary condition.
• As the model crashes into the rigid pole, kinetic energy gets converted into internal energy due to plastic deformations happening in the model. Therefore, kinetic energy reduces and internal energy increases during simulation.
• Kinetic energy at the end of the simulation is found to be 16,911.1 kN-mm and the internal energy is 8626.54 kN-mm at the end of the simulation.
• Hourglass energy is very negligible (only 20.1394 kN-mm) since we have used QEPH element formulation.
• Since there is not much energy loss, the total energy remains almost constant throughout the simulation.

Checking mass and energy error

• After simulation, the Engine OUT file is opened in Notepad and checked for mass and energy error.

• The energy error after simulation is -1.3% and the mass error is 0.00004334% which are well within the limits.

CONCLUSION :

The Side Pole Impact analysis is done on the given Dodge Neon BIW reduced model and the results are analysed. There are different standards of conducting the crash analyses. The one which is followed in this project is FMVSS 214 standards.These tests are conducted to determine

• how much internal energy the vehicle is able to absorb during a crash
• the deformations occured in certain critical areas
• the occupant safety

These parmeters are then compared with the Standards and finally decide which level of safety category the particular vehicle fits into.