7. Side Pole Crash Simulation Using Hypermesh and Hypercrash

AIM:

• To perform side pole crash analysis of the neon car model and obtain the simulation results and plot the required graphs.

OBJECTIVES OF THE PROJECT:

• To set up the car model for side crash analysis.
• To create appropriate interface for the model.
• To check the model for intersections and penetrations.
• To create a rigid cylindrical wall for the model to crash.
• To assign mass to the model upto 700kg.
• To perform mass balancing and bring the COG of the model to the desired region.
• To assign initial velocity of 35mph.
• To obtain the forces on the cross-members.
• To procure the desired output results.

PROCEDURE:

• The first step is to import the model in the Radioss profile.
• Go to FILE > IMPORT > SOLVER DECK > BROWSE > OPEN.

• Unit system-
• Now, we have to check the unit system for the solver.
• Go to MODEL > CARDS > BEGIN CARD to check the unit system. For this model we are following the kg, mm, ms unit system.

• Time step-
• Go to MODEL > CARDS > ENG_DT_NODA > TMIN = 0.0001.
• 

• Intersections and Penetration Checks-
• Next, we will check the interfaces and penetrations. Go to TOOLS > PENETRATION CHECK > COMPONENTS > ALL > CHECK.
• 
• We can see that there are no intersections and penetrations in the model.

• Interface Contact-
• Now, go to SOLVER > INTER and delete the predefined interfaces. Now, CREATE > INTERFACE > TYPE 7 with the recommended parameters.

Istf=4, Igap=2, Idel=2, Fscale_gap=0.8, Stmin=1KN, Fric=0.2, Gapmin=0.5, Iform=2 and Inacti=6.

• Rwall Plane-
• Now, we have to create a rigid pole. Go to SOLVER > CREATE > RWALL > CYLINDRICAL. Select the outermost elemental node on the door for the pole. The pole will be in Z-axis, hence give the normal in Z-axis as 1. Give a gap of 10 mm in the Y-axis such that the plane does not intersect the door panel. Provide search distance as 1000mm and Friction=0.1 and Diameter for the pole = 254mm.
• 
• The rigid pole will be created.
• 

• Initial Velocity-
• Now, we have to provide initial velocity for the model. Go to SOLVER > CREATE > INIVEL > TYPE: TRANSLATIONAL IN Y > GRND_ID= COMPONENTS=ALL. The conversion of 35mph in mm/ms is 15.6464.
• 

• Mass Balancing-
• Now, we have to balance the mass and obtain the COG in the desired region. The initial mass is observed to be 166kg. The COG of the vehicle is as obtained.
• 
• We have to bring the mass to 700kg approx for the whole model and the COG should be below the driver’s seat. So to obtain the required CG location, we have to do mass balancing by adding mass at the cross-members.
• Go to SOLVER > CREATE > ADMASS > MASS TYPE = 0 > GRND_ID > SELECT NODES > MASS.
• 
• In, this way the mass balancing is performed to get the required COG. The total mass of the model is brought approximately to 700kg. The added mass Location is as shown in the yellow circle.
• 
• The COG of the model is as defined by the black circle.
• 

• Sections-
• Next, we have to obtain the results for the defined cross sections. For that first we have to create moving frames. Go to SOLVER > CREATE > FRAMES > MOVING > CREATE BY NODE REFERENCE > ORIGIN > X-AXIS > XY PLANE > CREATE.
• 
• Then go to SOLVER > CREATE > SECT > FRAME_ID > DELTA T=0.1 > ALPHA = 1.94 > IFRAME = 12.
• 
• Similarly, we will create the moving frames and sections on both the cross-members.
• 

• Intrusions-
• Next, we have to create intrusions. To find the results we have to create moving frames at B pillar, Hinge pillar and Fuel tank region. Then, go to MODEL > OUTPUT BLOCKS > CREATE > INTRUSIONS > NODE_ID > I_SKEW. This will give the output result for the intrusions.
• 

• Output Blocks-
• Next, we have to define the outputs. Go to MODEL > OUTPUT BLOCKS > CREATE > VELOCITY and SECTIONS and RWALL CARDS.
• 
• This will define Radioss that these output results should be provided after simulation.

• Model Checker-
• At last, go to TOOLS > MODEL CHECKER > RADIOSS BLOCK > RIGHT CLICK ON ERROR > RUN. This will run the model checker for any errors if any.
• 
• We have no errors in the model and hence we can proceed to run the simulation.

• Analysis-
• Go to ANALYSIS > RADIOSS > INPUT FILE > INCLUDE CONNECTOR > OPTIONS = -NT 4 > RADIOSS.
• 
• This will run the Radioss simulation.
• Open .out engine file from saved folder and check final value of Energy error, Mass error, Simulation time and Total no of cycles.
• 
• Here, the energy error is shown in red box and mass error in the blue box. Energy error is -7.3% and mass error is 0.2144e-5. These values of energy error and mass error are within the acceptable range.
• 
• We can see that Radioss took 4hrs and 18 minutes to run the simulation file.
• Click on view Results, which will open Hyperview window.

• Hyperview-
• In Hyperview go to CONTOUR > RESULT TYPE > VON MISES > AVERAGING METHOD > SIMPLE > APPLY.
• 
• In the above simulation we can see that the vehicle body is impacting the pole. On impact the vehicle body starts deforming and gets contracted around the pole. The pivot of the body is around the B-pillar. The COG of the vehicle is in the axis of the pole and hence, the body contorts around the pole. The forces of the impact is taken by the cross-members as they receive compression forces.
• The pole is seen to be shifted upwards but the Rwall pole is an infinite pole, hence the results obtained are satisfactory.

• In Hyperview go to CONTOUR > RESULT TYPE > PLASTIC STRAIN > AVERAGING METHOD > SIMPLE > APPLY.
• 
• The initial deformation occurs at the B-pillar and the vehicle body folds around the pole. The plastic strain is obtained at the cross-members.

• Hypergraph 2D-
• Open Hypergraph 2D and load T01 file.
• Go to GLOBAL VARIABLES > INTERNAL ENEGRY, KINETIC ENERGY and TOTAL ENERGY > MAG > APPLY. This will plot the energy graph.
• 
• From the above plot, we can see that the kinetic energy around 85000 kgmm2/ms2 starts to reduce as it is coverted into the internal energy. This states that the kinetic energy(velocity) of the vehicle after the impact is absorbed by the body at the cross-members. After 60ms there is significant drop in th kinetic energy and total energy without rise in the internal energy. This is because the energy is lost in the Hourglass energy.
• At 60ms the vehicle body starts to reduce the kinetic energy as much of the deformationhas occured and now, the elements are close to each other. This enables the self-contact and the energy is lost in hourglassing.

• Go to NODE INTRUSION > DISP-RESULTANT DISPLACEMENT > APPLY. This will plot the intrusion graph.
• 
• For 123361, the distance between the node and the skew is 1319mm and the resultant displacement is about 240.16mm. Hence, the intrusion at the fuel tank region is 1319-240 = 1079mm.
• Similarly, the intrusion at B-pillar for node 123322 is 1312-306 = 1006mm.
• Similarly, the intrusion at hinge pillar for node 123346 is 1317-574 = 743mm.
• Now, at the fuel tank region the displacement is about 240mm. As there is much displacement at the fuel tank region, the fuel tank can be crushed and there is risk of danger as the calorific value of the fuel is high. To avoid the displacement in the fuel tank region we can add an extra Cross-member in the region which would take up the impact forces and distribute the forces to the body resulting in less deformation.

• Go to NODE/PEAK VELOCITY > RESULTANT VELOCITY > APPLY. This will plot the peak velocity for the node.
• 
• From the above plot, we can see that the peak velocity at the node 337773 on the inner side of the door is 16.41mm/ms. The graph shows reduction in the velocity as the kinetic energy is absorbed and converted into internal energy.

• Go to SECTION > TOTAL RESULTANT FORCE > APPLY. This will plot the section forces.
• 
• The sectional forces in the front cross-member is less as compared to the resultant forces in the rear member. This is because the rear member is closer to the pole axis and takes up lot of forces. The maximum force in the front cross-member is 15 whereas the maximum force in the front cross-member is 2.3.

LEARNING OUTCOMES:

• To define INIVEL for the model.
• To measure PEAK VELOCITY at a node.
• To adjust the mass balance to get the desired COG location.
• To check for the COG location.
• To create Moving Frames.
• To create sections to obtain the results.
• To use model checker for checking errors.
• To provide the output results in the output blocks.

CONCLUSION:

• Hence, by performing this project we conclude that during the crash analysis of the neon car model, the location of the COG affects in the deformation of the model in certain way. The energy error in the simulation is observed to be -7.3% and mass error to be 0.2144e-5, which is pretty fine for the simulation.