Crash worthiness Project 1 - Frontal Crash Simulation

Crashworthiness Analysis using HyperMesh and Radioss

#Project 1 - Frontal Crash Simulation Challenge

AIM: To perform the crash on the frontal section of the car with wall and analysis where stresses are working on it.

OBJECTIVES:

Frontal crash-BIW

1. Checking the unit system and either following [Mg mm s] or [Kg mm ms].
2. Creating appropriate interface, friction 0.2 and recommended parameters.
3. There should be no penetrations and intersections.
4. Creating a rigid wall with friction 0.1.
5. Adding masses to reach target weight 700kg while getting CG about the required range.
6. Adding Initial velocity 35 mph.
7. Running a model checker to ensure good quality.
8. Time-step: 0.5 to 0.1 microseconds.
9. Running 80 ms.

Output requests:

1. Adding a sectional force in the rails at the location of indicated node 174247.
2. Adding Axial force received on the rails from the bumper.
3. Adding Shotgun cross sectional forces.
4. Adding a cross section to a pillar.
5. Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
6. Adding Intrusions on the dash wall at node 66695 and 66244.

ABSTRACT : Frontal area is the area where a car hits the air head on. Frontal area of the car has a good aerodynamic shape. There is a very high chance that a car can hit from front. These cause extremely high impact deformation on the frontal area of the car. The main objective of the frontal crash is to examine injury risk and potential of safety of the driver and passengers.

PROCEDURE OF OBJECTIVE 1: Checking the unit system and either following [Mg mm s] or [Kg mm ms].

STEP 1: Open the starter file neon_front_000.rad file, go to-

*Menu bar>file>import>solver desk>select .rad file>import

STEP 2: Checking unit system of the model

*Model browser>cards>begin card

PROCEDURE OF OBJECTIVE 2: Creating appropriate interface, friction 0.2 and recommended parameters.

*Model browser>groups>create group>

PROCEDURE OF OBJECTIVE 3: There should be no penetrations and intersections

*Menubar>penetration check>select group>check

PROCEDURE OF OBJECTIVE 4: Creating a rigid wall with friction 0.1.

STEP 1: creating Rwall go to-

*solver model>create>rwall

STEP 2: Rwall parameters and friction

• We can see that the Rwall Collector has formed automatically in the Model Browser with all parameters given by us.

PROCEDURE OF OBJECTIVE 5: Adding masses to reach target weight 700kg while getting CG about the required range.

STEP 1: Opening mass summary

*Menu bar>tools>mass details>mass,cog,inertia.

• We can see that the mass is less as it should be around 700 kg.

STEP 2: Set GRNODE

*Solver browser>GRNODE>create>GRNODE>node>select nodes

• Now again check the mass summary as shown in step 1 to check if the mass of the car increased or not as per our requirement. If not, again add few mass at some nodes as done in step 2

STEP 3: Adding mass to increase overall weight of the car

*Solver browser>ADMAS>create>extra mass>give GRNODE ID>give mass value.

• At final we can see that mass is reached around 700 kg

STEP 5: Checking CoG

*Menu bar>tools>mass details>mass,cog,inertia

• Initial COG

• Final COG after adding mass

• Here we got the coordinate number where the CoG lies.

PROCEDURE OF OBJECTIVE 6: Adding Initial velocity 35 mph.

STEP 1: Creating card

*Solver browser>create>boundary condition>INIVEL

STEP 2: Set GRNODE

*Solver browser>GRNODE>create>GRNODE>node>selcect nodes

STEP 3: Setting up INVEL Parameters

• We can see that the INIVEL is added to the model.

PROCEDURE OF OBJECTIVE 7 : Running a model checker to ensure good quality.

PROCEDURE OF OBJECTIVE 8 : Time-step: 0.5 to 0.1 microseconds.

*Model browser>cards>eng_anim_dt>Tfreq=5.0

PROCEDURE OF OBJECTIVE 9 : Running 80 ms.

*Model browser>cards>eng_run>Tstop=80.0

PROCEDURE OF OBJECTIVE 10 : Adding a sectional force in the rails at the location of indicated node 174247.

STEP 1: Displaying node 174247

*Tools>numbers>byconfig>type node number>display>on

STEP 2: Creating FRAME card in solver browser.

STEP 3: Giving Parameters to FRAME>MOV

*Solver browser>FRAME>MOV>give origin,axis,plane node

STEP 4: Creating SECT card in solver browser.

STEP 5: Giving parameters to Ring 1

STEP 6: Creating GRSHEL card and giving parameters in the solver browser.

STEP 7: Giving Output Request in Model Browser.

PROCEDURE OF OBJECTIVE 11 : Adding Axial force received on the rails from the bumper.

STEP 1: Creating new MOV collector in FRAME card.

STEP 2: Giving parameters to SECT

STEP 3: Setting up GRSHEL card for bumper.

STEP 4: Giving Output Request in Model Browser.

PROCEDURE OF OBJECTIVE 12 : Adding Shotgun cross sectional forces.

STEP 1: Creating new MOV collector in FRAME card.

STEP 2: Giving parameters to SECT

STEP 3: Setting up GRSHEL card.

STEP 4: Giving Output Request in Model Browser.

PROCEDURE OF OBJECTIVE 13 : Adding a cross section to a pillar.

STEP 1: Creating new MOV collector in FRAME card.

STEP 2: Giving parameters to SECT

STEP 3: Setting up GRSHEL card.

STEP 4: Giving Output Request in Model Browser.

NOTE: We have done this for one side of the car. The same cross section on pillar,bumper,ring and rail has also to be created on the other side of the car by the same procedure we’ve done from step 10 to 13.

PROCEDURE OF OBJECTIVE 14 : Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).

• Creating Accelerometer on one side of the car.

STEP 1: Creating ACCEL card in solver browser.

STEP 2: Giving parameters to the accelerometer.

STEP 3: Giving Output Request in Model Browser.

• Creating Accelerometer on another side of the car.

*Follow the same procedure of Objective 14 - Step 1,2 and 3.

PROCEDURE OF OBJECTIVE 15 : Adding Intrusions on the dash wall at node 66695 and 66244.

• Intrusions on the dash wall at node 66695

STEP 1: Creating a new local coordinate in SKEW collector of solver browser and giving origin,axis and plane nodes.

STEP 2: Giving Output Request in Model Browser.

• Selecting 66695 node in entity ID

• Intrusions on the dash wall at node 66244.

STEP 3: Creating a new local coordinate in SKEW collector of solver browser and giving origin,axis and plane nodes.

STEP 2: Giving Output Request in Model Browser.

• Selecting 66244node in entity ID

SIMULATION OF THE FRONTAL CRASH : Simulating and analysing car’s frontal crash.

STEP 1: Open Hyperworks in Radioss solver.

STEP 2: Import Solver desk Project_1_0000.rad file

STEP 3: Simulating model as it is.

*Analysis>Radioss>save as input Project_1_0000.rad file>Checkbox include collectors>Write (-nt 4) in options>Click Radioss

STEP 4: Switch to Hyper view

STEP 5: Select local model and result Project_1.h3d file

RESULTS:

To plot the graph we need to switch to Hypergraph,

*Toolbar>select application to Hypergraph 2D>select Project_1T01 type file

• Pillar 1 - 2

• Short Gun 1 - 2

• Bumper 1 - 2

• Rail 1 - 2

• Accelerometer 1 and Accelerometer 2

• Intrusion 1 and Intrusion 2

• Energy Graph

• Number of cycles it takes, energy error, mass error and simulation time.

The output file shows us the number of cycle, energy error, mass error.

Number of cycles	80001
Energy error	-1.2 %
Mass error	3.038 %
Simulation time	3842.75 s (01:04:02)

OBSERVATIONS:

• We saw in the animation that the most deformation took place in the frontal area and the stress is then passed to the rest of the components of the car.
• We observed that the impact of the crash is taking mostly at the frontal region of the car and by looking at this we can say that the setting area of the driver and passenger will be also impacted which can cause injury to them.
• The energy graph is shown of Internal energy, Kinetic energy, Contact energy, Hourglass energy and Total energy Vs Time.
• We can see that Internal energy increases with respect to time whereas Internal energy starts falling down from its peak as time increases.
• Contact energy hourglass energy graphs have values near to zero and Total energy remains almost constant as time increases.
• In accelerometer 1 and accelerometer 2, the curve fluctuates drastically during the crash.
• In Intrusion 1 and Intrusion 2 graph, the displacement curve linearly increases with respect to time.

• FINAL MODEL

LEARNINGS :

• Importing starter file runname_0000.rad file
• Using Radioss command
• Running runnane.h3D file in Hyperview to see animation
• Reading runname_0001.out file
• Using Hypergraph 2D.
• Observing energies graph.
• Creating Initial velocity.
• Creating a Rigid wall.
• Creating cross sections, accelerometer and intrusion.
• Changing Type 7 parameters.

Type 7: Type 7 card is used to simulate all types of impact between a set of nodes and master surface. Main advantage of type 7 is stiffness is not constant and increases with the penetration preventing the node from going through the shell midsurface.

Istf 4: Stfac and stiffness is computed from both master and slave characteristics.

Igap 2: variable gap + gap scale correction of the computed gap.

Idel 2: When a 4-node shell, a 3-node shell or a solid element is deleted, the corresponding segment is removed from the master side of the interface. It is also removed in case of explicit deletion using Radioss Engine keyword /DEL in the Engine file. Additionally, non connected nodes are removed from the slave side of the interface.

Stmin 1: minimum stiffness (N/M)

GAPmin : Minimum gap for impact activation.

Inacti 6 : Gap is variable with time but initial penetration is computed .

Iform 2 : Stiffness (incremental) formulation.

• Center of Gravity : The center of gravity (CoG) of an object is the point at which weight is evenly dispersed and all sides are in balance.
• Rigid Wall : Rigid wall is created in the HyperMesh where the car is going to make collisions.
• Penetration: There should not be any penetration because nodes get penetrated in the element and cause failure in simulation, removal of penetrated nodes is necessary.
• Accelerometer: An accelerometer is a device used to measure acceleration of the body.
• Intrusion: Intrusion is used to check that if the component is withstanding a crash making sure that the component does not fail.

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