Assignment 7-Side Pole Crash Simulation Challenge

 OBJECTIVE:

To perform Side Pole Crash Simulation with given Formulations and study abouy

• 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.

PROCEDURE:

Import:

The given neon_side_reduced_0000.rad file is imported using import tool.

Checking Unit system:

From neon_sied_reduced_0000.rad file:

Model Browser>Cards>BEGIN_CARD 

It is observed that, the unit system followed is Kg mm ms which is as given in the required unit system.

Penetration Check:

The given file is importrd to hypercrash. Under Contact Inerface browser, Check Penetrations for selected objects is selected after slecting the components.

Creating Interface:

The interface described in the model is deleted and a new interface is created under the solver browser 

Create>INTER>Type7

Type 7 recommended porperties are defined along with the given properties.

After Interface is created, It is added to the outputblock under solver browser

Create>TH>INTER

Creating RIGID Wall:

Rigid wall is created under solver browser by using

Create>RWALL>CYL.

Inorder to select a postion, outermost node on the door part is selected. 

A small gap is added to the Y cordinate to create Cylinder little away from the model. Since normal of the cylinderis on Z-direction, 0,0,1 is defined in the Normal tab.

Dsearch is defined till 1500mm.

Diamater of 250mm is defined.

Slide is set to 2 to incorporate a friction of 0.1 as specified.

Hence Rigid Wall (CYLINDER) is created with specified properties.

Mass Balancing:

To compare the Side_reduced model mass and to make the model weight equivalent to the full scale model weight, Hypercrash application is used.

To view CoG and mass, Mass>Balancing option is used.

It is observed that the scaled side_reduced model only weighs 166kg.

Also the position of COG is currenlty above the driver seat region which should be lowered to the floor region

Now to shift the COG to the desired area, some masses are added.

To Add mass, ADMAS option is used under solver browser

Create>ADMAS.

Hence the mass is corrected to approx 700kg to represent a real-life mass of a vehicle, and also the position of COG is now relocated to the desired position.

Defining Initial Velocity:

To define an initial velocity of 35mph (15.6464 mm/ms) under solver browser:

Create>Boundary Conditions>INIVEL

Creating Cross-Section and Frame:

Now before moving into simmulation, inorder to observe the outputs required, we have to create cross sections.

To view cross sectional force on the moving model, a frame which is movable should be created which act as reference to the cross section at which forces is to be computed.

To create a movable frame under solver browser using,

Create>Frame>MOV

In the frame creation window, we should select origin nodes and also the global axis directional nodes which can be created by translate tool and translating the duplicate of origin node to X and Y direction. Clicking on create after selecting nodes, creates a new frame with specific ID.

After Frame is created, now a section should be created for this frame which is created under the solver browser:

Create >SECT>SECT

In the newly created section, the elements are selected under grshel_id and the reference frame created is define by the Frame ID.

After Frames and cross sections are created, these are added to the TH under solver browser:

Create>TH>SECTIO

Intrusions:

To find the intrusions at B pillar,hinge pillar and fuel tank region, a frame for reference is created for each.

Frame and base node for intrusion is taken at the rocker due to its simple geometry, which might help in good results.

Then under time history block, the node is selected as Entity ID and frame is selected as iskew.

Peak Velocity at Door (Inner Node)

To find Peak Velocity at the specified node, A moving frame is created.

Then a TH/Node blpck is used specifying the node and the moving frame as iskew.

Run Time & Time Step:

The run time of the simulation is checked under ENG_RUN tab under model browser>cards

The time step is set to 0.00025ms under DT_NODA,DT_INTER and DT_BRICK tab.

Model Checker:

To check for any error in the model, 

Tools>Model Checker>RadiossBlock 

After the model checker tab opens, Run Checks option is clicked, and then auto correct option is clicked, which will rectify the errors and warnings.

All the error and warnings are displayed which is partially corrected using auto correct option. The error shown is due to not selecting N1, N2 and N3 to the newly created sections for Hinge-Pillar, B-Pillar and Fuel Tank which can be neglected. Rest of the warnings are also neglected.

After all the above formulaions are done, we can now perform simulation of the model to review the crash results.

Simulation:

The simulation is run using Radioss Tool under Analysis tab.

Once the analysis is done, neon_side_reduced_0001.out file is observed to check the stability of the  model.

From the .OUT file,

Energy error : 0% to -1.7%

Mass Error : 0.1308E-07 to 0.1768E-03

Hence Energy and mass error are within the stable limits.

Now the time for simulation and number of cycles taken to complete the simulation is also noted from the OUT file.

Plotting the energy curves using Hypergraph 2-D with the help of T01 File:

Internal energy, Kinetic energy and Total energy curve is plotted. It is observed that there is an increase in the internal energy in the model with the progress in simulation. With the increase in Internal energy, there is a proportional decrease in kinetic energy in the model.

Hence Total energy remains constant roughly due to compensation between kinetic and internal energy. Total energy shows a slight decrease due to slight increase in contact energy towards the end of the simulation after 30ms as shown in the above graph.

Hourglass energy remains negligible throughout the simulation and a slight increase in contact energy. 

Plotting the Cross-Sectional forces using Hypergraph 2-D with the help of T01 File:

At the start of the simulation, there is a small ripple type behavior on both the Cross Memebers.

Initially forces on cross member 2(Front cross member) is higher than the cross member 1 (rear cross member), but on further crashing, cross member 1 reaches a higher value very steeply than that of cross member 2.

At the start of the simulation, Forces on Cross member 2 is rises and falls gradually ,while towards end of simulation, rise and fall in forces are very rapid.

In case of Cross member 1, initially the rise and fall of cross sectional forces are very rapid, towards end of simulation the rise and fall of force becomes gradual.

Intrusions:

The plots for intrusions at Hinge Pillar, B-Pillar and Fuel tank is plotted 

Blue curve depicts Hinge Pillar, Red curve depicts B-Pillar and Green curve depicts Fuel tank intrusion characteristics.

Displacement in the direction of the Crash:

The Hinge Pillar displacement in Y-Direction is about 1037mm. 

The B-Pillar displacement in Y-Direction is about 1330mm. 

The Fuel tank displacement in Y-Direction is about 1366mm. 

Resultant Displacement during the Crash:

The Hinge Pillar displacement is about 1320mm.

The B-Pillar displacement is about 1385mm.

The Fuel tank displacemen is about 1455mm.

Recommendation to reduce Fuel tank intrusion

It can be seen that out of the intrusion that is measured at 3 different locations, the fuel tank region is having the maximum displacement.

This high displacement as compared to other region might cause serious damage to the fuel tank which might cause highly serious incidents like fuel tank explosion.

Also at other two regions, the presence of cross member helps in reducing the displacement during the crash since it also aborbs some part of energy during the crash. Hence addition of a cross member can be one of the possible solutions to reduce the high intrusion at the fuel tank region.

 Another recommendation to reduce fuel tank intrusion can be redesign the structure of the model in a fashio where the mesh flow will direct the crash forces away from the fuel tank region or in a more distributed manner which might help in reducing the amount of force flowing to the tank region.

Peak velocity of inner node of the door:

The peak velocity of the specified node is plotted. It ois observed that, at the start of the simulation, the velocity of the node is at 15.64mm/ms which is the defined initial velocity. This peak velocity gets reduced to 0 in under 0.5ms and remains 0 till end of the simulation. This is due to the fact that after the region near to node is crashed, it experiences no further movement due to the presence of rigid pole which makes the velocity of the node to 0mm/ms.

Animation and Contour plot of the simulation is obtained under Hyperview using the h3d file saved in the directory:

Above plot shows how the model crashes to a side pole with an initial velocity of 35MpH.

Contour plot values shows that a maximum of 0.41units of stress is generated during the crash.

CONCLUSION:

The given Side_reduced model is simulated for a side crash test on to a Rigid Pole.

The model properties are initially formulated as per recommendation and simulation is performed.

The energy curves are plotted to study the cross sectional force characteristics, Intrusions at specified points are measured and finally the peak velocity of the specified node is tracked.