Assignment 6-Frontal Crash Simulation Challenge

AIM: To run a simulation for the frontal crash [BIW] and to obtain a results in the post processing.

OBJECTIVE:

• To check the unit system in the solver.
• To create an appropriate interface ,friction 0.2 and recommended parameters.
• To check for the penetrations and intersections.
• To create rigid wall with a friction 0.1.
• To add extra mass to attain a target mass of 700 kg.
• To apply initial velocity to the car.
• To create sections and find sectional force in the Rails,Bumper,Shotgun,A Pillar.
• To create spring elements to get intrusions and to calculate the intrusions.
• To create accelerometer to calculate acceleration of the car.
• To create TH for all the inputs requested.
• To run the simulation.
• To plot the graphs in the post processing.

THEORY AND INTRODUCTION:

• Frontal impact is performed at 64kph (40mph), the car crashes into a deformable barrier with 40% of its width front on the driver side (offset). Readings taken from the crash test dummies are used to assess protection given to adult occupants in the front seat.
  Each car tested is subjected to an offset impact into an immovable block fitted with a deformable aluminium honeycomb face.
• This impact is intended to replicate the effect caused in the car when crashing 55km/h 50% offset frontal crash with a similar mass car. As most frontal crashes involve only part of each car's front, the test is offset to replicate a half width frontal impact between two cars.
• In the test, this is replicated by having 40 percent of the width of the car crashing into the aluminium deformable barrier. This represents the most frequent type of road crash, resulting in serious or fatal injury.
• The barrier face is deformable to represent the deformable nature of the cars. Two adult dummies are placed representing average size men in the driver's seat and front passenger and two children, aged 18 months and 3 years old, on child restraint systems are placed in the rear seat.
• Contact between the occupant and hard and intruding parts of the passenger compartment is the main cause of serious and fatal injuries for restrained adult car occupants.
• The test speed of 64 km/h represents a car to car collision with each car travelling at around 55 km/h and crashing 50% of their width.
  The difference in speed is due to the energy absorbed by the deformable face. Accident research has shown that this impact speed covers a significant proportion of serious and fatal accidents.
• By preventing intrusion, the chances of the occupant impacting the car's interior is minimised with space remaining for the restraint system to operate effectively.
• Steering wheel and dashboard mounted airbags are an important part of the driver's restraint system.

                               

According to FMVSS (Federal Motor Vehicle Saftey Standards).Assign a initial velocity of 35mph,1mph=0.44704 m/s,=35x0.4470,=15.6464 m/s.

PROCEDURE:

While opening hypermesh software,A user profile window will pop up,Switch to the radioss user profile as shown in below and start importing the model into the solver deck.

Now after switch the user profile to radioss,import the model (starter file) into the radioss solver deck.

To import the model,Go to Standard Panel >> Import >> Import Solver Deck. 

Import Solver Deck option should be selected to import the radioss starter file.

Here the import browser will appear as shown in above Figure 5,Select the appropriate starter file to import into GUI.

Switch the File Type to Radioss Block and import the model into GUI.

Here the model is in wireframe mode,Switch to the shaded mode as shown in below.

To switch to shaded mode,Go to Visualization Tab >> Shaded Elements and Mesh Lines.

Visualization Tab to Switch to the Shaded Elements and Mesh Lines.

Shaded Elements and Mesh Lines Mode.

Now go and check for the unit system of the model,To check for the unit system,Go to the Model Browser >> Control Cards >> BEGIN_CARD.

Check for the unit system is shown in below.

Now go to the HyperCrash,To go,Go to Menu Bar >> Applications >> HyperCrash.

Make sure whether the unit system in hypercrash is [ kN, kg, mm, ms].

Now import the model in hypercrash,To import the model,Go to Menu Bar >> File >> Import >> Radioss.

Here select the appropriate Radioss File and import the model into hypercrash. 

Here the COG is not in a proper position which is shown in below Figure 18.So we need add mass to get COG at proper position,Its like balancing.

To Check the Mass and COG [Centre of Gravity],Go to HyperCrash Menu Bar >> Mass >> Balancing,

 

After hitting on the specs icon which is shown in above.The initial position of COG will appear which is shown 

Now mass should be added to get COG in a proper position.It should be in centre of the cross member.

To bring COG to the centre of the cross member,We should add a mass.

To add mass,Go to Load Case >> Added Mass.Which is shown in below.

 

Now right click on the added mass browser and select Type=0,Where the mass will be added to every single node,Which is shown

 

Here right click on the [grnod_ID] Support* to pick the nodes to add mass,which is shown

Here in the above,The nodes were picked on the model to add mass.

Here after adding mass on the nodes,The COG position is changed which is shown

Here,Similarly pick the nodes on the other side of the model and add mass to bring the COG at centre of the cross member.

The nodes have been picked and mass added to the other side of the model,which is shown in below

Nodes Picked and Mas Added on the Other Side. 

We have attained the mass by adding the mass to the nodes,Which is shown

We have attained the mass by adding the mass to the nodes.

Now export this file and save it in a specified location and import this model into hypermesh and check the total mass.

Now import the exported model from HyperCrash to the HyperMesh.

Next go and check in hypermesh,Whether the we have attained 700 kg mass.

To check,Go to Menu Bar >> Tools >> Mass Details >> Mass,COG,Inertia.

Here check for the penetrations,To check,Go to Menu Bar >> Tools >> Penetration Check.

 

Next select the groups [Interfaces] to define.Which is shown in below.

Then click on the check to check penetrations in the model,If the penetration exsist,It throw a error in the status bar,If the penetration dosen't exsist,it will display No Collisions Found which is shown in below.

Here for this model,TYPE 7 Contact Interface is created with the recommended parameters.Which is shown in below.

Select the slave and master nodes by switching to the coponents and select all the components for slave and master nodes which is shown in below

Here we have to create a section,the section should be created at the node.

To find we have to display the numbers in the display panel.Which is shown in below

Select the node by id and eneter the id number and click on which is shown in below,The node number will be displayed,We have to create a section there.

The node number is displayed

Next for creating section,We need frame,So we need to create frame first.To create frame Right click on the Solver Browser >> Create >> Frame >> Mov.

Next select the nodes to specify the location of the frame to be created on the model.

Switch to the create by node reference,Now select the Node at Origin >> Node at Z-axis >> Node at YZ Plane,

The Nodes selected to create a frame at a specified location

Then create a section,To create a section,Right Click on the Solver Browser >> SECT >> SECT.

After selecting the SECT to create section,A parameter window will be opened left side.

There will be Nodes (N1,N2,N3),Select the nodes to create a section.

Next select the Frame ID

Next Right Click on the grshell_id to select the elements,where we created the section.Which is shown in below.

Enter the values for deltaT and alpha.

Coefficient of filtering (alpha=0.67).

Time step for saving the data (deltaT=0.001).

Every Parameters have been specified which is shown

Every Parameters have been specified which is shown

Now we have to check whether the section created for the rail component is fine or not fine.

If all the nodes get realized in the elements,then the section created for rail component is fine.Which is shown in below Figure 52.

A one row of elements should be maintained.

To check Right click on the Section in the Model Browser >> Review.

Similarly,We have to create a section in the other side.

For that,Create a temp node at 174247 node,and translate the node to the other side and create a frame and section which is shown in below.

To create a temp node,Go to Geometry >> Temp Nodes >> Select the Node at the Required Location >> Add.Which is shown in below

The Section is created for the two rail components which is shown.

Similalry create the sections for the two Shotguns ,Bumper, A Pillar which is shown.

Here we have to create a accelerometer at the B-Pillar.To create a accelerometer,Right Click on the Solver Browser >> Accelerometer >>ACCE.

The accelerometer is created which is shown in below

After creating accelerometer,In the Accelerometer parameter window,We have to specify the node ID.

To specify the node ID,First we have to create a node on the B-Pillar base component which is shown in below.

Now create a base node to reflect that node to the other side.

To create a base node,Go to Geometry >> Nodes >> Interpolate Nodes >> Select the Nodes List >> No of Nodes Between=1 >> Create.Which is shown in below

Now select these two nodes which is shown in above,To create a accelerometer for the B-Pillar Base Component.

The accelerometer is created for the B-Pillar Base Component which is shown in below

Here the initial velocity should be given,Cause the car shhould go and hit the rigid wall,So th initial velocity shiuld be given.

To give intial velocity,Create INIVEL Control Card,To create Right Click on the Solver Browser >> Create >> Boundary Conditions >> INIVEL,Which is shown in below.

After creating the INIVEL card,Select all the components of the car,Cause the initial velocity should be given to the whole car,Cause the whole car should go and hit the rigid wall.

Expand the gmd_ID in the parameter window and select all the components which i shown.

After creating the INIVEL card,Select all the components of the car,Cause the initial velocity should be given to the whole car,Cause the whole car should go and hit the rigid wall.

Expand the gmd_ID in the parameter window and select all the components which i shown.

According to FMVSS [Federal Motor Vehicle Saftey Standards].Assign a initial velocity of 35mph,1mph=0.44704 m/s,=35x0.4470,=15.6464 m/s.

After giving the initial velocity,The model will appear as which is shown in below

Here we have to create intrusions at the specified nodes.

First we have to create temp node at specified location.

To create nodes,Go to Display Panel >> Switch On Display Numbers >> Select the Nodes by ID >> On.

Now translate and create the two temp nodes to the cross member component's face

Rigid Walls allows the user an easy way to define an interface between a rigid surface and nodes of a deformable body.

A Rigid Wall is a non-yielding retaining wall which is defined by the user Master Node and a group of Slave Nodes.

Rigid Walls allow for an easy way to define an interface between a rigid surface and nodes of a deformable body.

To create Rigid Wall,Go to Solver Browser Right Click >> Create >> RWALL >> Plane.

Next the nodes should be selected to to create a plane to define the rigid wall.

Next translate the node to 20mm,While translating the node make it as duplicate and translate it in X-Axis.

The node translated in x-axis to 20mm which is shown in below.

The D-Search distance can be used around the range of 2500 mm. All the Nodes within this distance will be considered as salve nodes for the contact between the car and the Rigid Wall.

The rigid wall is created which is shown in below.

Here the timestep should be assigned to the model to run the simulation.

The required values to be entered in the ENG_DT_BRICK,ENG_DT_INTER,ENG_DT_NODA control cards which is shown.

Next the TH should be requested for the Accelerometer,Interfaces,Sections,Intrusions.

First request TH for the Accelerometer,To request TH for Accelerometer,Right Click on the Solver Browser >> Create TH >> ACCEL.Which is shown in below.

Next at the bottom,there will be a window,there go to the Entity IDs option and select the accelerometers,A window will pop up,Select all and hit on ok.Which is shown in below

Second request TH for the Interface,To request TH for Interface,Right Click on the Solver Browser >> Create >> TH >> INTER.Which is shown

Next at the bottom,there will be a window,there go to the Entity IDs option and select the groups,A window will pop up,Select all and hit on ok.Which is shown in below

Similarly create the TH for sections as created for previous case.Which is hown

Now run the simulation,To run simulation,Go to Analysis Panel as shown in below Figure 100.

Go to Analysis Panel >> Radioss >> Select the Input File >> Save it in Different Folder and Rename it as Test-1 >> Run.

Check the Include Connectors,If there are any connectors in the model,The connectors will also be taken into account.

Type -NT 4 in options tab,This will make the simulation faster.

Where NT indicates No of threads,4 indicates assigning the task to 4 cores in the system.

After completing the simulation,the radioss will pop up a solver window stating Radioss Job Completed which indicates the simulation has been completed.

Here the number of animation steps obtained are shown in below

Now go and open the 00001.out file with notepad.

The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown

The time taken to complete the simulation and the elapsed time is shown in below.

1) Review the Simulation using -HyperView :

Hyperview allows for loading and viewing result files obtained from several sources.

Based on the solver type of the files and the results you would like to visualize and analyze,there are differnt ways to load the input deck and their corresponding results into hyperview.

First to begin the postprocessing in the Hypermesh,Split the Screen as shown in below.

Import the animation file .h3d into the hyperview.

To access the load model panel

Select Load Model Button from the HyperView Panel and open .h3d file as shown

After loading the model into hyperview,It will be represented as shown.

After importing the .h3d file into the GUI,Enable the contour.

The contour tool create contour plots of a model graphically visualize the analysis results.

To enable contour,Go to Results ToolBar >> Contour

Now switch to the Von Misses Stress in result type and select the component,select the averaging method as simple and then click apply as shown in below

After applying ,Run the Simulation,The Simulation animation in terms of Von Misses Stress and Displacement is shown.

After running the simulation,We have to check for the intrusions.

Note :The allowable intrusion is 15 cm.

To check for the intrusion,Measure the distance between the springs where we created.

To measure,Go to Measure tool from HyperView and select the end node of the springs to know the distance between them,which is shown in below

After defining the nodes at the end of the spring at the initial position before the collision,The magnitude for the spring at the node 66244 is 736.746 mm.

After defining the nodes at the end of the spring after the collision,The magnitude for the spring at the node 66244 is 644.678 mm.

1. Spring [At Node 66244] = 736.746-644.678 = 91.966 = 9.1966 cm.

2. Spring [At Node 66695] = 759.192-626.617 = 132.575 = 13.2575 cm.

2) Plot the graphs using -Hypergraph 2D :

Now plot the graphs using Hypergraph 2D,We are plotting the graphs to see what is happening in the rail component.

Hypergraph 2D is a powerful data analysis and plotting tool with interfaces to many popular file formats.

It is sophisicated math engine capable of processing even the most complex mathematical expressions.

Hypergraph 2D combines these features with high quality presentation output and customization capabilities to create a complete data analysis system for any organization.

Here switch to the Hypergraph 2D to plot the graphs.

To switch,Go to Client Selector >> Choose the Hypergraph 2D as shown in above.

[Note : Before plotting the graphs,Make sure to split the screen into three or four and then plot the graphs.]

The first graph is plotted for the Righ Rail at the created section.

To plot the graph,Go to Hypergraph 2D >> Data File >>Frontal_CrashT01 >> Apply.

Right Rail :

The graph obtained for the Right Rail which is shown in below.

The maximum sectional force on the Right Rail is 39.4447 KN.

Left Rail :

The graph obtained for the Left Rail which is shown in below.

The maximum sectional force on the Left Rail is 17.687 KN.

Right Shotgun :

The graph obtained for the Right Shotgun which is shown in below.

The maximum sectional force on the Right Shotgun is 9.12966

Left Shotgun :

The graph obtained for the Left Shotgun which is shown in below.

The maximum sectional force on the Left Shotgun is 15.4251 KN.

Right Bumper :

The graph obtained for the Right Bumper which is shown in below.

The maximum sectional force on the Right Bumper is 26.9859 KN.

Left Bumper :

The graph obtained for the Right Bumper which is shown in below.

The maximum sectional force on the Left Bumper is 29.2241 KN.

Right B-Pillar :

The graph obtained for the Right B-Pillar which is shown in below.

The maximum sectional force on the Right B-Pillar is 4.8738 KN.

Left B-Pillar :

The graph obtained for the Left B-Pillar which is shown in below Figure 125.

The maximum sectional force on the Left B-Pillar is 5.51905 KN.

Right B-Pillar Base Component Acceleration :

The graph obtained for the Right B-Pillar Base Component Acceleration which is shown in below Figure 126.

The maximum acceleration on the Right B-Pillar Base Component is 1.82399 m/s.

Left B-Pillar Base Component Acceleration :

The graph obtained for the Right B-Pillar Base Component Acceleration which is shown in below Figure 127.

The maximum acceleration on the Right B-Pillar Base Component is 3.38479 m/s.

Interface [Type 7 Contact] :

The graph obtained for the Interafce [Type 7 Contact] is shown in below Figure 128.

The maximum force is 188.102 KN.

All Energies :

Internal energy:

Kinetic energy:

Contact energy:

The contact energy will increase slightly when the car hits the rigid wall. Because,Only some of the elements at the front will be having the contact.

The contact energy graph is shown in above

Internal energy:

The internal energy will gradually increases.Due to increase in displacement.

The internal graph is shown in above

Total energy:

The total energy will be slightly decreasing due to the decrease in kinetic energy.

The total energy graph is shown in above

Hourglass energy:

Hourglass Energy Graph:

There will be no hourglass energy. Because, the element formulation is specified with recommended parameters.

The recommended parameters have been assigned.Here Ishell=24 QEPH is used,Due to this there is no houglass effect. the hourglass energy graph is shown in above

Result :

• Hence the COG from the initial position has been changed to the required position by mass balancing.
• Hence the penetrations and intersections has been verified successfully.
• Hence the interfaces created newly.
• Hence the accelerometers created at the base of B-pillar to obtain the acceleration.
• Hence the initial velocity was assigned.
• Hence the springs were created to obtain the intrusions.
• Hence the rigid wall was created successfully.
• Hence the TH for all inputs were created inorder to obtain outputs.
• Hence the simulation was runned successfully without any errors.
• At last all the graphs were plotted with the obtained results.

Conclusion and Learning Outcome :

• In this Challenge,I came to know about
• How to change the COG position.
• How to check for the penetrations and intersections.
• How to create the interfaces and how to find connectivity,To check whether the free parts exsist in the component.
• How to create the accelerometers.
• How to assign the initial velocity.
• How to create the springs to obtain intrusions.
• How to create a rigid wall.
• How to request outputs.
• Learned about the FMVSS[Federal Motor Vehicle Saftey Standards] 208.
• Learned about the sectional forces,axial forces.