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 correct rigid bodies if any issues.
• 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 35mph to the car.

Output Deliverables :

• Sectional force in the rails at location of indicated node 174247.
• Axial force received on the rails from bumper.
• Shotgun cross sectional forces.
• A pillar cross section.
• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
• Intrusions on the dash wall 66695,66244.

Software used : Explicit solver - Radioss 2022.

Theoretical Framework :

• Frontal car crash tests are an essential part of evaluating the safety of vehicles. During these tests, cars are crashed head-on into a solid barrier at a specific speed, typically around 35 to 40 miles per hour.
• These tests assess how well the vehicle's structure absorbs and dissipates the energy of the impact, as well as how effectively the safety features, such as seat belts, airbags, and crumple zones, protect the occupants.
  
• Crash test dummies equipped with sensors are used to measure the forces experienced by the occupants during the crash.
• These tests provide valuable data that manufacturers use to improve the safety of their vehicles and help consumers make informed decisions when purchasing cars.

         

 

• In India, frontal car crash test standards are primarily overseen by the Bharat New Vehicle Safety Assessment Program (BNVSAP), which was introduced to enhance vehicle safety standards in the country. The BNVSAP is administered by the Ministry of Road Transport and Highways (MoRTH) and is aimed at improving vehicle safety through crash tests and other assessments.
• While the BNVSAP does not have its own testing facility, it relies on certified testing agencies to conduct crash tests according to established protocols. These protocols typically align with international standards to ensure that vehicles sold in India meet global safety benchmarks.
• In the United States, FMVSS regulations established by the National Highway Traffic Safety Administration (NHTSA) include standards for frontal crash testing. FMVSS 208 specifies requirements for occupant protection in frontal crashes.

 

Procedural steps :

Step 1 : Check unit system 

Step 1A : Import the solver deck model

                File > Import > solver deck > browsed to select neon_front_0000.rad file > imported it. 

                

 

Step 1B : Check the unit system.

• Model Browser > Control Cards > BEGIN_CARD > checked unit system.

       

 

Step 2 : Import the model in Hypercrash application.

•   Menu Bar > Applications > HyperCrash > Shown in below unit system 

 

•  In hypercrash > File > import > radioss >  neon_front_0000.rad file 

        

 

Step 3 : Mass balancing of the model 

• Check the Mass and COG by HyperCrash Menu Bar > Mass > Balancing.So , total mass of the model is 188 Kg.

       

 

• Initial position of COG.

        

 

Step 4 : Add mass of the model 

• 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 by  Menubar > Load Case > Added Mass.
• Right click on added mass tree > create new > Type:1 > In Support > graphics display by pick mode option n- by pick one node on the FE model.
• Then add remaining mass 700-188 =512 Kg in added mass option .
• Now mass should be added to get COG in a proper driver seat position.

         

         

                           COG is located exactly near the driver's seat

        

         

• Now checked the added mass in total mass of the model.

       

 

Step 5 : Export the hypercrash file into radioss file 

             Menubar > file > export > Radioss format > saved it .

 

Step 6 : Import the radioss file in the Radioss deck solver and check the mass and COG details.

• Menubar > file > import > Radioss format > imported it .
• Then check the mass of the miodel by Tool > mass details > Mass, COG & Inertia.

         

 

Step 7 : Penetration check 

•  Menu Bar > Tools > Penetration Check- 0 collisions found.
• 

 

Step 8 : Creation of contact interfaces

Step 8A : Creation of Self contact interfaces of all components.

• RMC on the model tree to create contact .
• The slave and master node settings, all the components in the model are selected. Therefore, this interface card will cover all the components in the model.

         

 

• TYPE 7 Contact Interface is created with the recommended parameters.

        

       

 

Step 8B : Creation of contactbetween the bumper and headlight brackets.

• This interface is done to calculate the force transfer in this region.
• The slave nodes will be the Bumper and the master nodes will be the brackets. Other than these changes rest of the properties will be the same as in the previous case.

        

       

 

Step 9 : Creation of section

Step 9A : Find the Node id

•  To create a section,the section should be created at the node.
• To find the node id we have to ON the display the numbers in the display panel.

           

 

• Select the node by id and eneter the id number - 174247  and click
• The node number will be displayed,We have to create a section there.

            

        

 

Step 9B : Creation of frame

•  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. 

        

 

•  Selected the node of od-174247 as origin node and selected the adjacent node as Z-axis and selected the other node as YZ-plane.

         

                                 Frame created at the node id 174247

        

       

        

Step 9C : Creation of 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 by picking coordinate in the model.
• Enter the values for deltaT and alpha.
• Coefficient of filtering (alpha=0.67).
• Time step for saving the data (deltaT=0.001).
• Then RMC on the grshel_id to create/ edit to create set by the below 2nd image method.

           

 

          

         

       

                                                         Section created 

        

       

Step 9D : Check the creation of section

• 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.
• A one row of elements should be maintained.
• To check Right click on the Section in the Model Browser >Cross section >  Review.

        

 

Step 9E : Creation of section of the right side rail apoosite to the left side rail.

        

 

 

 Step 9F : Creation of  the sections for the two Shotguns.

        

 

  Step 9G : Creation of  the sections for Bumper.

        

 

  Step 9H : Creation of  the sections for the left anf right side A-pillars.

         

        

Step 10 :  Create Accelerometer at the B-Pillar 

• To create a accelerometer,Right Click on the Solver Browser > Accelerometer >ACCE .

        

 

• Select the node id in the B_pillar base left side component.
• Similarly Select the node id in the B_pillar base right side component. 

       

 

            Acceleromter node created on tboth sides of B_pillar base

      

 

Step 11 : Give the Initial Velocity 35 mph 

•  Create INIVEL Control Card,To create Right Click on the Solver Browser > Create > Boundary Conditions > INIVEL.

        

     

•  According to FMVSS [Federal Motor Vehicle Saftey Standards.
•  Select all the components in the model.
•  Assign a initial velocity of 35mph =15.6464 mm/msec.

         

                                    Velocity assigned to the model

        

 

Step 12 : Create Intrusions on the Dash Wall :

• To create intrusions at the specified nodes.

 

Step 12A : Find node ids 66695 and 66244

• To find the node id we have to ON the display the numbers in the display panel.
• To create nodes,Go to Display Panel > Switch On Display Numbers > Select the Nodes by ID > On.
• Select the node by id and eneter the id number - 66695 and 66244 and click.

        

 

Step 12B : Create the two temp nodes to the cross member component face

• To create temp node at specified location of node ids.
• Now translate and create the two temp nodes to the cross member component's face.

 

       

      

 

Step 12C : Create the spring elements.

• Creation of spring elements to study the intrusions (forces inside the cabin causing deformation/rupture).
• Create 2 parallel spring elements from the indicated nodes (66695, 66244) till the Crossbeam ( created temp nodes).
• Springs can be created from the 1D Panel > Springs .

       

         

 

Step 12D : Create and assign the property to spring elements.

• Model Browser > Create > Property > Rename as Springs.
• Spring card image is P4_spring.
• Mass =0.001 and stiffness =0.001.

             

• Assign the property to spring elements.

          

 

Step 13 : Create Rigid Wall With Friction 0.1. 

• Rigid Walls allows the user an easy way to define an interface between a rigid surface and nodes of a deformable body.
• Solver Browser Right Click > Create > RWALL > Plane.

        

 

• Temp node creation on the bumper center.

         

• Temp node is duplicated then translated into 20mm distance.

        

 

•  Selected the translated temp node and normal direction as (-1,0, 0) with friction 0.2.

       

      

 

Step 14 : Request TH File for the Required Outputs and Give Time Step Value 

•  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.

               

           

Step 15 : TH for Accelerometer

• To request TH for Accelerometer.
• Right Click on the Solver Browser > Create TH > ACCEL.

        

 

•  In entity IDs select the B_pillar base 2 accelerometer node datas.

     

 

Step 16 : TH for Interface 

 

• To request TH for Interface,Right Click on the Solver Browser > Create > TH > INTER.
• In entity IDs select the 2 interface contact already created in model browser as a groups. 

 

       

 

Step 17 :TH for the Sections 

 

• Similarly create the TH for sections as created for previous case.

       

 

     

• In entity IDs select the 8 sections already created.

      

 

Step 18 :TH for the intrusion

•  Create the TH for Springs as created for previous case.

      

• In entity IDs select the 2 spring elements already created.

   

 

Step 19 : Setup the simulaion time

 

• In the model browser, Cards > ENG_RUN to change the simulation time.
• In the entity editor, T_stop is given the value of 80ms.

        

 

Step 20 : Model checker :

• To check the solver deck model by the following steps .
• Menubar > tools > model checker > Radioss block.
• If error is found need to be fixed.

         

       

Step 20 : Run the Simulation 

• 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-7 > 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.

       

 

      

 

STEP 21 : Check engine 0001.rad file.

• After the end of the solver output go and check whether the engine has been edited or not.
• To check go to the file location where you have saved the starter file.
• Open the Test_7_neon_front_0001.rad file.

        

Step 22: Check the output file 

• 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   

       

• The acceptable energy error is -15% to +5%.
• The acceptable mass error range is 0 to 2 % .

 

STEP 23 : Post processing

1) Review the Simulation using -HyperView.

2) Plot the graphs using -Hypergraph 2D.

3) Review the Simulation using -HyperView.

• First to begin the postprocessing in the Hypermesh,Split the Screen .
• Import the animation file .h3d into the hyperview.
• 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.

        1.)Stress contour :

 

        Max stress developed = 0.306 Mpa.

 

         

        2.) Displacement contour :

 

        Max displacement = 1285 mm

 

       

 

 

   3.) Intrusion graph :

            Intrusion at node 66695 = 853.42 mm 

       

               

                  Intrusion at node 66244 = 918.87 mm 

           

 

   4.) Sectional force in the rails at location of indicated node 174247.

         Sectional force in the rails at location of indicated node 174247 = 15.18KN     

            

 

 

5.)    Axial force recieved rails from bumper.

        Axial force recieved rails from bunper is 21 KN.

              

6.) Shot gun cross sectional forces .

       a.) Left side Shot gun cross sectional force = 4.72 KN

            

 

      b.) Right side Shot gun cross sectional force = 5.85 KN

            

 

7.) A-pillar cross sectional forces.

      a.) Left side A-pillar cross sectional force = 0.640 KN

              

 

        b.) Left side A-pillar cross sectional force =  1.84 KN.

               

8.) B-Pillar Base Component Acceleration :

     a.) Left B-Pillar Base Component Acceleration = 12.80 mm/msec²

                 

           

 

     b.) Right B-Pillar Base Component Acceleration =  11.42 mm/msec²

          

9.) Plots of energies :

      a.) Internal energy :

• The internal energy will gradually increases.Due to increase in displacement.
• Max Internal energy developed = 20116 kg mm²/ msec²

       

      b.) Kinetic energy :

• The kinetic energy decreases.Due to the decrease in velocity.Because the given velocity is initial velocity, which may reduce.
•  Max Kinetic energy started =  85620  kg mm²/ msec²
•  Min Kinetic energy at the end of the crash =  62954  kg mm²/ msec².

          

       

     c.) 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.
•  Max contact energy at the end of the crash =  1913  kg mm²/ msec².

             

             d.) Hourglass energy:

                    Max hourglass energy at the end of the crash =  234 

                  

       e.) Total energy :

•  The total energy will be slightly decreasing due to the decrease in kinetic energy. 
•  Total energy before crash =   85620  kg mm²/ msec²
•   Total energy at the end of the crash = 83071  kg mm²/ msec²

                          

 

      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.
• Atlast 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.