Assignment 7-Side Pole Crash Simulation Challenge

AIM :

       To simulate the NEON side pole crash using the body in white components, make a model as per the given requirement and extract the required results in the post-processing.

OBJECTIVES :

       Check the unit system.

       Create an appropriate interface, recommended parameter & friction force is 0.2 between the components.

       Check the penetration & Intersection between the components.

       Create the rigid wall, 0.1 as a friction force between rigid wall & car.

       Adding the extra mass to attain the 700kg as a target mass.

       Apply the initial velocity to the car. 

       Keep the time step minimum of 0.1micro sec & maximum of 0.5micro sec.

       Run the model up to 80 milliseconds.

       Finding the sectional force in the Cross member.

       Calculate the intrusions at the B-pillar, Hinge pillar, Fuel tank region.

       Calculate the peak velocity of an inner node of the door.

       Check the model to ensure good quality.

       Plotting all the required results. 

INTRODUCTION :

       A Side pole crash test is one of the most common crash tests that help us to evaluate how well a vehicle might protect the passenger when another vehicle collided on the sides of the car.

       Automotive companies are using two methods to conduct crash tests such as physical crash tests & Virtual crash tests.

Physical Crash test:

      In a physical crash test, we are using the real vehicle to conduct the frontal crash to collide on the reinforced concrete wall. An automotive vehicle collides on the wall or barrier at some speed, then calculate the deformation of the vehicle & How airbags are opened when a vehicle collides on the barrier.

       An "anthropomorphic test device" is commonly used as a "Crash test dummy" in the automotive testing vehicle, it is used to calculate what are impact forces a passenger suppose to receive.

       For each crash test, have to use the new vehicle. It will lead to an increase in the cost & time.

Virtual Crash test:

       In a Virtual crash test, by using powerful computers we can perform the same crash analysis and get the proper results whatever we want. We have to set up the model as same as in real crash scenarios & get the results.

       We can perform an N number of tests with some changes as per our requirement. Eventually, we save a lot of money & time.

       But, the accuracy of the results is slightly changed then the physical test.

 

PROCEDURE FOR OBTAINING THE OBJECTIVES :

1) Checking the Unit system :

      Open the "Begin_card", check the unit system which is followed by Milligrams, millimetres & seconds unit system. And also we can check the unit system in the starter file.

      

2) Apply interface to components:

      Create a Type 7 (Nodes to the surface) contact, set the parameters as per the recommended crash application & then provide 0.2 as the coefficient of friction.

Igap : Determines how the size of the gap is calculated.

An "Igap = 2" is a set variable gap to take into account the true distance between parts.

GAPmin : Minimum gap for activation of the interface.

A "GAPmin = 0.5" is a specify the minimum thickness of the model to avoid numerical issues. Typically, it takes half of the thinnest part.

Inacti : Action to takes if initial penetration exists.

An "Inacti = 6" is to remove initial penetrations where possible. Elsewhere, reduce to less than 30% of the defined gap value and adjust the gap with the "Inacti" parameter.

Istf : Affects how the stiffness of the interface is calculated.

An "Istf = 4" is to set stiffness of interface based on the softer of master and slaves.

Iform : Friction formulation. 

A "Iform = 2" is sliding forces are computed using the stiffness of the interface, which usually results in a bigger time step.

Stmin : Minimum stiffness to use in the interface.

A "Stmin" is a specify a minimum stiffness in the contact to avoid too soft contact

Idel : Behaviour of slave and master segment if an element fails.

An "Idel" is removed slave nodes from contact because of element deletion.

 

Have changed the contact card image as shown below.

3) Checking the Penetration & Intersections :

     Open the "Penetration & Intersections" checking tab, chosen all groups as a selection, keep "0" as Minimum penetration depth and "1" as a thickness multiplier.

     There's no intersections & penetration are presented in between the components as marked below.

      

4) Creating the rigid pole :

       Create a new "rigid wall" in the model browser, change the Geometry type as "Cylinder" instead of "Infinite plane".

       Select the one node near the front door handle. Then have to tweak some coordinates to keep the node away from the car.

       A pole axis should be lies on the z-axis. So, keep unity for the z-axis and keep zero for the remaining two coordinates. Provide the diameter of the pole as 150 mm.

       To define the friction value between BIW & Side pole, we have to switch to "Sliding with friction" as the Slide option. Then provide the friction value as 0.1.

      

      After creating the rigid pole at the side of the car, it looks like as below.

      

5) Adding the extra mass to attain target mass :

      A given model total mass is 188 kg only. But, actually full-scale 300k nodes model mass is 700 kg.

     So, we have to provide the remaining mass on a given model.

     

     Create a new Add mass card, set the ground id.

     Chosen "0" as a Mass type which means, a mass is added to each node of the node group. So, we have to provide the mass value is "Remaining mass is divided by the number of nodes selected on the model"

     Mass = 534/858

             = 0.622 kg

        

      Nodes are selected for adding the mass to achieve the target mass of the vehicle.

     

     After adding the mass to the model, it reaches the target mass of 700 kg.

         

6) Apply the Initial velocity :

    Create an "INIVEL" card for applying the boundary condition on the model.

    Create a new ground id, select all components as entity id.

    Provide the 15.64 as velocity in y translational direction & the remaining two directions are constrained.

    An initial velocity is applied to global coordinate systems, that's why we didn't consider skew id or local coordinate system.

    After gave the velocity on x translational direction, a number is showing from the model.

     

7) Set the time step :

DT_ELTYPE_KEYWORD_IFLAG_SUPPORT:

     In this option, we can create different types of time step control options such as INTER, NODA, BRICK, QUAD, SHELL, TRUSS, BEAM, SPRING & other few.

     After, we have to select the type of time step control such as CST, CST1, CST2, AMS, STOP, DEL.

     In this case, we have created INTER & NODA as a type of time step option

ENG_DT_INTER:

     This method is used for controlling the time step from the element.

     A Type of time step option is "INTER" and the time step control type is "DEL"

     Keep the 0.67 as a scale factor on the time step.

     Keep the 0.0005 ms as a minimum time step.

     If the model time step is reduced below the minimum time step, this algorithm will add some mass to the element so which will lead to maintaining a time step which more than the minimum time step.

    

ENG_DT_NODA:

      This method is used for controlling the time step from the Node.

     A Type of time step option is "NODA" and the time step control type is "CST"

     Keep the 0.67 as a scale factor on the time step.

     Keep the 0.0001 ms as a minimum time step.

     As same, If the model time step is reduced below the minimum time step, this algorithm will add some mass to the node so which will lead to maintaining a time step which more than the minimum time step.

    

8) Creating the sectional cross-sections:

      To calculate the sectional force that passes through the cross rails, we must create a section, frame, cross-section & add it into output blocks.

      First of all, create a "Moving frame" in the solver browser on the location as a reference.

      After creating the moving frame, a new system has been created and properly select the three nodes for defining the coordinate orientation.

      

     Next, followingly create a new section, similarly, properly select the nodes. Properly assign the frame id and provide the delta T value as 0.1 & Alpha value as 1.67.

    Create a new ground shell id, select the three or four rows of elements properly on where we want to calculate the sectional force.

    Make sure to switch with "12" as an Iframe which keeps the coordinate at the location of the centre of gravity.

      

      Here below is how I select the elements for calculating the force passing through this sectional cross-sectional area.

      

      Create "Cross-sections" in the model browser, all data are stored by default once we created the section in the solver browser.

      

      Finally, create a new one under the output blocks & name it a cross-section. Assign the created cross-section into entity id.

      

      Similarly, do the same process for another cross rail.

9) Calculate the intrusions :

      We have to calculate the intrusions on the B-pillar, Hinge & Fuel tank region when a car collides on the side pole rigid body. And also calculate the velocity of the door gets intrusions.

      For calculating the intrusions, choose the appropriate node location on where we want to measure.

      Here below, a node is selected for calculating the intrusions of the B-pillar component.

      

     Here below, a node is selected for calculating the intrusions of the fuel tank region.

      

      Here below, a node is selected for calculating the intrusions of the hinge component.

      

      Here below, a node is selected for calculating the intrusion velocity of the front door component.

      

     We have to measure the displacement or velocity of the respective skew. So, create a skew for individual one which created on the opposite component.

     Create a new moving skew, properly select the node for defining the orientation of the coordinates.

      

      After creating the skew reference for the B-pillar, Fuel tank region, Hinge & Front door. It looks as same below.

      

      Then create a new node time history, a node entity selection is shown above images.

      Assign the appropriate skew id to the node time history as below.

      

      At the post-processing, a calculate the displacement along y-direction for Fuel tank region, B-pillar & Hinge. For the Front door, we calculate the velocity along the y-direction.

10) Check the quality of the model :

     In this model, there's no major error that will not cause the analysis.

     So, we move this model to the next process which is solving.

     

ANALYSIS OF THE MODEL :

     Select the "Radioss" sub-panel under the "Analysis" panel, save the file in the separate folder, and click the radioss button to solve the problem by solver itself.

     After calculating the model, a solver is generated different files such as the Starter listing file, Engine listing file, Animation files, Time history file and then restart file.

     

      A model time step is to go below 0.001 which means the model time step value is less than the minimum time step value set in the NODA time step. So, the solver has taken a constant time step value which 0.001, because we enabled the CST algorithm.

     A mass is added on the node-based upon time step difference from minimum time step to model time step.

     An energy error is negative which means there's some energy is dissipated. But, those come within the acceptable range.

     

POST-PROCESSING :

      Post-processing is a process of extracting useful data from the solved model.

Hyperview :

      After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

      Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot of Displacement:

      A maximum displacement reaches up to 1420 mm from the original place.

      

Contour plot of Von Mises stress:

       More stresses are generated at the region of the B-pillar and also cross rails.

       A Von Mises stress value seems low because applied initial velocity is low.

    

Hyperview :

      Switch to the "HyperGraph 2d" interface instead of the "Hyper View" interface for plotting the required data.

      Import the appropriate time history file.

Energies plot:

       Both Kinetic energy & Internal energy is maintained as constant up to car sides gets collided on the cylinder pole.

       After the car gets collided on the pole, the velocity is decreased due to impact. So, the kinetic energy also is decreased because kinetic energy is directly proportional to velocity. It started around 85000 and ended up with 67000.

       There's no hourglass energy is generated since we used the QEPH shell element formulation.

        The total energy is a combination of Internal energy & kinetic energy. 

      

Intrusion of B-pillar component :

      A Maximum intrusion of the B-pillar component is reached up to 28mm at the time of 42 milliseconds.

      Such maximum intrusion is very large, it's not recommended one. Because high chance a passenger gets injured due to high intrusions of the B-pillar.

      

Intrusion of Fuel tank region :

      A Maximum intrusion of the fuel tank region component is reached up to 48mm at the time of 42 milliseconds.

      We have to protect the fuel tank while the car gets collided on the side pole. This level of intrusion is not recommended, because that will cause the explosion.

      

Intrusion fo Hinge component :

     A Maximum intrusion of the Hinge component is reached up to -300mm over the period of time. A more hinge intrusion will cause leg injuries.

     

Intrusion velocity of the front door :

     A Peak velocity of the front door node is around 1.5 mm/ms.

     

Sectional force of the Front cross rail:

       The cross-sectional force of the front cross rail is reached up to 2.05 N

     

Sectional force of the Center cross rail:

      The cross-sectional force of the centre cross rail is reached up to 0.95.

     

CONCLUSION :

       Successfully ran the side pole crash simulation as per the given requirements on the given BIW components.

       Calculated all the outputs requests such as sectional forces, axial forces, acceleration & Intrusion of the dash wall.