Assignment 7-Side Pole Crash Simulation Challenge

SIDE POLE CRASH SIMULATION OF NEON CAR

PROJECT 2- SIDE POLE CRASH ANALYSIS USING HYPERMESH, RADIOSS, AND HYPERCRASH.

AIM: To perform the simulation for Side pole crash analysis of a car with recommended parameters and to plot energy graphs and identify the differences.

Objectives: For the requested outputs there are certain objectives that are:

1. To perform the crash analysis on the side section of the car and to check where stresses are acting on it.
2. To check the unit systems and change if necessary.
3. Creating interface of type 7 with friction value of 0.2 and recommended properties.
4. Creating a rigid wall with friction 0.1.
5. Compare the model weight with the full scale 300k nodes model and by using mass addition to reach the target of 700kg while maintaning center of gravity with in the driving line of car.
6. To move the object with initial velocity of 35mph.
7. Providing time step : 0.5 to 0.1 micro second.
8. Providing run time as 80ms.

Requested Output:

• Sectional force in the cross member.
• Intrusion at B pilaar,hinge pillar and fuel tank region. And to provide a recommendation on what can halp to reduce fuel tank intrusion.
• Peak velocity of inner node of the door.

BRIEF:

A crash test is a virtual reconstruction that replicates the same forces and speeds that would occur if the vehicle was to be involved in actual crash.In this type of testing, since nothing is physically impacting the Body-in-white(BIW). No physical deformation or damage occurs to the body's structure, allowing multiple crashworthiness tests to be conducted in the successsion. This type of simulation is an integral part of the design process and can help save both time and money.

For this project, case setup and simulation are to be done in Hypercrash, where as Hyperview and Hypergraph2D will be used for post-processing. Hypergraph will be used to plot energies, von misses stresses, plastic strains, accleration curves, and Hyperview will be used to view the simulation.

In the part of simulation we will be creating a rigid wall, providing a initial velocity of 35mph, manipulation of masses to ensure the total weight of 700kgs with maintaning centre of gravity in specified region.

WHAT IS A CRASH TEST?

A crah test is a form of destructive testing usually performed in order to ensure safe design standards in crashworhiness and crash compatiblity for various models of transportation or related systems and components.

Various crash tests:

• Frontal Impact test: In this test fully front structure of the vehicle collides with another object like another vehicle, rigid wall etc, at a given speed.
• Offset Test: In this test a part of front portion of the vehicle strikes on some barrier a particular speed.
• Side Impact Test: In this test some time the vehicle is in static condition or in dynamic and another vehicle or an objec collide additional relative speed.
• Roll-Over test: In this test a vehicle is in roll over condition having a certain angle with support itself a dynamic impact.
• Road side hardware: It is performed to test the crash barriers, and crash cushions will protect vehicle occupants from road side hazards.
• Old vs New: In this impact, an impact is done between an old car against a new car and big car vs small car to compare the advancements in crashworthiness.

Crash tests are conducted under rigorous scientific and safety standards. Each Crash test is very expensive so the maximum amount of data must be extracted from each test. Usually, this requires the use of high-speed data acquistion, at least one tri-axial accelerometer and a crash test dummy, but often includes more. A crash test is much important which helps in minimizing the losses such as deaths, injuries, and property damages from the vehicle crashes on the roads.

In this project, we must perform a frontal crash of the vehicle. Frontal impacts are the impacts undertaken against the soild barrier. Frontal impacts are the impacts undertaken against the solid barrier with precise speed. The test requires the front portion of the vehicle to impact the barrier.

In the New car assessment program(NCAP), passenger vehicles are crashed at 35mph into a rigid barrier that covers the full width of the vehicle. The institute runs offset side pole tests .

How crash testing works?

A crash test is destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibilty for various modes of transportation related systems and components.

Crash test dummies have been the subject of public service announcements, cartoons, parodies, even the name of a band. Real crash test dummies, however, are true life-savers as an integral part of automotive crash tests. Even thought cars get a little safer each year, and fatality rates are declinig, car crashes are still one of the leading causes of death and injury in the United States.

One of the reasons cars have been getting safer is because of a well-established testing program.

The dummies contain three type of instrumentation:

1. Accelerometers: These devices measure the accelration in aparticular direction. This data can be used to determine the probabilty of injury. Acceleration is the rate at which speed changes. The crash test dummy has acceleromters all over it. Inside the dummy head, there is an acceleromter that measures the accleration in all the three directions(fore-aft, up-down, left-right). There are also acceleromters in the chest, plevis, legs, feet and other parts of the body.
2. Load sensors: Inside the dummy are load sensors that measure the amount of force on different body parts during a crash.
3. Movement sensors: These sensors are used in the dummy's chest. They measure how much the chest delfects during a crash.

Requirements in Crashworthiness:

The vehicle structure should be sufficiently stiff in bending and torsion for proper ride and handling. It should minimize high-frequency fore aft vibrations that give rise to harshness. In addition, the structure should yield a deceleration pulse that satisfies the following requirements for a range of occupants sizes, ages and crash speeds for both genders: Deformable, yet stiffness, front structure with crumble zones to absorb the crash kinetic energy resulting from frontal collisions by plastic deformation and prevent intrusion into the occupant compartment, especially, in case of offset crashes and collisions with narrow objects such as trees.

Procedure:

• Check for UNIT SYSTEM.
• Importing the model in Hypercrash.
• Check for pentrations and intersection.
• Add masses to reach a target weight of 700kg.
• Export changes file and import in HYPERMESH.
• Create a interface contact between component and bumper.
• Create a rigidwall
• Add velocity to the nodes.
• Creating a cross section.
• Creating acceleration nodes.
• Create springs to check deflection.
• Assign property to springs
• Create TH for section forces, intrusion springs, inreface contacts.
• Create crads.
• Model checker.

Unit system used for analysis is "kg mm ms".

Importing the model:

• For importing the model go to file>import>solverdeck>select file.
• Import the 0000.rad file using solver deck as shown in below image.

Imported model Image:

CHECKING FOR UNIT SYSTEM:

For checking unit system we have two files

• Neon_side_reduced_0000.rad known as starter file which has information in it like:

1. Nodes
2. Load conditions
3. Velocity
4. Boundary Conditions
5. Has ASCII standard file
6. And it always in 0000.rad format.

• Neon_side_reduced_0001.rad file known as engine input file. And it stores information such as

1. Simulation Run_time
2. Simulation Speed Control Parametres, such as No of Animation Files, No of Time History File, Size of the history file and animation frequency, etc.
3. Has ASCII standard file.
4. We can also manipulate the engine file directly through the control cards.
5. It always ends with 0001.rad format.

Images for Starter and Engine file in Notepad format.

• So here the unit system is in 'kg mm ms' System only.

CHECKING FOR PENETRATIONS AND INTERSECTIONS:

• Penetrations is defines as the overlap of the material thickness of shell elements, where as intersection is defines as elements that pass completely through one another. All models and especially impact models should be checked for penetrations and intersections and they should be De-penetrated to ensure the integrety of the model. Pnetrations adversely affect results and should be removed.
• To check penetration and intersection: Import the 0000.rad file in Hypercrash and Go to Quality>check all solver contact interfaces>select parts> click on check penetration.
• Refer below images for checking Intersections and Penetrations.

Compare the model weight with full-scale 300k nodes model and use added masses to reach a target weight of 700kgs while maintaining the CoG in specified region.

• A Vehicles centre of gravity or CG is the theoritical point where the sum of all masses of each of ots individual components effectively acts. Carrying weight up-high such as panoramic sunroof will paise a vehicle CG while placing heavy subsystems low in a vehcle, such as battery pack, will work to lower it.Lower is better from a handling standpoint, as it reduces weight transfer during cornering and braking.

MASS ADDITION AND POSITIONING OF COG:

• Mass balancing: In order to maintain the CoG of a car, we must add mass for the given components, In the given model here are so many parts are missing because of the node limit in the student version.
• To check the CoG, Go to menu>mass.Balancing>Show CoG point.

Images for Viewing CoG point.

• By above image we can see that Mass of the body is around 750.2 Kgs which meets the target.
• For adding the masses manually select Loadcase>Added Mass>Select nodes.

We must add the masses in sucha way that the centre of gravity is exactly in the middle of cross Beam to simulate the real world model. It is only bothered about the position CoG and not the height(Z-axis). We generally use Type1 mass, where mass is distributed on each node of the selection process.

• Refer below images for adding of masses and their parameters.

• The added mass tab is used for scale factor for mass.
• Grnod_ID referred as support is for set of selected nodes for assigning mass to them.
• Generally, for assigning mass right click on 'grnod_ID'>select in graphics>select nodes.
• And click on save to assigning masses.

Creating Type7 Contact interface:

In this case, the TYPE7 contact interface is defined. Interface TYPE7 is a multi-usage impact interface, modelling contact between a master surface anda group of slave nodes. It is also possible to consider heat transfer and heat friction.

All limitations that were encountered with interfaces TYPE3,TYPE4 AND TYPE5 are solved with this interface

• A node can at the same time be a slave and a master node.
• Each slave node can impact each master segment; except if it is connected to this segment.
• AA node can impact m,ore than one segment.
• A node can impact on the two sides, on the edges and on the corners of each segment.
• It is a fast search algorithm without limitations.

The main limitations of this interface are:

• Time step is reduced in case of high impact speed or contacts with a small gap.
• It does not work properly if used with a rigid body at high impact spped or a rigid body with a small gap.

It does not solve edge to edge contact to solve this, /INTER/TYPE11 should be used along TYPE7).

• At the beginning there was a 6 interfaces of type 7 used to the BIW structure but there was no proper connection present in the whole model so for the betterment of the model we have to delete those interfaces present and have to create a new interface the whole model for proper connection.

TYPE7 : NODE TO SURFACE

This interface simulates the most general type of contacts and impacts. TYPE7 interface has the following properties:

• Impacts occur between master surface and a set of slave nodes, like the TYPE5 interface.
• A node can impact one or more master segments.
• A node can impact on either side of a master surface.
• Each slave nodes can imoact each master segment except if it is connected to this segment.
• A node can belong to a master surface and as et of alave nodes.
• A node can impact the edge and corners of a master segment. None of the previous interfaces allow this.

Recommended Properties:

• We need to give in the slave nodes and the master segment. Since we are defining a self-impact in the model, the slave and master segments fro this contact will be the entire given model. So we then select all the nodes for both segments respectively as shown below.
• Also, delete all the other compnonents under Groups as they are not assigned to any part in the model.

Image of TYPE7 properties:

• Properties are assigned to TYPE7 with recommended paramters.
• To ensure the selected components make sure to review the select parts.

CREATING A Side Pole:

• To create an RWALL: Go to solver browser>create>RWALL>CYL
• We need a refernce node to create an RWALL so for that we are creating a temp node in the middle of bumper.
• After that translate that node to create some gap between car and wall which will be created at the translated node or you canmanually create a gap by putting the increased value of the temp node in the x axis as shown in below image.
• Create a temporary node on the front end of the car.
• Enter co-ordinates X,Y AND Z values.
• Enter the co-ordinates of the Temp node[XM,YM,ZM]>Enter the direction of the normal[-1,0,0]>select grnod_ID 1 : SET DISPLAYED NODES> DSEARCH: 1000/1500.
  
  

The SIDE POLE is facing opposite to the car so the normal is on the negative X- axis that is why the value of normal x axis as -1.

• Apply frictional parameters for the rigid wall when the slave nodes come in contact.
• Fric_type[Slide]= 2:Sliding with Friction.
  Fric_coeff[FRIC]= 0.1.
• Dsearch distance we can use around the range of 1000mm. A ll the nodes within the distance will be considered as slave nodes for the contact between the car and the rigid wall.

Image of Side Pole created:

Creating Velocity:

• Initial velocity is 35mph
• We get 1mph=0.447ms, there fore 35mph=15.6464ms.
• Go to solver browser>create>Boundary conditions>Inivel.
• Apply the parameters and select whole nodes of the components to experience initial velocity.

Images of Initial velocity created:

For sectional force in Cross Member:

CREATING FRAME FOR ANALYSIS:

• To create frame . right click on browser>create>frame>mov>select 3 nodes for axis>create.
• Rememeber while creating loacal co-ordinates, slect the nodes in such a way that the z-axis should be in the direction of initial velocity applied.
• Create a frame and assign FRAME on each section accordingly.
• Now assign a section card in the next process.
• Refer the below image as shown in below image.

Creating sectional parts for analysis:

• We need to create sections at A- pillar, shot gun, rails and bumper plates in order to study the sectional forces.
• We should know how the forces are transmitted from the bumper to the dashboard and the rate of deformation. It is done in order to ensure the safety of passenger.
• TO create a section part go yo browser>create>section>SECT.

Image for creating section:

• Select three nodes for making frame. For creation of frame you have to slect 3 nodes for the section card you have to select again those partcular 3 nodes( N1,N2,N3). In this 3 node taken as reference frame for calculationg nodes across the section.

Image for selecting 3 nodes in frame card.

• Then under the frame select Frame_ID you have to select the frame made earlier .
• Put the values of delta T and alpha as 0.10 and 1.96 and iframe value as set to 12.
• Create grshel_ID select a section of elements on a component where we should calculate forces going through them.

Creating Springs:

• Intrusions here means how much displacements the B-pillar, Hinge pillar and fuel tank.
• We need to plant spring elements to study the intrusions.
• For creating the spring elements go to 1D>SPRINGS>SPRING2 and select 2 nodes as shown in below image.
• Select the node at the required node id as shown below and then, select another node on other end to create spring.

• Now that the springs are created we need to create property card spring and assign it to the spring element created.
• Go to model browser>create>property>Rename intrusion springs.
• Then assign the property to the spring component.

Study of peak velocity of inner node of the door.

• To find peak velocity at the inner node of the door, we will create a moving frame at the node location by create>skew>MOV.

Output block for peak velocity on inner door:

• The next step is to create a Time History(TH) output specifically for this step.
• Create an Output block by going to model browser and right click>create>output block.
• The entity ID is going to be just one node- node 338460 and for Iskew we need to select the skew created.

Deleting the existing TH card and creating new card:

• Delete all the unnecessary TH files and create a Time History files for the bpoundary conditions that we have created for side impact crash model.
• This will help us reduce some time in running simulations as solver only calculates TH for required outputs.

EDITTING CARDS:

• Before running the simulation check all these cards and assign the values accordingly.
• To check these parameters go to Hypermesh and navigate to crads under model Browser.
• Check for ENG_DT_NODA, ENG_RUN, ENG_ANIM_DT and assign the values as shown in below images.

Creating Output Blocks:

• Output blocks contain the datat whic hwe need to create graphs after the simulation.
• Therefore, we need to create 5 different output blocks for different sets of data.
• Request for only required outputs blocks as this makes simulation fast.

Checking for errors:

• After assigning all the values in the model check for errors in tools>Model checker.

RUNNING THE SIMULATION:

• Now that the all parameters are checked now run the simulation analysis by going to Analysis>Radioss>start.
• Refer the following images for change the required parameters.

ANALYSING THE RESULT FILE:

• The next step is to check for the energy, mass errors and this can be observed by checking 0001.output file. This can be viewed from the input specified folder before running the simulation.

• As we can see that energy error is -4.4% and it is in acceptable range of -10% to +5% error. In addition to that, the mass error is 0.01940, which means that a negotiable qauntity of mass was added during the simulation.
• Total simulation time is 1984.29s which is 33 minutes.
• No 0f cycles :80001.

Animation files of Simulation:

• To view the simulation animation we need to open .h3d in input specified folder or switch HyperView and open the model.
• Then the contour is applied which makes the model in colours of maximum and minmum stress induced.

Animation of Displacement:

Animation of Von misses stress induced:

• From the animation we can state that initially doorstep starts crushing then the forces are transferred to the B pillar then from there these forces are transferred to outer rail, side imapct beam , cross beam.
• From the von misses plot we can say that the stress distribution is quite good in the vehicle even after the crash. There are very areas where we can see stress concentration.

Generating the Plots:

Graphs for Global variable energies:

• The changes in kinetic and internal energies occur at the exactly when BIW body comes in contact the rigid wall. At the same time, it absorbs the forces and this results in an increase in internal energies andas a reslut the deformations occur. Thus the total energy in the system is almost constant to 86000J and due to some energy loss we an see in energy error, there is some decrease in total energy.

Conatact energy graph:

• Contact energy is a type of energy that is formed when one element meets the other or neighboring elements. The opposing force created by this element forms the contact energy.
• The increase in contact energy affects the overall energy of this system, which is why there is a decrease in total energy over the period of simulation.

Output requests:

Sectional forces on cross bars:

• During the side impact the vehicle is going to impact the cylindrical rigid walls. At the time of impact, this vehicle will have some kinetic energy possessed and the rigid wall will try to oppose direction of kinetic energy. So while impacting the rigid wall the kinetic energy of the vehicle will be reduced in the vehicle component.

Intrusion springs:

• Here by the above graphs we can see that the intrusion is recorded in the mm/ms at 8.5ms. The form of displacement.
• As there are no other components in the middle section of the vehicle like the absence of engine,radiator, seats and other assemeblies are there with very huge deformation.
• The max displacement recorded in 3 nodes is displayed in the above graphs.

What can help FUEL TANK:

• To counterbalance this intrusion we can add the reinforcement structure near the fuel tank inside the door panels.Additionally we can add the cylindrical beam with higher thickness of upto-mm can be provided the additional strength to avoid the fuel tank intrusion.
• From the above graph, the peak velocity of the node on the door is about 15.9mm/ms at 8.5ms.

Learning Outcomes:

• Importane CoG and its recommended region.'
• Usage of interfaces and its values that are recommended for the project.
• Created initial velocity, intrusion, frames , sections and local co-ordiantes.
• Rectified time history cards and output blocks
• Simulation in run, animations are captured.

Conclusion:

• All the required objectives are fullfilled according to the given question.
• Side pole crash analysis was carried out on the gievn half of a BIW model of Dodge neon car as per given requirements.
• The forces are transferred through the most amount of energy.
• The cross section at B pillar is experiencing maximum forces due to the pole is placed near the B pillar.
• The maximum intrusion is at B pillar followed by area near fuel tank.
• The stiffness should be increased of the componenet near fuel tank so there will be less intrusions.