Assignment 6

ASSIGNMENT-6

VIRTUAL FRONTAL CRASH ANALYSIS OF NEON BIW {Body In White}

OBJECTIVE:

The main objective of frontal crash analysis of neon BIW is to know how much force is recieved at different components of neon BIW, like cross rail, shot gun A-pillar. And to know about intrusions of a model, as well as accelerations. The other objective of frontal crash analysis of neon BIW is to create a global contact interfaces, rigid wall, add the masses to reach a target weight of 700kg while getting COG [ CENTRE OF GRAVITY] about the required range, initial velocity of 35 mph. Finally creating cross sections, as well as intrusions.

All this preprocesssing process are carried out in hypermersh , simulation is performed by using Radioss, and cross sectional forces recieved on various components, intrusions on the dash wall at 66695, 66244 and acceleration curve received on the accelerometer at base of B-PILLAR [ on B-pillar rocker].

CASE SETUP AND EXECUTION:

STEP-1:

CHECK THE UNIT SYSTEM: WE HAVE CHECKED THE UNIT SYSTEM IN THE neon_front_0000.rad file AND WE FOLLOWED Kg mm ms throughout the process.

STEP-2:

IMPORTING THE MODEL:

The model is imported into to hypermesh, by click on import solver deck- search the neon_front_0000.rad file and click on import.

FIG: IMPORTING THE MODEL

STEP-3:

Create a appropriate interface with friction 0.2 and recommended parameters.

Already a contact is defined in the model we have to delete that interface and to create a new interface [TYPE7] with recommended parameters.

Important Interface Parameters:
Igap = Determines how the size of the gap is calculated

Gapmin = Minimum gap for activation of interface

Inacti = Action to take if initial penetrations exist

Istf = Affects how the stiffness of the interface is calculated

Iform = Friction formulation

Stmin = Minimum stiffness to use in the interface

Idel = Update For Deleted Elements Due To Failure

The recommended contact parameters for interface Type 7:
• Istf = 4

• Igap = 2

• Fscale_Gap = 0.8

• INACTI = 6

• Gap_min = 0.5

• Fric = 0.2

• Iform = 2

STEP-4:

Now run the model analysis to check for errors and warnings.

Make sure of no penentrations and intersections. if there is any penentrations correct it or simply use the gapmin value to reduce the penentrations.

Rigid body issues, if any are corrected. by using hyper crash.

STEP-5

RIGID WALL CREATION:

An obstacle like infinite rigid wall is created infornt of the bumper with some parameters like friction = 0.1 and Dsearch as 1000

A rigid wall is created by clicking on solver - right click - create -rigid wall - plane - ok. then a dialogue box will open and assign the rquired values.

FIG: RIGID WALL CREATION

STEP-6:

ADDED MASS:

Initially the model has a weight of 188.42 kg. We have to add the mass to reach a target weight of 700kg to get the COG about the required range. We have to add the mass at the floor of the BIW in order to get the COG at required range.

A wide variety of mass type options are available to add the mass, we have to choose the option-1 for better results.

FIG: ADDED MASS

BEFORE ADDED MASS ADDED MASS AFTER ADDED MASS

STEP-7

INITIAL VELOCITY:

We have to create a initial velocity in order to perform the crash. Generally we have to give a initial velocity of 35 mph, which is a standard value according to the crash standards. As we have following the kg mm ms units we have to change the 35 mph to required value.

we know that,

1 mile = 1.609344 km

1 km = 1000m

1m = 1000 mm

1 sec = 1000 ms

Based on this value we changed the value from 35mph to 15.6464 mm/ms.

We have created an initial velocity with 15.6464mm/ms. in Vx-direction which is perpendicular to the rigid wall.

STEP-8

TIME STEP: 0.5 TO 0.1 micro seconds.

We have to create a time step in between 0.5ms to 0.1ms. And we have created the respected values as shown below. Run time as 80ms and Tfreq as 5ms. Use the model checker to ensure good quality.

STEP-9

OUT PUT REQUESTS:

We have to create the cross sections at diffferent components of BIW in order to get cross sectional forces, accelerometers to get accelerations curve, intrusions to know the displacement.

• 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.

CROSS SECTIONS CREATION:

We have to create the cross sections to know the forces acting on that particular sections. we have to create sections on the following components, with both right hand side as well as left hand side.

cross section at

rails both LH and RH

Shot gun LH and RH

A-pillar LH and RH

Go to solver - right click - create - sec - sec - ok. Then a diologue box will be open.

Before creating the cross sections we have to create a movable skew at the respected location and add that skew in this diologue box. Then select the elements around that skew in at least two columns of elements through out all sides as shown below. Select the grshel_id if we got the quad element at respected skew, and select the grtria_id if we got the tria element at respected skew. Assign some values to that card such as ISAVE as 0, deltaT as 0.1 alpha as 0.65 and Iframe as 12. perform the same method for other components and create the required cross sections.

FIG: CREATING CROSS SECTIONS.

After creating all cross sections we have to create the accelerometers.

STEP-10

creating accelerometers: To get an Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker) we are creating the accelerometers.

click on solver - right click - create - accelerometers - ok.

we have to create the the accelerometers on both sides. just simply click on the node and select the node at respected place where we have to create the accelerometers. finally we got accelerometers.

FIG: ACCELEROMETERS.

STEP-11

CREATING INTRUSIONS:

We have to create an intrusions on the dash wall at a location of 6665 66244, to know the displacement of the particular wall into the occupant area. For this we have to create a fixed skew and make the respected node numbers in one position. The below figure shows the all out put requests.

FIG: WITH ALL OUT PUT REQUESTS.

STEP-12

CREATING OUTPUT BLOCKS: [TIME HISTORY]

Finally we have to delete the already requested output blocks and create a new out put blocks for cross sections, acccelerometers, intrusion at 66695, and intrusion at 66244.

STEP-13

RUN THE SIMULATION: [BY USING RADIOSS AS SOLVER]

After creating all required out puts in hyper mesh, we have to run the simulartion by using Radioss [solver]. keep the export options as all, run options as analysis, run number as 1, options as -nt 4.

The below figures shows the simulation files.

FIG: SIMULATION FILE.

FIG CHECKING FOR ENERGY AND MASS ERROR.

From the above figures we got,

Remaining time {simulation time} = 3390.16 s

Elapsed time = 2969.13 s

Energy error = -1.3%

Mass erorr = 0.3586E-01

TOTAL NUMBER OF CYCLES = 80001

WE GOT NORMAL TERMINATION

ENERGY ERROR: Basically energy error must be negative and decreasing.The Error must be less than 15% at the end of computation, as per the condition. If the error is below 15% than the results could be acceptable.

So from the above figure, at the end of computation the energy error is -1.3% and mass error is 0.3586E-01 As per the condition the energy error is -1.3% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

SIMULATION:

PLOTING GRAPHS:

SECTIONAL FORCE IN THE RAIL COMPONENTS:

From the above plot we can see that the maximum force in left hand side of a rail is 22.5KN, which is around the 13ms, via in right hand side of a rail is 20KN at around 14ms, and the mimimum force in the left hand side of a rail is 9KN which is around 22ms, via in right hand side of a rail is 0.2 KN at around 60ms.

SECTIONAL FORCE IN THE SHOT GUN COMPONENTS:

From the above plot we can see that the maximum force in left hand side of a shot gun is 14.8KN, which is around the 36ms, via in right hand side of a SHOT GUN is 10KN at around 37ms, and the mimimum force in the left hand side of a SHOT GUN is 0.1KN which is around 74ms, via in right hand side of a SHOT GUN is 1.2 KN at around 78ms.

SECTIONAL FORCE IN THE A-PILLAR COMPONENTS:

From the above plot we can see that the maximum force in left hand side of a A-PILLAR is 6.9KN, which is around the 46ms, via in right hand side of a A-PILLAR is 4.8KN at around 47ms, and the mimimum force in the left hand side of a A-PILLAR is 2.5KN which is around 32ms, via in right hand side of a A-PILLAR is 0.25 KN at around 72ms.

• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).

From the above plot the maximum acceleration on the left hand side is 7mm/ms2 where as in right hand side the maximum acceleration is 1.67mm/ms2

Intrusions on the dash wall 66695,66244.

The purpose of intrusion to know the displacement of the particular wall into the occupant area.

INTRUSION ON DASH WALL AT NODE 66695:

.

After collision the distance between two point is 642.305 mm.

From the above plot the intrusion of bashboard is 125.27mm.

INTRUSION ON DASH WALL AT NODE 66244:

The intrusion is measured with respect to node 122048.

Before collision the distance between two point is 781.808 mm.

After collision the distance between two point is 635.897 mm.

From the above plot the intrusion of bashboard is 145.911 mm.

GLOBAL VARIABLES:

RESULT:

CONCLUSION:

When a collison is take place a reaction force will generate from the wall, which is generally called as kinetic energy. this energy has huge amount of impact. if it is taken by the passenger There is chance of injury. In order to over come this the energy should be absorbed by the car component itself. From the plot we can see that there is a increase in internal energy and decrease in kinetic energy. By this we can say that the energy is absorbed by the components. The total energy remains constant. So the kinetic energy is converted into internal energy.

The contact energy remains constant due to implementation of recommended parameters.

The hour glass energy is also remains constant due to use of recommended parameters.

FINALLY WHAT WE CONCLUDE IS THE ENERGY IS ABSORBED BY THE COMPONENTS WITH A DECREASING MANNER.

HOWEVER SOME SORT OF ENERGY WILL BE IMPACT BY THE PASSENGER IN A REAL LIFE CRASH SENARIO.

DIFFICULTIES FACED: I have faced difficulties while doing simulation, where i got errors. The error in TH GROUP, that i have not defined the cross section for left shot gun, finally I rectified it and while creating crossection as well as creating intrusion I faced some difficulties, that finding coorect tools for performing the work.

LINK: https://drive.google.com/drive/folders/1hs-lfd0wZTIzv_m1fC7USOW78m-Yz0um?usp=sharing