Assignment 6-Frontal Crash Simulation Challenge
AIM-
frontal car crash simulation of dodge neon BIW using RADIOSS solver and preproccesing using hypermesh /hypercrash.
OBJEJECTIVE-
frontal crash - BIW-
1) to check the unit system and either follow ( mg mm s) or (kg mm ms).
2) to create the appropriate interface, friction 0.2, and recommended parameters.
3) to make sure of no penetration and intersections.
4) to correct rigid bodies if any issues.
5) to crate a rigid wall with friction of 0.1.
6) to compare the model weight with the full scale 300k nodes model and use added masses to reach at
target weight at 700kg while getting CG About the required range.
7) to create an initial velocity of 35 mph.
8) to input time-step 0.5 to 0.1 microseconds and run 80ms.
OUTPUT REQUESTES-
1) Sectional force is in the rails at a location of indicated node 174247.
2) axial force received on the rails from the bumper.
3) shotgun cross-sectional forces.
4) a pillar cross-section .
5) accelartion curve received on the accelometer at the base B pillar ( on B piller rocker.)
6) intrusion on the dash wall 66695,66244.
PROCEDURE-
1) check for unit system.
2)import model in hypercrash.
3) check for penetration and intersection.
4) add mases to reach a target weight of 700kg.
5) export changes file and import in hypermesh.
6) create interface contacts.
7) create interface contact between the component and bumper.
8) create a rigid wall.
9)add velocity to the nodes.
10) create cross-sections.\
11) create spring to check deflection.
12) assign property to springs.
13) create TH for section forces,intrusion springs, and interface contacts.
14) create cards.
15) model checker.
CHECK FOR UNIT SYSTEM-
in the data, we have two files-
1)neon_front_000.rad(starter file) stores information about.
i) nodes.
ii) load conditions.
iii) velocity.
iV) Boundary conditions, etc.
v) basically, it an ASCII ( american standard code for information interchange) file that contains the model information.
vi) the starter file should always end with " 000.rad"
2) neon_front_0001.rad ( engine input file) the engine file store about.
i) simulation runtime.
ii) simulation speed control parameter such as no. of animation file no of time history files, size of the history file and animation frequency, etc.
iii) basically, it is an ASCII( american standard code for information interchange) file that discribe the run controls.
iv) we can also edit the engine file dirctly through the control cards.
v) the starter file should alwys end with "000.rad"
1) CHECKING THE UNIT SYSTEM AND EITHER FOLLOWING ( mg mm s) or ( kg mm ms)-
step 1- open the starter file neon_front_0000.rad file,
i) go to menu bar > file > import > solver desk > select 0000.rad file > import.
STEP 2- Checking the unit system of the model .
go to model browser > cards > begin cards.
3) THERE SHOULD BE NO PENETRATION AND INTERSECTION-
go to menu bar > tools > penetartion check > select group > check.
4) CORRECT RIGID BODIES IF ANY ISSUES-
to check, rigid bodies go to the option panel > tools > find connectivity.
( if any free parts are there, then mannualy fix them by creating rigid connectivity in that region.)
the check the connectivity to connectivity in proper.
5) CREATING THE RIGID WALL WITH FRICTION 0.1-
for creating RWALL.
go to solver model > create > RWALL > plane.
in order to select the position , the outermost and centrenode on the bumper part is selected .
a small approx gap of 20mm is added to the x coordinates to create a wall a little away from the model. since the normal of the wall is in neagative x-direction , -1,0,0 is defined in the normal tab.
Dsearch is defined till 2000mm.
slide is set to 2 incorporate friction of 0.1 as specified.
6)ADDING MASSES TO REACH A TARGET WEIGHT OF 700KG WHILE GETTING CG ABOUT THE REQUIRED RANGE-
opening mass summary-
go to menu bar > tools > mass details > mass , cog , inetria.
we can see that the mass is less as it should be around 700kg.
also, the position of cog is currently closer to the dashboard region whereas it should be near to the driver seat region.
now to shift the COG The desired area , some masses are added to the rear part.
the added mass will be account for fuel tank, passenger's weight, additional luggage load etc.
i) to add mass,ADMAS option is used under the solver browser,
ii) go to create > admas.
step 3 adding mass increase overall weight of the car.
go to solver browser > admas > create > extra mass > give GRNODE ID > give mass value.
the right click on the grnode_id to create GRNODE, then select node under entity id's and proceed. i select mass type as i mass/n is added to each node of the group so i am simply the added in mass two astep to first in 406 then added the 106. to create the cog mass node.
then the mass and COG is checked in hypermesh . to view the COG position, a point is created with the obtained COG coordinates. hence the mass is corrected to 700kg to represent a real life mass of a vehicle and also the position of COG is now relocated the desired position.
7) DEFINING INITIAL VELOCITY-
to define an initial velocity of 35 mph (15.6464 mm/ms ) under solver browser.
go to create > boundary condition > INVEL.
The right click on grnd_id to create GRNOD, then select the nodes under entity id's and all component procced.
8) USE MODEL CHECKER TO ENSURE GOOD QUALITY-
go to tool > model checker > radiossBlock > run > fix ( if any error ).
9) CREATE TIME STEP-0.5 TO 0.1 MICROSECONDS-
CASE 1- go to model browser > cards > ENG_ANIM_DT> tfreq=5.0
CASE 2- Go to model browser > cards >ENG_DT_NODA> tmin = 5.0/1000=0.0005 = tscale=0.9
the we convert the time step value 0.5 microseconds to 0.5/1000 ms. and put in Tmin.
10) RUNNING 80 ms-
go to model browser > cards > eng_run > tstop =80.0
OUTPUT REQUESTS >
now before moving into the simulation, in order to observe the output required, we have to create. cross section on rail, shotgun, and a pillar to create an accelerometer, and an intrusion on dash wall specified nodes.
to view cross-sectional force on the moving model, a frame that is movable should be created which act as refrence to cross-section are force are computed.
go to create > frame > mov.
in the frame creation window, we should select the or origin nodes and also the global axis directional nodes which can be created by the translate tool and translating the duplicate of the origin node to x and y direction. clicking on create after selecting nodes, creates a new frame with a specifid id.
after the frame created , now a section should be created for this frame which is created under the solver browser.
go to create > sect > sect
in the newly created section the elements are selected under grshel_id and the reference frame created is defined by the frame id.
similarly , the frame and sections are created at all positions as recommended rails, shotgun, bumper-rail, and A-pillar.
1) ADDING SECTIONAL FORCE IN THE RAILS AT THE LOCATION OF INDICATED NODE 124247-
STEP 1- displaying node 174247
go to tools > numbers > by id >type node number > display > on.
step 2- create FRAME card in the solver browser.
step 3- giving paramter to frame > mov
go to solver browser > frame > mov > give origin, axis, plane node > create.
step 4 - create a sect card in the solver browser-
step 5- giving parameter to sect card.
now thein sect we assign n1,n2,n3 value and frame _id from FRAME 1system node_id
now, right click grshell ids > create > entity ids > select nearby elements > proceed.
step 6- giving output request in model time history file (TH).
go to solver browser > create > th > SECTIO
now, assign the cross section under entity id's
2) Axial force received on the rails from bumper.
accelerometer
at the base of B-piller an accelometer is created under the solver browser by-
go to solver browser > create >ACCEL.
the node at which the accelerometer is to be placed is also selected.
STEP 1-create ACCEL card in the solver browser.
> select the node under node_id > proccesed for acceleorometer. and put fcut as 1.9.
step - 2 giving the output request in model browser time history outputs.
in entity id's select the appropriate acceleromter for th outputs.
3) INSTRUSION O N THE DASH WALL 66695,66244-
Instrusion-
to find the instrusion on the dash wall at nodes, 66695 and 66244, a frame for reference is created then under TH block, the nodes selected as entity ID.
step-1 first find those node ids by using tool > numbers > by ID > put node IDs > enter > on.
step-2 then go to 1D > spring > select two nodes under spring 2.
step-3 create a property card for spring under the model browser & put low mass / stiffness value (k).
step 4- assign spring properties to spring components.
step-5 giving output request in model browser time history file (th)
go to solver browser > create > th > spring.
go to entity id's > elements > select springs > proceed.
MODEL CHECKER-
to check for any error in the model,
go to option panel tools > model checker > radiossblock.
after that model checker tab opens, run checks option is clicked, and then the auto correct option is clicked, which will rectify the errors and warnings.
SIMULATIONS-
the simulation is run using radioss tool under the analysis tab.
once the analysis is done the frontcrash_0001.out file observed to check the stability of the model.
from the 000.out file.
energy error 0% to - 2.5%
hence energy and mass error are within stable limits.
now the time for simulation and the number of cycle taken to complete the simulation is also noted from the OUT file.
> plotting the energy curves using hypergraph 2-D with the help of T01 file.
internal energy, kinetic energy, and total energy curve are plotted. it is observed that there is an increase in the internal energy in the model with the the progress in simulation. with the increase in inetrnal energy, there is proportional decrease in kinetic energy in the model.
hourglass energy remains negligible throughout the simulation and a slight incrase in contact energy.
hence total energy remains constant roughly du to compansation between kinetic and internal energy. total energy shows a slight decreases du to a slight increase in contact energy as shown above the graph.
> plotting the cross-sectional forces using hypergraph 2-D with the help of T01 File-
1) sectional force in the rails at the location of indicated node 174247.
2) axial force received on the rails from the bumper-
3) shotgun cross-section forces-
4) A-pillar cross-section-
5) acceleration curve received on the accelerometer at the base of B pillar ( on B pillar rocker)
accelerometer readings at the base of the B-Pillar are plotted. A accelerometer is used to measure the acceleration forces at the base of the B-Pillar .
it can be seen that there are many spikes in the graph which show sudden movement at the specified region. the highest impact is recorded at around 2.22 mm/ms2 for B_pillar _R &3.41mm/ms2 for B_pillar_i for the simulation
6) instrustions on the dash wall 66695, 66244.
> node 66695 >
> node 66244>
it is observed that, there is a maximum Elonagation of about 146.15mm on the 66244 node and 179.74mm at 66695 node.
animation and contour plot of the simulation is obtained under hyperview using then h3d file saved in the directory.
at the start, it is observed that the bumper absorbs most of the energy during the crash.
further simulation shows that the forces du to crash is distributed throughout the model components with very less stress concentarion at specific locations.
being scaled model, the rear part of the model under simulation is found to bend inwards which is not desirable.
initialy bumper deforms, then the forces transmiting through rails to the rest of the model components. the front part of the model gets lifted du to the crash which shows the real life scenario to certain extent but since there are no tyres, engine, and associated parts in the model. it cannot be compared fully with real crash also, the rear passenger seat parts bends inwards which will be du to the load applied to correct the mass and might be du to the position of the centre of gravity.
CONCLUSION-
the given frontal crash model is analyzed for a frontal crash scenario and the requested output aspect the obseved.
the forces and energy curve at specified locations are observed.
https://drive.google.com/file/d/1tOlc5l0ydBZ1rFikNEqkYJOOFf8ZMArc/view?usp=sharing. to accept the project1 front crash file .