Challenge

Week - 4 - Crash Box Simulation

MM Dilip Kumar11 Aug 2021

LS-DYNA

Week - 4 - Crash Box Simulation:

objectives:

To simulate a crash test for a crash box in lsdyna and plot the result for the respective output that has been stated.

procedure:

import the keyword file to the ls dyna,FILE>open>k file>ok
As we know in LS-DYNA every entities are created by the *KEYWORDS,so now we have to create a deck by using *KEYWORD to make it ready for it to solve the problem.
first thing create *MAT and *SECTION for the both the cellphone and the ground.
Go to the Keyword manager and click on 'all'.

create a *SECTION for the part and enter the thickness as 1.2 same for the next model we have to enter the thickness of 1.5. for reduce the hourglass I used ELFORM16 which increases integration points and also i give NIP2 which increase the integration point along thickness
There is a chance of getting hourglass as we subject this crashbox for bending.

Once *SECTION and *MAT is created associated with the *PART

as in this you can also see that i gave a HGID,to give the hourglass ID you need to create a *HOURGLASS (measure the hourglass for individual component) and once the *HOURGLASS is created associated with the respective part.

If you use *CONTROL HOURGLASS it measure the global hourglass energy.

I gave IHQ as 4 as per the problem to increase my stiffness response,there are many for more u can refer the manual to give IHQ.
as i know it will be self contact because of the given velocityu and mass, I request for *CONTROL_AUTOMATIC_SINGLE_SURFACE,so it is going to self contact give the set for the slave to insert on the card.

create a CNRB at the tail of the crashbox and add mass on the middle node.

create a SPC at the tail end for constranint motion because in real crashbox the tail will be fixed.

create a velocity card from the *INTIAL and enter the velocity about the which axis you want to give the velocity.before that we need to create a set to give the velocity.when creating set for applying velocity you also add up the CNRB as we have applied mass on it.Give velocity about axis 13.44mm/ms.

Add *RIGIDWALL keyword and translate at the distance of 15mm as we following (g,ms,mm)

I gave the control termination as 20ms(millisecond)

even requesting *GLSTAT you cant measure the hourglass energy,so create a *CONTROL_ENERGY keyword

give HGEN and SLNTEN as 2 ,as it can give the output at *GLSTAT and *SLEOUT card.

The keywords that ive used is

At last request for ascii and binary output files from the *DATABASE
In ascii request for GLSTAT(total energy),SLEOUT(sliding energy due to contact),SECFORC(cross section force),RCFORC(contact force),and enter the value at DT as 0.05.
In binary request for D3PLOT(animation)
save the file and run it in ls manager or ls run.

stimulation of 1.2mm thickness crashbox

ENERGY VS TIME:

CROSS-SECTIONAL FORCE:

ACCELERATION PLOT:

EFFECTIVE PLASTIC STRAIN:

EFFECTIVE PLASTIC STRESS:

DIRECTIONAL STRESS ALONG THE LENGTH:

DIRECTIONAL STRAIN ALONG THE LENGTH:

For all the three axis the strain is same 5e-1

-----------------------------------------AS DO FOR THE THICKNESS 1.5---------------------------------------------------------------------------------------

OUTPUT FOR 1.5MM THICKNESS