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drop test with stacking

Altair Forum User

Hi,

I performed drop test of single jar with fluid and now require to perform a drop test of box which consist no. of jar which positioned in stacking condition.

Is it necessary to model no.of jars in a box to perform drop test, or can we replicate the same jar which we have modeled once?

After that also consider the stacking of box and require to perform drop test.

We want to observe effect on jars as well as box after drop, so we have to model both jars as well as box.

Please suggest the solution.

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Radioss

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Altair Forum User

We want to observe effect on jars as well as box after drop, so we have to model both jars as well as box.

Yes you need to add jars. You can just copy the existing jar and position according to your setup.

Altair Forum User

Hi,

Many thanks for replying.

Surely we can copy but my concern is if we increases the no.of bottles and boxes then analysis run time also increases.

We just want to replicate the no.of models i.e. 'box carrying jars' , but at the same time want to keep the run time less, please advice.

Can we make replicates with invisible kind, so that analysis output is for stacking, but run time is less?

Altair Forum User

Hi,

Waiting for reply....

Altair Forum User

Hi,

You need to create the whole setup for the analysis, and meanwhile you can control the time step for reducing the simulation time.

You can try with /DT/NODA/CST or with Advanced Mass Scaling technique, where AMS does not modify the global mass so that the global momentum of the related nodes are conserved.

For more info on time step control without compromising the accuracy, please visit the link below:

http://www.altairhyperworks.com/html/en-US/rl/RADIOSS_Simulation_91212.htm

Altair Forum User

Hi Tushar,

Maybe you can also check with Multi body simulation about the feasibility of the analysis, if your interest is only to study the packaging.

Altair Forum User

Hi George,

Shared video is very useful.

Will you shared any tutorial in which AMS is used?

Or can you explain me how to apply AMS to particular analysis?

Thank you.

Altair Forum User

Hi Tushar,

Please refer our tutorial Example 44 - Blow Molding with AMS in Help Menu.

Altair Forum User

Thanks George.

I go through the Example 44 - Blow Molding with AMS.

After importing deck file and check min time step for whole model is 1.506e-6.

In AMS,

Tscale=0.67

Tmin=1.150e-4 Tol_AMS=1.0e-4

How these values are to be decided?

In my drop analysis min time step is 7.665 e-04.

How to decide AMS values like Tmin and Tol_AMS for this time step?

Also According to /AMS in help menu,

'AMS cannot apply to parts using ALE, Euler or SPH formulation. Thus, the part group specified in /AMS should not include these parts, but it still can apply to the other (structural) parts'.

In my analysis, jars contain SPH particle as a fluid, then according to /AMS is applying to jars ?

Suggest the solution.

Thank You.

Altair Forum User

Hi Thushar,

There is no standard rule but as a fair practice we can tell,

Any targeted model for AMS application should run first in /DT/NODA/CST with a reasonable energy error and acceptable added mass along its simulation time.Computational convergence and accurate results can be obtained by choosing a minimum time step, Tmin, from 10 to 20 times than the one used in /DT/NODA/CST.

Tsca is 0.67 for running AMS.

Since your analysis deal with SPH particles, the solving time will be more. You can try with /DT/NODA/CST to control the time step but monitor the mass error.

Altair Forum User

Hi,

Already imposed the /DT/NODA/CST to control the time step and run the analysis.

But it take long time to complete the analysis.

So, I thought to run the analysis with AMS.

Is it possible wtih AMS and completing the analysis with lesser time?

Thank You.

Altair Forum User

Proceed with /DT/NODA/CST for time step control and normally simulations including SPH particles will take more time.

Altair Forum User

Thanks very much.

Altair Forum User

Hi,

I have one more query regarding re-run the deck files.

Actually I run the analysis and it created 45 animation files and my run remain incomplete due to power off.

Can I re-run the analysis after already created 45 animations file?

Thank You.

Altair Forum User

Create the second Engine file Model name_0002.rad. Simply copy the first Engine file and that is all. Launch this second Engine file and then RADIOSS will continue the job after your stopping point.

Please try this.

Altair Forum User

Hi,

As per your suggestion created the second engine file top1_0002.rad and launch this engine file in radioss solver and run it.

It gives following error;

** ERROR: FILE top1_0001_0001.rst NOT FOUND
ERROR TERMINATION

==== End of solver screen output ====

==== Job completed ====

Suggest the some solution

Altair Forum User

Check that the RESTART file Runname_0000_0000.rst (written by Starter) that appears in the directory where RADIOSS Engine has been run.

There are two different ways to restart your job.

1.If you want to stop the job during the computation and later continue the computation after that stopping point, create a control file.

For example: Your model named TEST_0000.rad for Starter and TEST_0001.rad for Engine.

Then create TEST_0001.ctl in the current folder. In this file, assign the following keyword:

/STOP

Then, RADIOSS will read this control file, will stop the job and also writes a restart file.

Now to continue the job, create the second Engine file TEST_0002.rad. Simply copy the first Engine file and that is all. Launch this second Engine file and then RADIOSS will continue the job after your stopping point.

2.You could also define the frequency restart files in your Engine file beforehand, so that you can later restart your job with any of your restart files.

For example: Your model named TEST_0000.rad for Starter and TEST_0001.rad for Engine.

First, in the Engine file TEST_0001.rad, /RFILE/n will need to be defined. For example, if you want to create a restart file for each 100 cycles, then do the following:

/RFILE/100

100 1 1

Then in your current folder, you may have the following restart files, depending on your model:

TEST_0001_0001_I.rst

TEST_0001_0001_J.rst

TEST_0001_0001_K.rst

TEST_0001_0001_L.rst

TEST_0001_0001_M.rst

TEST_0001_0001_N.rst

…

Note: The file name always begins with Restart Letter=I. Here it begins with TEST_0001_0001_I.rst.

Now to continue your job, the second Engine file TEST_0002.rad needs to be created. In this Engine file, assign the keyword /RUN/Run Name/Run Number/Restart Letter.

For example:

/RUN/TEST_0001_0001_K/3/K

100

Now launch the second Engine file, RADIOSS will continue the job after the point of TEST_0001_0001_K.rst.

Note: Run Numbers are defined below:

TEST_0001_0001_I.rst Run Number = 1

TEST_0001_0001_J.rst Run Number = 2

TEST_0001_0001_K.rst Run Number = 3

TEST_0001_0001_L.rst Run Number = 4

TEST_0001_0001_M.rst Run Number = 5

TEST_0001_0001_N.rst Run Number = 6