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Time Integration, Characteristic Length, and Mass Scaling


A short presentation on the Explicit and Implicit time integration schemes which I use in my advanced LS-DYNA class is included here. Its a evolving document but the latest version is available for download.
Time Integration (PDF, 346 Kb)

Note: Fixed the corrupted PDF file. Sorry for the inconvenience.

  • Susheel Khanna says:

    Hi,

    If you check the formula of sound speed in shells given on page 22 of this documents, this has term 1 v^2, i think it should have been 1-v^2.

    Kindly cross check

    Regards,
    Susheel Khanna.

  • amir says:

    Hi Suri,

    selective timestep?

    I have already dyna 971 in use, how can I set up this feature?
    Is it a method to accelerate a calculation with different types of mesh sizes?

    That means I can speed up a model let say 90% dominated by 1 micro s and 10% 0.2 micro s timestep. No more obligation to run the entire model with 0.2 micro s. Am I right?

    If yes, wonderfull.

    Is it for both smp and mpp, or there are some restrictions?

    Sorry for too much questions

    Regards
    Amir

  • Suri Bala says:

    Amir,

    Selective mass-scaling can be invoked using the IMSCL parameter in *CONTROL_TIMESTEP. It is supported by both SMP and MPP.

    Suri

  • Suri Bala says:

    Susheel,

    Thanks for the correction. The new document reflects this (v1).

    Suri

  • Nihar says:

    Hi Suri,

    The pdf file is damaged, unable to open !

    Regards,
    Nihar

  • Amir says:

    Hi Suri,

    I didn´t see any difference with IMSCL and without.

    Her is my input:


    *CONTROL_TIMESTEP
    $$ DTINIT TSSFAC ISDO TSLIMT DT2MS LCTM ERODE MSIST
    0.000 0.900000 0 0.000 -2.000E-7
    0.000 0 -11
    *SET_PART_LIST_TITLE
    selective_time_step
    11
    200075

    Couls you please specify more the usage and impact of it.

    Regards
    Amir

  • Suri Bala says:

    Amir,

    For relatively low mass-scaled timestep, both should perform the same. You could try using 1e-6 and study the differences between the two which should show the significance of the selective mass-scaling.

    Suri Bala

  • Akram Abu-Odeh says:

    Suri,

    I tried to open this document (also save and then open) from the link provided.
    However, I got the ADOBE error

    “The file is damaged and could not be repaired”.

    Is there a special way of reading this document?

    Thanks

    Akram

  • Prakash Jadhav says:

    Dear sir ,
    Now i have started learning LS dyna on my own , how can i begin with , what all the basic things that i need to learn before begin with crash analysis and understanding the
    basic Fea for Simulation .
    Please guide me
    expecting your reply
    with best regards
    Pragash

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