LS Dyna

LS Dyna

Version issue

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    • Ailin Chen
      Subscriber
      I am doing a 2D ballistic testing with a velocity range about 60-500m/s and run into the following issue.
      1. How will the simulation result be different (~20%) when using 2022 vs 2020? We use the same k file but run it on a different LS-Run. One residual velocity I get is 4m/s and the other is 7m/s with a starting velocity of 60m/s.
      2. What are some majors update of the software that can cause this issue?
      2. How will the simulation result be different (~20%) when using Windows vs Linux?
      Thank you!
    • Reno Genest
      Ansys Employee

       

      Hello,

      The results should not change based on the LS-RUN version you are using. LS-RUN is only used to run LS-DYNA and to send the LS-DYNA execution command lines in the background. The LS-DYNA solver crunches the data. So, which LS-DYNA version are you using? The latest version is R13, but you could be running any version (R12, R11, R10, R9, R8, R7, etc.). You can download any LS-DYNA solver here:

      LSDYNA » Downloader (ansys.com)

      You can also check the release notes to see what has changed between versions:

      Index of /anonymous/outgoing/support/FAQ/ReleaseNotes (lstc.com)

      After you run a model, you can open the d3hsp file in a text editor to see which version you used:

      To get consistent results between runs in SMP, make sure you use consistency checking by setting ncpu=-4 (this is negative 4) to a negative number. This way, your results should be consistent when using different number of cores:

       

      If you are running MPP, you will get slightly different results with different number of cores. So, pick a number of cores and stick with it to calibrate your model.

      At last, improvements in newer versions of LS-DYNA can lead to different results compared with older LS-DYNA solvers. For this reason, please calibrate your model and stick to a revision of LS-DYNA. For example, if you calibrate your model with R13, then stick with R13. This is why some compagnies (car manufacturers, aerospace  companies, etc.) stick to the same version of LS-DYNA for some time, even though many new versions are  released.

       

      Reno.

       

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