ASTM E8 Tensile Test - Explicit or Implicit

I am investigating stress/strain relationship using LS-DYNA SPH Form 12 and Johnson Cook material model for different strain rates starting with ASTM E8 crosshead strain rate of 0.015 s-1. However, when I use explicit in LS-DYNA it is taking 2777777 hrs 46 mins.

I then tried Implicit by invoking the implicit solver. Took very long and no additional d3plot after initial.

Obtained a paper online that says to use Time Condense. But do not understand how to set it up in explicit.

Based on the specimen dimension, the crosshead speed is 0.008 mm/s. Then I need to double this 4-5 times. But I am stuck with a very long simulation time for the first run (0.008 mm/s)

Can you kindly assist in solving my issue. I am using a school supercomputer.

Comments

  • MTLCYMTLCY ???Member

    Maybe use quasi-static technique could address your issues.

    You can check this paper :Benchmarking concrete material models using the SPH formulation in LS-DYNA, and this vedio: https://www.youtube.com/watch?v=2P0cuAmjIc8

  • ubasuubasu Member

    Please try FORM=1, unless you have a very specific reason to use FORM=12. If using FORM=12, keep a constant smoothing length for this formulation by setting HMIN = 1.0 and HMAX = 1.0 in *SECTION_SPH. Implicit SPH is still in development, and is available only in the Dev version.

  • ssagarssagar Member

    Thank you both for your informed response. I used Explicit using mass scaling as well to assist in bringing down the run time. I was experiencing Tensile Instability with previous forms of SPH so I used Form 12. Very reasonable necking and overall deformation but need to look at the Yield Strength results and Youngs Modulus. Thanks again you all.

    S

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