ASTM E8 Tensile Test – Explicit or Implicit

- August 6, 2020 at 6:36 pm
  
  ssagar
  Subscriber
  
  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. nI then tried Implicit by invoking the implicit solver. Took very long and no additional d3plot after initial. nObtained a paper online that says to use Time Condense. But do not understand how to set it up in explicit. nBased 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)nCan you kindly assist in solving my issue. I am using a school supercomputer. n
- August 12, 2020 at 11:36 pm
  
  MTLCY
  Subscriber
  
  Maybe use quasi-static technique could address your issues. nYou can check this paper :Benchmarking concrete material models using the SPH formulation in LS-DYNA, and this vedio: https://www.youtube.com/watch?v=2P0cuAmjIc8nn
- August 14, 2020 at 10:04 pm
  
  Ushnish Basu
  Ansys Employee
  
  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.nn
- October 7, 2020 at 12:31 am
  
  ssagar
  Subscriber
  
  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. nSn