LS Dyna

LS Dyna

How to consider initial temperature with Johnson-Cook model in LS-DYNA

    • Haiquan
      Subscriber

      Hello

      I am doing an aluminum metal cutting simulation using Johnson-Cook material model, the constants are from a paper. The aluminum working piece has an initial 400°C high temperature. We know that Johnson-Cook has thermal softening effect. I try two methods to consider this initial temperature in k file, one is *LOAD_THERMAL_CONSTANT, another is *INITIAL_TEMPERATURE_SET. Both methods don't work. How to consider the initial temperature?

    • Ram Gopisetti
      Ansys Employee
      the issue is with the material used. You can choose Johnson cook simplified from the LSDYNA material model tab in the engineering data, but I hope it will not serve you the purpose.
      After you do it , follow with the initial temperature set card to patch the bodies.
      If you use workbench your node numbers has to be match as in the LSDYNA named selection Manager as shown in below
      corresponding USER ID----------> use this in the commands.
      The following image shows the outcome after the right material model and initial temperature is patched
      The rigid bodies will have 22 degree followed by the billet 400 degree. Pay attention to model while using the Thermal Material model in workbench, it might be trouble to find the TMID to the scoped body.
      Comment down for further help and post your results.
      Cheers Ram.
      *MAT_JOHNSON_COOK
      $ MATID RO G E PR DTF VP RATEOP
      2 2.700E+03 2.600E+10 6.890E+10 0.330000 0.000000 0.000000 0.000000
      $ A B N C M TM TR EPSO
      3.241E+08 1.138E+08 0.420000 0.002000 1.340000 582 298 1.000000
      $ CP PC SPALL IT D1 D2 D3 D4
      896 0.000000 0.000000 0.000000 -0.770000 1.450000 -0.470000 0.000000
      $ D5 C2/P
      1.600000 0.000000
      *EOS_LINEAR_POLYNOMIAL
      $ EOSID C0 C1 C2 C3 C4 C5 C6
      2 0.000000 7.420E+10 6.050E+10 3.650E+10 1.960000 0.000000 0.000000
      $ E0 V0
      0.000000 0.000000
    • Haiquan
      Subscriber
      Thank you very much for your comments!
      You mentioned that LSDYNA WB will not accept the Material model from the Engineering data especially of any strength models, but if I check the k file exported from WB, I find that the Johnson-Cook strength and failure model have been well defined as shown below. I add the *INITIAL_TEMPERATURE_SET in LS-PrePost to give 400┬░C to the working piece as shown below. But I still cannot see different results between these two k files. Is it because that TMID is not defined in *PART as shown below in green box? By the way, how do you plot the initial temperature? Thank you in advance!


    • Ram Gopisetti
      Ansys Employee
      As said in my previous comments, TMID has to be edited manually in the prepost, Check the Misc tab in the output for the temperature results in d3plots.
      Cheers, Ram
    • Haiquan
      Subscriber
      Thank you very much for your quick response, it really helps me! I tried to introduce *MAT_THERMAL_ISOTROPIC, got the TMID and apply the TMID value 1 to all *PART. I am very new to LS-DYNA especially the k words files, could you please attach the k file of your previous case or just post the k files? Really appreciate!



    • Ram Gopisetti
      Ansys Employee
      check this following keyword file and comment down your response.
      change the extension to .k and open in lsprepost.
      Cheers, Ram

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