LS Dyna

LS Dyna

Unrealistic resulst of my Compression Test

    • goktug.yilmaz
      Subscriber

      Hi everyone,

      I am trying to perform a quasi static analysis of an aluminium profile, but my results are not realistic. A bucling occurs, and I can not understand the reason behind it.

      Here is my result;

    • Ram Gopisetti
      Ansys Employee
      I hope i have answered this kind of query a long ago and i would like to point to the same.
      for proven stability, you can switch the section solid to have 27 node solid element and make sure you are lording vis displacement on the top. I am sure you might be getting the following result. Moreover, you can also try constraining the solid to have only y-free. Since you need it in quasi static, make sure you evoke Implicit cards in the given .k file.


      Comment down your response for further help. Cheers, Ram
    • goktug.yilmaz
      Subscriber
      thank you very much for your help. I get stuck with this problem. Whatever I did does not work. I also have tried to look at the file you sent, but an error occured. I have added the same controls that you used, but after running until about %3, it has been terminated. Here is the .txt file for my last analysis.
      And here is the content of my file if you are not allowed to download.

      $#title
      Tripe-Chamber Crushbox meshed by AMEEN TOPA
      *CONTROL_ACCURACY
      $#osuinnpidosuiacc
      1411
      *CONTROL_BULK_VISCOSITY
      $#q1q2typebtypetstype
      1.50.06-200
      *CONTROL_ENERGY
      $#hgenrwenslntenrylenirgen
      22222
      *CONTROL_HOURGLASS
      $#ihqqh
      10.1
      *CONTROL_IMPLICIT_AUTO
      $#iautoiteoptitewindtmindtmaxdtexpkfailkcycle
      11150.00.00.000
      *CONTROL_IMPLICIT_DYNAMICS
      $#imassgammabetatdybirtdydthtdyburiratealpha
      00.50.250.01.00000E281.00000E2800.0
      *CONTROL_IMPLICIT_GENERAL
      $#imflagdt0imformnsbsigscnstnformzero_v
      10.001212000
      *CONTROL_IMPLICIT_SOLUTION
      $#nsolvrilimitmaxrefdctolectolrctollstolabstol
      1211150.0010.011.00000E100.91.0000E-10
      $#dnormdivergistifnlprintnlnormd3itctlcpchk
      2110000
      $#arcctlarcdirarclenarcmtharcdmparcpsiarcalfarctim
      000.012000
      $#lsmtdlsdiriradsradawgtsred
      420.00.00.00.0
      *CONTROL_IMPLICIT_SOLVER
      $#lsolvrlprintnegevorderdrcmdrcprmautospcautotol
      202040.010.0
      $#lcpackmtxdmpiparm1rparm1rparm2
      205001.00000E-90.001
      $#emxdmprdcmem
      00.85
      *CONTROL_OUTPUT
      $#npoptneechonrefupiaccopopifsipnintikeditiflush
      00000.001005000
      $#iprtfierodetet10s8msgmaxipcurvgmdtip1dblteocs
      0025000.000
      $#tolevnewlegfrfreqminfosolsigmsgflgcdetol
      20100010.0
      $# phschngdemdenicrfilespc2bndpenoutshlsighisnoutengout
      00000000
      $#insfisolsfibsfissfmlkbag
      00000
      *CONTROL_PARALLEL
      $#ncpunumrhsconstpara
      1020
      *CONTROL_SOLID
      $#esortfmatrixniptetsswloclpsfailt10jtolicohedtet13k
      100100.000
      $#pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10
      0000000000
      *CONTROL_SOLUTION
      $#solnnlqisnanlcintlcaccncdcf
      00010001
      *CONTROL_TERMINATION
      $#endtimendcycdtminendengendmasnosol
      1.000.00.01.000000E80
      *DATABASE_BNDOUT
      $#dtbinarylcurioopt
      0.001001
      *DATABASE_NODFOR
      $#dtbinarylcurioopt
      0.001001
      *DATABASE_NODOUT
      $#dtbinarylcuriooptoption1option2
      0.0010010.00
      *DATABASE_RBDOUT
      $#dtbinarylcurioopt
      0.001001
      *DATABASE_RCFORC
      $#dtbinarylcurioopt
      0.001001
      *DATABASE_BINARY_D3PLOT
      $#dtlcdtbeamnpltcpsetid
      0.010000
      $#iooptratecutoffwindowtypepset
      00.00.00.000
      *DATABASE_NODAL_FORCE_GROUP
      $#nsidcid
      20
      *BOUNDARY_PRESCRIBED_MOTION_RIGID_ID
      $#idheading
      1Displacement of plate
      $#piddofvadlcidsfviddeathbirth
      2321-1.001.00000E280.0
      *BOUNDARY_SPC_SET_ID
      $#idheading
      1Fixed Bottom
      $#nsidciddofxdofydofzdofrxdofrydofrz
      10111111
      *SET_NODE_LIST_TITLE
      Bottom_Nodes



    • goktug.yilmaz
      Subscriber
      I also opened your file and import my models in it to use the exact same settings with you. However, my rigid plate just don't move during analysis. It is waiting at the same position. I really don't know why.
    • goktug.yilmaz
      Subscriber
      I have worked a bit more on the analysis. I have used the same settings with yours. Actually, I have opened your file, deleted your models and imported mine. I haven't changed the material. The only difference is that I have removed your segment entities which you use to define contacts. I have defined masters and slaves as parts. As I said before, This is the only difference. Here is my resul;
      Could you help me improve my result? I have also tried to use 27 node solid elements, but it has given an error.

      Best regards.

    • Ram Gopisetti
      Ansys Employee
      The keyword I gave you is in the explicit domain, based on your initial data you are proceeding in the implicit domain. Anyways, you can check the following link for setting up the model as per standard.
      you can change the section to be shell rather than solid and compare them with the experiment .
      Cheers, Ram
    • Ram Gopisetti
      Ansys Employee
      Moreover, check this thesis for further help.
      cheers, Ram
    • goktug.yilmaz
      Subscriber
      Thank you very much for your answer. I am trying to do an explicit analysis now, to obtain similar results to your simulation. I am also using the same material with you. Now, I have done the simulation again by making contact definitions the same with yours by creating segment entities as you can see below.
      However, the result is still inaccurate. I will also try to model this geometry in Ls-Dyna and perform the analysis by using shell section.

      Thank you for your help and sources you have shared with me.

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