LS Dyna

LS Dyna

Applying bending moment to a solid element

    • king79
      Subscriber

      Hi,

      I modelled a solid cylinder surrounded by soil and would like to apply a bending moment at the top and check the nodal rotations. Can this be achieved in Ls-Prepost?

      I am trying to capture the response of a pile foundation subjected bending moment. This analysis has been performed in Abaqus FEA using rigid body constraint but not sure if a similar approach can be achieved in Ls-Prepost. Please can you offer any assistance.

      Thank you

    • Ram Gopisetti
      Ansys Employee
      you can apply moment via boundry_precribed_motion and setting the DOF=respective to axis.VAD =2 and define the rate of twist(angle) as curve.
      bending moment is the output of an beam type via DISBOUT.
      Cheers, Ram

    • king79
      Subscriber
      thanks for the feedback. I also want to extract the rotation at the the top of the pile. Is there a way to do so in Ls-prepost. Results for translations are available but no output for rotation.
    • Ram Gopisetti
      Ansys Employee
      perhaps an NDV fringe might help in this case, and you can also use vector plot to visualize the rotation as displacement criteria.
      Cheers, Ram
    • Andreas Koutras
      Ansys Employee
      of course nodal rotations cannot be applied to solid elements because solid elements do not have rotational DOFs. Your approach in Abaqus was correct. You can do the same in LS-DYNA by using *CONTSTRAINED_NODAL_RIGID_BODY to impose a rigid body constraint to the nodes at the top face of the pile. Then you can apply moment or rotation to the CNRB through *LOAD_RIGID_BODY or *BOUNDARY_PRESCRIBED_MOTION_RIGID respectively. The rotation at a node at the top of the pile can be extracted through *DATABASE_NODOUT.
    • king79
      Subscriber
      Hi I tried the suggestion and ran the analysis, but I got an error message indicating that LOAD_RIGID_BODY requires at MAT_rigid part. When I assigned a Mat_rigid material to the pile then ran the analysis, I got an error message indicating that Mat_rigid and LOAD_RIGID_BODY cannot be used together.
    • king79
      Subscriber
      Actually, the error message was related to Constrained_Nodal_Rigid_Boday and Load_Rigid_Body not permitted in the same analysis. Not sure why.
    • Andreas Koutras
      Ansys Employee

      *LOAD_RIGID_BODY can be applied to a *CNRB. I suggest you try it in a new test model.
      Best regards
    • king79
      Subscriber
      How do I apply a *LOAD_RIGID_BODY to *CNRB when the part ID does not show up in the drop-down menu?


    • Andreas Koutras
      Ansys Employee
      That's a known issue of LSPP. Please enter the *CNRB part id manually, thanks.
    • king79
      Subscriber
      I followed the suggestion and still get an error message:


    • Andreas Koutras
      Ansys Employee
      Try the following example.

      $# LS-DYNA Keyword file created by LS-PrePost(R) V4.9 (Beta) - 20Sep2021
      $# Created on Sep-22-2021 (03:12:47)
      *KEYWORD
      *TITLE
      $#title
      LS-DYNA keyword deck by LS-PrePost
      *CONTROL_TERMINATION
      $#endtimendcycdtminendengendmasnosol
      0.099900.00.01.000000E80
      *DATABASE_BNDOUT
      $#dtbinarylcurioopt
      1.00000E-4001
      *DATABASE_SECFORC
      $#dtbinarylcurioopt
      1.00000E-4001
      *DATABASE_BINARY_D3PLOT
      $#dtlcdtbeamnpltcpsetid
      1.00000E-40000
      $#iooptratecutoffwindowtypepset
      000
      *DATABASE_EXTENT_BINARY
      $#neiphneipsmaxintstrflgsigflgepsflgrltflgengflg
      00301111
      $#cmpflgieverpbeamipdcompshgestsszn3thdtialemat
      00011121
      $# nintsldpkp_sensclphydromssclthermintoutnodout
      001.0000
      $#dtdtrespltneipbquadsldcubslddeleres
      00000
      *DATABASE_CROSS_SECTION_PLANE_ID
      $#csidtitle
      1
      $#psidxctyctzctxchychzchradius
      1-10.0-10.025.0-10.0-10.030.00.0
      $#xhevyhevzhevlenllenmiditype
      30.0-10.025.040.040.012
      *SET_PART_LIST
      $#sidda1da2da3da4solver
      10.00.00.00.0MECH
      $#pid1pid2pid3pid4pid5pid6pid7pid8
      10000000
      *BOUNDARY_SPC_SET
      $#nsidciddofxdofydofzdofrxdofrydofrz
      10001000
      *SET_NODE_LIST_TITLE
      Base
      $#sidda1da2da3da4solver
      10.00.00.00.0MECH
      $#nid1nid2nid3nid4nid5nid6nid7nid8
      123410111920
      270000000
      *LOAD_RIGID_BODY
      $#piddoflcidsfcidm1m2m3
      25110000.00000
      *PART
      $#title

      $#pidsecidmideosidhgidgravadpopttmid
      11100000
      *SECTION_SOLID
      $#secidelformaetunusedunusedunusedcohoffgaskeit
      1100.00.0
      *MAT_ELASTIC_TITLE
      Steel ton, mm, sec
      $#midroeprdadbnot used
      17.80000E-9210000.00.30.00.00.0
      *DEFINE_COORDINATE_NODES
      $#cidn1n2n3flagdir
      13334361X
      *DEFINE_CURVE
      $#lcidsidrsfasfooffaoffodattyplcint
      101.01.00.00.000
      $#a1o1
      0.00.0
      0.110.0
      *SET_NODE_LIST_TITLE
      Top
      $#sidda1da2da3da4solver
      20.00.00.00.0MECH
      $#nid1nid2nid3nid4nid5nid6nid7nid8
      101102103104110111119120
      1270000000
      *CONSTRAINED_NODAL_RIGID_BODY
      $#pidcidnsidpnodeiprtdrflagrrflag
      2020000
      *ELEMENT_SOLID
      $#eidpidn1n2n3n4n5n6n7n8
      1112345678
      21210113614157
      31431920872324
      4131127197153123
      513334353637383940
      613442433538464739
      713635515240395556
      813543595139476355
      91567833343536
      10161415734424335
      11187232436355152
      121715312335435951
      13137383940101102103104
      14138464739102110111103
      15140395556104103119120
      16139476355103111127119
      *NODE
      $#nidxyztcrc
      10.00.00.000
      210.00.00.000
      310.010.00.000
      40.010.00.000
      50.00.010.000
      610.00.010.000
      710.010.010.000
      80.010.010.000
      1020.00.00.000
      1120.010.00.000
      1420.00.010.000
      1520.010.010.000
      1910.020.00.000
      200.020.00.000
      2310.020.010.000
      240.020.010.000
      2720.020.00.000
      3120.020.010.000
      330.00.020.000
      3410.00.020.000
      3510.010.020.000
      360.010.020.000
      370.00.030.000
      3810.00.030.000
      3910.010.030.000
      400.010.030.000
      4220.00.020.000
      4320.010.020.000
      4620.00.030.000
      4720.010.030.000
      5110.020.020.000
      520.020.020.000
      5510.020.030.000
      560.020.030.000
      5920.020.020.000
      6320.020.030.000
      1010.00.040.000
      10210.00.040.000
      10310.010.040.000
      1040.010.040.000
      11020.00.040.000
      11120.010.040.000
      11910.020.040.000
      1200.020.040.000
      12720.020.040.000
      *END

    • king79
      Subscriber
      Is there a link to the file for this example on your website? If not, can you explain how to input the command script in Ls-Prepost? Thanks
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