General Mechanical

General Mechanical

How can I model a tapered cross section beam?

    • javier.medina.galera
      Subscriber

      Hi, I would like to model a tapered beam forming a hollow conical geometry as a transition piece between two cylinders of different diameter. I need it to be a beam type for further calculations in Aqwa.

      I'm aware that with APDL you can create a tapered cross section and then assign it to a line. Is there any way to do this in Design modeler or Space claim? Can I run the APDL code inside DM or SC??

      Thank you very much.

       

    • Erik Kostson
      Ansys Employee

       

      Hi

      You can not do that.

       

      It is only possible to define the tapered beam inside mechanical using APDL command snippet.

      Never done this but perhaps it is possible (see the help manual for tapered beam, e.g., sectype,3,taper, sectype,2,beam, and sectype,1,beam, etc)

      All the best

       

      Erik

       

    • Ankush Choudhary
      Subscriber

      Hi Javier,

      Spaceclaim, Design Modeler, and Mechanical Gui do not support the tappered beam section. For defining the tapered section, you need to insert the APDL script inside the mechanical.

       

      Thanks,

      Ankush

    • javier.medina.galera
      Subscriber

      Hi Erik and Ankush,

      Thank you very much for your answers. I've tried to follow your advice but I'm stuck, I'm not familiar with working with snippets or running scripts inside mechanichal so I may be missing something.

      I've written this APDL script that generates my desired geometry:

      FINISH
      /CLEAR ! clear database
      /PREP7 ! enters the preprocessor

      ! MATERIAL PROPERTIES
      YNGMOD = 2e11 ! Young's modulus
      PCOEF = 0.27 ! Poisson coefficient
      MDENS = 7850 ! Material density

      ! SECTION DIMENSIONS
      ! CTUBE1
      Intrad1 = 6470
      Extrad1 = 6500
      !CTUBE2
      Intrad2 = 9370
      Extrad2 = 9400


      ! Element types
      ET,1,BEAM189 ! create 3-node beam element
      ET,2,SHELL281  

      !define material
      MPTEMP,,,,,,,,
      MPTEMP,1,0
      MPDATA,EX,1,,YNGMOD ! Young's modulus
      MPDATA,PRXY,1,,PCOEF ! poisson coef.
      MPDATA,DENS,1,,MDENS  ! Density. For considering own weight

      ! Keypoints Definition
      K,1,0,0,0
      K,2,0,0,-4000
      K,3,0,0,-12000
      K,4,0,0,-120000
      K,5,0,0,10000

      SECTYPE,1,BEAM,CTUBE,CT,0
      SECOFFSET, CENT ! Origin of section located at CoG of section
      SECDATA,Intrad1,Extrad1,64,0,0,0,0,0,0,0,0,0 ! Variables of section

      LSTR,1,2! Straight line connecting each KP
      LSEL, , , ,       1 ! Selecting the generated line
      LATT,1, ,1, ,       , ,1   ! Assigning the variable section, element type and material properties to line
      LESIZE,1,400 , ,, , , , ,1  ! Size of Mesh
      LMESH,      1  ! Line Meshing

      SECTYPE,2,BEAM,CTUBE,CT,0
      SECOFFSET, CENT ! Origin of section located at CoG of section
      SECDATA,Intrad2,Extrad2,64,0,0,0,0,0,0,0,0,0 ! Variables of section

      LSTR,3,4! Straight line connecting each KP
      LSEL, , , ,       2 ! Selecting the generated line
      LATT,1, ,1, ,       , ,2   ! Assigning the variable section, element type and material properties to line
      LESIZE,2,800 , ,, , , , ,1  ! Size of Mesh
      LMESH,      2 ! Line Meshing

      LSTR,2,3! Straight line connecting each KP
      SECTYPE,3,TAPER, ,TC   ! We define a taper to generate a variable section. Tower's transition piece.
      SECDATA,  1 ,0,0,-4000, ! Initial base of variable section
      SECDATA,   2,0,0,-12000,
      LSEL, , , ,       3 ! Selecting the generated line
      LATT,1, ,1, ,       , ,3  ! Assigning the variable section, element type and material properties to line
      LESIZE,3,400 , ,, , , , ,1  ! Size of Mesh
      LMESH,      3 ! Line Meshing

      ! Upper section
      K,5,0,0,10000
      LSTR,1,5! Straight line connecting each KP
      LSEL, , , ,       4 ! Selecting the generated line
      LATT,1, ,1, ,       , ,1   ! Assigning the variable section, element type and material properties to line
      LESIZE,4,1000 , ,, , , , ,1  ! Size of Mesh
      LMESH,      4 ! Line Meshing

      /ESHAPE,1.0

      And the result is

       

      Actually, the part of the code I would like to implement is this, where I define a tapered section from the sections already defined above for the rest of the line bodies:

      LSTR,2,3! Straight line connecting each KP
      SECTYPE,3,TAPER, ,TC   ! We define a taper to generate a variable section. Tower's transition piece.
      SECDATA,  1 ,0,0,-4000, ! Initial base of variable section
      SECDATA,   2,0,0,-12000,
      LSEL, , , ,       3 ! Selecting the generated line
      LATT,1, ,1, ,       , ,3  ! Assigning the variable section, element type and material properties to line
      LESIZE,3,400 , ,, , , , ,1  ! Size of Mesh
      LMESH,      3 ! Line Meshing

      What I've tried so far:

      • Use design modeler to build the line bodies and the two CTUBES, transfer the geometry to a mechanichal model (tried to implement the snippet by inserting an apdl command to the desired line body, but it doesn't make any change) and then to the hydrodynamic diffraction module.
      • Archive the apdl model and load it in workbench using the external model option, but workbench is reading the the tapered section as a constant CTUBE equal to the start of the tapered section
      • Use the spaceclaim 'extract' option under 'prepare' tab to extract the tapered section, but the hydrodynamic difraction doesn't like it

      I would really apreciate if you could help me implementing the code inside mechanichal. Thank you very much for your help.

       

      Best regards,

      Javier

    • Erik Kostson
      Ansys Employee

       

       

       

      Hi

       

      Have not used this much and it is not really convenient.

      So the way to use it in WB / mech. (define 3 line bodies/geom., and then change the section of the taper as shown in the apdl command snippet placed under it in the tree below).

       

       

      We can not view it (taper) in mechanical ui – so only way is in APDL (used an image to view it – see below)

      The last snippet is:

      /eshape,1,ON
      /SHOW,png
      EPLOT
      /show,close

       

       

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