General Mechanical

General Mechanical

rotational springs to connect link elements

    • julsmo
      Subscriber

      Hi all


      I relatively new to ansys and have trouble creating rotational springs. the explanations in ansys help didn't help much.


      I attached my ansys code and the iges geometry to import. I am trying to create rotational springs at each intersection. Was aiming to do that with combin39 elements but get weird movements as the nodes can't be coincident for that and I'm not sure if I implemented the springs right anyway.


      Goal would be to create stiffness with the springs to get some kind of s-shaped curves when I pull on the net in the y direction.


      appreciate any help. thanks!


       


      code:


      /prep7


       


      et,1,link8


      r,1,10,0.001


      mptemp,1,0


      mpdata,ex,1,,100000


      mpdata,prxy,1,,0.2


       


      esize,,10


      lmesh,all


       


      /solu


      nsel,,loc,x,0


      d,all,uz


      d,all,ux


       


      nsel,,node,,41


      nsel,a,node,,1


      d,all,uz,0


      d,all,uy,20


       


      nsel,,node,,100


      nsel,a,node,,138


      d,all,uz


      d,all,uy


       


      nsel,,node,,2


      nsel,a,node,,80


      d,all,uz


      d,all,ux,5


       


      nlgeom,on


      alls,all


      solve

    • peteroznewman
      Subscriber

      I recommend you use beams instead of links and rotational springs, since a beam is just an infinite number of links and springs.



      If there is a reason to use links and rotational springs rather than beams, you can explain it further.


      Attached is the Workbench ANSYS 18.2 version of your geometry from the IGES file above.


      I don't use APDL much, but I did manage to see you wanted a 20 mm deformation in the y direction.

    • julsmo
      Subscriber

      Hi thanks for answering!


      There is indeed a reason I use links. It's for my thesis and there is a previous thesis where all elements were modelled as beams but that apparently didn't picture the behavior of the cable net correctly. So I want to simplify it further assuming in the simplest version a cable is just a tnsion only link and add torsinal springs to get stiffness perpenicular to the cable since it's only unidirctional cables...

    • julsmo
      Subscriber

      Hi peter, just in case you see this. I am still working on the problem.. I have found a link element that works an dconnect it with spring elements, but can't couple the remaining dofs in a fixed way so both spring points move along the same distance. tried with a nonlinear mpc (rigid link).


      attached is my skript and if you tell me how to attach an igs with my geometry, i can also do that


      /prep7


       


      nx = 2 !Maschenanzahl horizontal                                                     !!!ANPASSEN!!!


      ny = 2 !Maschenanzahl vertikal


      maschx = 40 !Maschenbreite                                                     !!!ANPASSEN!!!


      maschy = 2 !Maschenhöhe


      vorspannx = 5


      vorspanny = 8


       


      et,1,link8


      r,1,10,0.001


       


      et,2,combin14


      keyopt,2,1,1 ! nichtlineare Berechnung


      keyopt,2,2,6 !Feder rotz


      r,2,10e10,,10e10


       


      et,3,mpc184


       


       


      mptemp,1,0


      mpdata,ex,1,,100000


      mpdata,prxy,1,,0.2


       


      ksel,all


      nkpt,,all


      cm,feder1,node


      *get,min1,node,0,num,min


      *get,max1,node,0,num,max


       


      nsel,,loc,x,0


      nsel,a,loc,x,maschx*nx


      nsel,a,loc,y,0


      nsel,a,loc,y,ny*2


      d,all,uz


      nsel,,loc,x,0


      d,all,ux


      nsel,,loc,x,maschx*nx


      d,all,ux,vorspannx


      nsel,,loc,y,0


      d,all,uy


      nsel,,loc,y,ny*2


      d,all,uy,vorspanny


       


       


       


      ksel,all


      nsel,none


      nkpt,,all


      cm,feder2,node


      nmodif,all,,,1


      d,all,rotz


       


      *get,min2,node,0,num,min


      *get,max2,node,0,num,max


       


       


      type,1


      real,1


      esize,,10


      lmesh,all


       


      cmsel,,feder1


      nsel,inve


      nummrg,node


       


      cmsel,,feder2


      nsel,inve


      nummrg,node


       


      type,2


      real,2


      nsel,all


      *do,i,min1,max1


      *set,j,max1+i


      e,i,j


      *enddo


       


      type,3


      *do,i,min1,max1


      *set,j,max1+i


      e,i,j


      *enddo


       


      nsel,,loc,x,maschx*nx*0.5


      nsel,r,loc,z,0


      f,all,fz,1


       


      /solu


      nlgeom,on


      alls


      solve


       

    • peteroznewman
      Subscriber

      Unfortunately, I am a beginner with APDL.


      I am highly skilled in Workbench and use an occasional Command object.


      Someone else is going to have to help you with this.


      Regards,
      Peter

    • julsmo
      Subscriber

      thanks anyways!

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