## 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

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

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

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.