Learning Forum

[Pranav_2496]

how to use Matrix 27 in work bench for connecting 2 interfaces with stiffness like we do in APDL.

[Bill Bulat]

I would define two remote points - one for each of the surfaces that you intend to join with MATRIX27. You would then need a command object to define the MATRIX27 attributes and the element itself (which joins the two remote point nodes). Defining the individual matrix values (real constants) can be a bit tricky. I found the following discussion which may be helpful to you:
Stiffness between all 6 DOFs of two nodes using MATRIX27 with no cross coupling between DOFs, i.e. Fxi = Kx(UXi ÔÇô UXj)
Fyi = Ky(UYi ÔÇô UYj)
Fzi = Kx(UZi ÔÇô UZj)
Mxi = Tx(ROTXi ÔÇô ROTXj)
Myi = Ty(ROTYi ÔÇô ROTYj)
Mzi = Tz(ROTZi ÔÇô ROTZj)
Fxj = Kx(-UXi + UXj)
Fyj = Ky(-UYi + UYj)
Fzj = Kz(-UZi + UZj)
Mxj = Tx(-ROTXi + ROTXj)
Myj = Ty(-ROTYi + ROTYj)
Mzj = Tz(-ROTZi + ROTZj)

The matrix looks like this:
Kx00000-Kx00000
0Ky00000-Ky0000
00Kz00000-Kz000
000Tx00000-Tx00
0000Ty00000-Ty0
00000Tz00000-Tz
-Kx00000Kx00000
0-Ky00000Ky0000
00-Kz00000Kz000
000-Tx00000Tx00
0000-Ty00000Ty0
00000-Tz00000Tz

So the real constant input should be as follows:

rmod,1,1,Kx! K_UX
rmod,1,7,-Kx
rmod,1,58,Kx

rmod,1,13,Ky! K_UY
rmod,1,19,-Ky
rmod,1,64,Ky

rmod,1,24,Kz! K_UZ
rmod,1,30,-Kz
rmod,1,69,Kz

rmod,1,34,Tx! K_ROTX
rmod,1,40,-Tx
rmod,1,73,Tx

rmod,1,43,My! K_ROTY
rmod,1,49,-My
rmod,1,76,My

rmod,1,51,Mz! K_ROTZ
rmod,1,57,-Mz
rmod,1,78,Mz

I also found the following MAPDL input file that might help you construct your command object:

fini
/cle

k_ux=1
k_uy=2
k_uz=3

k_rotx=10
k_roty=20
k_rotz=30

/prep7
et,1,27,,,4

r,1

rmod,1,1,k_ux ! K_UX
rmod,1,7,-k_ux
rmod,1,58,k_ux

rmod,1,13,k_uy ! K_UY
rmod,1,19,-k_uy
rmod,1,64,k_uy

rmod,1,24,k_uz ! K_UZ
rmod,1,30,-k_uz
rmod,1,69,k_uz

rmod,1,34,k_rotx ! K_ROTX
rmod,1,40,-k_rotx
rmod,1,73,k_rotx

rmod,1,43,k_roty ! K_ROTY
rmod,1,49,-k_roty
rmod,1,76,k_roty

rmod,1,51,k_rotz ! K_ROTZ
rmod,1,57,-k_rotz
rmod,1,78,k_rotz

n,1
n,2

e,1,2

d,2,all

fini

/solu

d,1,all ! LS 1: CHECK UX
d,1,ux,1
solv

d,1,all ! LS 2: CHECK UY
d,1,uy,1
solv

d,1,all ! LS 3: CHECK UZ
d,1,uz,1
solv

d,1,all ! LS 4: CHECK ROTX
d,1,rotx,1
solv

d,1,all ! LS 5: CHECK ROTY
d,1,roty,1
solv

d,1,all ! LS 6: CHECK ROTZ
d,1,rotz,1
solv

fini

/post1

set,1
*get,r_ux1,node,1,rf,fx
*get,r_ux2,node,2,rf,fx

set,2
*get,r_uy1,node,1,rf,fy
*get,r_uy2,node,2,rf,fy

set,3
*get,r_uz1,node,1,rf,fz
*get,r_uz2,node,2,rf,fz

set,4
*get,r_rotx1,node,1,rf,mx
*get,r_rotx2,node,2,rf,mx

set,5
*get,r_roty1,node,1,rf,my
*get,r_roty2,node,2,rf,my

set,6
*get,r_rotz1,node,1,rf,mz
*get,r_rotz2,node,2,rf,mz


Kind regards Bill