how to define a spring to earth with 3 different stiffnesses ?

[MB03]

Hello,
I'm new in Ansys. I'm trying to put a spring to earth on a keypoint with 3 different stiffnesses (along x,y and z).
I tried to use a COMBIN14 element with KEYOPT(3) = 0 but then, I don't know where to enter the 3 different values of the stiffnesses. Then I tried to use 3 COMBIN14 elements with KEYOPT(2) = 1,2 and 3, and coincident nodes i and j, with the following commands :
!Element types
ET,3,COMBIN14
ET,4,COMBIN14
ET,5,COMBIN14
KEYOPT,3,2,1
KEYOPT,4,2,2
KEYOPT,5,2,3
!Node corresponding to the keypoint where I want to put
!the spring
N,1,0,0,0,
!definition of 3 springs on this node
TYPE,3 (stiffness along x)
REAL,15 (value of the stiffness)
E,1,1 (element with coincident nodes)
TYPE,4 (stiffness along y)
REAL,16
E,1,1
TYPE,5 (stiffness along z)
REAL,17
E,1,1
But when I try to solve, Ansys ask to put constraints with the D command, as if it didn't link the 3 springs to earth.
I don't understand !!
Thanks for your help

 

[juzz]

Hello, MB03!

You need to define D constraints. Of course, the question that arise is if I block node 1 how the springs work?
The problem is that you need to use coincidental nodes (not the same node). These nodes have same locations but have different number. You could include in your model three new nodes at the same location and block them. Will be something like this:

!Element types
ET,3,COMBIN14
ET,4,COMBIN14
ET,5,COMBIN14
KEYOPT,3,2,1
KEYOPT,4,2,2
KEYOPT,5,2,3
!Node corresponding to the keypoint where I want to put
!the spring
N,1,0,0,0,
N,2,0,0,0,
N,3,0,0,0,
N,4,0,0,0,
!definition of 3 springs on this node
TYPE,3 (stiffness along x)
REAL,15 (value of the stiffness)
E,1,2 (element with coincident nodes)
TYPE,4 (stiffness along y)
REAL,16
E,1,3
TYPE,5 (stiffness along z)
REAL,17
E,1,4

See the differences! After that in

/solu
.......
d,2,all ! or at least ux (is the same thing)
d,3,all ! or at least uy (is the same thing)
d,4,all ! or at least uz (is the same thing)
.......

I hope this will be useful!

Best regards,

Juzz
--------------------------------
Justin Onisoru
Researcher
Romanian Academy
Institute of Solid Mechanics
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