[CERIG] It should stay flat while it rotates and expands

[last4ever]

Hi.

I have a 3D model, which is apparently constrained as I want (i.e. behaving as we expect), but I'm not sure why. Can anyone please provide some clarification?

The model is 3D with solid elements. The nodes in the solid elements have only displacement degrees of freedom (SOLID95). I have a flat side of the model starting in the X-Z plane. I want all the nodes on that side to remain in a plane. The plane should be able to move back and forth in the X direction and to rotate about the Y axis.

I seem to have achieved this by use of the CERIG command. I have tied UX for all the nodes on the plane to UX in a separate master node(10000). Unlike the nodes in the plane, the master node also has rotational degrees of freedom. All of the master node's degrees of freedom are constrained, except for UX and ROTY.



N,10000,x1,y1,z1 ! MASTER NODE

D,10000,UY,0
D,10000,UZ,0
D,10000,ROTX,0
D,10000,ROTZ,0

TYPE,4 ! MASS21
REAL,4
E,10000

NSEL,,LOC,X,0 ! SLAVE NODES
NSEL,A,NODE,,10000

CERIG,10000,ALL,UX
ALLSEL,ALL



As stated above, these constraints are having the desired effect. The slave nodes in the plane are staying planar and tilting so that UX is proportional to Z.

It appears that because the master node was left free in ROTY, that it's X axis is tilting, and that the UX constraint between the master and slave nodes is enforced relative to the rotated X axis.

Does this make sense, i.e. am I interpreting the effect of the constraints correctly?

Thanks.