Inactive DOF of node when I applied the moment load
Inactive DOF of node when I applied the moment load
(OP)
Hello
As I defined a moment load at the free end of a tube, an error occured describing the following message
***ERROR: DEGREE OF FREEDOM 6 IS NOT ACTIVE ON NODE 12 INSTANCE OUTERTUBE-1 -
THIS LOADING IS NOT VALID
***NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE TO
INTERPRET SOME DATA. SUBSEQUENT ERRORS MAY BE CAUSED BY THIS OMISSION
***ERROR: DEGREE OF FREEDOM 6 IS NOT ACTIVE ON NODE 12 INSTANCE OUTERTUBE-1 -
THIS LOADING IS NOT VALID
***ERROR: 1 nodes have inactive dof on which boundary conditions are
specified. The nodes have been identified in node set
ErrNodeBCInactiveDof
This was a simplified model. The cross section of the tube lies in the X-Y plane. I added a moment at one node at the free end of the tube with value of CM3. The cross section surface at another end was constrained in Z direction and one node on the surface was constrained in X and Y direction to avoid the rigid body motion. The boundary condtion of X-Y plane rotation on this surface was also added.
Node 12 in the error message is the node where the moment load added. I am sure that there were no over-constraints. so I am confused with this situation. Is it the problem degree of freedom of element? The linear brick element C3D8 was utilized.
Thanks for the reply.
As I defined a moment load at the free end of a tube, an error occured describing the following message
***ERROR: DEGREE OF FREEDOM 6 IS NOT ACTIVE ON NODE 12 INSTANCE OUTERTUBE-1 -
THIS LOADING IS NOT VALID
***NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE TO
INTERPRET SOME DATA. SUBSEQUENT ERRORS MAY BE CAUSED BY THIS OMISSION
***ERROR: DEGREE OF FREEDOM 6 IS NOT ACTIVE ON NODE 12 INSTANCE OUTERTUBE-1 -
THIS LOADING IS NOT VALID
***ERROR: 1 nodes have inactive dof on which boundary conditions are
specified. The nodes have been identified in node set
ErrNodeBCInactiveDof
This was a simplified model. The cross section of the tube lies in the X-Y plane. I added a moment at one node at the free end of the tube with value of CM3. The cross section surface at another end was constrained in Z direction and one node on the surface was constrained in X and Y direction to avoid the rigid body motion. The boundary condtion of X-Y plane rotation on this surface was also added.
Node 12 in the error message is the node where the moment load added. I am sure that there were no over-constraints. so I am confused with this situation. Is it the problem degree of freedom of element? The linear brick element C3D8 was utilized.
Thanks for the reply.
RE: Inactive DOF of node when I applied the moment load
corus
RE: Inactive DOF of node when I applied the moment load
RE: Inactive DOF of node when I applied the moment load
For solid elements a moment can be applied by applying two forces (a couple) in equal and opposite directions at an equidistance away from the bending axis. As the saying goes: Every couple have their moment.
corus
RE: Inactive DOF of node when I applied the moment load
Using *AMPLITUDE command? But it is described in the manual as following:
Complex time- or frequency-dependent boundary conditions, loads, and predefined fields can be specified by using the AMPLITUDE parameter on the prescribed condition option to refer to an amplitude curve.
I tried with user subroutine, but the definition of CLOAD is not provided in it.
What else can I do? If *AMPLITUDE is suggested, I wish you can give the tips with a little bit more detail.
Thanks
xiazhn
RE: Inactive DOF of node when I applied the moment load
If you're applying a variable force along the length of the tube to apply your moment then it's probably easier just to edit the input file manually. Alternatively you could apply a variable pressure along the length equivalent to your forces in a similar way to applying a hydrostatic pressure distribution.
corus
RE: Inactive DOF of node when I applied the moment load
Have a nice weekend.
RE: Inactive DOF of node when I applied the moment load
I tried to follow your tipps in applying the linear distributed moments. But unfortunately the problem hasn't been solved.
For pressure or hydrostatic, it is only possible to be normal to the outside surface of the tube, and it produces no moment at all.
In the case that the mesh along with the tube is fine enough, it is nearly mission impossible to edit the input file manually.
So, any way else?
Sorry that trouble you so much. Thank you.
RE: Inactive DOF of node when I applied the moment load
corus
RE: Inactive DOF of node when I applied the moment load
P R E S S U R E
|-------------------|<- fixed translations
|-------------------|<- fixed translations
global axes
Y
|
|
|----- Z
pressure applied in -ve Y direction?
-- drej --
RE: Inactive DOF of node when I applied the moment load
corus
RE: Inactive DOF of node when I applied the moment load
"The cross section of the tube lies in the X-Y plane. I added a moment at one node at the free end of the tube with value of CM3. "
In ABAQUS CAE, CM3 refers to the value of the moment in the third direction, i.e. Z direction. So I meant the load was applied in the term of torsion, and the moment should be in the X-Y plane.
|
.
|------------
. |-->>M(torsion moment in the direction
|------------ according to right-hand system)
.
global coordinate system
Y
|
|
|----- Z
In this case, any pressure normal to the outside surface of the tube produces no moment to Z-axis, and this moment is what I expect.
Thanks.