Learning Forum

[Zainaba98]

Hi everyone,

So I have a cube, where I have applied an angular displacement (using remote displacement). When I wanted to measure the moment reaction on that face, I have two location methods: Boundary Condition and Geometry Selection. Each one of these methods, is giving very different results.

Can any1 explain this to me please?

1- BC:

[1shan]

The remote displacement moments is calculated at the corresponding remote point , while the moment reaction scoped to the geometry face is calculated at the face of the centroid (summation point) to which it is scoped. In your case these 2 do not match and hence the difference in results. You could scope the remote point to center of the face (use the 'click to change option' and select the face) and check whether results match. You could check the location of summation point by viewing the arrow head displayed when using the moment probe.
When you apply a remote displacement the solver internally creates rigid spider elements (click on solution information to visualize these) which link the scoped geometry nodes to the remote point. When you apply a remoted displacement, it is applied to this remote point (and not to the face). So even though the faces moves in X,Y,Z the remote point doesn't. You can refer to this informative discussion by Peter /forum/discussion/19833/how-to-apply-rigid-body-element-2-rbe2-in-ansys-mechanical.
Regards Ishan.

[Zainaba98]

Hi Shan,
thanks for your reply.
In fact as u see in the following picture, the remote point is scoped to the center of the face HOWEVER, the moments calculated by selecting remote point are not the same as when selecting 'geometry selection':
1-

2- Just to make sure I well understood your point, if I have a remote point scope to the center of a face, and we apply a rotation to the remote point, the face it's scoped to is going to rotate by the same angles but it's not the case for translational displacement?

[Zainaba98]

I would like to also note that even for other simulations where I apply a displacement on a face (no remote points just ordinary displacements), I get a difference in the moment reaction calculation when selecting the face by 'geometry selection' vs when I choose 'Boundary Condition', however the difference is not as significant as with BC's with remote points...
BC:

Moment reaction by 'Boundary condition':
Moment reaction by 'geometry selection':