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# Implementing a cylindrical boundary condition

## Implementing a cylindrical boundary condition

(OP)
Hello all,

I am trying to achieve something similar to the description in thread799-306416: ABAQUS Cylindrical Boundary Conditions - in this case, pure rotation of a set of nodes (defining one edge of a part) about an axis. I need the nodes to maintain their original radial distance from the axis of rotation, and rotate together by a given angle. I am aware of the ability to define cylindrical coordinate systems and of the *TRANSFORM keyword, but haven't been able to correctly implement the boundary condition using these, and I don't know where else to look within the documentation or elsewhere online. Could anyone give me any tips about how to proceed?

Thanks very much,
Lukor

### RE: Implementing a cylindrical boundary condition

(OP)
Hello all,

I hate to double-post, but if anyone has any insight about how to define a boundary condition using R and Theta coordinates, I would greatly appreciate your help - I've looked hard at the documentation and even called customer support and haven't been able to resolve this. If it can't be done directly, I'd love to know what the best way to go about it in rectangular coordinates would be.

Thanks,
Lukor

### RE: Implementing a cylindrical boundary condition

Well, there are two points in your question:
1. Restraining the radial distance. That's simple. Define a cylindrical CSYS in the center of the part and restrain the 1-direction. Make sure the orientation of the CSYS is correct. The 3-axis is the axial direction. 1 is radial. 2 is tangential.

2. Rotation about a given angle. That's no so easy. It can't be done with a boundary on the nodes of the part. You have to couple nodes of the part to a reference node at the center and apply the rotation there.

But when you do #2 at all nodes and #1 at the same time, then your body can't deform. In this case you can have it all much easier. Just make a rigid body out of that part, place the ref node in the center and rotate that.

### RE: Implementing a cylindrical boundary condition

(OP)
Thanks so much, Mustaine3! That's exactly what I was looking for. More specifically, I made a second, rigid body defining the radius of rotation, used a tie constraint to fix it to the boundary of the deformable body that I was interested in, and rotated it about its reference point.

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