# Planar Constraint in ANSYS Mechanical

Member
edited November 2020

Please indulge my rookie question.

Is it possible to specify planar constraint for a specific surface boundary in a 3D structural analysis such that the surface remains in its original plane?

An ANSYS equivalent of this described Abaqus plugin is exactly what I'm looking for.

Thanks.

## Best Answer

• Member
edited November 2020 Accepted Answer

1) My suggestion works for any flat surface in space. If your surface is normal to a global axis, then you don't need to make a new coordinate system.

2) Use a Remote Displacement and assign Rotation about X = 0 and Rotation about Y = 0, leaving the other four DOF set to Free. The nodes will remain in a plane parallel to the original plane.

There are two behaviors to set in a Remote displacement: Rigid or Deformable. In a Rigid behavior, all the nodes on that plane are locked into a rigid relationship, but can move as a group in any direction except for the two rotations that are set to 0. The other behavior is Deformable, where the nodes are allowed to move relative to one another, but it is only the average of all the nodes that is set to zero rotation about X and Y.

## Answers

• Member

One way to do that is by creating a new coordinate system for that plane. If you make the Z axis of that new coordinate system normal to the plane, then you would use a Displacement boundary condition of Z = 0 and set the coordinate system in the Details window to the new coordinate system instead of Global. Leave the other two directions Free. This BC would allow the nodes on that surface to move in X and Y and rotate about Z in the new coordinate system, which is what a Planar constraint does.

• Member

Thanks @peteroznewman. Sorry, I have two follow up questions

1) How would your suggestion be different from just inserting a displacement BC and imposing the zero displacement condition on the normal axis (using the global coordinates, without creating a new coordinate system)

2) What if I needed the surface to move in the surface normal direction, with the only restriction that all nodes on that surface remain in plane if they move?

• Member
edited November 2020 Accepted Answer

1) My suggestion works for any flat surface in space. If your surface is normal to a global axis, then you don't need to make a new coordinate system.

2) Use a Remote Displacement and assign Rotation about X = 0 and Rotation about Y = 0, leaving the other four DOF set to Free. The nodes will remain in a plane parallel to the original plane.

There are two behaviors to set in a Remote displacement: Rigid or Deformable. In a Rigid behavior, all the nodes on that plane are locked into a rigid relationship, but can move as a group in any direction except for the two rotations that are set to 0. The other behavior is Deformable, where the nodes are allowed to move relative to one another, but it is only the average of all the nodes that is set to zero rotation about X and Y.

• Member
edited November 2020

@peteroznewman Okay got it. I will try your suggestions per your response to 2) and will let you know how it goes. Thanks again!

Sign In or Register to comment.