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Enforced Rotation - DOF Question

I have a problem with a setup.

In either SOL101 or SOL601 I want to get a component to rotate 60 Degrees in order to get the mechanics to lock together.

When I setup the enforced displacement I set Rot Z 60 Degrees.
Trying to solve this the program states that I cant to this as I have to specify more DOF in the enforced displacement as the component is made from a solid mesh.

I think this is very strange as the component as the component cannot be displaced other than by rotation. It is in contact with a surface below, has a cylindrical constraint in its axis (rotation around Z free) and will be locked by a fricktional surface in Z upwards when it starts to rotate.

Why does the program not let me rotate the component?

I have tried different degrees of rotation (1, 5, 60) - the same result.


Re: Enforced Rotation - DOF Question

Siemens Builder Siemens Builder
Siemens Builder

The solid element formulation only defines translational stiffness terms. In an all solid mesh, there is no rotational stiffness at any grid point, so loads/constraints cannot be applied to DOF 4, 5 or 6. Note that this is true of any standard continuum stiffness element formulation in any finite element solver - it's not particular to NX Nastran.

To be able to apply a rotation, you need to add elements with formulations that provide stiffness in the rotational DOF you want to load/constrain. Typical methods to do this include embedding 1 row of shell elements into the solid mesh, using a RBE2 "spider" element to couple the loaded/constrained grid to several surrounding grids or manually creating a "spider" with legs consisting of CBAR/CBEAM.

Note that 60 degrees is a large rotation, so SOL 101 (linear, small displacement theory) would probably not be appropriate. You can use SOL 106 or 601,106 for a geometric nonlinear analysis. Note that if you use SOL 106, the RBE2 method noted above will not work because the constraints do not update with displacement.

Jim Bernard
Advanced Applications Engineer

Siemens PLM Software
2000 Eastman Dr., Milford, OH 45150-2712

Re: Enforced Rotation - DOF Question

Thanks very much!
I'll try this.