Ansys Mechanical / Workbench Spherical Constraint
Ansys Mechanical / Workbench Spherical Constraint
(OP)
I'm analysing a structure which has a cylinder and both the rod ends have spherical constraints. Free rotation x,y,z but can react translational loads in x,y,z. These spherical constraints are not grounded and are within the structure itself. When I use a body to body spherical contact the analysis does not run. Further reading tells me this is because solid elements need to be further constrained or the spherical contact surface has can infinetly rotate. However as it is body to body I can't put any global constraints at the contact surface.
Does anyone have any suggestions?
Does anyone have any suggestions?





RE: Ansys Mechanical / Workbench Spherical Constraint
Rick Fischer
Principal Engineer
Argonne National Laboratory
RE: Ansys Mechanical / Workbench Spherical Constraint
I have managed to set up a model using contacts, but it is very expensive with regards to running time.
RE: Ansys Mechanical / Workbench Spherical Constraint
Generally, a model in a static structural analysis needs to be tied down somewhere of you get solution problems, typically a deflection limit exceeded or negative pivot ratios. Presumably the thing you are modeling is tied down somehow, so start with that. You can do this with a zero deflection, a fixed boundary condition, or a fixed joint. I would turn on both weak springs and large deflections. Large deflections is especially important of something is rotating.
I've found the easiest way to hose up a model with joints is to get the coordinate system wrong. Make sure the origin is at the center of the sphere and that it makes physical sense with respect to your model.
Rick Fischer
Principal Engineer
Argonne National Laboratory
RE: Ansys Mechanical / Workbench Spherical Constraint
Globally the boundary conditions are correct. The problem is with the body to body contact being underconstrained, this was the problem with the first few runs as stated in the error message. Hopefully this latest run will work and the local and global reactions should prove this.
Thanks for your input.
RE: Ansys Mechanical / Workbench Spherical Constraint