Shaft simulation in Nastran In-CAD

[Anonymous]

Hi.

I want to perform a simple Linear Static shaft simulation in Nastran In-CAD. The shaft is supported on two bearings on two sides of shaft: one allows shaft to move only in axial direction, the second do not allow shaft to move in any direction. Of course I don't want to inlcude a bearing models in my simulation and I want to focus only on the shaft. How can I set up my constraints and connectors to achieve this behaviour? I think that I should use Rigid Body conncetor but I'm a little confused with this tool and using it always cause an E5000 error (I'm doing something wrong).

Could you tell me how we can replace bearings in Nastran In-CAD? How we should set up constraints and connectors? I will be very thankful.

[KubliJ]

Hi @Anonymous,

Welcome to the forums.  From the description, it doesn't sound like you need to use rigid elements.  If one bearing prevents all movement, could you not fix that surface?  And then for the other bearing, you said it only allows axial motion.  Assuming it is aligned with the global coordinate system, you could can lock all the translational degrees except the one in the axial direction.

Now I know you said bearings, so I assume they should allow rotation of the shaft.  But unless you have something preventing the rotation, you will get E5000 errors as it is not statically stable.  Even if your load shouldn't technically induce rotation.  Roundoff error will create some sort of tiny rotational force and without a constraint, will be statically unstable.

Assuming you have the rotation prevented some other way and you do not want to 'fix' the surface, creating rigid elements that connect the surface to the center axis is probably the best way to go.  I recommend creating a workpoint at the center of rotation for the bearings/shaft and using that to help define the rigid.

Thanks,

James