Lost in constraints

[Anonymous]

I am a student using Nastran In Cad to perform a FEA inside Inventor. Both versions are 2018, in case it is relevant.

The analisys to be performed is related with how teeth work. In my case, mandible is constrainted to be fixed (reverse of how it trully works). My problem comes with the maxilla's constraints. I want it to be able only to rotate in Z axis of a coordinate system previously created in the natural axis of rotation, which is not contained in the geometry of the maxilla. The situation is showed in the picture.

There is a remote force applied to the top surface of the maxilla.

Initially, I set a constraint at the maxilla's top face only turning available rotation Rz based on the coordinate system I created, expecting that, due to the remote force, the maxilla closes against the mandible as it is allowed to rotate in that Z axis.

It turns out to be that I do not get it to work. The result is an unstressed geometry except for the face the maxilla constraint is applied. I do not get to know how can I introduce into Nastran in Cad the constraint needed, do I need rigid body connectors?

I hope I gave a decent explanation of my doubts. Thanks in advance for your help and advice

[g.ceruti · Accepted solution]

Hi Pablo,

I think you need to:

• create a workpoint on the rotation axis
• create a rigid body connector type "Rigid" from the top surface of the maxilla to the previous created workpoint
  • select only Tx Ty Tz degree of freedom if your mesh is a 3D thetraedeal mesh
• constrain the workpoint Tx, Ty Tz translations and Rx Ry rotations selecting your local coordinate system (only Rz about Z-local axis should be free)
• apply the load by means of rigid body connector type "interpolation" connecting the top surface of the maxilla to the loading point (You can use two rigid body connectors on the same surface only if one is "rigid" type and the other is "interpolation" type, or both are "interpolatoin" type, but NOT both "rigid" type 

Furthermore you need to create some conctact interations between upper and lower teeth, otherwise maxilla would pass throug the mandible.