Pin Constrain Vs Real Pin behavior

[CCarreiras]

Hi!

When we apply the pin constrain in this shaft we get this result:

This deformation behavior doesnt represent correctelly the real conditions.

I Saw this result (image below), but i cant  get the same result.

I create a Rigid body in the external faces, and a fix constrain in the center point (already in the model), but i cant get the kind of deformation as the image below. Any help?

[John_Holtz · Accepted solution]

Hi Carlos,

Some day I will write a book. Chapter 1 will be "Rotations do not exist in life or FEA"

Your first example with the constraints on the face is not in the model, but from the image it looks like you have TxTyTz constraints on the face of the shaft. The problem is this prevents the nodes from moving in the manner that is required for "rotation". So those constraints are not correct. This figure tries to explain the concept.

Figure 1:

1. If this face is constrained in TxTyTz ...

2. ... how can the nodes move to this location? (That is the motion that would be required in order to simulation rotation.)

You were close to the correct solution with the rigid connectors. The problem is the constraints you applied are fully fixed which prevents the connectors from rotating about the Y axis. You need to free the Ry in the constraints. (The connectors can only transmit forces to the nodes on the shaft; a solid element cannot accept a moment load. So technically the connectors only need to have Tx Ty Tz checked.)

[CCarreiras]

I was close... Releasing Ry did the trick, and worked well, Thank you!!