Does Modal analysis solution depend on mesh size ?

- October 18, 2021 at 12:34 pm
  
  jojimat33
  Subscriber
  
  I am doing a modal analysis of a motor rotor assembly where upon increasing my mesh size, the first mode (rotation along axial) is fluctuating and not converging. How to find a good mesh for this?
- October 19, 2021 at 2:27 pm
  
  Aniket Chavan
  Forum Moderator
  
  are the mode shapes the same?
  -Aniket
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- October 19, 2021 at 6:30 pm
  
  dlooman
  Ansys Employee
  
  Is axial rotation constrained? Sometimes a rigid body mode produces a non-zero contact due to penalty based contact. If mode 1 is actually a rigid body mode (no constraint of axial rotation) try switching to MPC based contact to reduce the artificial rotational constraint of penalty based contact.
- October 20, 2021 at 6:03 pm
  
  jojimat33
  Subscriber
  
  The mode shapes are the same. The other modes are converging, but only the first mode is not converging as seen from the results
- October 20, 2021 at 8:03 pm
  
  jojimat33
  Subscriber
  
  Axial rotation is kept free as I have used a Cylindrical support at bearing support face with tangential as free.
  As you said Mode 1 might be rigid body mode. Could you give me some more idea on "switching to MPC based contact to reduce the artificial rotational constraint of penalty based contact"? Does MPC based contact completely remove the first mode with axial rotation ?