General Mechanical

Approximate Bearing Modeling

• NicolaChiodetto
Subscriber

Hi,

I am trying to simulate the rotor vibrations for a rotating bearing assembly. I would like to see a rotor-bearing interaction too. Unfortunately the way of modeling bearings as contacts requires a full stiffness matrix to be defined for the bearing set. These values are almost impossible to get, also from the manufacture, also because they are very dependent on loads and operating speed of the rotating system.

I have been trying to work around this situation and think how I can possibly model the interaction approximately:

1) I used an elastic support, as the only value I have from the manufacture is a single radial stiffness value in terms of N/mm. Then, i convert this value in N/mm^3 dividing the radial stiffness by the cross section area of the bearing (basically the axial span times the outer diameter of the bearing). I have seen this suggested in some research papers, but I am not sure whether this is reasonable or not. Finally, I impose the elastic support along the face where the bearing is fitted onto the shaft.

Is this approach reasonale, or there's some physical nonsense I have missed?

2) An alternative suggested was also to use a cylindrical support instead, placed around the same round face. In this case I do not have a clear idea how to treat the contraints. Supposing I have no motion axially, should I leave the boundary condition free in radial and tangential direction (the bearing has some degrees of freedom no matter how stiff it is).

Please, if you have any suggestion or advice it would be very appreciated and beneficial.

Kind regards,

Nicola