Applying LOAD on rolling shaft?

[Fabi0]

Hi

i've a bearing with inner ring fixed at position and outer ring rotating at a speed omega (rpm).

On the outer ring acts a radial load (force) that i've modeled in static analysis with a pressure directed on the outer surface: now i need to investigate dynamic behaviour, so how can i apply that radial load, if the outer ring is moving around its axes?

The radial load is fixed in its direction, so there's relative motion between outer ring and the load.

Fabi0

 

[corus]

Use user subroutine DLOAD and have the load varying with position or time of an element or use *Amplitude to have the load varying with time.

Tara

 

[Fabi0]

Corus, thx again for your help. Tell me if you organize an "abaqus school" because i'll be there!

 

[corus]

On second thoughts, DLOAD is probably the best way as you'd have to have amplitudes specified on each element, which isn't feasible.

Ta

Tara

 

[Fabi0]

Now i'm reading about DLOAD (it's first time i use it), but at moment is not so clear how i can tell abaqus where to apply pressure. The elements where pressure acts change with the rotation of the outer ring, so i have not to change amplitude but elements.
The position of pressure is the same if we look at the global CSYS, but change if we consider outer ring CSYS.

To apply pressure in static analysis i've create a partition in the outer ring (like picture) but i believe that it's not possible to use the same technique with DLOAD.

Fabi0

 

[corus]

DLOAD is the same as pressure, you just put PNU instead of P in the command line, and use magnitude 1. Apply the pressure to the whole of the outer surface of the ring, and just have lines in the subroutine that says if theta is between 0 and 180 (say) then F=A.sin(theta), where theta is atan(y/x).

Tara

 

[Fabi0]

I'm a bit confused: if i use F=A.sin(theta), than my force move with theta. But in my model i need a force (better pressure) that is always on the x axis (of global csys): its orientation doesn't change, the only thing that change is the application area on the outer ring because of outer ring rotating speed. So, looking at the global CSYS, also the pressure area on the outer ring is always in the same position, but occuped by different elements of the outer ring.

 

[corus]

Not sure that is correct as with large displacement analyses the co-ordinates change with time rather than being as the original geometry in a small displacement analysis. Theta would refer to the global go-ordinates as the co-ordiinates changed. If in doubt run a simpe test case job of a spinning round cylinder. If it doesn't work just introduce the time variable to modify theta with the time step of the analysis.

Tara