Zero reaction force

[niranjanbt]

Hi,

I am working on a wheel like structure in contact with a surface. Its a load based model in which a predefined load is applied at the centre of the wheel. Once the wheel is fully loaded, I am supposed to witness the reaction force on the surface to be equal to the applied load.

But in my case, although the "job is completed successfully", I notice zero reaction force on the surface. Has anyone experienced the same? If yes, what was the problem? Any insights into this problem is highly appreciated.

Please let me know if you need further information about this model.

Thanks,
Niranjan

 

[oriol]

Hi,

I guess it depends how you modeled the surface.
I'm modeling contact with a surface as well and my surface is a 3D analytical shell. Then I made it rigid because I didn't care how the surface itself reacts or deformes but how is the solid that gets in contact with the surface. The contact reaction can be seen on the solid not the surface.

Hope it helps.

Oriol

 

[corus]

Even if the surface is rigid, you'll have a reference point and that will have a reaction force. You could plot the CPRESS, contact pressure distribution, to make sure you do have contact and hence a reaction force.

Tata

 

[oriol]

Ok!

Will check that. Sorri Niranjan

Oriol

 

[niranjanbt]

Thank you Oriol and Corus. But unfortunately, my problem is not yet solved.

@ Corus: I dont see even a single node in contact with the surface (CPRESS values are zeros).

My question now is, how can Abaqus solve a job "successfully" when equilibrium equations are not satisfied?

-Niranjan

 

[corus]

For a dynamic analysis it doesn't matter if you have contact or not as you don't need equilibrium of forces as such. Alternatively if you have a static analysis and have simply applied a fixed displacement to make contact, then you can get equilibrium of zero forces, even though there is no contact. Otherwise you must have some restraint somewhere if you have applied a load in a static analysis.

Tata

 

[niranjanbt]

Thanks corus. I am performing a load based static analysis.

Actually, I am using this model for optimization purposes. I am varying certain dimensions and material properties every iteration. I see that the analysis is completed with sensible results in some cases, while in some other cases 'zero RF' issue crops up. I am trying to figure out whats causing this.

Anyways, thank you. Will keep you posted.

-Niranjan

 

[niranjanbt]

'Element size' was the culprit
A finer mesh solved the problem.

Thanks,
Niranjan