Frictional contact separation

1

Hello everyone!

I’m having trouble reaching a valid solution for a set of frictional contacts.

I need to simulate the torque that I can apply to a shaft, held by a clamp, before its starts slipping.

I’m interested in the average contact pressure over the contact area.

For the sake of simplicity I have omitted the clamping bolt, a traction force is sufficient.

I have tried to incorporate the suggestions that I’ve found on the internet and this forum (expecially on this video), unfortunately without valid results.

Calculix results - displacement field
Calculix results - displacement field1282×650 209 KB

I was able to get the following results using Ansys :

Is someone willing to help me make this simulation run, and share with me his debug process?

Thank you very much.

Link to files : Proton Drive

2

The Displacement_Rotation-2 boundary condition has no effect because it’s trying to fix rotational DOF (UR2) of solid elements while those elements don’t have rotational DOFs. Did you want to apply U1=0 BC there ?

Also, surface belonging to rigid/stiffer body should be master in contact pair. And if you want to check contact pressure, you have to create output request for it.

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3

This is how I would face this problem.

STEP 1. I would start with an interference fit. Same elements order as in your model but much less elements. Rings with similar radious as your model. Inner and Outer surfaces rigid with no additional BC on the contact area.
Interference fit has an analytical solution and it is described with examples in the forum. You can obtain a very good starting solution with an homogeneous and well defined contact pressure.

STEP 2. Once the interference is solved, input a increasing moment on the outer ring RB. The expected breakage of the contact due to moment can be anticipated very precisely. Try to find that point and confirm it with analitycal solution. If you can’t solve this problem, stay with ansys.

If you manage to solve it, It will help you to understand how contact and friction relate and work in this particular problem and ccx.
Will give you some orientation on how to read the results and you will face the complex model more confident.

Good Luck

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4

The rest of the real object continues after the surface without the bolt, in a rigid and slender fashion.

I’d like for that surface to be able to shrink and translate but not to rotate, as this would not have physical sense.

Do I need to create a constraint with a reference point? Wouldn’t it be too rigid?

5

Although the displacement field can be simplified to a triangle (one of the catheti being the bolt), the fact that it’s wrapped around a circle makes it tricky to 3D model.

If Calculix struggles with the whole problem, why not brake it down?

What if i could import the displacement field (.frd) of the solution of a simulation in “stress control”, as input of a simulation in “strain control” ?

Would I be able to create a valid iterative loop ?

Iterative_pressure
Iterative_pressure1280×720 87.2 KB

Link to files : Proton Drive

6

If you want to simulate torque resistance of the shaft you can not impose symmetry in the model neither in calculix nor in Ansys.

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