Radial expansion when sinulating torque. 1

[AndersHansson]

Hi,

I'm trying to do a simple simulation with Nastran 6.0.
It is a shaft with fixed constrains in the bolt holes in the flange and a torque applied on the "upper" (see attachment) cylindrical part.
My problem is that it seems to be not only a pure torque, but also radial forces that makes the shaft expand where the torque is applied.
I have tried to do "cylindrical constrain" on the very part of the shaft where the torqe is.
Anyone have any idea of how to apply a pure torque to the shaft?

Anders Hansson
Engineer

 

[cowski]

Seems to be a large deformation, are you within the elastic limits of your material? Is this a linear or non-linear problem?

 

[AndersHansson]

Yes it is ~2% radial deformation.
The von-mises stresses is around 40MPa and it is a linear problem.
It is forged steel so im far under the plastic deformation.
When trying to apply the torque on the inner cylinder the radial expantion is much higher, due to the reduced lever i guess.

 

[BlasMolero]

Dear Anders,
Please note the deformation in NX AdvSim is exagerated, surely if you plot ddisplacement resultants you will see the displacement is very small, then if you plot at scale 1:1 (simply go to Tools > Results > Post View > Deformation > Results > Scale 1.0 > Absolute) simply the model is not deformed at all.

In fact, if you prescribe a torque moment, the deformation trend is the one you have in the screen.

Best regards,
Blas.

 

[AndersHansson]

Thank you BlasMolero.

You were correct regarding the exagaration in deformation.
The visual displaying of the part combined with my carelessness in reading the displacement (actually the displacement were 0.02%)was the reason to my faulty result.

//Anders