Symmetrical Cylinder with torsion moment

[zeke27]

Hi,

I guess that it´s a very simple problem but I can´t find the solution. I simulated a hollow cylinder, the applied load is a torsion moment in the Z-Axys (3D model). To apply it I create a RP and I coupled this RP to the front surface (Kinematical Coupleing). The BC are applied at the rear surface (Fully Fixed). This model works well!.

The problem is when I try to simulate a quarter or half cylinder to verify the symmetry. In fact, I get some results but it´s completly diferent to the others (the entire cylinder).

Could anyone tell me what should I change to get the same results?

Thanks a in advance!.

PD: If I change the load from Torque to Pressure, then the results are the same for both cases.

 

[rstupplebeen]

Your loading is not symmetric. The initial symmetry planes will become skewed with the torsion load. The symmetry constraints are acting like a sink for your loading forces. I believe that you can do this with an axisymmetric analysis. Depending on your geometry you may be able to make an assumptions that planar sections remain planar and include some coupling. The axisymmetric solution would be what I would do though.

The pressure loading is symmetric.

I hope this helps.

Rob Stupplebeen

 

[zeke27]

Hi Rob,

Thanks a lot for your answer. So there is no way to simulate a half cylinder (3D) with a torsion moment.

I will validate the resutls with the axysimmetric.

Best regards.

Zeke

 

[johnhors]

An axisymmetric analysis can model internal/external pressures on a pipe or pressure vessel with a 2D mesh. It cannot model torque on a shaft.

However a segment (say 10 or 15 degrees) can be modelled and when cyclic symmetry boundary conditions are applied it is then legitimate to apply the correct proportion of the total torque (10/360 or 15/360 depending on the size of segment) to the model.

 

[zeke27]

Hi Johnhors,

Thanks for your help. I´ve started to read the Manual about the Cyclic Symmetry but it´s no quite clear.

I´ve modelled a quarter of the cylinder (45 degrees, first quadrant) and according to the manual I should have to define the master and slave surface or nodeset.

My question is: Should I define one edge of the model as slave and the other as a master?

If not, how should I do?

Thanks in advance!

 

[rstupplebeen]

Sorry about the axisymmetric error.

Not to be picky but the first quadrant is 90 degrees.

In the CAE users manual section 15.13.13 Defining cyclic symmetry explains how to do this. What are you having difficulty with?



Rob Stupplebeen

 

[zeke27]

Hi,

Yes you are right!, it´s 90 degrees not 45.

I read the manual but I´m having dificulties to define the master and slave surface. As my model is just a quarter of the cylinder in the first quadrant, which surface should be the master and which one the slave?.

I´ve attached the model.

Thanks.