Axisymmetric simulation

Altair Forum User

Hi all,

 

I would like to know if there is an in-built way to do axisymmetric analysis ? 

 

I only found the element property /PROP/SPR_AXI, and I looked for this kind of option for 2D elements, with axial symmetry. How is it possible to run such a simulation ? 

 

Thank you,

Alice

 

Altair Forum User

Hi Alice,

There is no specific built in way for axisymmetric analysis. USe N2D3D = 1 for /ANALY card in the Starter file.Ensure that the elements are defined in YZ plane and their normals have to be in the positive X-position.

Please refer Example 8 - Hopkinson Bar from the Help Menu which is an axisymmetrical analysis.

Altair Forum User

Hi George,

 

Thank you for this tipp. I modeled my circular plate with 2D QUAD elements as in the Hopkinson bar example. However they are not compatible with the implicit option; Is that right ? I get an error in the engine and the computation stops with this error : 

 

 ** ERROR : 2D ANALYSIS IS NOT AVAILABLE WITH IMPLICIT OPTION

...

  ***** WARNING : IMPLICIT FORMULATION IS NOT AVAILABLE WITH 
    QUAD 2D   ELEMENT : STIFFNESS IGNORED *****

...

   **ERROR: STIFFNESS MATRIX IS NOT DEFINITE** 

...

 ** ERROR : RADIOSS IMPLICIT STOPPED DUE TO MODELLING DATA **

 

 

Is there any possibility to solve this problem by keeping the implicit option ? 

Or how would it be possible to run the explicit computation in the same way as the implicit one ? 

 

 

Altair Forum User

Hi Alice,

I don't think so.   N2D3D = 1 should work for implicit cases also.

Can you try the same with explicit computation?. 

Attaching a simple model for your reference.

 

Unable to find an attachment - read this blog

Altair Forum User

Hello George,

 

Thank you for the file, which is working. However this is not what I wanted, as I wanted to simulate an axisymmetrical case, that is to say a 2D mesh with axial symmetry.

Therefore I need to use QUAD elements - if I understand it right - which do not seem to be compatible with the implicit option. 

 

I am now trying to run an explicit analysis. But please tell me if you know how to do an axisymmetric model with implicit option.

Thank you,

Alice

Altair Forum User

I would like to ask you a question, concerning the file you attached : I saw you applied a uniform pressure on the surface nodes of the plate. But if you look at the displacement you obtain, and scale it by 1000, you can see that the displacement is not very logical as it seems to me. (see attached screenshot). 

 

I have this problem on other computations too, would now how to explain this ? 

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

And yet another question : I try for the explicit model to simulate an impact of one object on my plate.

However, with axisymmetric QUAD modelisation, I don't have a master surface and my simulation stops due to empty master surface. The hopkinson bar example avoids this problem by 'attaching' all elements. Is it possible to put interfaces into the axisymmetric model ? 

 

Thanks again,

Alice

Altair Forum User

Hi Alice,

It is not recommended to continue with axisymmetric option.It may not be compatible in many cases as it has some limitations.

Please try to solve this analysis in explicit computation.

The above displacement for a bending of an edge-clamped circular plate under the action of pressure seems logical. Since the ends are clamped the displacement will be as in the simulation.

 

 

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi George, 

 

Thank your reply. I will not continue with axisymmetrical model, although I think it is a pitty not to have this option in such a powerfull software.

 

However I do not think that the above deflection in logical and I solved the problem with a better element aspect ratio and Isolid = 17.

 

 

Altair Forum User

Hi Alice,

Thanks for your update. In the upcoming versions axisymmetric analysis will be more enhanced.