Simulation not being sucessful

[Anonymous]

Hey Guys,

So I have this model I have been trying to get to work. The idea is essentially a pressure powered compression device around a tube. What i want to see is the force on the tube as I use different pressures in my tube.

I am not sure what I am doing wrong.

Since everything is stored on the cloud this should be the link to the file

http://a360.co/2a49QgO

Cheers,

Edgar

[josef.kucera]

Hi @Anonymous,

is this what you see when resolve the study?

From what I can see when open your design I would say there are missing some "Separation + Sliding" contacts on the other side of the model...

Josef

[Anonymous]

Hey Josef,

So i was getting something like that, but I have now added all the no contact and sliding and I am getting something closer to what I want but still not quite there and there are still some bodies clipping each other. Also it keeps telling me I have 2 unconstrained bodies but everything looks constrained to me.

Cheers,

Edgar

[josef.kucera]

There might be also problem for solver to get proper results for your thin parts of your design (warning shown during solve). Support for thin parts (sheet metals) is not implemented yet (it is planed for future release according to this roadmap).

Regards,

Josef

[Sualp.Ozel]

Hi Edgar

You have two major issues with your setup. please see attached images for clarification

1. Geometry:

a) the "modified smooshed tube" links have a very small connection volume. The simulation in Fusion is based on FEA (finite element analysis), which means the software has to be able to mesh the geometry in order to analyze it. unfortunately, meshing such small features will really tax the system. Also manufacturing such a feature without the part breaking is not easy. You may want to look in to your CAD design to make sure it represents reality.

b) you have created interfering volumes in this design , which is not realistic.

2. Simulation:

At the moment Fusion 360 offers linear static stress , modal, thermal and thermal stress as available analysis types. This setup requires a nonlinear analysis type as the "modified smooshed tube" will have to deform under pressure before coming into contact with the "pipe". One can not analyse such a setup using the Linear static stress assumptions. This setup violates the "boundary conditions do not change" assumption.

http://help.autodesk.com/view/ASMECH/2017/ENU/?guid=GUID-EAB7BAC6-59B8-4113-AAB0-83E870B6F30D

Linear

Linear analyses follow these basic assumptions (unless otherwise noted):

• The loading causes only small deflections or rotations.
• The change in direction of the loading due to deformation is small and can be neglected.
• The materials are linear within the elastic region on the stress-strain curve.
• The boundary conditions do not change.

Best regards

Sualp Ozel, PE.

Product Line manager

Autodesk Simulation

[Anonymous]

Hey Sualp,

Thank you so much for your post. I really cleared a lot of things up.

So in order to run the non-linear analysis, which I need for my simulation, I should use Nastran in cad?

Cheers,

Edgar

[Sualp.Ozel]

You can use Autodesk Simulation Mechanical or Autodesk Nastran InCAD

Best Regards
Sualp Ozel, PE

Autodesk, Inc.
6425 Living Place
Suite 100
Pittsburgh, PA 15206
www.autodesk.com<>

[Anonymous]

Is there one you prefer?

I was working on nastran earlier and the simulation refused to run but when i did the same things in fusion it just worked which was puzzling.

Cheers,

Edgar

[Sualp.Ozel]

you have to fix the geometry issues first.