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Topology Optimization doesn't make sense

Creator
Creator

Hello,

 

I am a new user of the Topology Optimization NX Nastran (version 12.0).

I did the Siemens tutorials and tried to reproduce the same steps for another geometry that I created. However, the optimized geometry's displacement is way too high. It results in 25 mm, although I set a constraint for it to be not hight than 3 mm.

Also the material density results make no sense: if I use a Lower Bound equivalent to 0.04 some random meshes (which are not even connected) appear; if I set the lower bound to 0.03, the whole geometry appears.

 

 

Does anyone know what is happening?

 

Thanks!

10 REPLIES 10

Re: Topology Optimization doesn't make sense

Siemens Genius Siemens Genius
Siemens Genius

I would have to take a look at your model to tell anything.  One thing to double check when setting constraint limits in NX12 is that you have the Units set correctly. This should be handled if you are using the simplified UI method to define the design constraint,  but if you are using the advanced method, you need to input your values correctly to get the units right.

Re: Topology Optimization doesn't make sense

Creator
Creator

Hello SteveP,

 

I checked the constraint units and they are fine. Also I used the simplified UI.

I wasn't able to attack the simulation files (FEM and SIM), neither the CAD geometry. I get a warning saying "The contents of the attachment doesn't match its file type". Is there an alternative way that I could send you them?

 

Thanks in advance!

Re: Topology Optimization doesn't make sense

Siemens Genius Siemens Genius
Siemens Genius

Did you try putting the files into a zip file?

Re: Topology Optimization doesn't make sense

Creator
Creator

I haven't tried before, but I am now. I hope it works.

Re: Topology Optimization doesn't make sense

Siemens Genius Siemens Genius
Siemens Genius

You have your loading in the Z diration, but your Displacement design constraint is in the X direction. Is that really what you wanted?

 

Re: Topology Optimization doesn't make sense

Siemens Genius Siemens Genius
Siemens Genius

topo1.jpg

Also, when setting the displacement constraint limits, make sure you account for positive and negative values for the displacement.  After changing the Displacement constraint to Z with limits of -.35 to +.35, I get more reasonable results.

 

Re: Topology Optimization doesn't make sense

Creator
Creator

It indeed lead to better results. Thank you very much for the help!

I would also like to know how is it possible to change the a already set design constraint. When I clicked to "Edit", it opened a window on which I couldn't visualize what type of constraint it was, what nodes were selected, neither on which direction was the displacement. I chose to delete the previous one and create a new one with your reccomendations. 

Re: Topology Optimization doesn't make sense

Siemens Genius Siemens Genius
Siemens Genius

The simplified UI alcatually creates 2 Modeling Objects. One is the actual Design Constraint with the limits. This one points to a Design Response Modeling Object to define the actual response (eg: Displacement, etc).  Unfortunately, if you edit it, it reverts to editing the underlying Modeling Objects, so the editing has to be done in 2 steps. (eg: the first part has the limit values and the reference to the response, then for the second part, you can edit the referenced response to change any of it's settings.).   This has been changed for the next release of Simcenter Topology Optimizaiton to make things a lot easier to work with.   But, for NX12, when you create a Design Constraint using the simplified UI, you will actually see 2 Modeling Objects get created in the Modeling Objects list in the navigator.

 

Re: Topology Optimization doesn't make sense

Creator
Creator

Thank you once again!