## Topology optimization

About the development of the FEM module/workbench.

Moderator: bernd

fandaL
Posts: 383
Joined: Thu Jul 24, 2014 8:29 am

### Re: Topology optimization

Very interesting that different elements give different results, even if you use hundreds of them. Would be interesting what the reason for this is. Mhh neiter nature nor materials does not know femelements. Which one is best ?! It is may be like a path. If the optimizer is on a specific path it just goes this way. There must be academic papers about this.

Mhh and tria3 give a better result than tria6 and quad4 (IMHO) really strange ...
About differences – there might be more reasons: One can be newly created boundary which is dependant on specific mesh. If new boundary is smoother it gives more efficiently used elements whereas if it is bumpy it “handicap” elements. Another, harder to explain simply, is manner of using stress distribution and its filtering. Stress is taken as average from integration points (more for 2nd order elements) and taken as if it acts in the centre of gravity, which decreases advantage of 2nd order elements. Results of filtering in each iteration are given by filter range. Here I used range as 2 times element size, but there might be some more convenient values for different element types.

I should definitely read more in literature.
makkemal
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Location: South Africa
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### Re: Topology optimization

This is simple a results of numerical optimisation applied to a discrete system.
In discrete system it is not uncommon to have more than one local optimum.
Depending on the algorithm and starting point a different optimum will be obtained.
Various techniques exist to find the global optimum but it will install finding numerous local optima and determining which local optima is the best.
http://www.springer.com/gp/book/9780387243481

Regards
Michael
PrzemoF
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### Re: Topology optimization

@fandaL: Could you try to run something with face load?
sgrogan
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### Re: Topology optimization

Very interesting topic!
I was lucky to recently attend the am3d-conference
There were a few interesting presentations on topological optimizations. I found one in particular interesting. In addition to the pareto method trying to find the global optima from a series of local optima. The result of the software is a smooth surface, I wonder if they fit a nurbs surface somehow to the hexahedron elements after the optimization?
"fight the good fight"
fandaL
Posts: 383
Joined: Thu Jul 24, 2014 8:29 am

### Re: Topology optimization

Could you try to run something with face load?
It works. I didn't try nonlinear analysis, but I expect that there will be difficulties with face loads in optimization domain due to extreme deformation of "void" elements (they have still loaded nodes, but very small modulus).
optimization_with_face_load_hexa8.png (24.81 KiB) Viewed 2131 times
@sgrogam: Thank you for the links.
As regards nurbs surface, I guess it depends on sw. Perhaps DMST1990 in his scripts under Blender uses some kind of this functions. In Nastran it is after optimization possible to run function which smooth elements on the new boundary by changing position of nodes.
DMST1990
Posts: 7
Joined: Fri Jun 24, 2016 7:43 am

### Re: Topology optimization

In most cases like "Solid Thinking" (Altiar) they use a geometric approach.
In my case i use Blender for smothing the surfaces with computational geometry methods (Thats the case why i use blender for the post processing). You get a geometric structure with a lot of polygon surfaces. Automatic Polygon --> NURBS works in most cases by redesigning the optimization result. You can also use "Geomagic"(Not free). In this application you can transfer polygons into nurbs by 1 click.
You can also use mesh morphing for smoothing the results directly, but in this case you have a lot of boundarys according to numerical problems.
So i think in the end they use some geometric approach with polygons (new descrete mesh which is smothed by some method).

sgrogan wrote:Very interesting topic!
I was lucky to recently attend the am3d-conference
There were a few interesting presentations on topological optimizations. I found one in particular interesting. In addition to the pareto method trying to find the global optima from a series of local optima. The result of the software is a smooth surface, I wonder if they fit a nurbs surface somehow to the hexahedron elements after the optimization?
Attachments
SmothingMethod
SmothingMethod.PNG (311.34 KiB) Viewed 2056 times
Jee-Bee
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Location: Netherlands

### Re: Topology optimization

Nice!! Looks interesting... Would be nice to see this in master!!
jnxd
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Joined: Mon Mar 30, 2015 2:30 pm

### Re: Topology optimization

bernd wrote:There is another OpenSource topology optimization software available. Just found http://en.z88.de/z88arion/ but did not test it.
I must apologize but I can't see any indication that Z88 is open source. They ask you to email them if you intend to use it for commercial purposes.
PrzemoF
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Joined: Fri Jul 25, 2014 4:52 pm
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### Re: Topology optimization

I think it's worth double checking. wikipedia says Z88 it uses a version of GPL, They use word "freeware", but I'm quite sure it used to be something different (I'm allergic to that word). Ubuntu repository says "Open source". That note "If your company is interested in a free commercial use of Z88Aurora, please send us an email including your contact details." doesn't look likee GPL. Can someone with good German check the license?

saso
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### Re: Topology optimization

http://en.z88.de/z88os/ (https://github.com/LSCAD/Z88OS) is GPL, I guess this is the fem kernel (older version?)... http://en.z88.de/z88aurora/ and http://en.z88.de/z88arion/ should be sort of the gui for it and are under the more restricted "freeware"...

http://en.z88.de/overview/

PS: Has anyone looked at http://www.agros2d.org/ (https://github.com/hpfem/agros2d)?

PrzemoF wrote:Can someone with good German check the license?