Topology optimization

About the development of the FEM module/workbench.

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fandaL
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Re: Topology optimization

Postby fandaL » Fri Sep 09, 2016 6:32 am

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.
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makkemal
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Re: Topology optimization

Postby makkemal » Fri Sep 09, 2016 7:24 am

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

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Michael
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PrzemoF
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Re: Topology optimization

Postby PrzemoF » Fri Sep 09, 2016 9:18 am

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

Postby sgrogan » Fri Sep 09, 2016 10:53 pm

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?
fandaL
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Re: Topology optimization

Postby fandaL » Sat Sep 10, 2016 2:13 pm

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
optimization_with_face_load_hexa8.png (24.81 KiB) Viewed 1462 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
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Re: Topology optimization

Postby DMST1990 » Mon Sep 26, 2016 10:04 am

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?
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SmothingMethod.PNG
SmothingMethod
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Jee-Bee
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Re: Topology optimization

Postby Jee-Bee » Mon Sep 26, 2016 10:37 am

Nice!! Looks interesting... Would be nice to see this in master!!
jnxd
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Re: Topology optimization

Postby jnxd » Tue Oct 11, 2016 5:29 pm

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.
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PrzemoF
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Re: Topology optimization

Postby PrzemoF » Tue Oct 11, 2016 6:43 pm

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?

http://download.z88.de/z88aurora/license.pdf
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saso
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Re: Topology optimization

Postby saso » Tue Oct 11, 2016 6:55 pm

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?

http://download.z88.de/z88aurora/license.pdf
I think this google translate of the basic part of it is quite exact to the German original...
The use of the Z88Aurora® software is permitted only for scientific purposes. The license allows the licensee to run the programs for scientific purposes. Legal restrictions are not affected by this.

The usage rights for the software are limited to the respective semester of the download. The usage rights are extended by one semester each, unless a different communication is made 2 weeks before the end of the semester on the website z88.de or a new version of the software is made available. If necessary, the notification is sent to the e-mail addresses registered for the newsletter.
A semester represents the time frame from 1 April to 30 September or from 1 October to 31 March of the respective year.
Last edited by saso on Tue Oct 11, 2016 7:19 pm, edited 1 time in total.