Interpretation of Material Design by an Streamline Approach

At OPT-I 2014, Kos, Greece, 4-6 June 2014, www.opti2014.org I gave the following talk:

Interpretation of local oriented microstructures by a streamline approach to obtain manufacturable structures from fwein

It demonstrates, how a material design result of oriented anisotropic structures (here crosses) can be interpreted.

We are still in the early phase, e.g. removing the blind line segments and going to 3D.

Topology optimization of saturated flows

In 2013 I spent most of my time for a topology optimization project for Procter & Gamble. Technically it we perform transient multi-material optimization for the nonlinear Richards equation which models unsaturated flow. The product behind is a Pampers diaper. The first phase of the project is successfully finished. It was quite hard and computationally and numerically the most complicated and expensive problem I had to deal with up to now.

During summer slump when there is nothing else to report in the local newspaper, we even had two interviews. Well, I doubt this is the career boost a colleague sees in it - and the article is really written for the broad public by non-technicals journalists.

Sorry, all in German.

14. August 2013, Nuerberger Zeitung
Das High-Tech-Produkt für den trockenen Babypopo

15. August 2013, Nordbayrische Nachrichten
Gutes für den Baby-Po: Erlanger Forscher suchen nach der Super-Windel

Here the announcement of the Cluster of Excellence Advanced Materials
http://blogs.fau.de/news/2013/07/30/gutes-fur-den-baby-popo/

Talk on Local Optimal Polarization

I'm just back from the piezo-workshop 2013, correctly, the 9th Int. Workshop on Direct and Inverse Problems in Piezoelectricity in Weimar, organized by Prof. Tom Lahmer, a former colleague.

On the workshop 2012 and at WCSMO-10 I presented piezoelectric Free Material Optimization (FMO), however, this makes not that much sense for piezoelectricity, as weak material is the generally best and the optimum is just controlled by the lower bound. For elasticity, where stiff material is in general good, this is a complete different story.

Doing orientational optimization, which has the physical interpretation of local polarization, the problem makes much sense and indeed has potential.

Local Optimal Polarization of Piezoelectric Material from fwein

Two further examples I want to solve are dynamic problems (can the resonance frequency be moved by polarization, I guess so but it might be a small effect) and a solid auxetic (negative Poisson's ratio) device, what would be really impressing if this is possible.

WCSMO-10 is over

WCSMO-10 is over, and again I realized, that the WCSMO is by far the most interesting conference for me. The whole numerical topology optmization community was there and I enjoyed it very much. I have the impression that I meanwhile know a lot of the important people (at least a little :)).


I held a talk on piezoelectric free material optimization, similar to what I talked about on the last Workshop on Direct and Inverse Problems in Piezoelectricity, but this time not starting with the music of Jean Michel Jarre :)

Free Material Optimization of Piezoelectric Material

People liked our tensor stiffness visualization, maybe I should put the Python code online ...

I also had a poster at the poster session about self-penalization. The content is from a former talk and can be also found in my thesis. My impression is, that private and direct communication/ discussion is best for the topic. The poster can also be downloaded.

This time Jamie Guest was almost omnipresent with a very large group. He appeared on 13 talks as (co-)author compared to 8 talks (co-)authored by Ole Sigmund. Well, numbers are one thing but it's impressive.

My favorite talk was by Alexander Verbart from the group of Fred van Keulen; A new approach for stress-based topology optimization: internal stress penalization. I did a little on stress optimization (e.g. piezoelectric stress optimization) but for me there are two open problems: have not grayness to confirm to the constraints and the miracle of the min vol problem which would be best for rho = rho_min. The idea of Alexander has neither stress penalization nor globalization parameters, subregions or anything else. The approach would allow gray material to confirm with the stresses but with some luck the optimizer won't find this solution. I'll have to give it a try.

The new TopOpt App from DTU

Ole Sigmund's DTU topology optimization team released their TopOpt App for iOS, Android and Web. This is pretty cool stuff. It allows to play with any variant of a compliance problem. With respect to the original TopOpt web application it is interactive and as such it is as interactive as our our iTop web application (eamc080.eam.uni-erlangen.de/iTop. IMHO, the TopOpt app suits better a tablet than a smartphone/ iPod, but on a tablet it is really interactive, and it is real fun to play with it. I let my 5 years old daughter play with the TopOpt app what would not work with iTop.

With the TopOpt app being an off-line app, I started to show almost any person (I have a beer with and who is not escaping fast enough) what this topology optimization stuff is all about on my iPod.

From the technical point of view I'm impressed by the performance. It is clear, that despite their user experience, the ARM processing power is significant slower than our iTop Xenon CPU. I would have guessed that the performance wouldn't be sufficient and I would have been wrong! I wonder about the direct solver and the Heaviside filter parameters.

So what it the difference to iTop? The TopOpt app is self-explaining while iTop deserves explanation (especially as we still did not write any documentation). But using iTop as a demonstrator tool it allows to explain what is behind

• penalization,
• regularization.
• choice of optimizer,
• the phenomenon of self-penalization,
• start designs/ local optima.

I'm pretty sure the force inverter problem will be soon integrated into the TopOpt app, while interactive material design via inverse homogenization might be a unique feature of iTop for a longer time.

Congratulations, Niels, Morten and Casper! :)

Thesis published

Finished! :)

On the 19th of December 2011 I had the defence of my thesis (Dr. Ing.).



I published my thesis online. You can access it at UB Erlangen-Nuermberg.

The thesis

Topology Optimization of Smart Piezoelectric Transducers

has three main topics:

• topology optimization of a piezoelectric loupspeaker
• topology optimization of a piezoelectric cantilevered energy harvester
• self-penalization in topology optimization

Thank's a lot to my colleagues for the great hat!! :)

I will continue as PostDoc at my current position, working for Prof. Stingl at the chair of applied mathematics from Prof. Leugering.

Interactive Self-Penalization

I added mechanism design to our iTop tool, see also my last post. This allows to play with the force inverter problem. Volume constraint bounds can be switched, regularization can be disabled by setting "reg. value" to one. It makes sense to play with "start optimization from current design". Local solutions are really a problem. Sometimes it helps to play with the physical lower bound (rho^p) and penalization values.

Clearly, the results are not necessarily more "desirable" than the volume constraint results. But IMHO this is not the point. Here not the practical relevance of the result is interesting but the strong self-penalizing effect.

BTW, I finished my PhD! :) More to write about this next week when I officially publish my thesis (online).