Shape Mapping Paper and Phononic Band Gaps releasend

I'm happy to have two new papers published the last week.

The one is my shape mapping approach, a general description:

Wein, F. & Stingl, M. A combined parametric shape optimization and ersatz material approach. Struct Multidisc Optim (2017). https://doi.org/10.1007/s00158-017-1812-3

https://link.springer.com/article/10.1007/s00158-017-1812-3

In the second article I present the 2D phononic band gaps. My colleague Max Wormser did the interpretation for 3D, printed the structure by electron beam melting with titanium and performed measurements:

Wormser, M.; Wein, F.; Stingl, M.; Körner, C. Design and Additive Manufacturing of 3D Phononic Band Gap Structures Based on Gradient Based Optimization. Materials 2017, 10, 1125.

http://www.mdpi.com/1996-1944/10/10/1125

Edit: The statistics of this article are amazing (for my standards)! 60+ downloads in the first week. Might it be the world record breaking phononic band gap optimization or the printing and measuring of a 3D sample by Max.

WCSMO12 is over

WCSMO 12 link is just over.

After the previous once (for me) in Lisbon, Orlando and Sydney, Braunschweig sounds unexcitedly. It was just a 4 hours drive with the car. We were a total of 8 people with 7 from Michael Singl's group.

However, it turned out to be a quite nice and successful conference. To my personal impression the quality of the talks was better than in Sydney. There were about 550 people with up to 7 parallel sessions. Session hopping done very much but also possible due to close rooms and good time management of the chairs. However the sessions were in my eyes also organized in a way that you need session hopping. Sometimes the "big" names were in rooms to small for them.

There was for my interest to much overlapping of parallel tasks I was interested. E.g. Niels Aaage's and Rasmus' talk parallel to my own session. I wish there were less parallel sessions but I don't known how to achieve this, maybe minisymposia would help.

I was not that happy about the poster session. It was parallel to three session and as I had my talk there I could only be at the poster session in the break before. The poster session was nicely prominent in Orlando but also in Sydney I was not that happy with the poster session. I personally often feel that posters are often treated as less valuable whereas I indeed often prefer them against talks.

Beside this the organization was quite well done. Long breaks with enough time for talking, cake and beverages all the time. The crew was excellent! The welcome reception was the best I ever had: Good food, a lot to drink and a lot of space and room to talk and meet. Wetter was very good, we could open the windows for fresh air most of the time.

Compared to ECCOMAS 2016 in Crete there was not really something big new. The overhang constraints from Matthijs Langelaar evolved. The laminate interpretations from Ole's group based on Olivier Pantz' ideas was nice, something like my old streamline stuff done right and rigorous :) However I personal think, it needs to become 3D and when the issues there are solved, I'll be very impressed! The talk I liked most was actually Dan's the state-of-the-art talk. I could not attend Kurt Maute's talk, but my colleagues were quite impressed.

Phononic Band Gaps up to relative 8!

This is my presentation of "Parametric Shape Optimization of Lattice Structures for Phononic Band Gaps" I gave at WCSMO-12 June 2017 in Braunschweig.



I'm quite proud of my phononic band gaps up to relative 8 and normalized 1.6.

I already presented the idea at ECCOMAS 2016 in Crete but there I made the embarrassing mistake of not enforcing square symmetry. However this is a non that uncommon mistake I meanwhile learned. Also my results are much better now.

WCSMO-11 is over

Some time passed since the last WCSMO-11 which was held in Sydney in June 2015. Still I know of no regular conference which comes any close to the World Congress of Structural and Multidisciplinary Optimization. The first OPTi in 2014 held in Kos came close but I see no hint that OPTi will be continued.

To my opinion people were (in the beginning) not happy to travel as far as Australia for a conference - something like the place with the furthest traveling distance for almost everyone I meet at conferences. 

And indeed I missed some participants from the US and Europe where on the other side many speakers came from China. The total number of participant also was a little below the previous numbers. 

I personally was disappointed by the average quality of the presentations. The two worst presentations I attended were from the US and Europe and I had the impression that both speakers did not even understand / could handle the SIMP method at the level of the 99 lines code. But there were more disappointing talks. To my personal opinion there are not too much groups worldwide driving topology optimization further with solid research while there are still plenty of challenging issues and problems, which can be solved by topology optimization. I cannot compare this against the previous WCSMO’s due to too many parallel sessions and I regularly missed some important talks. 

So maybe it would be a good idea to reduce the number of presentations and increase the average quality for the WCSMO but concurrently introduce regional conferences where PhD students have the opportunity to present their works and more importantly can come into contact to their regional experts, especially when they don’t stem from one of the established groups.

My highlight of the WCSMO was the high-performance optimization done at the DTU and I very much acknowledge that they contribute the PETSc base implementation with a parallel linear elasticity, MMA, density filter and PDE filter. More on that in a separate blog post. 

To summarize, the WCSMO-11 2015 in Sydney was again not only a good conference but almost the only conference (to my knowledge) for structural optimization. It was well organized; it was pretty cool to have a conference banquet at “Hogwarts” (the great hall of the University of Sydney). I personally also enjoyed Sydney and my short trip to the Blue Mountains.

What I really missed was that there was no possibility to just sit (and talk) when I did not want to attend a presentation. There was nothing like a lobby or close cafeteria. Especially when it was cold and raining and one could not go outside.

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.