On 9 December 2024, Steffen Hoffmann defended his doctoral thesis with the title
"Modellierung und Design akustischer Schwarzer Löcher".
In his dissertation, Mr Hoffmann looked in detail at how vibration-damping measures can be incorporated into components as early as the design phase. To this end, he used so-called acoustic black holes, which, thanks to their special geometry, allow an increase in the vibration amplitudes in the wave field and thus a locally greatly increased dissipation due to the larger strains. The main aim of the work was to derive recommendations for the numerical modelling and design of acoustic black holes on the basis of numerical parameter studies as part of a practical consideration of the measure.
We would like to congratulate Mr Hoffmann on this milestone!
On 11 October 2024, Harikrishnan Sreekumar defended his doctoral thesis with the title
‘Surrogate modelling of high-dimensional vibroacoustic problems using parametric model order reduction’.
In his dissertation, Mr Sreekumar dealt in detail with how large savings in computing time and computer resources can be achieved in the simulation of phenomena in vibroacoustics without having to compromise on the accuracy of the solution. To this end, he has utilised and further developed projection-based Krylov subspace reduction methods. The methods developed have great potential for practical applications, as Mr Sreekumar demonstrates using a complex aircraft fuselage model for the assessment of cabin noise.
We congratulate Mr Sreekumar on this milestone!
On 09.07.2024, Prof. Ulrich Römer gave his inaugural lecture entitled "Vom Zufall zur Berechnung: Modellierung unter Ungewissheit im Computational Engineering". After words of welcome from the President Prof. Angela Ittel and the Dean of the Faculty of Mechanical Engineering Prof. Markus Böl, Prof. Römer gave an insight into his research activities. Based on classical concepts of data assimilation, he showed how new variants of the finite element method can be used to incorporate sensor data, automatically select models and determine valid confidence intervals. After the lecture, the numerous guests were able to round off the day with a cold drink and tasty snacks. We would like to congratulate Prof. Römer on this milestone and the successful presentation.
Florian Flaig's research work at the Institute of Dynamics and Vibrations (now: Institute for Acoustics and Dynamics) began with the realization that the methods from lubricated friction can also be used for the simulation of adhesive flows and culminated in his successful doctorate. After the presentation and examination on May 29, 2024, the Institute for Acoustics and Dynamics congratulates Mr. Flaig on this achievement.
In his dissertation, Mr. Flaig describes a simulation method for the flow of adhesives in thin gaps. It deals with the fundamental question of how to ensure that there are no air voids and unfilled areas in an adhesive bond, but that the proportion of excess or leaking adhesive is still minimal.
The core statements of Mr. Flaig's work are that the optimal application patterns for bonding two joining surfaces are all variations of a star-shaped basic distribution and that it is actually possible to precisely bond even geometries that appear to be more complex. In addition, Mr. Flaig showed that the application patterns are independent of the viscosity and therefore of the adhesive, and that high compression ratios can counteract the retention of large air bubbles in joints.
These results were obtained as part of a three-year DFG project in collaboration with the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research (IFAM) in Bremen. A simulation program was expanded and modified, which can now not only describe the flow of the adhesive and the force conditions during the pressing together of two joining surfaces, but is also able to calculate the initial application pattern of the adhesive for a desired target geometry by means of backward simulation. Experimental investigations at IFAM enabled the simulations to be compared and the high level of accuracy combined with low calculation times in the range of seconds to minutes to be confirmed.
Mr. Flaig's results can be used not only in industrial applications, but also in the private use of adhesives. For example, for the next private bonding of two paper squares, the adhesive outflow can be minimized by applying the adhesive in the form of a cross with tapered tips.
Once again this year, 22 interested schoolgirls from grades 5 to 11 joined InAD to spend a day as acousticians and dynamicists. Together we had the opportunity to explore the world of acoustics and dynamics with exciting experiments. From eigenmodes that can be visualised on the acoustic plate (see picture), to the vibration of a loudspeaker that we 'slowed down' using a stroboscope, to the excitation of the natural frequency of a singing bowl, we introduced the girls to the fascinating world of physics and showed them how diverse and exciting science can be. The stereomicroscope, which allowed the girls to experience the nature and surface of their own objects, was also of particular interest. We would be delighted if we could inspire some of them to take a further interest in science.
We would like to take this opportunity to thank all the participants, staff and organisers. See you again in 2025.
The 50th Annual Meeting for Acoustics (DAGA24) took place from March 19-21, 2024 at the Congress Centrum (HCC) in Hanover. The President of the German Society for Acoustics, Prof. Sabine C. Langer (InAD), officially opened the event. The DAGA24 was hosted by the LU Hannover.
The Institute of Acoustics and Dynamics was also represented not only with exciting talks, but also with posters: Poster presentations enabled participants to find out about innovative projects and research results and enter into dialog.
A jury consisting of the heads of the DEGA technical committees selected the winners of the DAGA poster awards from the more than 100 poster presentations. We congratulate Juliette Dietrich from the Institute for Acoustics and Dynamics on winning the DAGA Poster Award 2024. On the poster, she presented the results of her master's thesis on the synthesis of dynamic stochastic loads on aircraft structures at the DLR Institute of Lightweight Structures. Congratulations to her!
From November 25–27, 2024, the SynTrac team gathered at the University of Stuttgart's Internationalem Begegnungzentrum IBZ for its Annual Meeting. With over 50 members from the partner organizations Technische Universität Braunschweig, University of Stuttgart, German Aerospace Center (DLR) and Leibniz Universität Hannover in attendance, the event was a vibrant showcase of research achievements from 2024 and a springboard for planning an exciting 2025.
Each research area held dedicated poster sessions, sparking lively, interdisciplinary discussions. A highlight of the meeting put a spotlight on gender dimensions in STEM research. We were delighted to host Jan Büssers for an inspiring guest lecture, inviting us to take another look at diversity and inclusion in engineering and science.
A heartfelt thank you to the team at Institut für Luftfahrtantriebe (ILA) - Universität Stuttgart for organizing this event!
The fact that even the smallest amounts of lubricant are sufficient to dramatically reduce the coefficient of friction between two surfaces is not only known from the oiling of squeaky door hinges or the "Caution, slippery!" signs on freshly mopped floors. The question of how this effect can be systematically described was the subject of our colleague Yan Tong's dissertation.
Using numerical simulations, Mr Tong investigated the influence of the amount of lubricant in a contact on the coefficient of friction and thus laid the foundation for extending the Stribeck curve, which describes the course of the coefficient of friction of lubricated systems, by a further dimension and thus developing a Stribeck surface. He has shown that even the smallest amounts of lubricant are sufficient to significantly reduce the coefficient of friction.
In order to be able to carry out the necessary simulations in acceptable calculation times, Mr Tong described the systems as part of the isogeometric analysis using NURBS. This subgroup of the FEM not only allows systems to be described geometrically in an efficient manner due to more complex but flexible ansatz functions, but also allows their solution to be modelled in the best possible way. In addition, necessary complementarities and couplings were efficiently described by Mr Tong, and with this method not only the hydrodynamics but also the coupled solid deformation was modelled in continuum mechanics. Mr Tong has not only presented his results, methods and modelling approaches in his dissertation, but has also published them in more detail and expanded them in high-quality publications.
At the institute retreat in October, we as an institute had the opportunity to spend three days in intensive dialogue: In addition to discussions on organisational topics, the programme included poster sessions in which the doctoral students presented their research projects. A visit to the Escape Room, where we put our puzzle and problem-solving skills to the test together, provided variety and team-building.
The InAD was represented by two delegates at this year's World Congress on Computational Mechanics in Vancouver. With the contributions
‘A mortar-based isogeometric model for partially lubricated contacts’ by Yan Tong and
‘IGA-based modelling of wet grinding processes with special focus on hydrodynamic properties’ by Paul Thunich
the work of the Nonlinear Dynamics and Friction Group on the mathematical modelling of lubricated friction and wet grinding processes was presented on an international stage.
In addition, during the conference, which took place from 21 July to 26 July 2024, a large number of smaller lectures from the field of computational mechanics could be attended, alternating with larger main lectures by almost all major active personalities in the field of computational mechanics.
At this year's Public Authorities Relay Marathon on 5 June, the InAD selection achieved a solid midfield position with a 41st place out of 84. Amongst the selection teams of various police headquarters, tax offices and research institutions, the scientific staff of the Institute and Prof. Müller ran with the team name "Mach/100" with a time of 3:33:34 over 42 km, just missing the self-imposed target of "Mach/100" = 3.43 m/s. The Institute congratulates the relay team on this achievement and thanks them for their sporting presentation.
From 3 to 7 June 2024, the ECCOMAS Congress took place in the beautiful city of Lisbon. The InAD was represented with three presentations:
1. "Surrogate-Based Bayesian Updating of Finite Element Solutions for State Monitoring" by Prof Ulrich Römer
2. "Application of the Fourier generalised Polynomial Chaos Expansion to Model Limit Cycles under Uncertainty" by Lars de Jong
3. "Ensemble Kalman Filtering for Stochastic Phase-field Models of Brittle Fracture" by Lucas Hermann
The conference provided an excellent opportunity to exchange knowledge and network with colleagues from all over the world. In addition to the exciting presentations, we also enjoyed the culinary highlights of the city, especially the delicious pastéis de nata.
On 26 March 2024, Meike Kollmanthaler successfully defended her doctoral thesis entitled „Methode zur systematischen Entwicklung von akustisch effizienten Leichtbau-Fahrzeugstrukturen“. She took us into the conflicting goals of lightweight vehicle construction and acoustics in the vehicle interior. We are delighted that Meike was able to successfully complete this important milestone and wish her all the best for the future.
In November 2023, the winners of the Machine Dynamics Challenge from the summer semester of 2023 were honored by the Institute for Acoustics and Dynamics. In this challenge, students had the opportunity to work on small additional tasks weekly during the semester, which complemented the lecture with varying levels of difficulty.
The winners were awarded 3D-printed trophies themed around the lecture and the institute during an invitation to coffee and cake with Kassandra Kampen, a staff member of the institute. Professor Müller congratulated students Clemens Focke and Florian Borowski on achieving first place in the challenge for their successful completion of the tasks. In second place were students Fynn Luca Lampe and Jacques Meimann, whose award was accepted by their team colleague on their behalf. The third-place was secured by the trio Artjom Vostrukhin, Omar Elbehairy, and Emir Sagdani.
In addition to the trophy presentation and congratulations, discussions about the institute's work and general study planning framed the meeting. "We always welcome inquiries regarding the supervision of student projects, not only within the strict framework of the advertised projects on the website, and we strive to find the most suitable topic together with the students," described Prof. Müller the procedure for upcoming student projects to the bachelor students. Müller emphasized that it was also possible, in connection with the institute's test stands at the location in Schleinitzstraße, to find the right balance between modeling and practical work for each participant, and invited everyone to get to know the work at the institute through an interesting student assistant position.