@article{63800,
  abstract     = {{In this contribution, we address the estimation of the frequency-dependent elastic parameters of polymers in the ultrasound range, which is formulated as an inverse problem. This inverse problem is implemented as a nonlinear regression-type optimization problem, in which the simulation signals are fitted to the measurement signals. These signals consist of displacement responses in waveguides, focusing on hollow cylindrical geometries to enhance the simulation efficiency. To accelerate the optimization and reduce the number of model evaluations and wait times, we propose two novel methods. First, we introduce an adaptation of the Levenberg–Marquardt method derived from a geometrical interpretation of the least-squares optimization problem. Second, we introduce an improved objective function based on the autocorrelated envelopes of the measurement and simulation signals. Given that this study primarily relies on simulation data to quantify optimization convergence, we aggregate the expected ranges of realistic material parameters and derive their distributions to ensure the reproducibility of optimizations with proper measurements. We demonstrate the effectiveness of our objective function modification and step adaptation for various materials with isotropic material symmetry by comparing them with the Broyden–Fletcher–Goldfarb–Shanno method. In all cases, our method reduces the total number of model evaluations, thereby shortening the time to identify the material parameters.}},
  author       = {{Itner, Dominik and Dreiling, Dmitrij and Gravenkamp, Hauke and Henning, Bernd and Birk, Carolin}},
  issn         = {{0888-3270}},
  journal      = {{Mechanical Systems and Signal Processing}},
  keywords     = {{Material parameter estimation, Waveguide, Nonlinear optimization, Inverse problem, Least squares}},
  pages        = {{113904}},
  title        = {{{A modified Levenberg–Marquardt method for estimating the elastic material parameters of polymer waveguides using residuals between autocorrelated frequency responses}}},
  doi          = {{https://doi.org/10.1016/j.ymssp.2026.113904}},
  volume       = {{247}},
  year         = {{2026}},
}

@techreport{65426,
  abstract     = {{In diesem Forschungsprojekt wurde ein Messverfahren zur Bestimmung akustischer Materialparameter von Polymeren im Ultraschallfrequenzbereich entwickelt. Das Verfahrens sollte, die üblichen standardisierten Prüfmethoden erweitern, die bislang primär im quasistatischen oder niederfrequenten Bereich eingesetzt wurden. Im Gegensatz zu bestehenden Verfahren wie dem Zeitstandversuch oder der Dynamisch Mechanischen Analyse (DMA) nach [DIN6721] sollte die neue Methode eine nicht-invasive Charakterisierung der (visko-)elastischen Materialparameter im Frequenzbereich von 0,75 MHz bis 2,5 MHz ermöglichen. Das entwickelte Ultraschallmesssystem arbeitet nach dem Puls Echo-Prinzip und kann eine räumlich segmentierte, ringförmige Anregung erzeugen. Die Bestimmung der frequenzabhängigen Materialparameter geschieht hierbei über ein inverses Verfahren. Die Ergebnisse des Projekts zeigen, dass die Segmentierung der Anregung, die Geometrie der Probe sowie das Puls-Echo-Messprinzip die Messergebnisse sowie die Sensitivität gegenüber Scherparametern wesentlich beeinflussen. Im Rahmen des Projektes wurde auch eine statistische Auswertung des Optimierungsverfahrens hinsichtlich transversal-isotroper Materialsymmetrie mit Rayleigh-Dämpfung durchgeführt. Die Ergebnisse zeigen, dass das entwickelte Verfahren gute Konvergenzeigenschaften aufweist und sich durch verbesserte Robustheit auszeichnet.}},
  author       = {{Dreiling, Dmitrij and Itner, Dominik and Birk, Carolin and Gravenkamp, Hauke and Henning, Bernd}},
  keywords     = {{Materialcharakterisierung, Polymer, Inverses Problem, Ultraschall, Optimierung}},
  pages        = {{12}},
  publisher    = {{Hannover : Technische Informationsbibliothek}},
  title        = {{{Vollständige Bestimmung der akustischen Materialparameter von Polymeren II}}},
  doi          = {{https://doi.org/10.34657/33602}},
  year         = {{2026}},
}

@inproceedings{65586,
  author       = {{Zeipert, Henning and Claes, Leander and Hölscher, Jonas and Wippermann, Mareen and Henning, Bernd}},
  booktitle    = {{Fortschritte der Akustik - DAGA 2026}},
  pages        = {{1566–1569}},
  title        = {{{An Approach for the Efficient Solution of Eigenvalue-based Inverse Problems for the Material Characterisation Using Guided Acoustic Waves}}},
  doi          = {{10.71568/DAGA2026.043}},
  year         = {{2026}},
}

@inproceedings{65625,
  author       = {{Friesen, Olga and Hölscher, Jonas and Siegmund, Michael B. K. and Claes, Leander and Henning, Bernd}},
  title        = {{{Experimental and Numerical Investigation of Jump Phenomena in the Frequency Response of Piezoelectric Systems}}},
  year         = {{2026}},
}

@article{65242,
  abstract     = {{With the growing demand for lightweight solutions to reduce emissions, especially in the transportation, automotive and aerospace sectors, recyclable, continuous fiber-reinforced plastic composite laminates with a thermoplastic matrix are of rising interest. To achieve their maximum mechanical properties, the fiber-matrix adhesion (FMA) is critical. In this work, continuous fiber-reinforced thermoplastic laminates (CFRTPL) with a polypropylene (PP) matrix and twill woven glass fiber fabrics are produced by film stacking. The films used contain different amounts of maleic-anhydride-grafted PP (MA-g-PP) as a coupling agent to produce CFRTPL of different mechanical strengths. To analyze the FMA, the CFRTPL are subjected to Charpy-impact and tensile tests. Additionally, single fiber pull-out tests (SFPT) are conducted to further investigate the effect of MA-g-PP on the FMA. The results of the SFPT show an improvement in apparent interfacial shear strength (AIFSS) when the MA-g-PP content is increased, which can be attributed to an increase in FMA. However, the research shows that MA-g-PP has a low impact on the mechanical properties if the force is applied parallel to the warp and weft threads during tensile testing and the results of the Charpy-impact testing suffer from embrittlement of the matrix material. Subsequently, the results of this study are compared to three-point flexural tests conducted in a previous study. It can be concluded that tensile and impact tests are not suited to investigate FMA on a macroscopic scale, while SFPT and flexural tests provide a better alternative.}},
  author       = {{Moritzer, Elmar and Brandes, Philipp and Wittler, Maurice and Claes, Leander and Wippermann, Mareen and Haag, Markus and Gries, Thomas and Henning, Bernd}},
  issn         = {{0930-777X}},
  journal      = {{International Polymer Processing}},
  publisher    = {{Walter de Gruyter GmbH}},
  title        = {{{Fiber-matrix adhesion in glass fiber reinforced thermoplastic composite laminates and its effect on mechanical properties}}},
  doi          = {{10.1515/ipp-2025-0077}},
  year         = {{2026}},
}

@article{65785,
  abstract     = {{Simulation-based design of high-power ultrasonic systems depends on the accurate modelling of the electromechanical behaviour of piezoceramic materials. In practical transducer applications, the relevant operating points are influenced by mechanical preload and heating, both of which give rise to changes in the elastic, dielectric, and piezoelectric material properties. Material parameters identified under idealised, unloaded conditions are therefore insufficient to represent piezoceramic material behaviour under realistic operating conditions. To overcome this limitation, experimental setups are developed that enable the measurement of electrical impedance spectra under controlled thermal and mechanical conditions. The acquired impedance data are used in an inverse identification procedure, in which the behaviour of a finite element forward model is iteratively fitted to the measurements using a block coordinate descent optimisation strategy guided by a sensitivity analysis. This yields effective linear material parameters as a function of temperature and mechanical stress at varying operating points. The identified temperature-dependent parameters, for instance, can be employed in a coupled thermo-electromechanical simulation framework to predict the temperature-dependent material behaviour during operation. The linear identification based on varying operation points provides an initial approximation of the nonlinear material response, establishing a basis for the development of corresponding nonlinear material models.}},
  author       = {{Friesen, Olga and Claes, Leander and Hölscher, Jonas and Henning, Bernd and Scheidemann, Claus and Hemsel, Tobias and Kuess, Raphael and Walther, Andrea and Spieker, Carsten and Förstner, Jens}},
  issn         = {{0171-8096}},
  journal      = {{tm - Technisches Messen}},
  keywords     = {{tet_topic_piezo}},
  publisher    = {{Walter de Gruyter GmbH}},
  title        = {{{Measurement of multiphysical material parameters of piezoceramic components for high-power ultrasonic applications}}},
  doi          = {{10.1515/teme-2026-0042}},
  year         = {{2026}},
}

@inproceedings{59683,
  abstract     = {{Woven fibre-reinforced polymers are used in a variety of application, especially where a low mass to stiffness ratio is required. Of paramount importance for the tailored mechanical properties these composite materials exhibit is the type and geometry of the fibre weave. Especially continuous fibre-reinforced thermoplastic composites are fabricated as laminates and subsequently exposed to forming processes which alter the geometry of the fibres unit cell and thus the local mechanical properties of the material. An approach utilising broadband ultrasonic waves is proposed to non-destructively determine the geometry of the unit cell of the weave.

The dispersive behaviour of woven fibre-reinforced sheets is described in accordance with the Flouquet-Bloch theorem as a phononic crystal. In order to develop a model for a description of these periodically structured waveguides, the smallest repeating unit of the wave is modelled with periodic boundary conditions. The resulting dispersion diagram exhibits similarities to that of a homogeneous plate, but additionally displays a periodicity in the wavenumber regime, which correspond with the size of the unit cell. Experimental studies of the dispersive behaviour of acoustic waves in woven fibre-reinforced samples also show a periodicity in the wavenumber regime, enabling a measurement procedure of the unit cell geometry.}},
  author       = {{Wippermann, Mareen and Claes, Leander and Brandes, Philipp and Moritzer, Elmar and Henning, Bernd}},
  location     = {{Copenhagen}},
  title        = {{{Determination of the unit cell geometry in fibre-reinforced polymer sheets using guided acoustic waves}}},
  doi          = {{10.71568/DASDAGA2025.116}},
  year         = {{2025}},
}

@inproceedings{59688,
  author       = {{Claes, Leander and Zeipert, Henning and Brandes, Philipp and Moritzer, Elmar and Henning, Bernd}},
  location     = {{Copenhagen}},
  title        = {{{Assessment of Fibre-Matrix Adhesion in Reinforced Polymers by Modal Damping of Guided Acoustic Waves}}},
  doi          = {{10.71568/DASDAGA2025.052}},
  year         = {{2025}},
}

@article{59995,
  abstract     = {{<jats:title>Abstract</jats:title>
               <jats:p>Ultrasonic transmission measurements can be used for material characterization, as the propagation time of sound waves and thus their velocity depends on the elastic material parameters. Measurement results for the elastic material parameters are acquired non-destructively using ultrasonic transmission measurements of hollow cylindrical polymer specimens. To determine the material parameters, an inverse approach is used comparing measurements with simulated data. Previous studies show that the procedure exhibits low sensitivity with respect to the shear parameters of the material. In order to increase the sensitivity, we propose to apply a spatially annular excitation on the base of the specimen. As a measure to analyse the sensitivities with respect to all parameters and their linear independence, we observe the volume of the parallelotope of the sensitivity vectors. Here, a scaled boundary finite element formulation of wave propagation in the specimen is expanded to yield derivative information directly, and a sensitivity analysis can be carried out efficiently. Finally, the results of this sensitivity analysis with regard to the annular excitation are also applied to the measurement setup.</jats:p>}},
  author       = {{Dreiling, Dmitrij and Itner, Dominik and Gravenkamp, Hauke and Claes, Leander and Birk, Carolin and Henning, Bernd}},
  issn         = {{0957-0233}},
  journal      = {{Measurement Science and Technology}},
  keywords     = {{Sensitivity analysis, Ultrasonic transducer, Guided waves, Polymers, Gram determinant}},
  publisher    = {{IOP Publishing}},
  title        = {{{Increasing the sensitivity of ultrasonic transmission measurements for elastic material parameter estimation}}},
  doi          = {{10.1088/1361-6501/add9b6}},
  volume       = {{36}},
  year         = {{2025}},
}

@inproceedings{62300,
  author       = {{Claes, Leander and Hölscher, Jonas and Friesen, Olga and Scheidemann, Claus and Hemsel, Tobias and Henning, Bernd}},
  booktitle    = {{2025 International Congress on Ultrasonics}},
  pages        = {{142–145}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{Estimation of third order elastic constants of piezoceramics using DC biased impedance measurements}}},
  doi          = {{10.5162/ultrasonic2025/a18-a6}},
  year         = {{2025}},
}

@inproceedings{62301,
  author       = {{Dreiling, Dmitrij and Itner, Dominik and Gravenkamp, Hauke and Birk, Carolin and Henning, Bernd}},
  booktitle    = {{2025 International Congress on Ultrasonics}},
  pages        = {{102–105}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{A Measurement Setup for the Determination of Temperature-Dependent Viscoelastic Material Parameters Using an Ultrasonic Pulse-Echo Technique}}},
  doi          = {{10.5162/ultrasonic2025/a12-c5}},
  year         = {{2025}},
}

@inproceedings{62294,
  author       = {{Zeipert, Henning and Nellius, Tom and Schönlau, Nikolas and Wippermann, Mareen and Claes, Leander and Nicolai, Marcel and Prager, Jens and Henning, Bernd}},
  booktitle    = {{2025 International Congress on Ultrasonics}},
  pages        = {{207----210}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{Monitoring the curing process of adhesive bonds using selective excitation of guided ultrasonic waves}}},
  doi          = {{10.5162/ultrasonic2025/c6-a3}},
  year         = {{2025}},
}

@inproceedings{62299,
  author       = {{Friesen, Olga and Scheidemann, Claus and Claes, Leander and Hemsel, Tobias and Henning, Bernd}},
  booktitle    = {{2025 International Congress on Ultrasonics}},
  pages        = {{138–141}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{Sensitivity Analysis and Material Parameter Estimation of a Pre-Stressed Langevin Transducer}}},
  doi          = {{10.5162/ultrasonic2025/a18-a4}},
  year         = {{2025}},
}

@inproceedings{62298,
  author       = {{Kuess, Raphael and Friesen, Olga and Henning, Bernd and Walther, Andrea}},
  booktitle    = {{2025 International Congress on Ultrasonics}},
  pages        = {{134–137}},
  publisher    = {{AMA Service GmbH}},
  title        = {{{Identification of temperature-dependent material parameter functions in piezoelectricity}}},
  doi          = {{10.5162/ultrasonic2025/a18-a3}},
  year         = {{2025}},
}

@inproceedings{59689,
  author       = {{Friesen, Olga and Meihost, Lars and Koch, Kevin and Claes, Leander and Henning, Bernd}},
  location     = {{Copenhagen}},
  title        = {{{Estimation of piezoelectric material parameters under varying electric field conditions}}},
  doi          = {{10.71568/DASDAGA2025.078}},
  year         = {{2025}},
}

@inproceedings{60502,
  author       = {{Zeipert, Henning and Claes, Leander and Stoeckel, Chris and Mulay, Shubham and Henning, Bernd}},
  location     = {{Nürnberg}},
  title        = {{{Evaluation of piezoelectric micromachined ultrasonic transducers (PMUT) for the broadband detection of ultrasonic elastic waves}}},
  doi          = {{10.5162/SMSI2025/D5.2}},
  year         = {{2025}},
}

@article{61140,
  author       = {{Nicolai, Marcel and Bulling, Jannis and Narayanan, M.M. and Zeipert, Henning and Prager, Jens and Henning, Bernd}},
  issn         = {{0041-624X}},
  journal      = {{Ultrasonics}},
  publisher    = {{Elsevier BV}},
  title        = {{{Dynamic interface behavior in coupled plates: Investigating Lamb wave mode repulsion with a spring-based model}}},
  doi          = {{10.1016/j.ultras.2025.107799}},
  volume       = {{158}},
  year         = {{2025}},
}

@inproceedings{63441,
  author       = {{Moritzer, Elmar and Brandes, Philipp and Wittler, Maurice and Claes, Leander and Wippermann, Mareen and Henning, Bernd}},
  booktitle    = {{40th International Conference of the Polymer Processing Society}},
  keywords     = {{Faser-Kunststoff-Verbunde (FKV), Faserverstärkte Kunststoffe (FVK), Organobleche, Ultraschall}},
  title        = {{{Non-destructive fiber-matrix adhesion measurement of glass fiber reinforced thermoplastic composite laminates using ultrasound}}},
  year         = {{2025}},
}

@inproceedings{60504,
  author       = {{Nellius, Tom and Henne, Kevin and Hartinger, Maximilian and Meihost, Lars and Hetkämper, Tim and Zeipert, Henning and Claes, Leander and Henning, Bernd}},
  location     = {{Nürnberg}},
  title        = {{{Ultrasonic phased array interface using programmable I/O and microprocessor clock synchronisation}}},
  doi          = {{ 10.5162/SMSI2025/A5.4}},
  year         = {{2025}},
}

@inbook{63439,
  author       = {{Moritzer, Elmar and Brandes, Philipp and Claes, Leander and Henning, Bernd}},
  booktitle    = {{PIAE EUROPE 2025}},
  editor       = {{Wissensforum GmbH, VDI}},
  pages        = {{347–360}},
  publisher    = {{{VDI Verlag}}},
  title        = {{{Ultrasound based measurement of mechanical properties of continuous fiber reinforced thermoplastic laminates – A non-destructive method to identify changes in fiber matrix adhesion}}},
  doi          = {{10.51202/9783181024461-347}},
  year         = {{2025}},
}