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Perspektivenwechsel. Bildinformationen anzeigen

Perspektivenwechsel.

Foto: Universität Paderborn

Prof. Dr. Bernd Henning

Kontakt
Publikationen
Prof. Dr. Bernd Henning

Elektrische Messtechnik (EMT)

Leiter - Professor

Telefon:
+49 5251 60-3022
Büro:
P1.5.18.1
Besucher:
Pohlweg 47-49
33098 Paderborn

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2021

Efficient semi-analytical simulation of elastic guided waves in cylinders subject to arbitrary non-symmetric loads

D. Itner, H. Gravenkamp, D. Dreiling, N. Feldmann, B. Henning, Ultrasonics (2021)


Investigating peculiarities of piezoelectric detection methods for acoustic plate waves in material characterisation applications

L. Claes, H. Schmiegel, C. Grünsteidl, S. Johannesmann, M. Webersen, B. Henning, tm - Technisches Messen (2021), 88(3), pp. 147-155

Acoustic waves in plates have proven a viable tool for testing and material characterisation purposes. There are a multitude of options for excitation and detection of theses waves, such as optical and piezoelectric systems. While optical systems, with thermoelastic excitation and interferometric detection, have the benefit of being contactless, they usually require rather complex and expensive experimental setups. Piezoelectric systems are more easily realised but require direct contact with the specimen and usually have a limited bandwidth, especially in case of piezoelectric excitation. In this work, the authors compare the properties of piezoelectric and optical detection methods for broad-band acoustic signals. The shape (e. g. the displacement) of a propagating plate wave is given by its frequency and wave number, allowing to investigate correlations between mode shapes and received signal strengths. This is aided by evaluations in normalised frequency and wavenumber space, facilitating comparisons of different specimens. Further, the authors explore possibilities to utilise the specific properties of the detection methods to determine acoustic material parameters.


    Modelling damping in piezoceramics: A comparative study

    N. Feldmann, V. Schulze, L. Claes, B. Jurgelucks, L. Meihost, A. Walther, B. Henning, tm - Technisches Messen (2021), 88(5), pp. 294 - 302

    The progress in numerical methods and simulation tools promotes the use of inverse problems in material characterisation problems. A newly developed procedure can be used to identify the behaviour of piezoceramic discs over a wide frequency range using a single specimen via fitting simulated and measured impedances by optimising the underlying material parameters. Since there is no generally accepted damping model for piezoelectric ceramics, several mechanical damping models are examined for the material identification. Three models have been chosen and their ability to replicate the measured impedances is evaluated. On the one hand, the common Rayleigh model is considered as a reference. On the other hand, a Zener model and a model using complex constants are extended to model the transversely isotropic material. As the Rayleigh model is only valid for a limited frequency range, it fails to model the broadband behaviour of the material. The model using complex constants leads to the best fit over a wide frequency range while at the same time only adding three additional parameters for modelling damping. Thus, damping can be assumed approximately frequency-independent in piezoceramics.


      Simulation of guided waves in cylinders subject to arbitrary boundary conditions for applications in material characterization

      D. Itner, H. Gravenkamp, D. Dreiling, N. Feldmann, B. Henning, PAMM (2021)



      Optimised Multi-Electrode Topology for Piezoelectric Material Characterisation

      L. Claes, N. Feldmann, B. Jurgelucks, V. Schulze, S. Schmidt, A. Walther, B. Henning, 2021, pp. 237-238


      Measurement and Simulation of Lamb Waves in Adhesive-bonded Multilayer Systems

      H. Zeipert, L. Claes, S. Johannesmann, M. Webersen, Y. Lugovtsova, J. Prager, B. Henning, 2021, pp. 91 - 92


      2020


      Reduction of systematic measurement deviation in acoustic absorption measurement systems

      L. Claes, E. Baumhögger, T. Rüther, .J. Gierse, T. Tröster, B. Henning, in: Fortschritte der Akustik - DAGA 2020, 2020, pp. 1077-1080


      The Influence of Hydrothermal Aging on the Material Properties of Continuous Fiber-Reinforced Thermoplastics and its Non-Destructive Characterization

      E. Moritzer, M. Hüttner, B. Henning, M. Webersen, in: Advances in Polymer Processing 2020, Springer, 2020


      Recombination mechanisms of luminescence type gas sensors

      M. Poeplau, S. Ester, B. Henning, T. Wagner, Physical Chemistry Chemical Physics (2020)

      <p>The impact of the recombination mechanisms in luminescent materials is discussed with regard to luminescence based gas-sensing applications and the use of semiconducting materials, as an alternative to organic–metal complexes, is outlined.</p>


        Estimation of acoustic wave non-linearity in ultrasonic measurement systems

        L. Claes, C. Steidl, T. Hetkämper, B. Henning, arXiv.org (2020)


        Solving piezoelectric inverse problems using Algorithmic Differentiation

        N. Feldmann, V. Schulze, B. Jurgelucks, B. Henning, in: Fortschritte der Akustik - DAGA 2020, 2020, pp. 1125-1128


        Determination of Murnaghan constants of plate-shaped polymers under uniaxial tensile load

        S. Johannesmann, S. Becker, M. Webersen, B. Henning, in: SMSI 2020 - Measurement Science, 2020


        Inverse piezoelectric material parameter characterization using a single disc-shaped specimen

        N. Feldmann, V. Schulze, L. Claes, B. Jurgelucks, A. Walther, B. Henning, tm - Technisches Messen (2020), pp. 50-55

        The increasingly simulation-driven design process of ultrasonic transducers requires several reliable parameters for the description of the material behaviour. Exact results can only be achieved when a single specimen is used in the identification process, which typically is prone to the problem of low sensitivities to certain material parameters and thus high uncertainties. Therefore, a custom electrode topology for increased sensitivity is proposed for a piezoceramic disc. The thereupon conducted measurements of the electric impedance can be used as a starting point for an inverse approach where an equivalent simulation model is used to identify fitting material parameters. An optimisation strategy based on a preliminary sensitivity analysis is presented that leads to a good agreement between measurement and simulation. Furthermore, the proposed measurement procedure is able to evaluate the quality of the simulation model. Hence, different frequency-dependent damping models are presented and evaluated.


          2019


          Analysis of Lamb wave mode repulsion and its implications to the characterisation of adhesive bonding strength

          Y. Lugovtsova, S. Johannesmann, B. Henning, J. Prager, in: 2019 International Congress on Ultrasonics, Acoustical Society of America, 2019


          Akustische Charakterisierung der mechanischen Eigenschaften künstlich gealterter Polymere

          M. Webersen, M. Hüttner, F. Woitschek, E. Moritzer, B. Henning, in: Fortschritte der Akustik - DAGA 2019, 2019


          P2.9 Comparison of deep feature extraction techniques for varying-length time series from an industrial piercing press

          C. Thiel, C. Steidl, B. Henning, in: 20. GMA/ITG-Fachtagung. Sensoren und Messsysteme 2019, 2019

          The continuous refinement of sensor technologies enables the manufacturing industry to capture increasing amounts of data during the production process. As processes take time to complete, sensors register large amounts of time-series-like data for each product. In order to make this data usable, a feature extraction is mandatory. In this work, we discuss and evaluate different network architectures, input pre-processing and cost functions regarding, among other aspects, their suitability for time series of different lengths.


            Störeffektunterdrückung in 2D-Messdaten mittels DiscoGAN

            S. Johannesmann, D. Springer, C. Thiel, B. Henning, in: Fortschritte der Akustik - DAGA 2019, Deutsche Gesellschaft für Akustik, 2019, pp. 1055-1058


            Quantification of frequency-dependent absorption phenomena

            L. Claes, S. Johannesmann, E. Baumhögger, B. Henning, in: 2019 International Congress on Ultrasonics, 2019


            Evolutionary algorithm for the design of passive electric matching networks for ultrasonic transducers

            T. Hetkämper, L. Claes, B. Henning, in: 2019 International Congress on Ultrasonics, 2019


            Characterization of the linear-acoustic material behavior of fiber-reinforced composites using lamb waves

            S. Johannesmann, M. Webersen, J. Düchting, L. Claes, B. Henning, in: 45th Annual Review of Progress in Quantitative Nondestructive Evaluation , 2019


            Acoustic absorption measurement for the determination of the volume viscosity of pure fluids / Messverfahren für die akustischen Absorption zur Bestimmung der Volumenviskosität reiner Fluide

            L. Claes, L.M. Hülskämper, E. Baumhögger, N. Feldmann, R.S. Chatwell, J. Vrabec, B. Henning, tm - Technisches Messen (2019), pp. 2-6


            A sensitivity-based optimisation procedure for the characterisation of piezoelectric discs

            N. Feldmann, B. Jurgelucks, L. Claes, B. Henning, in: 2019 International Congress on Ultrasonics, 2019


            2018

            Guided ultrasonic waves for determining effective orthotropic material parameters of continuous-fiber reinforced thermoplastic plates

            M. Webersen, S. Johannesmann, J. Düchting, L. Claes, B. Henning, Ultrasonics (2018), 84, pp. 53-62


            Efficient optimisation of initial values for characterising piezoelectric material parameters

            N. Feldmann, B. Henning, in: Fortschritte der Akustik, 2018, pp. 1275-1278


            Einfluss mechanischer Vorspannung auf das mechanische Materialverhalten von Polymeren

            M. Webersen, S. Johannesmann, T. Brockschmidt, F. Rump, L. Claes, B. Henning, 2018


            Akustische Charakterisierung der richtungsabhängigen elastischen Eigenschaften faserverstärkter Kunststoffe

            M. Webersen, S. Johannesmann, J. Düchting, L. Claes, B. Henning, in: Fortschritte der Akustik - DAGA 2018, 2018, pp. 1263-1266


            An inverse approach to the characterisation of material parameters of piezoelectric discs with triple-ring-electrodes

            N. Feldmann, B. Jurgelucks, L. Claes, V. Schulze, B. Henning, A. Walther, tm - Technisches Messen (2018), 86(2), pp. 59-65


            An acoustic waveguide-based approach to the complete characterisation of linear elastic, orthotropic material behaviour

            S. Johannesmann, J. Düchting, M. Webersen, L. Claes, B. Henning, tm - Technisches Messen (2018), 2018(85), pp. 478-486


            Extraction of Interpretable Features from Temporal Measurements using Approximate Prototypes

            C. Thiel, N. Feldmann, B. Henning, in: Sensoren und Messsysteme 2018, VDE Verlag GmbH, 2018, pp. 536-539



            Acoustic material characterization of prestressed, plate-shaped specimens

            S. Johannesmann, T. Brockschmidt, F. Rump, M. Webersen, L. Claes, B. Henning, in: Sensoren und Messsysteme, VDE Verlag GmbH, 2018, pp. 231-234


            Additiv gefertigte, akustische Diffusor-Strukturen für Ultraschallanwendungen

            L. Claes, H. Zeipert, P. Koppa, T. Tröster, B. Henning, 2018


            Optimization of triple-ring electrodes on piezoceramic transducers using algorithmic differentiation

            B. Jurgelucks, L. Claes, A. Walther, B. Henning, Optimization Methods and Software (2018), pp. 1-21


            Vollständige Charakterisierung von piezoelektrischen Scheiben mit Ringelektroden

            N. Feldmann, B. Jurgelucks, L. Claes, B. Henning, 2018


            2017

            Evaluating the Influence of 3D-Printing Parameters on Acoustic Material Properties

            A. Jäger, S. Johannesmann, L. Claes, M. Webersen, B. Henning, M. Kupnik, in: 2017 IEEE IUS~Proceedings, 2017


            Material parameter determination of a piezoelectric disc with triple-ring-electrodes for increased sensitivity

            B. Jurgelucks, N. Feldmann, L. Claes, B. Henning, A. Walther, in: Proceedings of Meetings on Acoustics, 2017, pp. 030010



            Inverser Ansatz zur akustischen Charakterisierung plattenförmiger Materialproben

            S. Johannesmann, L. Claes, M. Webersen, B. Henning, in: Fortschritte der Akustik - DAGA 2017, Deutsche Gesellschaft für Akustik e.V. 2017, 2017, pp. 999-1002


            Additively manufactured acoustic diffuser structures for ultrasonic measurement applications

            L. Claes, H. Zeipert, P. Koppa, T. Tröster, B. Henning, in: Proceedings of Meetings on Acoustics, 2017, pp. 030004



            A Spectral Approach to Acoustic Absorption Measurement

            L. Claes, R.S. Chatwell, J. Vrabec, B. Henning, in: PROCEEDINGS -- AMA Conferences 2017, AMA Service GmbH, 2017, pp. 304-309


            Ultrasonic measurements in the characterization of viscoelasticity and aging of polymers

            F. Bause, L. Claes, M. Webersen, B. Henning, in: PROCEEDINGS -- AMA Conferences 2017, 2017, pp. 414


            Viskoelastizität und Anisotropie von Kunststoffen: Ultraschallbasierte Methoden zur Materialparameterbestimmung

            F. Bause, L. Claes, M. Webersen, S. Johannesmann, B. Henning, tm - Technisches Messen (2017), 84(3)


            Acoustic Material Characterization of Additively Manufactured Components

            L. Claes, A. Jäger, S. Johannesmann, M. Webersen, M. Kupnik, B. Henning, in: PROCEEDINGS -- AMA Conferences 2017, AMA Service GmbH, 2017, pp. 605-610


            Determining fractional Zener model parameters from low frequency DMA measurements

            N. Feldmann, F. Bause, B. Henning, in: Proceedings – AMA Conferences 2017, 2017


            2016

            An Approach to Non-Destructive Testing of Aged Polymers

            E. Moritzer, M. Hüttner, B. Henning, M. Webersen, 2016


            Molekularen Schäden auf der Spur

            E. Moritzer, M. Hüttner, B. Henning, M. Webersen, Kunststoffe (2016)(4), pp. 94-96


            Zerstörungsfreie Charakterisierung des hydrothermischen Alterungsverhaltens von Polymeren

            M. Webersen, M. Hüttner, F. Bause, E. Moritzer, B. Henning, 2016, pp. 683-688

            In der zerstörungsfreien Werkstoffprüfung sind bereits zahlreiche Verfahren etabliert, deren Ziel die Detektion makroskopischer Defekt- und Fehlstellen (z.B. Risse, Poren, Fremdeinschlüsse) ist. Insbesondere bei Polymerwerkstoffen muss jedoch auch die Materialalterung auf molekularer Ebene berücksichtigt werden, die sich (zumeist negativ) auf die Materialkenngrößen auswirkt. Gängige Verfahren zur Bestimmung dieser Kenngrößen arbeiten jedoch üblicherweise zerstörend und sind somit beispielsweise für die vorbeugende Instandhaltung oder die Online-Komponentenüberwachung nur eingeschränkt geeignet. In diesem Beitrag wird ein Verfahren zur zerstörungsfreien Charakterisierung des Alterungszustandes von Polymeren vorgestellt. Dazu wird der Zusammenhang zwischen akustisch (zerstörungsfrei, mittels Ultraschall-Transmissionsmessung) bestimmten Kenngrößen und klassisch (zerstörend, z.B. mittels Zugprüfung) bestimmten hydrothermischer Alterung auf das Material Polyamid 6 (PA6) untersucht. Die Ergebnisse Kenngrößen betrachtet. Exemplarisch werden die Auswirkungen zeigen einen engen Zusammenhang zwischen der zerstörend bestimmten Viskositätszahl, die ein Maß für die mittlere Molekülkettenlänge darstellt, und der akustischen Longitudinalwellengeschwindigkeit. Das Molekülkettenabbau (Depolymerisation) bestimmt ist, kann somit auch akustisch und zerstörungsfrei charakterisiert werden. Auf dieser Basis können neuartige, zerstörungsfrei arbeitende Messsysteme entwickelt werden.



              Detecting Molecular Damage

              E. Moritzer, M. Hüttner, B. Henning, M. Webersen, Kunststoffe International (2016)(4), pp. 43-45


              Erweiterung des Raman-Nath-Modells zur Analyse von Schlierenabbildungen

              S. Olfert, B. Henning, Technisches Messen (2016), 83(4), pp. 219-224


              Determination of the material properties of polymers using laser-generated broadband ultrasound

              L. Claes, T. Meyer, F. Bause, J. Rautenberg, B. Henning, Journal of Sensors and Sensor Systems (2016), 5(1), pp. 187-196


              Non-destructive characterization of hygrothermally aged polymers

              E. Moritzer, M. Hüttner, B. Henning, M. Webersen, 2016



              Ultrasonic transmission measurements in the characterization of viscoelasticity utilizing polymeric waveguides

              F. Bause, J. Rautenberg, N. Feldmann, M. Webersen, L. Claes, H. Gravenkamp, B. Henning, Measurement Science and Technology (2016), 27(10)


              Uncertainty estimation for linearised inverse problems comparing Bayesian inference and a pseudoinverse approach for acoustic transmission measurements

              N. Feldmann, F. Bause, B. Henning, tm - Technisches Messen (2016), 84(4)


              Ultraschallbasierte Charakterisierung von gealterten Polymeren

              E. Moritzer, M. Hüttner, B. Henning, M. Webersen, in: Jahresmagazin Kunststofftechnik 2016, 2016, pp. 2-7



              Characterization of Continuous-fiber Reinforced Thermoplastics Using Thermoacoustically Excited Ultrasonic Lamb Waves

              M. Webersen, S. Johannesmann, L. Claes, B. Henning, in: 2016 IEEE IUS~Proceedings, 2016



              2015

              Identification of temperature-dependent model parameters of ultrasonic piezo-composite transducers

              M. Webersen, F. Bause, J. Rautenberg, B. Henning, in: AMA Conferences 2015, 2015, pp. 195-200

              When performing measurements, the effects of the measurement system itself on the measured data generally must be eliminated. Consequently, those effects, i.e. the system’s dynamic behavior, need to be known. For the piezo-composite transducers in an ultrasonic transmission line, a model based approach is used to describe their dynamic behavior and take into account its dependence on the environment temperature and the acoustic impedance of the target medium. Temperature-dependent model parameters are presented, which are obtained by performing a multiplepart identification process on the transducer model, based on electrical impedance measurements [1]. The identification process uses an inverse approach for optimizing a subset of the model parameters. Additionally, algorithmic differentiation methods are used to determine accurate derivatives. In a final optimization step, impedance measurements taken at different temperatures are used to determine the temperature dependencies of the model parameters. These can then be used to assess the plausibility of the identification results. Additionally, the parameters can be expressed as polynomials in the temperature to take different operating conditions into account.


                Model based sensitivity analysis in the determination of viscoelastic material properties using transmission measurements through circular waveguides

                F. Bause, H. Gravenkamp, J. Rautenberg, B. Henning, 2015, pp. 204-207

                Several ultrasonic approaches for material determination are formulated in terms of an (nonlinear) inverse problem, e.g. immersion technique (Castaings et al. (2000)) or plate-waveguide techniques (Marzani et al. (2012)). In this contribution we focus on cylindrical waveguides for ultrasonic material determination and especially on the sensitivity of recorded transmission signals to the material properties. We utilize composite scaled sensitivities to determine the information content that can be achieved by the setup to certain parameters and discuss the limitations of the approach.


                  Utilizing guided acoustic waves to measure dispersive material properties of polymers

                  J. Rautenberg, F. Bause, B. Henning, in: AMA~Conferences 2015, 2015, pp. 130-135

                  This contribution will give a short introduction to the most important mechanic and acoustic parameters that are necessary to model and simulate frequency dependent sound propagation (dispersion) in isotropic but linear viscoelastic materials. Furthermore, several experimental techniques to measure these parameters will be discussed, like the dynamic-mechanical analysis and transient ultrasonic techniques. Finally it will be shown how to use the determined material parameters for the simulation of transient signals in a highly attenuative acoustic waveguide.


                    Detection of ultrasonic plate waves using ceramic strip transducers

                    L. Claes, F. Bause, J. Rautenberg, B. Henning, in: Proceedings SENSOR 2015, 2015, pp. 775-779



                    Transient modeling of ultrasonic guided waves in circular viscoelastic waveguides for inverse material characterization

                    F. Bause, H. Gravenkamp, J. Rautenberg, B. Henning, Measurement Science and Technology (2015)



                    Analyse integral erfasster Schallwechseldruckverteilungen in Schlierenabbildungen

                    S. Olfert, B. Henning, in: XXIX Messtechnisches Symposium, 2015


                    2014

                    Time-causal material modeling in the simulation of guided waves in circular viscoelastic waveguides

                    F. Bause, A. Schroder, J. Rautenberg, B. Henning, H. Gravenkamp, in: 2014 IEEE International Ultrasonics Symposium, 2014


                    Sensitivitätssteigerung im Rahmen eines inversen Ansatzes zur Materialparameterbestimmung für Piezokeramiken durch Elektrodenmodifikationen

                    C. Unverzagt, B. Henning, 2014, pp. 95-102

                    Simulationen mittels der Finiten Element Methode (FEM) sind heute ein fester Bestandteil im Entwicklungsprozess von Ultraschallsystemen. Durch die simulative Ermittlung der transienten Schwingungsvorgänge können Optimierungen bezüglich gewünschter Zielkriterien vorgenommen werden. Hierdurch lassen sich die aufwendige Prototypenfertigung reduzieren und günstige Entwurfspunkte schneller ermitteln.



                      Model based sensitivity analysis of Leaky-Lamb wave propagation to the variation of viscous lubricant properties

                      F. Bause, C. Brückner, J. Miedl, B. Henning, in: Beiträge der 17. ITG/GMA-Fachtagung, {VDE Verlag}, 2014



                      Methoden zur Zeit-Frequenz-Analyse bei der Untersuchung dispersionsbehafteter Signale

                      F. Bause, J. Rautenberg, N. Feldmann, L. Claes, B. Henning, 2014




                      Modellgestützte Analyse des Trocknungsverhaltens von Dispersionslacken aus Daten einer NIR-Multidetektoranordnung

                      C. Hoof, S. Appelhans, B. Henning, 2014

                      Zur schnellen und berührungslosen Materialfeuchtebestimmung wird unter anderem die Infrarotreflexionsmessung ge-nutzt. In dieser Untersuchung wird das Trocknungsverhalten von Dispersionslack auf einem rauen Substrat mit einer Multidetektoranordnung untersucht. Durch diese Anordnung ist es möglich, gerichtete und diffuse Strahlungsanteile zu detektieren, wodurch zeitvariable Glanzeffekte an der Lackoberfläche miterfasst werden. Mit Hilfe eines Raytracing-Algorithmus wird die Trocknung eines Dispersionslackes simuliert und anhand von Messdaten mit einem FTIR-Spekt-rometer verifiziert.


                        2013



                        Ultrasonic Waveguide Signal Decomposition Using the Synchrosqueezed Wavelet Transform for Modal Group Delay Computation

                        F. Bause, B. Huang, A. Kunoth, B. Henning, 2013

                        Due to the modal behavior of geometrically bounded media, ultrasonic guided waves propagate in waveguides as a combination of multiple dispersive wave packets, which can be simulated as a PDE-problem. Given an excitation in time and space, multiple eigen-modes derived from solving the PDE may propagate each with different dispersion characteristics and weight. Considering a broad-band pulse exciting from one side of a hollow cylindrical waveguide, the received signal at the other side consists of all propagating eigen-modes that can be considered approximately as the narrow band signals. The synchrosqueezed wavelet transform (SWT) is employed to sharpen the time-frequency representation (TFR) of the received waveguide signal. Using a ridge detection algorithm, we successively separate the synchrosqueezed TFR into several narrow band TFRs which can be identified as oscillatory components with time-varying frequency. Then those separated TFRs are reconstructed as narrow band signals using the inverse SWT. Based on an analytical model of the waveguide, we observe that the decomposed signals are similar to those dominant eigen-modes simulated above. Moreover, also the group delay and, therefore, the group velocity of each decomposed signal can be estimated well. This is of high interest when analyzing the characteristic of a given waveguide, such as acoustical property measurements or non-destructive testing.




                          Messsystem zur Bestimmung akustischer Kenngrößen stark absorbierender, transversal isotroper Kunststoffe

                          J. Rautenberg, F. Bause, B. Henning, tm - Technisches Messen (2013), pp. 28-37


                          Utilizing ultrasound material parameter determination for the characterization of different stages of ageing in Polyamide 6

                          F. Bause, C. Budde, J. Rautenberg, B. Henning, E. Moritzer, 2013, pp. 504-509

                          The condensation polymer Polyamide 6 (PA 6) is a thermoplastic resin with high tensile strength and rigidity at comparatively low costs for raw material and processing. This is why PA 6 is a common material for the production of ropes, gears or bearings. Apart from that, a relative new application is the thermoforming of glass fibre laminate sheets with PA 6 as matrix material. The prediction the rest of life period of such high-tech materials is still a research objective. A first step, and also part of this contribution, is the nondestructive investigation of the matrix material. The ageing of PA 6 is mainly affected by thermo- and photo-oxidation as well as post-condensation, which e.g. results in a change of physical properties. For this contribution the acoustical and mechanical material parameters of artificially aged PA 6 have been determined with high frequency ultrasound (1 MHz) and quasi-static experiments. We will give a short description of both experimental setups as well as the ageing procedure. Finally we will discuss the correlation between the experimental results, finding that there is a good correlation between sound velocity and tensile strength.



                            Influence of angular radiated ultrasound waves on the Schlieren tomogram

                            S. Olfert, L. Claes, B. Henning, in: Proceedings of the International Conference on Acoustics, DEGA, 2013, pp. 477-480


                            Multi Reflection of Lamb Wave Emission in an Acoustic Waveguide Sensor

                            M. Schmitt, S. Olfert, J. Rautenberg, G. Lindner, B. Henning, L. Reindl, Sensors (2013), pp. 2777-2785


                            Reliable Computation of Roots in Analytical Waveguide Modeling Using an Interval-Newton Approach and Algorithmic Differentiation

                            F. Bause, A. Walther, J. Rautenberg, B. Henning, Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (2013), 60(12), pp. 2597-2606


                            Improved Signal Processing for an Ultrasonic Distance Sensor with Reduced Blind Zone

                            A. Schröder, B. Henning, in: Proceedings of the International Conference on Acoustics, DEGA, 2013

                            Single transducer distance sensors have a blind zone because normally the electrical received signal cannot be detected during transmitting. There are several approaches to realize a simultaneous transmit and receive operation. Digital signal processing is the best solution for narrow band systems (air ultrasound transducer) especially when the transmitted signal is coded. Thereby a mathematical model is used to estimate the electrical received signal. A drawback of the digital signal processing is the required computing time to estimate the model and the time of flight of an echo. In this contribution the computing time is reduced significantly by using base band signals for the signal processing. The signal-processing is subdivided into the following steps: Preprocessing, model identification, estimation of the received signal and echo detection. Beside the model identification the signal-preprocessing is an important part of the system. It depends on the time of flight of an echo (close echo, far echo) and the state of the system (single measurement, averaging). The whole system is evaluated with measurements using a 40 kHz air ultrasound transducer in front of a reflector with varying distances between 0 mm and 1000 mm.


                              Detection of coatings within liquid-filled tubes and containers by mode conversion of leaky Lamb waves

                              M. Schmitt, K. Schmidt, S. Olfert, J. Rautenberg, G. Lindner, B. Henning, L.M. Reindl, Journal of Sensors and Sensor Systems (2013), pp. 73-84

                              <jats:p>&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; In this paper, a new acoustic sensor principle for coating detection within liquid-filled tubes and containers based on mode conversion of leaky Lamb waves is introduced. Leaky Lamb waves are excited and detected by single-phase transducers, which are attached on the outer side of a tube or container. By transmission time and amplitude measurements, coating formation within the liquid-filled tube and container is detected non-invasively. This new sensor principle is subdivided into the separate considerations of Lamb wave excitation, mode conversion and inverse mode conversion. The Lamb wave excitation by a single-phase transducer is visualized by scanning laser Doppler vibrometer imaging. The mode conversion process of leaky Lamb waves is measured by membrane hydrophone measurements and Schlieren visualization; afterwards, the measured emission angles are compared with the theoretical one. The inverse mode conversion process of pressure waves back to leaky Lamb waves is visualized by Schlieren images. By merging the results of Lamb wave excitation, mode conversion and inverse mode conversion, the new sensor concept is explained. Theoretical considerations and measurement results of adhesive tape coating inside a liquid-filled plastic tube and a liquid-filled stainless steel container verify the new acoustic sensor principle. Finally the measuring sensitivity and the technical realization are discussed.&lt;/p&gt;</jats:p>


                                Modified electrode shape for the improved determination of piezoelectric material parameters

                                C. Unverzagt, J. Rautenberg, B. Henning, K. Kulshreshtha, in: Proceedings of the 2013 International Congress on Ultrasonics, {Research Publishing}, 2013, pp. 758-763


                                Luftultraschall-Abstandsmessung mit digitaler Signalverarbeitung zur Verkürzung des Mindestabstandes

                                A. Schröder, B. Henning, tm - Technisches Messen (2013), pp. 196-200


                                Modellgestützte NIR-Materialfeuchtemessung mittels Multidetektoranordnung

                                C. Hoof, D. Wetzlar, B. Henning, Technisches Messen (2013)(12), pp. 435-441

                                Zur berührungslosen Materialfeuchtebestimmung wird unter anderem die Infrarotreflexionsmessung genutzt. Diese nichtinvasive und schnelle Methode ist geeignet sowohl zur Bestimmung der Feuchte von Schüttgütern als auch zur Charakterisierung von Trocknungsprozessen von Lacken. Die reflektierte Strahlung ist dabei abh{\"a}ngig von Absorption und Streuung in der Beschichtung sowie von den temporären und lokalen Reflexionseigenschaften des Messobjektes. ln dieser Untersuchung ist ein experimenteller Aufbau zur simultanen Messung der gerichteten und der diffus reflektierten Strahlungsanteile realisiert.



                                  2012

                                  Messsystem zur Bestimmung akustischer Kenngrößen stark absorbierender, transversal isotroper Kunststoffe

                                  J. Rautenberg, F. Bause, B. Henning, 2012, pp. 332-343

                                  Es wird ein Wellenleiter basiertes Messsystem vorgestellt, mit dem anhand einer einzigen Transmissionsmessung alle Daten bestimmt werden können, die zur Simulation von Schallausbreitungsphänomenen in stark absorbierenden und schwach anisotropen Materialien erforderlich sind. Auf diese Weise ist es fortan möglich die akustischen Kenngrößen (winkel- und frequenzabhängige Schallgeschwindigkeiten und frequenzabhängige Absorption) verschieden konditionierter Materialproben (Temperatur, Feuchtigkeit, Alter) simultan zu erfassen. Genutzt wird dazu die mehrmalige Modekonversion an den Mantelflächen eines hohlzylindrischen akustischen Wellenleiters, wonach ein Empfangssignal mehrere Signalgruppen aufweist, deren absolute Laufzeit, Laufzeitdifferenzen und Amplituden in Abhängigkeit der Materialkenngrößen stark variieren. Grundlegend für die realisierte und in diesem Beitrag beschriebene inverse Bestimmung der akustischen Kenngrößen ist ein ganzheitliches Modell der Schallanregung, -ausbreitung und -detektion, welches die schnelle Berechnung der Empfangssignale erlaubt. Die gezielte Variation der Modell-Eingangsgrößen führt schließlich zu einer bestmöglichen Übereinstimmung zwischen berechneten und gemessenen Empfangssignalen, sodass die final angesetzten Modell-Eingangsgrößen eine gute Approximation der gesuchten materialspezifischen akustischen Kenngrößen darstellen. Im Rahmen dieses Beitrags werden der Messaufbau, wesentliche Teile der Modellierung sowie die grundätzliche Vorgehensweise zur Anwendung der inversen Messmethode gezeigt. Anhand gemessener, berechneter und mittels Finiter Elemente Methode simulierter Signale wird das Verfahren für einen Werkstoff, spritzgegossenes Polypropylen, demonstriert.


                                    2D phononic crystal sensor with normal incidence of sound

                                    M. Zubtsoc, R. Lucklum, M. Ke, A. Oseev, R. Grundmann, B. Henning, U. Hempel, Sensors and Actuators A: Physical (2012), 186, pp. 118-124

                                    The contribution presents the sensor application of a resonance-induced extraordinary transmission through a regular phononic crystal consisting of a metal plate with a periodic arrangement of holes in a square lattice at normal incidence of sound. The characteristic transmission peak has been found to strongly depend on sound velocity of the liquid the plate is immersed in. The respective peak maximum frequency can serve as measure for the concentration of a component in the liquid mixture, if a beneficial relation to the speed of sound of the liquid exists. Experimental verification has been performed with mixtures of water and propanol as model system. Here we especially pay attention to numerical calculations based on EFIT and COMSOL which reveal more insides to the wave propagation characteristics. Experimental investigations with Schlieren method and laser interferometry support the theoretical findings.


                                      Geführte akustische Wellen zur Flüssigkeitscharakterisierung

                                      J. Rautenberg, F. Bause, B. Henning, tm - Technisches Messen (2012), pp. 135-142


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