TY - CONF A1 - Strangfeld, Christoph A1 - Bühling, Benjamin A1 - Maack, Stefan T1 - OsciCheck - A novel fluidic transducer for air coupled ultrasonic measurements N2 - Ultrasonic measurement technology has become indispensable in NDT-CE. Air-coupled ultrasonic (ACU) measurement techniques promise to reduce measurement time. However, the signal quality suffers from large specific impedance mismatch at the transducer-air and air-specimen interface. Additionally, large pressure amplitudes are necessary for the penetration depth required in NDT-CE applications. To address the specific requirements of ultrasonic testing in NDT-CE, a robust ACU transducer was developed, that generates ultrasound by quickly switching a pressurized air flow. The simple design of the fluidic transducer makes the device maintenance free and resilient against harsh environmental conditions. Since the signal is generated by aeroacoustics, there is no specific impedance mismatch between the transducer and the surrounding air. The ultrasonic signal exhibits frequencies in the 30-60 kHz range and is therefore well suited to penetrate heterogenous materials such as concrete. This contribution gives an introduction in the working principle and signal characteristics of the fluidic transducer. A detailed outlook is given to discuss the future potential of fluidic ultrasonic actuators. T2 - International Symposium Non-Destructive Testing in Civil Engineering CY - Zurich, Switzerland DA - 16.08.2022 KW - Air-coupled ultrasound KW - Nondestructive testing KW - Fluidics KW - Bistable amplifier KW - Aeroacoustics PY - 2022 AN - OPUS4-55529 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Non-destructive testing at BAM N2 - A brief introduction to non-destructive testing at BAM, Department 8 and its Divisions. T2 - AK Post Docs Symposium CY - BAM Berlin, Germany DA - 02.02.2021 KW - Non-destrucitve testing PY - 2021 AN - OPUS4-52063 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Adaption of fluidic devices for SHM of hydrogen tanks N2 - Frequency analysis of the tank during every filling Passive actuator is integrated inside filling nozzle/ pressure vessel Frequency from 5 kHz to 150 kHz Frequency sweep (Chirp) can be performed Works with every fluid: air, hydrogen, oxygen, argon, water. T2 - H2Safety Kompetenzzentrum CY - BAM Berlin, Germany DA - 07.07.2021 KW - Fluidic device KW - Structural health monitoring KW - Hydrogen tank KW - Ultrasound PY - 2021 AN - OPUS4-52930 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture transport and measurements at BAM N2 - An overview over material moisture measurements and modelling of building materials at BAM. T2 - Rilem TC MMS Constituent meeting CY - Rabat, Morocco DA - 09.03.2023 KW - Material moisture KW - Moisture transport KW - Sorption isotherm KW - Sorption theory KW - Diffusion coefficient KW - NMR KW - Knudsen effect PY - 2023 AN - OPUS4-57141 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Kick-off meeting DFG OsciFreq N2 - Das Bauwesen erfordert sehr hohe Flächenleistungen, so dass der physische Kontakt zur Oberfläche möglichst vermieden werden sollte, um eine hohe Verfahrgeschwindigkeit der Sensoren zu gewährleisten. Andererseits weisen luftgekoppelte, membranbasierte Aktuatoren durch den Impedanzsprung sehr hohe Verluste auf. Daher stellt das schnelle berührungslose Ultraschallmessen immer noch eine ungelöste Herausforderung im Bauwesen dar. T2 - VH_8294_Kick_off_Meeting_OsciFreq CY - Berlin, Germany DA - 17.06.2022 KW - Fluidic device KW - Beton KW - Luftgekoppelter Ultraschall KW - OsciFreq PY - 2022 AN - OPUS4-55126 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture distribution in amorphous porous materials N2 - Mesopores dominate the material moisture and influence the gas diffusion through materials such as concrete or sandstone T2 - Nano@bam Round Table Nano Materials CY - Berlin, Germany DA - 14.10.2022 KW - Physisorption KW - Mesopores KW - Amorphous materials PY - 2022 AN - OPUS4-55998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Frequency modulated, air-coupled ultrasound generated by fluidic oscillators N2 - The majority of ultrasonic devices used for non- destructive testing in civil engineering require contact with the surface of the concrete (specimen), which significantly increases the time required for the measurement. This makes it impractical for extensive investigation of large-scale structures such as bridge decks, foundations, or tunnels. In a pioneering approach, fluidic oscillators are used as contact free ultrasonic sources to overcome the aforementioned limi- tations. These robust and cost-effective actuators require only pressurised air and are ideally suited for harsh environments. At a constant supply pressure, they generate a continuous mono- frequent actuation signal. Further, varying the supply pressure via a fast pressure regulator was found to generate a frequency modulated signal which enabled time-of-flight measurement with an added advantage of increased signal to noise ratio. To demonstrate the feasibility of this novel idea of non-contact ultrasound, the results of the initial tests are presented. T2 - IEEE International Ultrasound Symposium CY - Venice, Italy DA - 11.10.2022 KW - Air-coupled ultrasound KW - Frequency modulation KW - Non-destructive testing KW - Civil engineering KW - Building materials KW - Fluidic oscillators PY - 2022 AN - OPUS4-56072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - TC 286-GDP STAR - chapter: Modelling moisture transport in porous media N2 - The current content and structure of the chapter "Modelling moisture transport in porous media" of the state of the art report is presented. T2 - RILEM Spring Convention 2021 CY - Online meeting DA - 06.04.2021 KW - Moisture transport KW - Porous media KW - Modelling mass transfer KW - Gas diffusion KW - Concrete PY - 2021 AN - OPUS4-52405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture testing and mapping N2 - Presentation of the Non-destructive testing and evaluation advanced training workshop of division 8.2 regarding moisture measurements. T2 - NDT&E Advanced Training Workshop CY - Berlin, Germany DA - 21.06.2023 KW - Material moisture KW - Moisture transport KW - Building materials KW - Concrete KW - Moisture measurement techniques PY - 2023 AN - OPUS4-57799 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - A brief introduction to wind turbine aerodynamics N2 - In general, wind turbines transform the kinetic energy of the wind into electric power. Thereby, the wind turbine blades are facing unsteady loads which are transferred to the hub to generate a rotation of the turbine’s axis. This brief introduction focuses on the aerodynamics of the blades and the corresponding loads. Starting with the basic flow field and loads of an airfoil, terms like stagnation point, boundary layer, Reynolds number, transition, and separation are introduced. For different geometries, lift and drag coefficient curves are discussed. Then, full wings will be considered, including their three-dimensional flow field due to wing tip vortices and crossflows. As a main source of increased loads, unsteady effects are explained in more detail such as gusts, tower passing, earth boundary layer crossing, free stream turbulences, yaw misalignment, etc. At the end, extra loads due to an oscillating free stream are introduced. T2 - QI-Digital: KI-Machbarkeitsstudie Thermografie Rotorblätter CY - Berlin, Germany DA - 13.12.2022 KW - Wind turbine KW - Nondestructive testing KW - Aerodynamics KW - Dynamic stall PY - 2022 AN - OPUS4-56728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -