New quantitative data processing methods could enable ultrasound as a potential diagnostic method for hip implant integration monitoring. For development of such methods, suitable acoustic simulation tools are essential. In this work, a novel 1D FDTD simulation tool for multilayer structures, considering frequency-dependent properties, is introduced, particularly meeting the special needs of this application. Simulation results show excellent agreement with experimental data, confirming accurate prediction of wave propagation in multilayer systems.

Since COVID-19, clean indoor air has become more of a focus due to airborne viruses. Conventional filters often fail to capture ultrafine particles. This work investigates how standing ultrasonic fields manipulate aerosols for more efficient cleaning. Gor’kov theory and FEM simulations used to evaluate the acoustic forces on particles. Experiments by light refractive vibrometry and high-speed camera observations confirm the model quality.

This paper explores an alternative approach to ultrasonic flow measurement using guided acoustic waves in cylindrical modes. Unlike conventional methods with diagonal sound propagation, the entire pipe including the fluid is excited to vibrate, reducing path-dependent correction factors. A ring-shaped sensor was developed for a DN15 steel pipe. Results show a signal time shift 2.5 times greater than with Lamb wave-based sensors, adjustable over distance. This approach enables precise, non-invasive flow measurement across various pipe diameters.

Zusammenfassung

Geführte Akustische Wellen (GAW) haben sich im Themengebiet des Structural Health Monitoring (SHM) etabliert. Neben ihren Vorteilen bei der Überwachung von Objekten und Detektion von Fehlstellen, gibt es jedoch auch einige Herausforderungen. Zu diesen zählt die dispersive Natur der häufig eingesetzten Lambwellen. Dispersion führt zu Signalverzerrung und reduziert dadurch die räumliche Auflösung und erschwert die Erkennung von schwach reflektierenden Fehlstellen. In diesem Beitrag wird der Einsatz eines Phased-Array-Systems zur Delaminationserkennung bei einem Mehrschichtsystem demonstriert, bei dem dispersive Lambwellen zum Einsatz kommen. Durch das Kompensieren der Dispersionseffekte kann die Sign Coherence Factor (SCF) Erweiterung des Total Focusing Method (TFM) Algorithmus eingesetzt und so auch schwach reflektierende Fehlstellen erkannt werden. Des Weiteren wird auf das Entstehen von Modenüberlagerungen bei Mehrschichtsystemen eingegangen, die bei der Auswahl der Arbeitsfrequenz und Sendesignallänge des Phased-Array-Systems berücksichtigt werden müssen.

Guided Acoustic Waves (GAW) are well established in the field of Structural Health Monitoring (SHM). However, in addition to their advantages in monitoring objects and detecting defects, there are also several challenges. These include the dispersive nature of the commonly used Lamb waves. Dispersion leads to signal distortion that reduces spatial resolution and makes it difficult to detect weakly reflecting defects. This paper demonstrates the use of a phased array system for delamination detection in a multilayer system using dispersive Lamb waves. By compensating for the dispersion effects, the Sign Coherence Factor (SCF) extension of the Total Focusing Method (TFM) algorithm can be used to detect even weakly reflective defects. Furthermore, the occurrence of mode superposition in multilayer systems is discussed, which must be taken into account when selecting the operating frequency and transmit signal length of the phased array system.

This study is focused on optimizing electromagnetic acoustic transducer (EMAT) sensors for enhanced ultrasonic guided wave signal generation in steel cables using CAD and modern manufacturing to enable contactless ultrasonic signal transmission and reception. A lab test rig with advanced measurement and data processing was set up to test the sensors’ ability to detect cable damage, like wire breaks and abrasion, while also examining the effect of potential disruptors such as rope soiling. Machine learning algorithms were applied to improve the damage detection accuracy, leading to significant advancements in magnetostrictive measurement methods and providing a new standard for future development in this area. The use of the Vision Transformer Masked Autoencoder Architecture (ViTMAE) and generative pre-training has shown that reliable damage detection is possible despite the considerable signal fluctuations caused by rope movement.

The study presents a unifying methodology for characterizing micromixers, integrating both experimental and simulation techniques. Focusing on Dean mixer designs, it employs an optical evaluation for experiments and a modified Sobolev norm for simulations, yielding a unified dimensionless characteristic parameter for the whole mixer at a given Reynolds number. The results demonstrate consistent mixing performance trends across both methods for various operation points. This paper also proposes enhancements in the evaluation process to improve accuracy and reduce noise impact. This approach provides a valuable framework for optimizing micromixer designs, essential in advancing microfluidic technologies.

The precise positioning of objects (especially on a flat surface), is crucial in numerous industrial applications, from large

object movement in machine tools to precise alignment in optical microscopes. This paper focuses on targeted movement

and positioning of smaller objects on a flat surface using piezoelectric actuators. Specifically, it investigates the stick-slip

motor principle for achieving high-speed transport and high-resolution positioning. The stick-slip motor utilizes the friction

between objects and surfaces to generate motion. The experimental setup includes a piezoelectric actuator inducing

asymmetric vibrations in a glass plate (stator), resulting in controlled movement of a slider (the object). An asymmetrical

excitation signal, generated by superimposing two sinusoidal waves, is applied to the piezoelectric actuator. The influence

of the different parameters of the excitation signal on the object speed is examined in more detail. The results demonstrate

successful movement and precise positioning of various objects. It concludes that the developed stick-slip motor can

efficiently move objects of different materials and sizes, offering a versatile solution for precise object positioning in

confined spaces.

Für die nicht-invasive Durchflussmessung werden meist Ultraschallsensoren verwendet, die reversibel an das zu untersuchende Rohrsystem angebaut werden. Die Messgenauigkeit dieser Sensoren wird durch mögliche Ablagerungen im Rohrinneren beeinflusst.

In dem hier vorgestellten Forschungsvorhaben, soll es mit Hilfe eines ultraschallbasierten Messverfahren möglich sein, sowohl die Materialeigenschaften und Wandstärke des Rohres direkt zu ermitteln als auch eventuell vorhandene Schichten im Rohrinneren zu detektieren und zu charakterisieren. Mit Hilfe dieser zusätzlichen Messgrößen soll zukünftig eine präzisere Durchflussmessung von klemmbaren Ultraschalldurchflusssensoren ermöglicht werden. Um die Algorithmen zur Charakterisierung der Materialeigenschaften zu erproben, wurden zunächst Simulationen zur Wellenausbreitung der geführten akustischen Wellen und deren Interaktion mit Schichten durchgeführt. Es erfolgte die Auswertung der beiden Grundmoden, A0 und S0, in einem definierten Frequenzbereich. Im Anschluss erfolgte die experimentelle Überprüfung auf einer ebenen Platte mit definierten Schichten von 415 μm und 780 μm. Die bisherigen Messergebnisse zeigen, dass es möglich ist mit dem entwickelten Algorithmus das Material und die Schichten zu charakterisieren. Die noch vorhandene Abweichung der Materialdaten von den Literaturwerten ergibt sich u. a. aus dem Schwingungsverhalten der Piezokeramik. Zukünftig soll die Auswertung durch direkte Messung der Schwingungseigenschaften der Piezokeramik weiter optimiert werden.

Environmental pollution is an ever-growing concern. Industrial sites as well as agricultural use areas can bear immense harmful burdens. Unintentionally improperly disposed of wastes as well as illegally dumped chemicals pose additional risks in the environment, while remains of pharmaceuticals are a regular concern in sources of drinking water. Pollutants such as PFAS and microplastics could even be detected in the most remote regions of the earth and are known for adverse effects on humans and their environment. Establishing a comprehensive overview of where pollution of which severity and with what substances occurs is thus important, so remediations can be planned and prioritized. This necessitates fast, versatile, reliable and cheap measurements, ideally directly at sampling sites.

A promising class of transducers for detecting a multitude of pollutants are DNA Quantum Clusters. QC:DNA are highly sensitive and selective transducers for many substances, showing responses in their fluorescent behaviors based on their chemical environment. Based on the specific design, QC:DNA can interact with different chemical species and exhibit tuned excitation and emission wavelengths.

For the use of such transducers, we present a fluorescence reader integrated around capillaries. The system is designed for easy and fast customization for a large range of excitation and emission wavelengths while focusing on system portability and striving for affordability. The microfluidic system controlling and performing the assay is based on droplet sequences to facilitate fast mixing while allowing for incubation times with minimal dispersion and enabling a temporary storage and a precise processing of samples.

Optoacoustics is a metrology widely used for material characterisation. In this study, a measurement setup for the selective determination of the frequency-resolved phase velocities and attenuations of longitudinal waves over a wide frequency range (3-55 MHz) is presented. The ultrasonic waves in this setup were excited by a pulsed laser within an absorption layer in the thermoelastic regime and directed through a layer of water onto a sample. The acoustic waves were detected using a self-built adaptive interferometer with a photorefractive crystal. The instrument transmits compression waves only, is low-contact, non-destructive, and has a sample-independent excitation. The limitations of the approach were studied both by simulation and experiments to determine how the frequency range and precision can be improved. It was shown that measurements are possible for all investigated materials (silicon, silicone, aluminium, and water) and that the relative error for the phase velocity is less than 0.2%.

Particularly in medical technology, biotechnology or the pharmaceutical sector, very small quantities of fluids often have to be transported or dosed. Noninvasive measuring methods for flow rate or volume flow measurement that work without direct contact to the fluid and thus meeting the high hygiene standards of these industries hardly exist. Sensors available on the market are either not suitable for precise measurement of the smallest flow rates in the microliter range or are very expensive. For this field of applications, a retrofittable ultrasound-based flow sensor was developed in cooperation with the company ibidi GmbH, which can be integrated into an existing system consisting of very thin tubes or cannulas or capillaries as well as thin flexible tubes.