Alexander Sutor

New CMOS-compatible mechanical shear stress sensor

A new approach to the measurement of mechanical stresses is presented. The new sensor design utilizes the fact that shear stresses in the silicon lattice generate an electric field perpendicular to an electric current. The sensor effect is characterized by a new piezo-bridge-coefficient, which relates the sensitivity of the sensor structure to its crystallographic orientation. The sensor is based on a CMOS-compatible structure. It offers the possibility to realize highly sensitive single-element stress sensors for use in MEMS or in smart force measurement strips, as well. An example of a signal conditioning circuit is shown. Special designs with improved sensitivity and low noise are presented. The response to parasitic magnetic fields is measured and strongly reduced. Furthermore, the temperature behavior was analyzed and finally optimized.

A modified Preisach hysteresis operator for the modeling of temperature dependent magnetic material behavior

In this paper, we present a model for temperature dependent hysteretic nonlinearities with nonlocal memories. This model can be applied to describe hysteretic material behavior. Common applications are ferromagnetic or magnetostrictive materials. Our model consists mainly of a Preisach operator with a continuous Preisach weight function. We choose a weight function which shows a strong correlation between the function’s parameters and certain properties of the hysteresis curve. As a new approach, the weight function is written as a function of temperature. The model parameters are customized to a set of symmetric hysteresis curves. We verify our model for magnetic materials with differently shaped hysteresis curves, different temperatures and magnetic field amplitudes.

Determination of Dynamic Material Properties of Silicone Rubber Using One-Point Measurements and Finite Element Simulations

The dynamic Youngs modulus, Poissons ratio, and the damping factor of silicone rubber are determined from a laser triangulation measurement of the top surface motion of a flat cylindrical sample excited by a shaker. These material parameters are estimated on the basis of an Inverse Method that minimizes the difference between measured data and a prediction from a finite-element model (FEM), in which the sought-after material data are the adjustable parameters. The results are presented for measurements within the 10-400-Hz frequency range under atmospheric pressure and temperature conditions. At first, the measured data are compared with FEM predictions using constant material parameters to show the material behavior in principle. Afterward, the frequency dependence of the moduli and Poissons ratios are determined by matching measurements with simulations within small frequency ranges. Finally, the material parameters determined are given as functions versus frequency. A sensitivity analysis shows the accuracy of the presented method. This paper is motivated by the need for a precise description of vocal fold models, commonly manufactured from silicone rubber.

Measurement of the elasticity modulus of soft tissues

A measurement setup combined with a Finite Element (FE) simulation is presented to determine the elasticity modulus of soft materials as a function of frequency. The longterm goal of this work is to measure in vitro the elasticity modulus of human vocal folds over a frequency range that coincides with the range of human phonation. The results will assist numerical simulations modeling the phonation process by providing correct material parameters. Furthermore, the measurements are locally applied, enabling to determine spatial differences along the surface of the material. In this work the method will be presented and validated by applying it to silicones with similar characteristics as human vocal folds. Three silicone samples with different consistency were tested over a frequency range of 20-250 Hz. The results of the pipette aspiration method revealed a strong frequency dependency of the elasticity modulus, especially below 100 Hz. In this frequency range the elasticity moduli of the samples varied between 5 and 27 kPa.

An Efficient Inverted Hysteresis Model with Modified Switch Operator and Differentiable Weight Function

This paper proposes a different inverted hysteresis model with modification of the classic Preisach switch operator. By using this new switch operator, the inverted model remains the wiping out and congruency properties. It also guarantees the symmetry and total positiveness of weight function in the Preisach plane. According to the change pattern of H(B) branches, a differentiable weight function is introduced in the inverted model. The weight function performs with good continuity and symmetry. This makes it possible to implement the inverted model in numerical analysis without iterative procedure. The identification work is done by means of the measured major loops. Here the Newton method algorithm is applied to optimize the mean squared error (MSE) between the measured and simulated data. By this way, the limited number of parameters can be determined. The inverted model was verified for both soft and hard magnetic materials. Besides major hysteresis loops, minor loops and first-order reversal curves (FORCs) can also be simulated. By comparison, the simulation results produced by the inverted hysteresis model show good approximation to the measurement data.

Estimation of material parameters for piezoelectric actuators using electrical and mechanical quantities

The reliability of Finite Element based simulations of the electrical and mechanical behavior for piezoceramic actuators strongly depends on the accuracy of the required material parameters. For many transducer shapes, the standard methods in order to determine the material parameters are not applicable. Therefore, we developed an alternative method for the parameter estimation, namely the Inverse Method. With the aid of this method, the deviation of simulation from measurement results is minimized. In this article, we present an extended Inverse Method, which considers both, the electrical as well as the mechanical behavior of the investigated actuator.

Artifact reduction in non-destructive testing by means of complementary data fusion of x-ray computed tomography and ultrasonic pulse-echo testing

In industrial non-destructive testing, x-ray computed tomography (CT) and ultrasonic pulse-echo testing play an important role in the investigation of large-scale samples. One major artifact arises in CT, when the x-ray absorption in specific directions is too intense, so that the material cannot be fully penetrated. Due to different physical interaction principles, ultrasonic imaging is able to show features which are not visible in the CT image. In this contribution, we present a novel fusion method for the complementary data provided by x-ray CT and ultrasonic testing. The ultrasonic data are obtained by an adapted synthetic aperture focusing technique (SAFT) and complement the missing edge information in the CT image. Subsequently, the full edge map is incorporated as a priori information in a modified simultaneous iterative reconstruction method (SIRT) and allows a significant reduction of artifacts in the CT image.

An efficient vector Preisach hysteresis model based on a novel rotational operator

The vectorial modeling of hysteresis phenomena is an important task with respect to precise numerical simulation of ferromagnetic materials. Many vector models are based on extended Preisach models. Approaches are known where the scalar Preisach models are defined in different space directions and the results are calculated by summation or integration. Within this approach, we suggest a Preisach model that uses only one Preisach plane, but an additional rotational plane. This rotational plane practically defines a direction for each Preisach element. Therefore, this operator can be evaluated in a very efficient way.

Sound Generation Using a Magnetostrictive Microactuator

In this paper, we present the design and performance of a MEMS-device based on the magnetostrictive effect, which can be used as a micro-loudspeaker. The device basically consists of a comb structure of monomorph bending cantilevers with an active area up to 3.0×2.5 mm2. It produces a sound-pressure-level up to 101 dB at 400 Hz in a standard 2 ccm measurement volume. We show our measurement setup as well as a mechanic-acoustic-coupled lumped element model to calculate sound pressure. The model incorporates finite element results for mechanical behavior. Measurement results validate our model assumptions.

Elektromechanischer Energiewandler auf Basis eines piezokeramischen BiegebalkensElectromechanical Energy Harvester Based on a Piezoceramic Bending Cantilever

Zusammenfassung Es wird ein elektromechanischer Energiewandler vorgestellt, der auf dem piezoelektrischen Wandlungsprinzip in Form eines Biegebalkens beruht. Er wandelt Umgebungs-Vibrationen in elektrische Energie. Ausgehend vom bekannten Aufbau mit konstantem Balkenquerschnitt wird der Energieertrag durch Modifikation des Balkenprofiles erhöht. Im Hinblick auf eine praktische Realisierbarkeit wird die analytisch gefundene optimale Geometrie durch ein lineares Profil approximiert. Die Ergebnisse werden mittels einer Finite-Elemente-Simulation verifiziert. Am Beispiel einer Vakuumpumpe als Schwingungserreger wird die Funktionsfähigkeit des Wandlers demonstriert. Es kann eine Leistung von 15mW und eine Leistungsdichte von 670W/m3 bei ohmscher Beschaltung erreicht werden. Eine selbstversorgende Elektronik wandelt die gewonnene Wechselspannung auf ein stabiles -3V-Potenzial.