Dorina Popovici

Analysis of the electrical steel single strip tester measurement repeatability

Measurement performance evaluation is important, because measurement results depend usually on the method used for measurement. The analysis of the repeatability has to be made under some exact conditions: the same measurement procedure, observer, measuring instruments. Also using the same laboratory and conditions, the measurements must be repeated over a short period of time. Usually, repeatability could be expressed and put in evidence in terms of the dispersion characteristics of the results. In this paper, it was study the repeatability of the measurements, done with a Brockhaus single strip tester on silicon iron alloy. The samples cut at 300 mm × 30 mm were characterized at three peak magnetic polarizations Jp = 40, 250, 900 mT, and at three frequencies f = 10, 50, 1000 Hz. Each measurement was repeated five times, and the specific power loss values were recorded and analyzed.

Electrical characterization of TiO2 nanotubes synthesized through electrochemical anodizing method

In the present paper, the electrochemical anodizing method was used for the obtaining of TiO2 nanotube layers, developed on titanium surface. Self-organized titanium nanotubes were obtained when an aqueous solution of 49.5 wt % H2O – 49.5 wt % glycerol – 1 wt % HF was used as electrolyte, the anodizing time being equal to 8 hours and the applied voltage to 25 V. Scanning electron microscopy shows that the one-dimensional nanostructure has a tubular configuration with an inner diameter of approximately 60 nm and an outer diameter of approximately 100 nm. The electrical properties of these materials were analyzed through dielectric spectroscopy method.

Analysis of the External Magnetic Field Influences on the Measurements Realized with a Single Strip Tester (SST) Using Finite Element Modeling

In this article it was studied the magnetic influence of an electromagnetic coil on the measurements, realized with a single strip tester. One major difficulty in modeling of the magnetic materials is the magnetic hysteresis. As a consequence, it was used the Frohlich-Kennelly model for defining the hysteresis of the soft magnetic material, from which is manufactured the magnetic core of the electrotechnical devices. A numerical study, based on finite element analysis, is proposed in order to model a Single Strip Tester (SST). For this it was made a geometrical description based on technical data of a SST developed by Brockhaus Messtechnik, which measures magnetic properties of silicon iron strips with an area of 280 × 30 mm2.

Analysis of the stress-strain state in single overlap joints using piezo-ceramic actuators

In this paper is presented a 2D approach to finite element modeling and an analytical calculus of a single lap bonded joint. As adherent material were selected a sheet of wood, aluminum and titanium. For adhesive part were selected Bison Super Wood D3 in case of the wood single lap joint and an epoxy resin type DGEBA-TETA for gluing together aluminum and titanium parts. In the article is described a combined method, which consists in the placement of the piezoelectric actuator inside of the adhesive part, in order to determine the tensile stress in the overlap joint. A comparison between the analytical and numerical results has been achieved through a multiphysics modeling - electrical and mechanical coupled problem. The technique used to calculate the mechanical parameters (First Principal Stress, displacements) was the three-point bending test, where different forces were applied in the mid-span of the structure, in order to maintain a constant displacement rate. The length of the overlap joint was modi...

A Combined Model for the Stress State Evaluation in Single Overlap Joints Using Piezo-Ceramic Actuators

In this paper is presented a 2D approach to finite element modeling of a single lap bonded joint. As adherent material a sheet wood was selected and as adhesive, Bison Super Wood D3. In the article a combined method is described, consisting in the placement of piezoelectric actuators on the surface of bonded joint, in order to determine the tensile stress in the overlap joint. A comparison between the experimental, analytical and numerical results has been achieved through a multiphysics modeling - electrical and mechanical coupled problem, in order to evaluate the experimental outcomes. The experimental technique used to measure the mechanical parameters (displacements) was the three-point bending test, where different forces were applied in the mid-span of the structure, in order to maintain a constant displacement rate. The length of the overlap joint was modified from 20 to 50 mm.

A FEM Model to Analyze the Structural Mechanical Problem in an Electrostatically Controlled Prestressed Micro-Mirror

In many industrial and biomedical applications (laser scanning displays, optical switch matrices and biomedical imaging systems) the sensing and actuation components are realized using micro-mirrors fabricated by MEMS technology. In this paper is evaluated, through numerical methods, the structural mechanical properties of the actuation mechanism of a ring shape micro-mirror. For the lift-off of the structure there are used four springs simulating a prestressed cantilever beam.