Solid State Phenomena Vols. 147-149

Abstract: The paper is devoted to an investigation of a Radio Frequency (RF) measuring-control system equipped with sensors and actuators distributed along the cable. Displacement, acceleration and strain sensors together with an actuator and PWM type control signals can be used. This system is configured to operate with the experimental setup specially developed to study MR damper performance for vibration suppression of cables. The RF measuring-control system structure, transmission protocol and radio disturbances problem are discussed. The experimental results for the cable laboratory system are presented.

Abstract: The purpose of this article is to measure fluid pressure drops against the changing velocity on the critical points of the fluid system by using mechatronics equipments and techniques. Critical points of the fluid system to be measured pressure drops are gate valve, globe valve, flow control valve, sudden enlargement, 45 or 90 junctions etc. Pressure drops occurs mentioned areas much more than other parts of fluid system. Pressure drop is directly concerning with flow rate of fluid. It was used venture-meter and orifice-plate to measure flow rate and fluid velocity in pipe. Pressure transmitters were used to measure pressure drops on the critical points of fluid system in according to changing flow rate of fluid. Pressure transmitters produce analog signals between 4-20 mA in according to changing pressure of fluid in pipe and analog input signals are interpreted through an A/D device, and is originate from pressure sensors. All the received data from pressure transmitters are transferred to computer via A/D cards. Received data from pressure transmitters is evaluated by using developed program to measure fluid friction losses with changing pressure differences and flow rate, velocity of fluid, Reynolds number, fluid type and some values can be seen on the screen of computer in real time.

Abstract: In this paper the reverse modelling process for mapping and reconstructing the geometric characteristics of element with free-form surfaces as virtual CAD model is described. The basic approach in reverse modelling process in middle range standard parametric 3D modeler such as SolidWorks system is presented. The digitizing process was performed on the coordinate measuring machine. Using surface-solid modelling tools the virtual solid models were created. They are based on prepareing 3D curves from cloud of points as a sectional profiles. As the next step, it is possible to realize various CAx applications based on 3D feature-based model. In our case an abrasive wear of rotor blade was estimated.

Abstract: The paper presents results of experimental measurements of the parameters of rowing process when rowing in a river, on the pool-type training facility and on “Concept II” rowing machine. The comparison of results of measurements showed the significant difference of rowing force generated by rowing in the machine and in the boat, thus the novel training facility is proposed having the hydrodynamic loading unit equipped with proportional flow control valve controlled by computer evaluating parameters of rowing, which is able to ensure loading on the oars more adequate to the real rowing conditions.

Abstract: This paper presents a modeling technique based on the integration in the classic deterministic simulation methods of probabilistic computational techniques such as uncertainty analysis and sensitivity analysis. As study case, it is presented a micro-comb resonator that is actuated electrostatically to vibrate in the plane parallel to the substrate. A deterministic Finite Element coupled electromechanical analysis is performed to evaluate the mode shapes and the corresponding eigenfrequencies of the mobile mass and afterwards a Monte Carlo simulation is used to determine the dispersion of the eigenfrequency of the mode shape of interest in function of the variations of the input parameters. The scatter of the results is analyzed and then it is presented a sensitivity analysis for establishing which of the input parameters have more influence on the variability of the microresonators performance.

Abstract: The first part of the paper treats the general problems concerning the shape memory alloy actuators and their operation principle. Then, our work referring to the developing a modular family of linear and rotational actuators, realized in many typo dimensions, in a compact design, with facile connection with the actuated mechanisms and supplying module is presented. The active elements of these actuators are shape memory alloy wires, ribbons and helical springs. The influence of the geometry of the active elements on the time response is studied. The most important solutions to reduce the resistive heating time of active elements and to improve the time response on cooling are identified.

Abstract: The paper presents results of research on the influence of regenerative heat treatment on structure and properties of G17CrMoV5 – 10 cast steel. Investigated material was taken out from a turbine frame serviced for over 250 000 hours (total service time) at the temperature of 535 oC. The cast steel after service revealed degraded bainitic-ferritic structure and was characterized by mechanical properties ranging below norm requirements. It has been proved that high tempering temperature in the case of cast steel with bainitic structure ensures optimum combination of mechanical properties and impact energy. It has also been shown that ferrite has a negative influence on impact energy of the cast steel with bainitic-ferritic structure.

Abstract: A series of amorphous hydrogenated carbon layers doped with nitrogen (a-C:N:H) was deposited on Si (001). The synthesis was performed from gaseous N2/CH4 mixture using PE CVD (RF CVD technique; 13,56 MHz). An influence of the processing conditions on layer-growth rate was analysed. Thickness of the layers deposited during 1 hour at various temperatures, pressures and RF powers were taken as a basis. It has been proved that the substrate temperature is a key parameter for the layer formation. Temperature rise results in the deposition rate decrease. This unfavourable effect may be reduced by application of increased gas pressure and/or higher plasma RF generator power. At optimal conditions (46 oC; 0,8 Tr; 60 W) the deposition rate reaches up to 600 nm/hour. FT-IR spectra of the layers were measured within 1250 - 4000 cm-1 and discussed with regard to the atomic structure. The intensities of the characteristic absorption bands were compared. The results show that the layers have various N/C ratios according to the applied processing conditions.

Abstract: Heat-resistant and high-temperature materials are used to manufacture components, devices, and systems operated at high temperatures, i.e. under severe heat loads. Gas turbines used in the power industry, the traction, marine, and aircraft engines, the aerospace technology, etc. are good examples of such systems. Generally, as the temperature increases, the mechanical strength of materials decreases. While making such materials, there is a tendency to keep possibly low thermal weakening. In the course of operating gas turbines, various kinds of failures/defects/ damages may occur to components thereof, in particular, to blades. Predominating failures/damages are those attributable to the material overheating and thermal fatigue, all of them resulting in the loss of mechanical strength. The paper has been intended to present findings on changes in the microstructure of blades made of nickel-base alloy due to high temperature. The material gets overheated, which results in the deterioration of the microstructure’s condition. The material being in such condition presents low high-temperature creep resistance. Any component, within which such an effect occurs, is exposed to a failure/damage usually resulting in the malfunctioning of the turbine, and sometimes (as with aero-engines) in a fatal accident. Failures/damages of this kind always need major repairs, which are very expensive.

Abstract: In this article, Turkish chromite concentrate was reduced with metallurgical coke at temperature between 1000-1500 °C with variables reducing times. The reduction mechanism and the microstructure of the reduced chromite were investigated. There were closer relationships between the reduction of chromite and the sample morphology, such as, the surface area and the porosities and cracks of the particle have positive effect on the metallization of iron and chromium oxides. The reduction of the iron chromite spinel started at 1000 °C, but picrochromite started to reduce at temperature around 1300 °C. At lower temperature, the formation of iron carbide phases was affected on the formation of ferro alloy and accelerates the reduction of chromium. The formation of carbon monoxide was also affected on the reduction of chromite spinel, especially around imperfections of grain where porosity, cracks and fractures act as diffusion channel for the reducing gas. For the charecterisation of the reaction products, X-ray diffraction techniques, SEM and EDAX were used.