Solid State Phenomena Vols. 147-149

Abstract: In this paper, structural sound and vibration control using passive and semi-active shunt piezoelectric damping circuits is presented. A piezoelectric patch with an electrical shunt circuit is bonded to a base structure. When the structure vibrates, the piezoelectric patch strains and transforms the mechanical energy of the structure into electrical energy, which can be effectively dissipated by the shunt circuit. Hence, the shunt circuit acts as a means of extracting mechanical energy from the base structure. First, different types of shunt circuits (such as RL series circuit, RL parallel circuit and RL-C circuit), employed in the passive damping arrangement, are analyzed and compared. By using the impedance method, the general modelling of different shunt piezoelectric damping techniques is presented. The piezoelectric shunt circuit can be seen as additional frequency-dependence damping of the system. One of the primary concerns in shunt damping is to choose the optimal parameters for shunt circuits. In past efforts most of the proposed tuning methods were based on modal properties of the structure. These methods are used to minimize the response of a particular structural mode whilst neglecting the contribution of the other modes. In this study, a design method based on minimization of the sound power of the structure is proposed. The optimal parameters for shunt circuits are obtained using linear quadratic optimal control theory. In general, the passive shunt circuit techniques are an effective method of modal damping. However, the main drawback of the passive shunt circuit is that the shunt piezoelectric is very sensitive to tuning errors and variations in the excitation frequency. To overcome this problem, the pulse-switching shunt circuit, a semi-active continuous switching technique in which a RL shunt circuit is periodically connected to a bonded piezoelectric patch, is introduced as structural damping. The switch law for pulse-switching circuit is discussed based on the energy dissipation technique. Compared with a standard passive piezoelectric shunt circuit, the advantages of the pulse-switching shunt circuit is a small required shunt inductance, a lower sensitivity to environmental changes and easier tuning. Very low external power for the switch controller is required so it may be possible to extract this energy directly from the vibration of the structure itself. Numerical simulations are performed for each of these shunts techniques focusing on minimizing radiated sound power from a clamped plate. It is found that the RL series, RL parallel and pulse-switching circuits have basically the same control performance. The RL–C parallel circuit allows us to reduce the value of the inductance L due to the insertion of an external capacity C. However, the control performance will be reduced simultaneously. The pulse-switching circuit is more stable than RL series circuit with regard to structural stiffness variations. Finally, experimental results are presented using an RL series/parallel shunt circuit, RL-C parallel shunt circuit and pulse-switching circuit. The experimental results have shown that the vibration and noise radiation of a structure can be reduced significantly by using these shunt circuits. The theoretical and experimental techniques presented in this study provide a valuable tool for effective shunt piezoelectric damping.

Abstract: In this article an experiment is described which is included into a course in materials science and allows for better understanding of a nature of sintering. It is a fusion of a computer simulation and a physical experiment – both performed in model systems. Part I of the experiment concerns microstructure of powders. Packing density and coordination numbers of the grains in the sintered powder are analysed with application of computer simulation. In part II of the exercise, the kinetics of the sintering of glass grains is measured via microstructure-evolution observations. The results may be used to discuss the mass transport mechanism.

Abstract: In the present work, laboratory experiments were carried out on the sintering of silicone nitride powder without any sintering additives. Silicone nitride powder was produced at own laboratory conditions by carbothermal reduction-nitriding of silica of which was presented elsewhere. It consists of mainly -Si3N4 (83%) and -Si3N4 (17%) phases with a small amount of minor constituents. Before compaction procedure, the powder was ball milled for 2 h and then 2 gr. of the sample was compacted uniaxially at a pressure of 25 MPa. The green compact was placed into furnace in a graphite crucible. The sintering process was carried out in a programmable muffle furnace at 1700 °C and held for 1 h. with a 20 °C/min. heating rate. The sintered compacts were analyzed using X-ray, SEM, SEM-EDS techniques. The results showed that the formation of liquid phase can accelerate the densification of the compact. The densification of the pure SIALON can be increased by adding of sintering aids that accelerates the formation of liquid phases in the sample. The densified sialons give better hardness and thermal properties of the sample. It was well demonstrated that for the densification of sialons large amount of liquid phase forming oxides are needed to add to initial composition. It is also suggested that there is linear relationships between densification and amount of liquid phase formed in the compact.

Abstract: In this study, two different starting compositions were prepared according to two cation values, and then the mixture was compacted uniaxially in a die and the green compacts were subjected to cold isostatic pressing. They were sintered at 1700 °C and 1750 °C for 30 and 120 min under nitrogen atmosphere. The sintered compacts were analyzed for hardness, densification phase and microstructure. The compacts were analyzed using X-Ray, SEM-EDS techniques. The density of the samples was measured by the Archimedes method. The results showed that starting composition was suitable for manufacturing of Y- SiALON ceramics. The addition of Y2O3 and Al2O3 were resulted in the formation of liquid phase, but alumina was increased the hardness and densification of the compacts. It was also suggested that, for the densification of the Y-SiALON compacts at 1700 °C, is suitable. Above 1700 °C, a shorter sintering time should be used since there was weight loss in the compacts, as a result of the vaporization of nitrogen from the nitrides and oxides structures.

Abstract: General assumptions of educational faculties at universities are specified by the instructions of the Polish Ministry of Science and Higher Education. In this paper, educational standards with the focus on the design subjects for the Mechatronic Faculty have been presented. Taking the instructions of the Ministry into account, the Mechanical Faculty of Wroclaw University of Technology has started the faculty. The studies general timetable has been created and discussed, indicating the position and scope of the design subjects in it. A curriculum of the subject concerning mechanical systems design for the studies has been suggested.

Abstract: Technologies of the Electronics Product Definition - EPD, Product Data Management - PDM and Product Lifecycle Management - PLM represent modern trends in the field of Technical Production Planning and a new quality in this sector. Efficiency of utilization of these technologies for specific manufacturing companies depends materially on correct selection of the system and correct user adaptation of the purchased technologies. The main problem in CR is that the companies do not have adequate knowledge of the issue and therefore the conceptual system of selection does not exist here. And this is why the situation of selection is based as follows: The company addresses the supply house with unclear requirements, is unable to be adequately depth-oriented and selection of the system is in principle carried out by the addressed supply house which results in the danger that the company introduces an expensive system not quite conforming to its character. Instead of the awaited effect the total costs continue rising materially. The methodology of selection of the PDM system should be designed so that the whole process of selection is managed by the company itself and is modified precisely to its requirements. This is the very topic of this paper.

Abstract: Developing technology is leading to cause the new vocational brands. Mechatronic technician is one of the new vocational brands. To find a job for the mechatronic technicians have been taken the most valuable education that comprises knowledge and skill. It is obvious that school-based education is not enough for industry. University-industry collaboration is inevitable for the mechatronic technician. In this study a work-integrated learning (WIL) project between Uludag University Vocational School of Technical Sciences (UUVSTS) and FIAT&TOFAS Co. that is one of the leading automotive companies in Turkey has been carried out in the frame of university-industry collaboration. The main objective of this project is to train technicians in the real working area and in this way to get them vocational qualification meets the industry requirements. In this study a WIL program which is applied in UUVSTS is discussed with technical and social contributions to students and introduced from viewpoint of making an ideal mechatronic program and cooperative education model for vocational schools.

Abstract: In this paper, the multibody approach to design in part environment in parametric CAD systems is described. Different kinds of multibody methods and tools which apply this approach are discussed. Some examples of solid part design performed in SolidWorks 2007 system are presented.

Abstract: Technology of virtual reality made large progress in the last few years. With desktop VR systems it’s possible to present artificial worlds using ordinary PC computer. Creating virtual equivalent of really existing laboratory was major aim of work described in this paper. Also there were created virtual laboratory classes. Application EON Studio from EON Reality was mainly used to achieve this. In this paper a process of building the simulation is presented, used programs are mentioned and final effects are shown.

Abstract: In the paper there is shown the way of increasing the accuracy of the Digital System of Position Measurement with the method of extrapolation. There is also shown the modified algorithm of the program of Digital Position Reading Device.