Slow steady-state flow of viscous fluid near vibrating cylinders; analytical solution for symmetric channel

Oscillating cylindrical body in a viscous fluid initiates oscillating and not oscillating, slow steady-state creeping, flows. Solution of the creeping flow can be deduced if flow of the ideal fluid is determined. In this paper plane steady-state flow of the ideal fluid past a circular cylinder, placed symmetrically in a channel, is found. The theory of analytical functions and conformal mapping are applie

Analysis of tribological properties of precise contact pairs

The aim of the presented research work is to investigate the possibilities of improving the tribological efficiency of different friction pairs by surface processing to obtain different roughness values and by modifying the friction surface with fluoroligomeric materials. Wear resistance and friction reduction abilities of precise friction pairs could be improved by the modification of their friction surfaces by surface processing to obtain a particular roughness level and by means of surface modification with fluoroligomeric materials. Tribological experiments of sealing friction pairs demonstrate that there is an optimal friction roughness magnitudes which results in the lowest friction coefficient and wear. The use of fluoroligomeric materials in such friction pairs could reduce the friction and wear of the shaft (up to 1,5 times). Fluoroligomeric materials can increase the serviceability of precise plunger pairs and the service life of the dies used for wire tensioning up to 4 - 6 times. These research results are the background to start the investigations aimed at improvement of the tribological properties of different high-precision friction pairs

Modeling of dynamic stability of flexible ultrasonic waveguides

The article considers mathematical model intended for study of dynamic stability and parametric resonance of flexible ultrasonic waveguides for applications in technology and medicine. Considered problem is reduced to the well-known Mathieu equation applied in the theory of dynamic stability of elastic systems. Parameters of the Mathieu equation defining stability of the waveguide are determined by means of finite elements method using ANSYS software and APDL programming languag

Piezo-and pyroelectric GAAS sensors integrated in one crystal with GAAS FET

One of important problems of recent electronics is non-cooled pyroelectric and piezoelectric sensors. They are realized usually in a hybrid integrated chip where thousands of ferroelectric ceramic elements are integrated with transistor matrix. Reported research work is devoted to the possibility of realization of one-crystal pyroelectric sensor. We revealed new effect of symmetry decrease that is used as a basis to develop one-crystal pyroelectric or piezoelectric sensor array using III-V crystals. In feasible sensor devices, the transducer, the amplifier and read-out electronics would be the various parts of one crystal chip. Voltage sensitivity of semi-insulating GaAs-type temperature sensor is the same as one of PZT pyroelectric ceramics. However, proposed device will be fully made from GaAs and related crystal layers by the standard in the micro-electronics technolog

Acoustic emission and methods of its registration (review)

Lately a tendency is observed for the steady growth of requirements applied both to construction materials as well as to the methods of estimation of their reliability and quality. Particular attention is paid to the development of new, physically reasonable criteria of structural durability of materials, based on comprehensive study of the phenomena, which form the basis of processes of deformation and fracture. Such approach is supposed to enhance our understanding of the nature of durability and mechanisms of fracture of materials on different scale levels. This is possible only when analysis of these phenomena is accomplished by means of modern physical research methods as well as applying acoustic emission techniques for diagnostics of the fractures

Identification of Physical and Mechanical Properties of Compound by Solving Inverse Problems

The paper presents a method of identification of physical and mechanical characteristics of the compound (calculated and experimental test method parameters). The idea of the method is that the studied material is connected with other materials, the characteristics of which are well known and differ from the characteristics of the material. Desired physical and mechanical properties should be considered unknown in the proposed calculation model, and the values of the parameters of trial constructions that can be measured accurately with experimental methods in the process of product operation, as well as characteristics of test materials and geometric dimensions of proposed structures are suggested to be placed in the same model as input information

Simulation of oscillation dynamics of mechanical system with the electrorheological shock-absorber

The paper presents the development of mathematical model of oscillating system by taking into account electrorheological (ER) characteristics. Characteristics of the ER shock-absorber (dependences of force on value of control electric signal considering shock-absorber geometry, rod displacement, rheological properties of ER fluid) are calculated. Comparison of simulation results of shock-absorber characteristics with experimental findings is performed. Analysis of calculated relations of amplitudes of output and input signals depending on value of a control electric signal is carried ou

Simulation of oscillation dynamics of vibroprotective system with the electrorheological shock-absorber

The paper presents development of a mathematical model of a three-mass oscillating vibroprotective system with electrorheological (ER) shock-absorber by taking into account influences of temperature and electric field. Performance characteristics of the ER shockabsorber are established including dependences of force on rod displacement for different absorber geometry, rheological properties of ER fluid and magnitudes of temperature and electric field. This research work also provides comparison of simulation results of ER vibroprotective system during its linear movement through road profile “the sleeping policeman” in time domain. Amplitude-frequency characteristics of the vibroprotective system with ER shock-absorber are determined as function of electric field strength and temperature

Electrosensitive glue for vibrotesting of radioelectronic industry items

The possibility of using electrocontrolled glue (ER glue) for fixing radioelectronic industry items during their vibrotesting is discussed. The schemes are presented for fixing items of different materials and shapes to the electrodes of the basic surface of the fixing device. The impact of technological factors is demonstrated to enable us to obtain an increase in the specific fixing force sufficient for mounting the items in order to conduct experiments in the required range of vibro-acceleration