Evguenia V Korobko

On damping vibrations of three-layered beam containing magnetorheological elastomer

In this article, we present the results of investigations of viscoelastic properties of magnetorheological elastomer containing carbonyl iron particles. Frequencies of natural vibrations of three-layered beam, supporting constructions of which are made from aluminum, and the inner layer—from magnetorheological elastomer—are calculated, and the dependence of vibrations on induction of the applied magnetic field is obtained. Nonstationary vibrations of the beam at pulse impact of magnetic field are found.

The effect of the synthesis conditions of aluminum-modified nanosized titanium dioxide on the efficiency of its use in electrorheological dispersions

A comparative study of the physicochemical properties of nanodispersed TiO2 samples synthesized from TiCl4 by the sol–gel and coprecipitation methods has shown the advantages of the former from the points of view of both the specific surface area and electrorheological response of the obtained filler in 5% electrorheological dispersions. A correlation has been revealed between the temperature of TiO2 treatment (600–800°C) and its structure, phase state and electrorheological response. The maximum shear stress increment has been observed for dispersions of TiO2 samples that contain 7–10 mol % Al and have been thermotreated at 700°C for 3.0–3.5 h.

Acoustical properties of magnetorheological fluids under applied magnetic field

This work is devoted to the experimental study of acoustical properties of magnetorheological fluids subjected to magnetic field. Evaluation of the change in velocity of ultrasonic waves and attenuation coefficients in magnetorheological fluids based on synthetic oil and carbonyl iron versus magnitude and angle φ between wave vector and intensity direction of applied magnetic field has been carried out by pulse-phase method at 1.52 and 2.5 MHz. It was found that the anisotropy of attenuation coefficient was ~5–6 dB/cm and the velocity of ultrasonic waves was up to ~1%−2% that is much more than in specimens of colloid solutions—magnetic fluids with the same dispersive phase content.

Synergistic effect in magnetoelectrorheological fluids with a complex dispersed phase

In this article, the results of investigation of structural interactions, generated by simultaneous impact of electric and magnetic fields on fluids containing a two-component dispersed phase, are presented. Dielectric, magnetic, and rheological characteristics of these fluids are considered. The characteristic features of the formed structures depending on the filler type, deformation conditions, and intensity of application of external fields are discussed.

Study of electrorheological sensitivity of suspensions based on hydrated aluminum oxides

The electrorheological fluids with the disperse phase formed by the particles of hydrated aluminum oxides prepared by the chemical precipitation from aluminum-containing solutions and subjected to heat treatment at different temperatures are studied. It is shown that the electrorheological activity of suspensions depends on the chemical and phase compositions of the dispersed phase. The influence of water, whose different forms comprise hydrated aluminum oxides, on the manifestation of the electrorheological effect of suspensions is estimated. It is established that the maximum gain in the effective viscosity of electrorheological fluids is related with water molecules forming hydrogen bonds in the interlayer space of the boehmite lattice.

Research of the influence of dissipative heating on the performance characteristics of electrorheological shock absorbers

The results of measurements (the dependences of temperature of the central part of the external surface on time; the dependences of the resistance force on the amplitude and frequency of motion of the rod of a electrorheological shock absorber) have shown that pressure drop in the annular channel and damper force of electrorheological shock absorbers are reduced on dissipative heating of an electrorheological fluid. A comparison of the performance characteristics of the developed shock absorber and a hydraulic passive shock absorber, and also with controlled shock absorbers of similar design but from two manufacturers of other countries, is carried out.

Physicochemical and electrorheological properties of titanium dioxide modified with metal oxides

The properties of electrorheological fluids containing dispersed phase of titanium dioxide nanoparticles prepared via the sol-gel method and modified with metal oxides have been studied. Titanium dioxide has the anatase structure with crystallite sizes of 8–10 nm and a specific surface area of 90–140 m2/g. It has been found that the magnitude of the electrorheological response of the filler is determined by the specific surface area and the content of a modifying component. The strongest electrorheological response has been revealed for titanium dioxide modified with aluminum oxide at an Al content of 6.5–7.0 mol % relative to TiO2.

Vibration Control of Oscillating System Based on Governing Visco-Elastic Characteristics of Absorber by Means of External Electric Signal

Electro-rheological fluids (ERF) allow us to create «smart» devices. One of the basic directions of application of such materials is damping in oscillating systems. This work describes simulation model and offers the results of experimental research by rheological properties and damping characteristic of ERF. Control signal is defined by electric field intensity, which is changed within the bounds of 0…0.5 kV/mm. Amplitude of oscillation – up to 5 mm, oscillation frequency is modified within the bounds of 0.5…5 Hz. The logarithmic damping decrement and natural oscillation frequency of oscillating system, shear stress and viscosity of ERF are determined.

Specific features of non-Newtonian magnetorheological fluid flow in the workpiece–instrument gap of a polishing facility:

The model of magnetorheological polishing fluid flow has been developed in the form of a jet formed in the gradient magnetic field in the gap between the workpiece and the instrument of a polishing facility. The model allows one to determine the shape of the transverse and longitudinal sections of the jet and the pressure acting on the workpiece surface being polished, while accounting for the known configuration of the gap and magnetic field strength distribution. The appearance of the nose surf and the stern concurrent wave producing an additional pressure drop in the workpiece–instrument gap has been established. The solution of the Navier–Stokes equation in the approximation of lubrication for magnetorheological polishing fluid with boundary conditions accounting for the action of inertial forces has shown that in the inlet section of the gap the pressure drop is positive, and the velocity profile is almost flat near the workpiece, whereas closer to the outlet from the gap, the pressure falls below the atmospheric pressure. The pressure is maximum at the forward edge of the workpiece, as in the case of the well-known phenomenon of hydroplaning.

Electro- and Magnetosensitive Adhesive Compositions

Special fixing devices have been developed for fixing articles. With the use of external fields, they allow one to realize reversal fixing of articles made from both metal and dielectric materials. The present investigations were aimed at creating controllable materials for fixing articles of electronic engineering and at developing efficient devices for the technology of vibrotesting.