The data of previous researchers on the structure formation of electrosensitive suspensions under the action of an external electric and on the resulting changes in the mechanical parameters of the medium (viscosity, plasticity, resilience) were used to develop a method of damping in a special cluthes, which were used for fixing thin-wall constraction, that surfaces are to undergo fine turning. As demonstrated, the use of a fluid, the structure of which responds to an electric field, as a cluthing layer improves the technological characteristics of the product and increase its reliability.
The present work is aimed at elucidation of the specific features in propagation of ultrasound waves in an electrostructurized medium, of their dependence on an applied electric field and implementation of the effects obtained in practice. In experiments, the use was made of electrosensitive liquid interlayers, which manifest the essential dependence of viscoelastic-plastic properties on a magnitude of an electric field applied to shear macroflows. The basis of a homogeneous suspension was the transformer oil, to which the finely divided silica powder, the corresponding surfactant and activator were added. To determine the velocity of ultrasound propagation in liquid media, the time of ultrasound signal propagation was compared with the delay time of the reference signal in the standard delay line.
The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.
The effect of temperature on the behavior of nonlinear viscoplastic, low-concentration suspensions of diatomite in transformer oil in strong electric fields in the presence of vibration is investigated experimentally. Temperature has proved to control the electrophysical and cross-linking properties of the test fluids.
Fluid disperse systems, sensitive to the external electric field-electrorheological fluids, are finding increasing use in various areas of industry and technology. Their physicomechanical, electrophysical characteristics determine the valuable specific properties of the materials with assigned structure, obtainable with everwide use of electric fields, which makes it possible to substantially enhance efficiency and productiveness of technological processes and to improve the control of operational regimes of the equipment which employ fluid disperse media. The present investigations has been undertaken with the aim of studying thermophysical properties and rheophysical behavior of low-concentration ER- fluid (diatomite in transformer oil) at different temperatures. It was shown that the electric field, which changes considerably the structure of electrorheological fluid, influences effective thermal conductivity and diffusivity coefficients. Their increase with electric field intensity and the increase of the effective viscosity with temperature are connected with the increase of the conductive component of the overall heat transfer through the contact spots between the solid particles, and with intensification of electric convection in the spaces between the dispersed particles.
The increased requirements on the accuracy of measurements with the aid of large-weight electronic-optical devices have entailed heavy demands for their efficient protection against low-vibration vibrations produced by an occasional external load or operator's pushes. In these cases, the means of active protection against vibrations used, e.g., in adjustment stands are considered to be the most efficient ones. Among actuating mechanisms of such systems, i.e. hydro- and pneumohydraulic, electromechanical and friction devices, the viscous-friction dampers show much promise since use of electrorheological fluids in the latter allows their functional capabilities to be extended owing to control of the elastoviscous parameters of a working fluid. An analysis is made of vibrations of a single-mass system (an electronic microscope column) whose vibroprotection scheme includes four ER-dampers. Their control is accomplished by a voltage unit in discrete as well as in follow-up linear and logarithmic regimes. The results obtained are compared with experimental data for the systems without dampers, with passive dampers and controllable ER-dampers. The latter are shown to be advantageous, in particular, a three- fold decrease of the Q-factor of the system under forced vibration is reached in the optimum control.
Based on a dependence of the high-concentration ER-fluid parameters (viscosity, elasticity) on an electric intensity and mechanical load-dependent characteristics, a theoretical analysis is made of an oscillatory single-mass system with electrorheological dampers. The results of an analytical solution of the equation of motion, calculation results are compared with experimental data on the mechanisms responsible for variation of the damping characteristics (damping decrement, transfer coefficient) of a vibroprotection system for the precision equipment. It is shown that for effective damping it is necessary to apply an electric field of low and moderate intensities (E less than 1 kV/mm). In this case, an increment of the effective viscosity of the ER-fluid is high and the natural frequency does not attain its maximum. This finding has been employed for designing a special-purpose controllable high-voltage source used in an active vibroprotection system for low-frequency and small-amplitude strains.
The data of previous researches on the structure formation of electrosensitive suspensions under the action of an external electric field and on the resulting changes in the mechanical parameters of the medium (viscosity, plasticity, resilience) were used to develop a method of pendulum damping in a damping element of a seismoreceiver. The design of a seismoreceiver is described in which the medium serves both as a sensor and an output regulator. An automatic correction system ofpendulum damping in the seismoreceiver is developed on the basis of the algorithm which relates variations of the viscosity due to temperature changes and input power conditions with the electrical control signal.
Keywords: seismoreceiver, electrorheological fluid, vibration, damping, viscosity
The results of an experimental study of the electrorheological sensitivity of dispersions based on a fibrous filler in a mineral oil are reported. A comparison is made with the powder analog-based ERS.