Damping of an Oscillatory System with Incomplete Sealing of the Air Cavity by a Magnetic Fluid

Abstract

Purpose. Investigate the damping of an oscillatory system with incomplete sealing of the air cavity with a magnetic fluid.Methods. The study was carried out on an experimental setup developed on the basis of known methods and equipment for magnetic measurements and manufactured independently. A ring neodymium magnet (NdFeB alloy) 60x24x10 mm in size was used as a magnetic field source. The magnetic field strength at the center of the magnet, measured with a TPU-01 milliteslamer, is 220 kA/m. An inductor, a GVT-427B amplifier, and a GwInstek GDS-72072 digital oscilloscope were used to display oscillograms. Samples of magnetic fluid based on Fe3O4 magnetite stabilized with oleic acid were studied. Kerosene was used as the carrier liquid.Results. The results of an experimental study of the elasticity and damping of an oscillatory system with incomplete sealing of the air cavity by a magnetic fluid bridge are presented. The level of sealing of the air cavity varies due to the process of pumping gas through capillaries of various radii. To explain the regularities obtained, a model theory is proposed in the approximation of a viscous gas flow according to the Poiseuille law, and the conclusions of the wellknown theory of sound propagation in molecular acoustics and the theory of sound ducts are also drawn. The relaxation mechanism imposes a restriction on the type of vibrational gas flow through the capillaries, which takes into account the "throughput" capacity of the capillaries. The proposed model explains the presence of a maximum in the dependence of the attenuation coefficient on the capillary radius and its decrease with an increase in the volume (height) of the gas cavity.Conclusion. The proposed relaxation theory of vibrational gas flow through capillaries predicts anomalously large damping coefficients and almost complete damping of an oscillatory system with a magnetic fluid inertial element. The use of the data obtained is advisable in the design of new shock absorbers, since a magnetic fluid damper with capillaries is capable of damping low-frequency oscillations.