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The Study of Behavior of Vibrating Systems Controllable by Devices with Rheological Fluid

Szary M. L., Weber P.

Archives of Acoustics

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2013

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Vol. 38, No. 2

217--222

EN

The nonlinear mathematical model of behavior of controllable viscosity fluid (CVF) under applied external field is presented. A large family of these fluids is commonly used to control responding forces of dampers in vibration control applications. The responding force of a damper with CVF has two components. The first one - uncontrollable - is proportional to the viscosity of a base fluid and velocity of its motion, the second one, which is controllable, depends on the strength of the applied external field. Both are involved in the process of dissipation of unwanted energy from the vibrating systems. An equivalent damping factor based on the principle of energy dissipated during one cycle of damper work under a constant strength external field was calculated. When mass or stiffness is variable the equivalent damping factor can be set accordingly by adjusting the strength of external field to have vibrating damped system purposely/continuously working in the critical or other chosen state. This paper also presents cases of applying periodically changing strengths of an external field synchronized with cycles of periodical motion of the vibrating system to continuously control the damping force within each cycle.

2

Noise Variability in Underground Room and Pillar Coal Mines

Szary M. L., Chugh Y. P., Hirschi J.

International Journal of Occupational Safety and Ergonomics

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2011

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Vol. 17, No. 3

301--308

EN

Noise in an underground coal mine has dominant components generated mainly from 3 sources: (a) continuous mining machines, (b) roof bolters, and (c) cars/vehicles used to transport personnel and/or coal. Each of these 3 noise sources also has a number of well-defined sub-sources with their own noise characteristics. Sound level meters were used to collect noise data in the form of instantaneous readings and also to check calibration of other sound measuring instruments. The most useful information was obtained from a spectrum analysis of continuous digital recordings of noise over time. This paper discusses the variability or dynamics of generated noise in both frequency and time domains in relation to several independent variables related to coal extraction and transportation processes.

3

The phenomena of electrorheological fluid behavior between two barriers under alternative voltage

Szary M. L.

Archives of Acoustics

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2004

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Vol. 29, no. 2

243-258

EN

Electrorheological (ER) fluids placed between two barriers have the ability to change some of their physical properties like the apparent viscosity and modulus of elasticity when an external electrical field is applied. Early investigations of the sound transmission loss (STL) under DC voltage showed that a normal stress that develops in ER fluid in response to an electrical field has a significant influence on the magnitude of STL. The tangentional (shear) stress had only a negligible effect on the STL. The aim of this study was to investigate the STL using a two-barrier system with ER fluid placed between them, and subjected to alternative voltage. The STL was investigated for various kinds of ER fluids in the presence of the variable alternative electric field density. The results showed that the STL had decreased with the increasing electric field density.

4

Experimental study of sound transmission loss in electrorheological fluids under DC voltage

Szary M. L.

Archives of Acoustics

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2002

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Vol. 27, no. 3

229-240

EN

The electrorheological (ER) liquids possess the ability to change their physical properties like the apparent viscosity and modulus of elasticity which is related to stiffness under influence of external electric field. They serve successfully in the field of semi-active/active vibration control - as well as in many other areas. The STL was investigated for various kinds of ER suspensions in the frequency range from 100 Hz to 2 kHz. An influence of the electric field density on the STL was different for normal and tangential sound wave propagation. In both cases the STL decreases with the increasing electric field density. Those properties can be potentially useful in sound propagation control applications.