Abstract.The concept of vibration controllability with smart fluids within flexible structures has been in the centre of interest in the past two decades. Although much research has been done on structures with embedded electrorheological (ER) fluids, there has been little investigation of magnetorheological (MR) fluid adaptive structures. In particular, a body of research on experimental work of cantilever MR beams is still lacking. This experimental study investigates controllability of vibration characteristics of magnetorheological cantilever sandwich beams. These adaptive structures are produced by embedding an MR fluid core between two elastic layers. The structural behaviour of the MR beams can be varied by applying an external magnetic field to activate the MR fluid. The stiffness and damping structural characteristics are controlled, demonstrating vibration suppression capabilities of MR fluids as structural elements. MR beams were fabricated with two different materials for comparison purposes. Diverse excitation methods were considered as well as a range of magnetic field intensities and configurations. Moreover, the cantilever MR beams were tested in horizontal and vertical configurations. The effects of partial and full activation of the MR beams were outlined based on the results obtained. Controllability of the beam's vibration response was observed in the form of variations in vibration amplitudes and shifts in magnitudes of the resonant natural frequency.
In this paper, the test results of a prototype hydrodynamic clutch with electrorheological fluid as a working fluid are presented. The hydrodynamic clutch with electrorheological fluid is controlled by flow resistance modulation in the pump and turbine channels created by electrodes connected to a high voltage source. The main aim of the performed study is to investigate practical ranges of the hydrodynamic clutch control by applying an electric field. The test results show that the concept of hydrodynamic clutch control is sound. For the tested clutch both the maximum change of speed and the maximum change of torque during the control are about 80% of the clutch input values.
This article presents the results of experimental investigations and simulations for a new design of a hydrodynamic clutch with a magnetorheological working fluid. The concept of magnetorheological fluid applications to improve the performance of a hydrodynamic clutch can be realized using resistant flow control inside a hydrodynamic clutch channel by changing the fluid shear stress with magnetic fields. The increase in the shear stress of a working fluid under a magnetic field causes an increase in the pressure drop in the channels, an increase in the flow losses, and a decrease in the transmitted power. Moreover, the steady-state and dynamic characteristics of the clutch are presented and the relations that occur between the design parameters are shown.
The article introduces the structure and results of experimental research concerning a specifically constructed combined clutch with an electrorheological (ER) fluid, controlled by changing the strength of electric field. The clutch consists of over a dozen parallelly connected hydraulic clutches with ER fluid. The purpose of the experimental research is to identify the steady-state and dynamic characteristics which are vital in the construction process of the combined clutch, including the selection of the control system. Depending on which singular clutch of the combined clutch construction is the one where the electric field is generated, an increase or decrease of the torque value is obtained.
The paper presents experimental results concerning the wear of heterogeneous electro-rheological (ER) fluids operating as working fluids in a complex clutch system consisting of a hydrodynamic clutch and a cylinder viscous clutch. The change of electric field intensity in the clutches results in change of sheer stress values in working fluids what causes the change of transmitted torque. This work shows that the most important factors affecting the wear of the ER fluid are the electric field of high intensity, the accompanying electrical breakdown, and the high temperature of the silicone oil. In addition, the water from the humid air absorbed mainly by hygroscopic particles influences a significant impact on the wear of the working fluid. Various forms of wear particles of the fluid depending on the prevailing conditions such as working mode are observed from the microscopic aspects. It is observed that the particles are flattened, rolled out or smashed into smaller fragments, partially melted, wrinkled and glued or caked. In addition, it is identified that the partial destruction of silicone oil is occurred due to the damage of the hydrocarbon chains, as evidenced by the decrease in its viscosity and the presence of the particle matter newly containing silicon.
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