The performance of magnetorheological fluid in squeeze mode

Abstract

Abstract. In a magnetorheological (MR) fluid, the rheological properties can be changed in a controlled way, the changes being reversible and dependent on the strength of a magnetic field. The fluids have potentially beneficial applications when placed in various geometrical arrangements. The squeeze mode is a geometric arrangement where two flat parallel solid surfaces, facing each other, are pushed towards each other by an external force, operating at right angles to the surfaces. The liquid initially in the gap between them is free to move away from this increasingly small gap, and it does so by flowing parallel to the surfaces, and collecting in a region where it is no longer in the gap between them. The performance of an MR fluid in compression (squeeze) mode has been studied with the magnetic field being generated by a coil carrying different magnitudes of DC electrical current. A test rig was designed to perform this operation with the flat surfaces being horizontal and being pushed together in a vertical direction and the liquid being forced to move in all directions in a horizontal plane. The rig operated by decreasing the size of the gap at a constant rate. For each trial the current in the coil was kept constant and the instantaneous compressive force was recorded. When plotting compressive stress against compressive strain for each trial, the slope of the curve was found to be larger in general when the current was larger. This was an expected result; however the behaviour is more complicated than this. For a significant range of values of the compressive strain, the slope falls to zero, so that the compressive stress shows no increase during this period, while the compressive strain continues

On the validity of continuous media theory for plastic materials in magnetorheological fluids under slow compression

“…A field dependence of H 0.91 was found for compression in contrast to the H 1.4 dependence observed under shearing. Constant area squeeze flow MR experiments were carried out by Mazlan et al (2007Mazlan et al ( , 2008. More recently, Gstöttenbauer et al (2008) designed a test rig to explore the flow behavior of MR fluids under sinusoidal loading modes.…”

Observations of MR Fluid Clumping Behaviour in a Squeeze-Mode Damper

“…The studies exploring MR fluids in the squeeze mode and the involved phenomena are but a few. For example, (Mazlan et al, 2007;Farjoud at al., 2009a, b) revealed that MR fluids can provide a much larger range of controllable force in small operational envelopes compared to flow and direct shear modes. Systematic investigation of MR fluids reported in squeeze mode research described in (Mazlan et al, 2012) showed that the fluids experienced rheological changes in three stages during compression and tension and that fluid-particles separation phenomenon was the main cause of the unique behaviour of MR fluids.…”

A State-of Art of Creative Sensor Devices Utilizing Magneto- Rheological Fluids

“…The basic properties and behaviour of MR fluid in shear mode actuation and damping are completely studied and reported [37][38][39][40]. The most powerful mode of operation of MR fluid is squeeze mode but relatively not much literature is reported [41,42]. The behavior of MR fluid is commonly represented as a Bingham -Plastic model having a variable yield stress τy, depending on the magnetic field H Where τ y (H) is the magnetic field dependent shear mode yield stress of the MR fluid, µ is the fluid viscosity and γ is the shear rate.…”