Abstract
The understanding of the tribological behavior of magnetorheological fluids is crucial for many applications, in particular for those related with high quality surface finishing. In this contribution, we describe a thorough experimental investigation on the tribological properties of magnetorheological (MR) fluids in poly(methyl methacrylate) (PMMA) point contacts. First, magnetic iron oxide particles with diameters of approximately 0.4, 1,3 and 2.0 µm were prepared using wet chemistry procedures. Then, MR fluids were formulated by dispersion of the magnetic particles in glycerol/water mixtures. The tribological experiments were run in a PMMA ball-on-three plates tribometer and Stribeck regions were identified for a wide range of sliding speeds. The wear tracks were also visualized in a confocal microscope to correlate them with friction coefficient data. The results show the effect of both particle size and applied magnetic field in the friction coefficient and wear scar volume, suggesting a slight decrease on the wear process when the magnetic field is present.
Highlights
Magnetic suspensions and colloids are defined as dispersions of relatively small magnetic particles in non-magnetic liquid carriers
We studied the effect of particle size on the tribological behavior of model MR fluids
The tribological behavior of MR-fluid-lubricated poly(methyl methacrylate) (PMMA)–PMMA point contacts was compared in a custom-built experimental set-up, both in the absence and in presence of magnetic fields
Summary
Magnetic suspensions and colloids are defined as dispersions of relatively small magnetic particles in non-magnetic liquid carriers. If we take into account the magnetic particles’ dimensions, two main types can be distinguished: 1- ferrofluids (FF) and, 2- magnetorheological (MR) fluids The former (FF) are, by definition, made of monodomain magnetic particles in the range of few nanometers (from 1 up to 20 nm diameter, approximately), whereas the later are prepared with multidomain magnetic particles (from 1 μm diameter and above). In this regard, magnetic particles with different sizes result in massive differences in the mechanical properties of the suspensions; while FF remain as a liquid when magnetic fields are applied (or absent), MR fluids show a clear “liquid-to-solid” transition when they are magnetized (Odenbach and Thurm, 2002; Park et al, 2010; de Vicente et al, 2011). Controlled abrasion using magnetorheological fluids has been previously studied. Duradji et al (2016) have shown, for instance, that magnetite particles dispersed
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