Dynamic and wear study of an extremely bidisperse magnetorheological fluid

Acceso a la versión publicada en Smart Mater. Struct. 24(12) 127001 (http://iopscience.iop.org/0964-1726/24/12/127001)"This is an author-created, un-copyedited version of an article accepted for publication/published in Smart Materials and Structures. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0964-1726/24/12/127001."In this work the friction and wear properties of five magnetorheologicalfluids (MRFs)with varying compositions are investigated. Considering that many of the proposed applications for these fluids involve lubricated contact between mobile metal –metal or polymer– metal parts, the relationship between MR response and wear behavior appears to be of fundamental importance. One of the fluids(MR#1)contains only the iron microparticles and base oil; the second and third ones(MR#2 and MR#3) contain an anti-wear additive as well. The fourth one(MR#4)is a well known commercial MRF. Finally, MR#5 is stabilized by dispersing the iron particles in a magnetite ferrofluid. The MR response of the latter fluid is better(higher yield stress and post-yield viscosity)than that of the others. More importantly, it remains(and even improves)after the wear test: the pressure applied in the four-ball apparatus produces a compaction of the magnetite layer around the iron microparticles. Additionally, the friction coefficient is larger, which seems paradoxical in principle, but can be explained by considering the stability of MR#5 in comparison to the other four MRs, which appear to undergo partial phase separation during the test. In fact, electron and optical microscope observations confirm a milder wear effect of MR#5, with almost complete absence of scars from the steel test spheres and homogeneous and shallow grooves on them. Comparatively, MR#2, MR#3 and, particularly, MR#1 produce a much more significant wear.MINECO Ramón y Cajal Programme (RYC-2014-16901)MINECO FIS 2013-07666-C3-1-RCEI Biotic BS27.2015Junta de Andalucía, PE2012-FQM-069

Rheological Properties of Magnetorheological Polishing Fluid for Micro Mould Polishing

Complex surface features such as micro-grooves on micro mould which was produced by the micro-milling process have a significant problem of raised edge or top burr formation. This problem can be solved by using magnetorheological polishing (MRP) technique. MRP capable to produce ultra-fine three-dimensional profile structures. However, a tailored magnetorheological polishing fluid (MRPF) need to be used. This paper presents the effects of MRPF mixture components on their rheological properties. D-optimal mixture design of experiment was used to formulate the MRPF with various composition. The MRPF samples than analyzed using MCR Rheometer for rheological properties. It is found that each MRPF component composition has a significant effect on rheological properties. The result indicates that an optimum composition of MRPF to meet the MRP requirement is by having a volume percentage of carbonyl iron particle (CIP) and abrasive particles at 35% and 10% respectively. The finding of this study produced a significant statistical model of MRPF composition that beneficial for micro mould polishing technology