Lubrication Property of Magnetorheological Fluid With Nano-Silica Additives Under Magnetic Field

Magnetorheological(MR)fluid is colloidal suspension and stiffens into semi-solid when subjected to a magnetic field.In order to investigate the effect of magnetic field on lubrication property of MR fluid with nano-silica additives,a pin-on-disc tribometer is used to carry out friction and wear experiment of steel under the magnetic field.The MR fluids with different additive concentrations are prepared and their theological properties are examined via a rotational rheometer.Different lubrication performance of the MR fluid with nano-silica additives with and without magnetic field is presented.In addition,through observing the morphology and analyzing the elemental composition of the worn surfaces,the effects of additives on the lubrication property are investigated.

Experimental Study of Material Removal Process of Fused Silica Glass Using MR Jet Polishing System

Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitable means of polishing complex shapes is to use a jet of abrasive fluid.However,aerodynamic disturbances and radial spreading are generated by the unstable polishing process of the jet on the surface of the workpiece when it is being polished.A method of jet stabilization has been proposed in which the original nozzle form of a jet of magnetorheological(MR)fluid contains abrasive particles that are magnetized using a magnetic.This paper details the design of an MR jet polishing system that uses an electromagnet,a nozzle,and a hydraulic unit to stabilize a slurry jet based on MR fluid, Second,for silica glass,the polishing spot and section profile are analyzed and the effect of the MR fluid jet polishing process is evaluated.The results of the experiment show that the removal profile is W-shaped and that,in this case,a stable can be proof of a distance of several tens of millimeters from the nozzle.Such results show the possibility of applying the proposed polishing method using MR fluids in ultra-precision micro and optical parts production processes. MR jet polishing shows great potential for use as a new type of precision surface polishing technology.In particular,this is a highly valuable process for the polishing of complex shapes such as micro parts,concaves parts,and cavities.

Rheological Properties and MR Polishing Characteristics of Core Shell-Structured Silica-Coated CI Particles

Recently,ultra-precision polishing processes using smart materials such as magnetorheological(MR)fluids have been used for optics parts such as aspheric lenses.The MR fluid applied in MR polishing is a phase controllable suspension comprising a mixture of CI particles and non-magnetic fluids such as mineral oil and water.The fluids are a kind of smart material that can be controlled according to their flow properties such as viscosity and stiffness. Water-based MR fluids are easily oxidized if the fluids are exposed and this oxidation can bring irregular polishing results. Also,this phenomenon is one of several factors that reduce the life time of MR fluids.In a previous work,CI particles were coated with a polymer or a composite for the improvement of dispersion stability and prevention of corrosion due to oxidation.From this study,the rheological properties such as viscosity and sedimentation of coated CI particles with silica were investigated with a rotational rheometer;MR polishing characteristics of BK7 glass were studied in order to investigate the surface roughness.The wheel speed and magnetic field intensity were chosen as variables.

An Evaluation of the Machinability of Nitinol SMA Using Combined Process of EP and MR Polishing

Nitinol,a shape memory alloy(SMA),is manufactured from titanium and nickel.It is employed in various fields for use in devices such as micro sensors,ultra-precision devices and satellite wings.It is highly recommended as a material in medical stents for insertion into the body because it has excellent organic compatibility.However,because they are intended to be inserted into the human body,products such as medical stents require a high-quality surface.Because nitinol has more of the characteristics of titanium than of nickel,one of its drawbacks is that heat generated in nitinol during machining is not discharged smoothly,leading to areas of inner stress which occur when traditional machining methods are used.To overcome this difficulty,various non-traditional machining methods,including non-contact machining,have been investigated for use with nitinol.This study is focused on the application of an effective fabrication method that combines electrolytic polishing(EP)and MR polishing to improve the surface integrity of nitinol through a series of experiments.Surface roughness variations of the polished nitinol were investigated by changing the imposed polishing conditions of EP and MR polishing,respectively.Finally,the variations in the surface roughness were observed with polished previously performed via the EP process.

Optimal Design of Bobbinless Rotary Magnetorheological Material Based Brake

The paper presents a novel configuration in order to improve the compactness and manufacturing cost of magneto-rheological material(or fluid)based brakes(MRB in short).In conventional configurations of MRBs,the coil is normally wound on a nonmagnetic bobbin which is placed on the housing.This causes difficulties in manufacturing of the brake and the bottle-neck problem of magnetic circuit.In the proposed configuration,the coil is wound directly on the inner cylinder of the housing.In this case,the inner cylinder of the housing should be designed in a special shape that maximizes the magnetic flux across the MR fluid(MRF)duct.After proposing of the new configuration of the MRBs,the modeling of the MRBs is performed based on Bingham rheological model of the MRF.An optimal design of the proposed MRBs and conventional MRBs is then performed based on finite element analysis results of magnetic circuit of the MRBs.A comparative work between the optimal parameters of the proposed MRBs and conventional MRBs is conducted and the advanced performance characteristics of the proposed MRBs are investigated.