Yoichi Akagami

Characteristics of magnetic compound fluid (MCF) in a rotating rheometer

As a new intelligent or smart fluid, we propose a magnetic compound fluid (MCF). This fluid has nm size magnetite and μm size iron particles in a solvent. The magnetic field effect on flow characteristics of MCF can demonstrate midpoint between magnetic fluid (MF) and magneto-rheological fluid (MRF). For example, the magnitude of shear stress to shear rate under a steady magnetic field in MCF can be larger than MRF by varying the compound rate of the magnetite and iron particles. This report shows an experimental data of shear stress to shear rate of MCF in rotating rheometers of cone and concentric cylinder types under transverse and longitudinal magnetic fields.

New microscopic polishing with magnetic compound fluid (MCF)

We propose a magnetic compound fluid (MCF) as a new smart fluid. This fluid includes nm size magnetite and mm size iron particles in a solvent. The magnetic effect can be expected to demonstrate between the magnetic fluid (MF) and magneto-rheological fluid (MRF). Moreover, the magnitude of the shear stress to the shear rate under steady magnetic field can be larger than MRF by varying the compound rate of the MF and MRF. This report shows an experimental application of microscopic polishing with the MCF. We examined the surface roughness of flat titanium material to the attached rotating plate with 15 rpm under magnetic field. By comparing the roughness between the MCF and the MR, the polished plate is more uniformly over the plate with the MCF than the MR. Further the roughness of Ry and Ra are larger under fluctuating magnetic field than steady magnetic field. The more effective polishing can be explained with the cluster model of particles.

ER Fluid Finishing Using Rotating Electrode

The solids in the particle dispersion type functional fluid have been found to reciprocate between electrode under AC field at low frequencies. This promotes the continued dispersion of the solids. Here, we have tested the positive use of this phenomenon in finishing process and have found that the process is assisted positively or negatively depending on the strength of applied electric field and the pressure applied to the finishing pad. The optimum electric field strength and pressure are 3.5 kV/mm and 24 kPa.

Characterization of Particle Motion for Polishing and Texturing under AC Field by Using Particle Dispersion Type ER Fluid

The authors have already proposed a new method of polishing using particle dispersion type ER fluid. And also have applied this method for polishing micro hole in a ceramic disk. In this paper, we characterize the particle dispersion type ER fluid and particle motion suitable for polishing and texturing. We selected the type of abrasive material to be used in ER fluid based on theoretical calculation of the force exerted by an individual particle under alternative electric field. And also, we have experimentally obtained the force generated by ER fluid dispersing diamond particles of different size range, concentrations and dispersing media with different viscosity. Furthermore, we have observed the particle response using a high-speed video camera.

COMPARISON OF FREQUENCY CHARACTERISTICS IN A DAMPER USING MAGNETIC FLUID, ER FLUID DISPERSING SMECTITE, AND MIXED ER MAGNETIC FLUID

This paper presents a new type of damper using electro-rheological (ER) magnetic fluid for improving magnetic fluid damper and ER fluid damper. Silicone oil based magnetic fluid dispersing 10 nm size of magnetite, silicone oil based ER fluid dispersing 2 nm to 50 nm size of smectite and a mixture, that is, ER magnetic fluid have been used in a piston type damper. Dynamic visco-elasticities of these fluids have been measured by considering chain (cluster) formations. Next, frequency characteristics of transmissibility (magnification factor) and phase in damper have been compared with those fluids under magnetic field, electric field and both fields. The Voigt or Maxwell model can be applied in those dampers depending on amplitude. ER magnetic fluid has showed the decrease of amplitude ratios at resonance point and higher frequency at any amplitude under both magnetic and electric fields as low-pass filter.

Electrorheological Rotating Disk Clutch Mechanism Under AC Electric Field: Part II - Efficiency Metrics

Electric power and efficiency on a rotating disk under AC electric field with suspension-type electrorheological fluid (ERF) were investigated. This report also dealt with the time lags of torque and current density from the applied eloctric field. Especially, the time lag of the current density was arranged by the power factor. The time lag of the torque is changed larger than the one of the current density. On the other hand, the data of the torque and the current density have steady and varying characteristics as amplitude components. Therefore, we need to investigate four electric powers: apparent power, effective power, steady power from the steady component of the current density and total power. From the three electric powers, we can deal with three efficiency of the electric power to the torque. They depend on the angular velocity of the disk, frequency and intensity of the electric field. The results were explained with the particles aggregation model.

PREPARATION AND ABRASION PROPERTIES OF MAGNETO-RHEOLOGICAL FLUID OF DISPERSED SILICA-COATED IRON

In this study, a magneto-rheological fluid dispersed by silica-coated iron was developed and its properties such as fluid viscosity (shear stress or shear rate) and abrasion were investigated. The metallic iron coated by silica dispersed in magneto-rheological fluid was prepared by H2 reducing of precipitated magnetite (Fe3O4). Then, the magneto-rheological fluid (MR fluid) for the seal was prepared with silica-coated iron or carbonyl iron (HQ type; diameter of 1.6-1.9 10-6m) and two solvent oils i.e. silicon oil (SH200cv, 10000cSt) and CVT oil (T-CVTF, automobile transmission oil). It was observed that the MR fluid viscosity of CVT oil with HQ particles is lower in every fluid condition. Furthermore, the surface roughness of polyvinyl plate after abrasion test for MR fluid with silica coated iron and CVT oil as solvent was higher compared to the other types of MR fluids. The results indicated that carbonyl iron (spherical particles) and silica-coated iron particles dispersed in silicon oil are feasible to be used where the low abrasion in mechanics is required.