15-10-2012, 10:27 AM
Resistance Force of a Shock Absorber Using Magnetic Functional
Fluids Containing both Micrometer-sized and Nanometer-sized
Magnetic Particles
Resistance Force of a Shock.pdf (Size: 324.9 KB / Downloads: 37)
Abstract
In this paper, properties of resistance force of a shock absorber using magnetic functional fluids having both micrometer- and
nanometer-sized magnetic particles are reported. The resistance force can be controlled by changing strength of the magnetic
field applied to the magnetic functional fluid. The resistance force is influenced by the mixture ratio of the micrometer- to the
nanometer-sized magnetic particles.
Introduction
Applications utilizing magnetic functional fluids having both micrometer- and nanometer-sized magnetic
particles have been developed [1]. The size of clusters, the meso-scale structure formation of particles and the
cohesion between the magnetic particles are affected by the mixture ratio of the magnetic particles of different sizes
in the magnetic functional fluids. Therefore, resistance force properties of the shock absorber using the magnetic
functional fluids are influenced by the mixture ratio of the micrometer- and nanometer-sized magnetic particles.
In this paper, resistance force of a shock absorber is investigated experimentally. Two magnetic functional fluids
whose mixture ratio of micrometer- and nanometer-sized magnetic particles is different are prepared for the
experiment. The resistance forces are measured when load is applied to the shock absorber under magnetic field.
Experimental method
Schematic diagram of the shock absorber is illustrated in figure 1. The cylinder (A) is filled with the magnetic
functional fluid. The piston (A) is moved with the shaft. The shaft penetrates the cylinder (A) so as to maintain the
capacity inside the shock absorber constant. The coil is installed on the cylinder (A) to apply magnetic field to the
magnetic functional fluid. Figure 2 shows the distribution of the magnetic flux density when an electric current is
applied to the coil. Figure 3 illustrates the schematic diagram of our experimental apparatus. The shock absorber is
attached in the plumb direction. When high pressure air in the air tank is opened by the solenoid valve momentarily,
pressure in the cylinder (B) suddenly rises and load is applied to the shock absorber through the piston (B). The load
can be changed by adjusting the pressure of the air in the tank. When a load is applied to the shock absorber,
displacement and resistance force of the shock absorber are produced. The displacement of the shaft is measured by
the laser displacement sensor and the amplifier unit (Keyence Corp., LB-300 and LB-1200), while the resistance
force is measured by the load cell and the strain amplifier (Kyowa Electronic Instruments Co., Ltd., LUX-A-1kN
and DPM-751A).
Result and discussion
Figure 4(a) illustrates the time history of the displacement. When the solenoid valve is opened and the load is
applied to the shock absorber at time of 0 second, the displacement of the shock absorber is increased in proportion
to the time. After about 0.1 second, the piston (B) is out of the cylinder (B). Thus, the load to the shock absorber
disappears and the displacement of the shock absorber becomes constant. Such a displacement pattern is the same in
all experimental conditions. However, the time when the displacement becomes constant and the gradient of the
displacement are different in each experimental condition.
Figure 4(b) shows the time history of the resistance force and displacement speed. The resistance force results
from viscosity and solid friction due to the particle