This study investigated the stick-slip characteristics of a magneto-rheological elastomer (MRE) against an aluminum plate. Herein, the MRE was manufactured, and a stick-slip tester was employed to evaluate the stick-slip performance of the MRE under different velocities and load conditions with and without a magnetic field. The fast Fourier transform (FFT) of the friction force of the stick-slip and the roughness of the aluminum plate surface were calculated to confirm the stick-slip phenomenon. After the tests, the wear surfaces were observed to evaluate the wear properties of the MRE regarding the stick-slip. Results showed that the stick-slip was smaller at lower velocity. At higher velocity, the reduction of the stick-slip under a magnetic field was more clearly observed. Moreover, the wear reduced with reduced stick-slip under a magnetic field.
− An ultra-high precise ejection process is essential in a dispensing system for fabricating various precision parts such as a semiconductor, LED, and camera module. The size of such parts has been decreasing, which implies that a precise ejecting technique is required. A phosphor-containing liquid is ejected via a dispenser using dual piezoelectric actuators that are used for generating a high-speed dispensing mechanism. The rod and nozzle continuously contact in high speed to eject the liquid. However, the high-strength filler or phosphor in the liquid causes wear on the surfaces of the rod and nozzle during the dispensing process. As a result, the ejection reliability decreases as the wear on the surfaces increases. Therefore, it is necessary to estimate the wear characteristics of the rod and nozzle via an experiment and FE analysis. Reliability rests up to 1,000 cycles are conducted under relatively severe conditions. The flow rate and surfaces roughness of the rod and nozzle are measured in each ejection cycle. The surface images and wear volume are obtained before and after the tests and the ejection reliability is confirmed by measuring the flow rate of the liquid. The experimental results show that the ejection reliability is maintained up to 1,000k cycles; these results are validated by the simulation results.
The dispenser ejects the ceramic filler and phosphor-containing liquid for making various products. When the particle-containing liquid is ejected under high-velocity conditions, however, the ejection reliability decreases because of the wear of the contact surface between the rod and nozzle even though these components are made of hard materials. It is therefore necessary to characterize the friction and wear properties of the hard materials, tungsten carbide (WC) and zirconium (Zr), with the high-viscosity liquid-containing nitride or yttrium aluminum garnet (YAG) particles under reciprocating conditions. Particle contents of 15 wt.% and 30 wt.% are added to the liquid. A reciprocating test was implemented to this end, and WC and Zr specimens were used. The liquid used in the experiment contains nitride and YAG. The experimental results show that the particles inside the liquid are worn out, leading to particle lubrication and the decrease in the coefficient of friction. Also, it is confirmed that the more the particles are, the less the coefficient of friction is due to particle lubrication. For each experimental condition, the coefficient of friction is measured and compared. Moreover, the contact surface of the specimen is analyzed using an electron microscope, and a profilometer is used to measure the surface roughness of the specimen before and after the test. The reciprocation friction and wear characteristics of WC and Zr with phosphor-containing liquid are evaluated by analyzing the experimental results.
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