• Journal of the Korean Society for Precision Engineering
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• v.23 no.12 s.189
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• pp.80-87
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• 2006

Seals are usually made from elastomer, a kind of rubber, and it has the non-linearity and hyper-elasticity. U-type seals are used to prevent the leakage of internal fluid sealed in hydraulic actuator because they have more excellent performance than O-rings or rectangular seals. As a core part of hydraulic actuator, U-type seal gives much effect on performance and reliability of actuator. This study considers an NBR U-type seal under high pressure of a hydraulic actuator, and provides its deformation, stress-strain characteristic and contact force using the non-linear finite element analysis. Analysis results are compared with the experimental ones performed by the self-developed testing equipment. Verification result shows that this study presents a good application process for the effective design of U-type seals under high operation pressure.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.121-128
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• 2001

This study has been performed to investigate formability of non-vinyl PCM(pre-coated metal)sheet. First, physical test of PCM sheets were tested to evaluate finish coating characteristic of PCM. And then, test equipment was made for friction test and three non-vinyl PCM sheets were tested by straight pulling method. This paper provides the results of the friction tests showing the influence of sheet surface texture and process conditions. It was found that the influence of contact pressure and speed had an effect upon the level of friction. Also using tests, the scratch resistance of a series of polyester coating has been investigated. This investigation aims to clarify the process conditions that prevent the scratch of PCM to form the good electrical appliances such as microwave oven, air conditioner and refrigerator etc.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.74-79
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• 2006

In this study, the tempering effect on the wear characteristics of induction-hardened SPS5 steel was investigated. For this purpose, three tempering conditions were applied to control the hardness of heat-treated SPS5 steel. Ball-on-disk wear tests have been performed using zircornia balls on the tempered specimens to determine the variation of wear characteristics. The results showed that friction coefficient decreased with increasing hardness for induction hardening conditions. This seems to occur because real contact area between specimen and mating ball was affected by the specimen hardness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.160-165
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• 1993

The cutting mechanism of ultrasonic vibration machining is characterized as two phases, that is an impact at the cutting edge and a reduction of cutting force due to non-contact interval between tool and workpiece. In this paper, in order to identfy cutting dynamics of a system with ultrasonically vibrated cutting tool, an ARMA modelling is performed on experimental cutting force signals which have a dominant effect on cutting dynamics. The aim of this study is, through Dynamic Data System methodology, to find the inherent characteristics of an ultrasonic vibration cutting process by considering natural frequencyand damping coefficient. Surface roughness and stability of cutting process under ultrasonic vibration are also considered

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.231-234
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• 2007

The solid state dye-sensitized saolrc cells (DSSCs) employing polymer electrolytes show high overall energy conversion efficiency as high as 4.5% at 1 sun conditions. The improved efficiency may be primarily due to the enlarged interfacial contact area between the electrolyte and dyes in addition to the increased ionic conductivity, which were done by utilizing liquid oligomers, followed by in situ self-solidification, to form the solid DSSCs "Oligomer Approach". The effect of the charge transfer resistance at the counter electrode side on the effciency has also been investigated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.261-268
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• 2004

For cam and roller-follower contacting surfaces, the effect of tangential loading on the subsurface stress field at an elaso-hydrodynamic lubrication condition has been studied numerically. As tangential load increases, the subsurface stress field extended more widely to the direction of the tangential load. The positions of the maximum shear stress and the maximum effective stress are getting closer to the surface with the increasing tangential load. The tangential load at the elasto-hydrodynamic lubrication condition is of little consequence to the subsurface stress field.

• KSTLE International Journal
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• v.2 no.1
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• pp.17-21
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• 2001

Surface treatment technologies are frequently used to improve mechanical properties of surface layers of machinery components in many practical situations. Surface hardness of piston in the oil hydraulic piston pumps is very important about wear resistance. To improve hardness, wear resistance of the oil hydraulic axial piston pump, it is needed to know the surface layer characteristics in the sliding contact parts. This paper reports an experimental study on surface treatment characteristics in the piston of the oil hydraulic axial piston pump. We investigated the surface wear of a piston between untreated and nitriding-treated surfaces. We obviously observed that the surface hardness of piston in the oil hydraulic axial piston pump plays an important role to have wear resistance and remain a longer life.

• Tribology and Lubricants
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• v.18 no.3
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• pp.219-227
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• 2002

A linear elastic fracture mechanics analysis of double subsurface cracks propagation in a half-space subjected to moving thermomechanical surface traction was performed using the finite element method. The effect of frictional heat at the sliding surface on the crack growth behavior is analyzed in terms of the thermal load and peclet number. The crack propagation direction is predicted in light of the magnitudes of the maximum shear and tensile stress intensity factor ranges. When moving thermomechanical surface traction exists, subsurface horizontal cracks are propagation in-plane crack growth rate at the beginning but they are propagation out-of-plane crack growth rate by the frictional heat which is occurrence by the repeated sliding contact.

• Textile Coloration and Finishing
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• v.31 no.4
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• pp.276-287
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• 2019

In this study, cotton fibers were coated with a different weight percentage of octadecyl dimethyl(3-triethoxy silylpropyl) ammonium chloride(ODDMAC) to improve antimicrobial and water repellent properties. First, the ODDMAC dissolved in ethanol to prepare a solution. Then the cotton fibers were immersed in the ODDMAC/ethanol solution for 10 minutes at ambient temperature and dried at 80℃ for 3 minutes followed by curing. The treated cotton fibers were characterized by scanning electron microscopy(SEM) and x-ray photoelectron spectroscopy(XPS). The treated cotton fibers revealed sufficient antimicrobial activity against Klebsiella pneumoniae(ATCC 4352) and Staphylococcus aureus(ATCCBAA-1707). The hydrophobic nature of the treated cotton fibers was characterized by contact angle measurement. The results showed that the cotton fibers treated with the ODDMAC showed excellent hydrophobic properties which improved to 121°.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.379-384
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• 2008

This paper examines permanent magnet eddy current couplings and brakes. Specifically, the effect of permanent magnet magnetization patterns on the magnetic field and force production is investigated. The eddy current couplings and brakes employ high energy-product neodymium-iron-boron (NdFeB) permanent magnets that act on iron-backed copper drums to provide torque transfer from motor to load without mechanical contact. A 2-dimensional finite element modeling is performed to predict the electromagnetic behavior and the torque-speed characteristics of permanent magnet type eddy current couplings and brakes under constant speed operation.