• Journal of the Korean Society for Railway
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• v.6 no.1
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• pp.21-28
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• 2003

Environment-dependent fatigue life of Cu-Cd alloy wires used as messenger wires was investigated. Tensile test results showed the decrease of tensile strength and elongation of messenger wires by 3.7% and 16.8%, respectively, in used specimens when compared to new ones. Messenger wires used at industrial region for 26 yeras showed 35∼50% decrease in fatigue life, which is partly due to the in stress concentrations by formation of corrosion products at the surface. Single wires showed better fatigue properties than stranded wires, especially at low cycle regions with higher stresses. Stranded wires showed shorter fatigue lives than single wires because of friction between wires by surface contact. Service life of messenger wires was dependent upon the environments which they were exposed to. SO$_2$ and humidity deteriorated the fatigue properties by environmental degradation.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1572-1574
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• 2000

In this paper, study on the properties of the thermal degradated epoxy resin which is used in cast resin transformer is performed to investigate the problems of the decreasing insulation characteristics and crack in the cast resin transformer. In the test, contact angle, weight loss, surface resistivity and relative dielectric constant are measured. As the results of the above measurements, the epoxy resin has increased to 150$^{\circ}C$ in the contact angle and surface resistivity but at the above 150$^{\circ}C$ the values have decreased. The relative dielectric constants have increased in the thermal treated samples with the degradation temperature. Consequently, the insulation properties of the epoxy resin which is used in cast resin transformer have increased by the 150$^{\circ}C$ but decreased in the above 150$^{\circ}C$.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.227-231
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• 2009

Mg and Mg alloys have been used for lots of applications, including automobile industry, aerospace, mobile phone and computer parts owing to low density. However, Mg and Mg alloys have a restricted application because of poor corrosion properties. Thus, improved surface treatments are required to produce protective films that protect the substrate from corrosive environments. Environmental friendly Plasma Electrolytic Oxidation (PEO) has been widely investigated on magnesium alloys. PEO process combines electrochemical oxidation with plasma treatment in the aqueous solution. In this study, AZ91 Mg alloys were treated by PEO process in controlling the current with PC condition and treated time, concentration of NaF, NaOH, and $Na_2SiO_3$. The surface morphology and phase composition were analyzed using SEM, EDS and XRD. The potentiodynamic polarization tests were carried out for the analysis of corrosion properties of specimen. Additionally, salt spray tests were carried out to examine and compare the corrosion properties of the PEO treated Mg alloys.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.956-960
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• 2004

Effects of ion implantation and deposition on the tribological properties of DLC film as a function of implanted energies and process times were investigated. TiC ions were implanted and deposited on the Si-wafer substrates followed by DLC coating using ion beam deposition method. In order to study tribological properties such as friction coefficient and behavior of DLC film on the modified surface as a function of implanted energies and process times, we used a ball-on-disc type apparatus in the atmospheric environment. From results of wear test, as the implanted energy was increased, the friction coefficient was more stable below 0.1.

• Journal of Fashion Business
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• v.16 no.1
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• pp.16-25
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• 2012

As the test results for surface color, dyeing durability, antibiosis of cotton fabrics and silk fabrics dyed with Agastache rugosa extract, the following conclusions were obtained. The surface color of all the dyed fabrics was confirmed mostly as a GY system. As the result of chrominance(${\Delta}E_{ab}$) measurement, in the case of cotton fabrics the dyed fabrics treated with $Al_2(SO_4)_3$ mordant showed the highest value and in the case of silk fabrics the non-mordant dyed fabrics showed the highest value. The dyeing durability of test fabrics dyed with Agastache rugosa extract are as follows. As the test results of colorfastness to laundry for cotton dyed fabrics, the discoloration degree showed 1st-2nd grade and the contamination degree showed 4th-5th grade. As the test result of colorfastness to dry cleaning for silk dyed fabrics, the contamination degree showed from 1st to 3rd-4th grade. As the test results of colorfastness to acid artificial perspiration, the discoloration degree showed from 1st to 3rd-4th grade and the contamination degree showed from 3rd to 4th-5th grade. As the test results of colorfastness to alkaline artificial perspiration, the discoloration degree showed from 1st to 4th grade and the contamination degree showed from 3rd to 4th-5th grade. The colorfastness to sunlight showed from 1st to 2nd grade. The colorfastness to rubbing showed from 3rd to 4th-5th grade in dry process and from 2nd-3rd to 4th-5th grade in wet process. As the test results of antibiosis, the decrease rate of germs to virus Klebsiella pneumoniae and Staphylococcus aureus showed at least more than 99% after the wash of 10 times. As the test results of antifungal activity to mycete Trichophyton mentagrophytes and Aspergillus niger, the both cotton and silk dyed fabrics didn't gain the significant antifungal effect.

• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.359-364
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• 2013

Purpose: This study was to observe characteristic of metal oxidation and bonding strength according to composition of Ni-Cr alloy for porcelain fused to metal crown. The three kinds of Ni-Cr alloy with different composition ratio of parent metal were observed general properties and chemical properties of each alloy surface and measured the shear bonding strength between ceramic and each alloys. The aim of study was to suggest the material for design of parent metal's composition ratio to development of alloy for porcelain fused to metal crown. Methods: The three kinds of alloy as test specimen was Ni(59wt%)-Cr(24wt%), Ni(67wt.%)-Cr(16wt.%) alloy and Ni(71wt%)-Cr(12wt%)alloy. The oxide on surface was observed by EDX. And the shear test was performed by MTS. Results: The surface property and oxide characteristic analysis of oxide layer, weight percentage of Element O within $Ni_{59}Cr_{24}$ alloy measured 23.03wt%, $Ni_{67}Cr_{16}$ alloy measured 21.13wt% and $Ni_{71}Cr_{12}$ alloy was measured 48.55wt%. And the maximum shear bonding strength was measured 58.02Mpa between $Ni_{59}Cr_{24}$ alloy and vintage halo(H2 group). Conclusion: The surface property and oxide characteristic three kind of Ni-Cr alloy was similar. and shear bonding strength showed the highest bonding strength in H2 specimens.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.23-23
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• 2018

In this study, new titanium alloys were prepared by adding elements such as tantalum (Ta), zirconium (Zr) and the like to complement the biological, chemical and mechanical properties of titanium alloys. The Ti-40Ta-xZr ternary alloy was formed on the basis of Ti-40Ta alloy with the contents of Zr in the contents of 0, 3, 7 and 15 wt. %. Plasma electrolytic oxidation (PEO), which combines high-voltage sparks and electrochemical oxidation, is a novel method to form ceramic coatings on light metals such as Ti and its alloys. These oxide film produced by the electrochemical surface treatment is a thick and uniform porous form. It is also composed of hydroxyapatite and calcium phosphate-based phases, so it has the characteristics of bone inorganic, non-toxic and very high bioactivity and biocompatibility. Ti-40Ta-xZr alloys were homogenized in an Ar atmosphere at $1050^{\circ}C$ for 1 hour and then quenched in ice water. The electrochemical oxide film was applied by using a power supply of 280 V for 3 minutes in 0.15 M calcium acetate monohydrate ($Ca(CH_3COO)_2{\cdot}H_2O$) and 0.02 M calcium glycerophosphate ($C_3H_7CaO_6P$) electrolyte. A small amount of 0.0075M zinc acetate and magnesium acetate were added to the electrolyte to enhance the bioactivity. The mechanical properties of the coated surface of Ti-40Ta-xZr alloys were evaluated by Vickers hardness, roughness test, and elastic modulus using nano-indentation, and the surface wettability was evaluated by measuring the contact angle of the coated surface. In addition, cell activation and differentiation were examined by cell culture of HEK 293 (Human embryonic kidney 293) cell proliferation. Surface properties of the alloys were analyzed by scanning electron microscopy(FE-SEM), EDS, and X-ray diffraction analysis (XRD).

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.761-772
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• 2023

The fire resistance design of timber structures involves calculating the residual section based on charring depth, which is then utilized in structural design. Charring depth is determined from fire-resistance test results in Korea, which currently do not account for the charring properties of the adhesive used in Glued Laminated Timber(GLT) production. This study fabricated GLT using various adhesives employed in domestic GLT production, comparing the charring properties by adhesive type and the fire resistance performance relative to the directionality of the laminated surface. Melamine demonstrated the most advantageous fire resistance performance, followed by resorcinol and polyurethane. Furthermore, it was established that the laminated section exhibited a higher charring rate, influenced by the adhesive, compared to the laminated surface, which significantly impacts the fire resistance performance.

• Journal of Surface Science and Engineering
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• v.34 no.5
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• pp.421-428
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• 2001

New WC-CrN superlattice film was deposited on Si substrate (500$\mu\textrm{m}$) using cathodic arc ion plating system. The microstructure and mechanical properties of the film depend on the superlattice period (λ). In the X-ray diffraction analysis (XRD), preferred orientation of microstructure was changed according to various superlattice periods(λ). During the Transmission Electron Microscope analysis (TEM), microstructure and superlattice period (λ) of the WC - CrN superlattice film was confirmed. Hardness and adhesion of the deposited film was evaluated by nanoindentation test and scratch test, respectively. As a result of nanoindentation test, the hardness of WC - CrN superlattice film was gained about 40GPa at superlattice period (λ) with 7nm. Also residual stress with various superlattice period (λ) was measured on Si wafer (100$\mu\textrm{m}$) by conventional beam-bending technique. The residual stress of the film was reduced to a value of 0.2 GPa by introducing Ti - WC buffer layers periodically with a thickness ratio ($t_{buffer}$/$t_{buffer+superlattice}$ ). To the end, for the evaluation of oxidation resistance at the elevated temperature, CrN single layer and WC - CrN superlattice films with various superlattice periods on SKD61 substrate was measured and compared with the oxidation resistance.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.77-88
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• 2017

PURPOSES : It is necessary to clarify the rheological properties of cement paste as a basic research in the development of mechanistic concrete mix design. The rheological properties of cement paste with different binder types, mix propositions, and with/without high range water reducers have been analyzed. METHODS : In this study, ordinary Portland cement, fly-ash, blast furnace slag, silica fume, and limestone powder were used as binders. The range of water-binder ratio was 0.3-0.5, and a total of 30 different mixes have been tested. The slump flow test, V-funnel test, and Dynamic Shear Rheometer (DSR) test were performed to analyze the rheological properties of cement paste. RESULTS : As a result of the slump flow test, it was found that the composition ratio of the binder contents greatly affected the paste flow when the high range water reducers were added. The results of V-funnel test showed that when the water-binder ratio was decreased without high range water reducers, the binder composition ratio had a large effect on the passing time of the V-funnel tester, but with high range water reducers the impact of the binder composition ratio was decreased. The slump flow and V-funnel have a certain relationship with the rheological factors (yield stress and plastic viscosity), but the correlation was not significant. Finally, we proposed the M-value considering the density and specific surface area of the binder. The correlation between rheological factors and M-value were better demonstrated than experimental values, but there is still a limit to predict the rheological factor in general mix design. CONCLUSIONS :In this study, the rheological properties of cement paste were analyzed. The binder type, composition ratio of binder, and with/without high range water reducers have combined to provide the complex effects on the rheological properties of cement paste. The correlation between the proposed M-value and rheological factor was found to be better than experimental results, but needs to be improved in the future.