• Proceedings of the KWS Conference
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• 2007.11a
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• pp.138-140
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• 2007

This study aimed to evaluate the low temperature properties of the 18Cr ferritic stainless steel weld. Applied welding methods were LB(Laser Beam) and GTA(Gas Tungsten Arc) welding to compare the different low temperature properties of the welds. Low temperature properties were evaluated by the Charpy impact, Erichsen and Expansion test at low temperature. LB weld showed superior low temperature properties in the cases of the Charpy impact test and expansion test at low temperature, while GTA weld showed a superior low temperature property in the case of Erichsen test at low temperature. The different low temperature properties with test methods are still under analysis and may be due to different crack path depending on the microstructure, test speed and stress concentration during test.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.4
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• pp.49-55
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• 2004

Properties of concrete using low heat portland cement is different from using ordinary portland cement and temperature of aggregate can be expected to have an important influence on its properties. In this study, experiment by setting up 5 levels (40, 30, 20, 4, $-2^{\circ}C$) by temperature of aggregate for evaluation properties of concrete using low heat portland cement was conducted. The experiments include slump test, air content test, change of slump, change of air content and compressive strength of concrete test. As the result of experiments, slump and air content was decreased by increasing temperature of aggregate. But it was not exceeding it's limit. Change of slump and air content was rapidly decrease by decreasing temperature of aggregate. At early age, compressive strength was influenced by the temperature of aggregate.

• Korean Journal of Materials Research
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• v.23 no.8
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• pp.423-429
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• 2013

Recently, steel structures have increasingly been required to have sufficient deformability because they are subjected to progressive or abrupt displacement arising from structure loading itself, earthquake, and ground movement in their service environment. In this study, high-strength low-carbon bainitic steel specimens with enhanced deformability were fabricated by varying thermo-mechanical control process conditions consisting of controlled rolling and accelerated cooling, and then tensile and Charpy V-notch impact tests were conducted to investigate the correlation between microstructure and mechanical properties such as strength, deformability, and low-temperature toughness. Low-temperature transformation phases, i.e. granular bainite (GB), degenerate upper bainite(DUB), lower bainite(LB) and lath martensite(LM), together with fine polygonal ferrite(PF) were well developed, and the microstructural evolution was more critically affected by start and finish cooling temperatures than by finish rolling temperature. The steel specimens start-cooled at higher temperature had the best combination of strength and deformability because of the appropriate mixture of fine PF and low-temperature transformation phases such as GB, DUB, and LB/LM. On the other hand, the steel specimens start-cooled at lower temperature and finish-cooled at higher temperature exhibited a good low-temperature toughness because the interphase boundaries between the low-temperature transformation phases and/or PF act as beneficial barriers to cleavage crack propagation.

• Fibers and Polymers
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• v.6 no.2
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• pp.169-173
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• 2005

Low temperature plasma (LTP) treatment was applied to wool fabric with the use of a non-polymerizing gas, namely oxygen. After the LTP treatment, the fabric properties including low-stress mechanical properties, air permeability and thermal properties, were evaluated. The low-stress mechanical properties were evaluated by means of Kawabata Evaluation System Fabric (KES-F) revealing that the tensile, shearing, bending, compression and surface properties were altered after the LTP treatment. The changes in these properties are believed to be related closely to the inter-fiber and inter-yam frictional force induced by the LTP. The decrease in the air permeability of the LTP-treated wool fabric was found to be probably due to the plasma action effect on increasing in the fabric thickness and a change in fabric surface morphology. The change in the thermal properties of the LTP-treated wool fabric was in good agreement with the above findings and can be attributed to the amount of air trapped between the yams and fibers. This study suggested that the LTP treatment can influence the final properties of the wool fabric.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.146-151
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• 2001

Low temperature fatigue crack propagation ratio and characteristics of the pressure structural steel which is used for the low temperature pressure vessels. Fatigue crack properties was studied at room temperature of $25^{\circ}C$ and low temperature ranges $-60^{\circ}C,\; -80^{\circ}C \;and\; -100^{\circ}C$ with stress ratio of R=0.05, 0.1, 0.3 in the logarithmic relationship between the fatigue crack propagation rate (da/dN) and stress intensity factor $\DeltaK$, in low temperature case the relationship was extend to the range of low crack propagation rate. The fractured specimens were examined by SEM tested. That results showed specimen failed at low temperature exhibit the quasi-cleavage fracture formation, however, considerable ductility proceed final fracture.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.695-700
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• 2006

This study investigates the effects of the material properties and the fatigue behavior in the SM490A material specimens due to the low-temperature atmosphere. In the fatigue behavior, the low-temperature affects the fatigue life. As the temperature get low, the fatigue limit increase, also As the yield strength and the tensile strength increase, the impact absorbed energy decrease. The difference of fatigue lift represents to normal distribution and it is larger between the room temperature and the low temperature, but in the result of the cumulative density function, the effect of temperature is not too large on it.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.3
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• pp.97-102
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• 2005

This research was a fundamental study for the low temperature sintering of PZTN by glass phase transient processing. To lower the sintering temperature, the glass phase Processing was used. Also to improve the electrical properties, the transient processing was utilized. After characterization, the various analytic techniques, such as Archimedes method for the measuring densification, x-ray diffraction patterns for the quantitative analysis of crystalline phases were utilized. Also the dielectric constant, dissipation factor, and piezoelectric coefficients were measured to evaluate the PZTN sintered at the $950^{\circ}C$ and $1050^{\circ}C$. This was confirmed that the sintering temperature of PZTN was reduced by $950^{\circ}C$ and the electrical properties were improved by the transition processing. Therefore, the glass phase transient processing can be applicable to low the sintering temperature with the dielectric and piezoelectric properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.476-482
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• 2016

Convectional PZT based piezoelectric ceramics have to sinter at high temperature about $1,200^{\circ}C$ for their suitable electrical properties. However, some issues: low temperature sintering piezoelectric ceramic composition and reliable internal electrode, have recently attracted a great deal of interest as a highly efficient multi-layered piezoelectric ceramics. In order to optimize low temperature sintering conditions of thick-film PMN-PZ-PT ceramic, it was investigated sintering and piezoelectric properties according to the change of $LiBiO_2$ contents. Thus, the superior piezoelectric properties were found at the pallet type PMN-PZ-PT optimized with low sintering processing at $925^{\circ}C$ including 7 wt% $LiBiO_2$ sintering aid. Consequentially, we successfully manufactured thick-film PMN-PZ-PT ceramics, which had superior piezoelectric and dielectric properties, with 5 wt% of $LiBiO_2$ sintering aid at temperature of $900^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.602-605
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• 2007

Soybean and rape seed are common feedstocks for biodiesel product ion in USA and Europe, respectively. On the other hand, South Eastern countries like Malaysia and Indonesia have surplus palm crops. However due to substantial amount of saturated fats in palm, the palm biodiesel has poor low temperature properties. To improve the low temperature flow properties as biodiesel, the dependence of the cold filter plugging point (CFPP) on the fatty acid compositions was examined. Two different kinds of biodiesels, palm and soybean biodiesels, were blended with the different volume ratios. And the low temperature flow properties of 0.5%, 1%, and 5% biodiesel in diesel blend fuels was tested. The decrease of CFPP was not observed for BD1 with Palm BD. Also, WDI test didn't exceed in the range of 4oC by the mixing of Palm BD upto 5% in commercial diesels.

• Korean Membrane Journal
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• v.10 no.1
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• pp.8-12
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• 2008

The electrochemical properties of Nafion type membranes as a function of temperature to examine the key factors affecting the cathodic protection process at low temperatures was investigated in this study. Variable temperature experiments for AC impedance, DC resistance were conducted. The resistances of 3 Nafion membranes (N 324, N 450, N MAC) were measured in 30% KOH (aq) for a range of temperatures between $-30^{\circ}C$ and room temperature. Membrane resistance increases exponentially with decreasing temperature. This behaviour is most significant at operational temperatures below $0^{\circ}C$. These membranes are stable under the low temperature and caustic conditions of the heat exchange system, but they place a much higher restriction on the cathodic protection of the stainless heat exchange stack. N 450 has the lowest AC impedence and DC resistance at temperatures below $0^{\circ}C$ and consequently is most suitable membrane of the three, for low temperature applications.