• Journal of the Korean Society for Heat Treatment
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• v.9 no.4
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• pp.229-233
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• 1996

This work has been carried out to reduce the softening of heat affected zone on laser surface alloying. Iron based rapid solidification material with $Cr_{5-10}$, $V_{1-3}$, $Mo_{3-7}$, $W_{2-5}$, $B_{7-8}$, $C_{2-3}$, $Si_{0.5-1}at%$ was alloyed on the surface of SM45C steel. The excellent softening resistance in alloyed and heat affected zone showed, which could be attributed to the formation of stable high temperature precipitates.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.121-124
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• 2004

In this paper, a series of fracture tests are performed for the chemically prestressed steel fiber reinforced concrete (SFRC) manufactured with addition of expansive additives for the study of fracture behavior and characteristics. Cracking loads of the chemically prestressed SFRC are greater than that of normal concrete and those are also increased by increasing of steel fiber volume. Thus, it is necessary to obtain optimum steel fiber volume to induce chemically prestressing effectively to concrete members. The result of three-points bending tests shows that early-cracking resistance of the chemically prestressed SFRC is increased without increase of fracture energy. From the test, the tension softening curves are also obtained by poly-linear approximation method and simulated behaviors by using the determined tension softening curves agree with experimental results. And it is confirmed that cracking and ultimate behaviors of chemically prestressed SFRC can be predicted by using obtained fracture characteristics.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.446-451
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• 2018

In this study, different formulations of magnesium oxide and various modifiers (phosphoric acid, ferrous sulfate, pure acrylic emulsion, silicone acrylic emulsion, glass fiber, and polypropylene fiber) were used to prepare magnesium oxychloride cement composites. The compressive strength of the magnesium oxychloride cement was tested, and the softening coefficients of the composites after soaking in water were also calculated. The results showed that a magnesium oxychloride cement sample could not be coagulated when the MgO activity was 24.3%, but the coagulation effect of the magnesium oxide cement sample was excellent when the MgO activity was 69.5%. While pure acrylic emulsion, silicon-acrylic emulsion, and glass fiber showed insignificant modification effects on the magnesium oxychloride cement, ferrous sulfate heptahydrate, phosphoric acid, and polypropylene fiber could effectively improve its water resistance and compressive strength. When the phosphoric acid, ferrous sulfate heptahydrate, and polypropylene fiber contents were 0.47%, 0.73%, and 0.25%, respectively, the softening coefficient of a composite soaked in water reached 0.93 after 7 days, and the compressive strength reached 64.3 MPa.

• Textile Coloration and Finishing
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• v.6 no.4
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• pp.1-8
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• 1994

To improve the antimicrobial activity and crease resistance of Korean traditional Hansan ramie fabrics, partially saponified polyethylene(PPS) was used as a softening water repellent agent and 3-(trimethoxysilyl)propyl dimethyl octadecyl ammonium chloride(QAC) as a antimicrobial agent. The antimicrobial activity was effective by treatments of PPS, QAC and PPS/QAC for shake flask test. For the halo test, PPS/QAC showed good antimicrobial activity. It was found that the desirable composition of H$_{2}$O/PPS/QAC is 98/1/1 for improving the antimicrobial activity and crease resistance of the fabrics.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.3
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• pp.279-286
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• 2015

To achieve lightweight design, research & development of various lightweighting technologies such as hydroforming are underway worldwide. In the case of hydroforming, application of ultra high strength steel is essential for weight reduction of the car. However, considering common high-strength carbon steel, it is not suitable to the actual hydroformed parts since the lack of formability. DP steel offers an outstanding combination of strength and formability as a result of their microstructure. DP steel has high strength and good formability but it's difficult to secure stable quality of welding section because of softening of weld section and chemical composition. Therefore, most of companies use LASER welding when making high strength tube. Electric resistance welding is excellent production method for steel tube manufacturing considering the productivity. Optimum electric resistance welding technology is needed to be developed for application of high strength hydroformed parts using DP steel. This study is comprehensive research & development from electric resistance welding to actual formabililty evaluation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.76-79
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• 1998

High temperature plastic deformation behavior of Al 6061 alloy was characterized by hot torsion test. The Al 6061 alloy deformed continuously in the temperature range of 400∼550$^{\circ}C$, and strain rate range of 0.05∼5/sec. The softening mechanism of Al 6061 alloy was dynamic recrystallization and identified by hyperbolic sine law and zener-Hollmon parameter. The evolution of grain size and deformation resistance were calculated by the relationships of deformation variables.

• Geomechanics and Engineering
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• v.12 no.3
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• pp.399-415
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• 2017

A series of direct shear tests were conducted to investigate the frictional properties of the interface between structures and the filling soil of Chongqing airport fourth stage expansion project. Two types of structures are investigated, one is low carbon steel and the other is the bedrock sampled from the site. The influence of soil water content, surface roughness and material types of structure were analyzed. The tests show that the interface friction and shear displacement curve has no softening stage and the curve shape is close to the Clough-Duncan hyperbola, while the soil is mainly shear contraction during testing. The interface frictional resistance and normal stress curve meets the Mohr-Coulomb criterion and the derived friction angle and frictional resistance of interface increase as surface roughness increases but is always lower than the internal friction angle and shear strength of soil respectively. When surface roughness is much larger than soil grain size, soil-structure interface is nearly shear surface in soil. In addition to the geometry of structural surface, the material types of structure also affects the performance of soil-structure interface. The wet interface frictional resistance will become lower than the natural one under specific conditions.

• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.93-100
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• 1987

Corrosion fatigue cracking of the austenitic stainless steel(bese metal & heat affected zone by TIG weld) was studied experimentally under the environments of various specific resistance and air. The characteristics of corrosion fatigue crack growth rate and the environmental constants of paris' rule were investigated for SUS 304 weldments in the various specific resistance. The influences of stress intensity factor range and corrosion on the crack growth rate were compared. The characteristics of corrosion fatigue cracking for the weldments were inspected from mechanical, electrochemical and microstructural point of view. Main results obtained are as follows: 1) As the specific resistance decreases, the environmental constant C of paris'rule increases(hence the corrosion fatigue crack growth rate is rapid), but the environmental constant m decreases, so the effect of corrosion to the crack growth rate is more susceptible than thet of stress intensity factor range. 2) As the stress intensity factor range decreases, the corrosion fatigue crack growth rate of heat affected zone is more susceptible than that of the base metal. 3) The corrosion fatigue crack growth rate of the heat affected zone is more rapid than that of the base metal, because of the phenomenon of softening and the less noble potential coused by wedlding heat cycle. 4) The corrosion fatigue cracking of SUS 304 weldment appears transgranular fracture.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.92-98
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• 2011

The influence of the cooling condition after solution treatment on the high temperature fatigue resistance of 23Cr-26Ni heat resistant steel was investigated. Two different cooling conditions were applied to the steel after solution treatment at $1200^{\circ}C$ for 3 hours. One specimen was water quenched immediately after the solution treatment. The other one was furnace cooled at a rate of $0.5^{\circ}C/min$ down to $750^{\circ}C$ after the solution treatment. Then, both specimens were aged at $750^{\circ}C$ for 5 hours. Under two different heat treatment conditions, the low cycle fatigue (LCF) test was performed at $600^{\circ}C$ and room temperature (RT). Only cyclic hardening continued from the beginning until fracture at all strain amplitudes during LCF at $600^{\circ}C$. This phenomenon was attributed to the increase in the dislocation density due to cyclic deformation, which resulted in the interaction between the newly created dislocations and precipitates. Cyclic hardening followed by saturation and cyclic softening was observed at RT. Cyclic softening was attributed to the dislocation annihilation rate exceeding the dislocation generation rate. Other probable factor for cyclic softening was some cavities formed around grain boundaries after 20 cycles. WQ and FC have a similar LCF behavior at RT and $600^{\circ}C$ as shown in the cyclic stress response curves.

• Journal of Adhesion and Interface
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• v.15 no.4
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• pp.145-150
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• 2014

Dicyclopentadiene (DCPD)-based hydrocarbon resins are widely used as tackifiers in many applications. In particular, hydrogenated DCPD-based hydrocarbon resins are widely used in premium hot-melt-type adhesives such as hot melt adhesives (HMAs) and/or hot melt pressure-sensitive adhesives (HMPSAs), because are water-white in color and possess excellent stability to light and heat. This article discusses the adhesive performance of various hydrogenated DCPD resins when they are used as tackifiers in styrene-block-copolymer (SBC)-based HMPSAs. This article shows the correlation between the characteristics of tackifiers and the adhesive performance of SBC-based HMPSAs. The higher the softening point of the tackifier, the higher is the $T_g$, softening point, and crossover temperature of the PSAs. High aromatic H wt% content reduces the high-temperature resistance of PSAs, as suggested by the decrease in the crossover temperature and softening point of the PSAs.