• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2007.11a
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• pp.9-13
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• 2007

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.279-286
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• 1998

Fatigue crack propagation behavior for variable load in high strength aluminum alloys was investigated in this study. The materials used in this study are aluminum 7075-T651 and 5052-H32 alloys. Crack length was measured from calibration curve, which was plotted by known crack length and resistance of standard specimens. Load was obtained from linear regression formula. Unloading elastic compliance method was ap;ied to check the crack closure and cracked area.

• Structural Engineering and Mechanics
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• v.27 no.4
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• pp.393-408
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• 2007

This paper presents the findings of an experimental study to evaluate retrofit methods which address particular weaknesses that are often found in reinforced concrete structures, especially older structures, namely the lack of the required flexural and shear reinforcement within the columns and the lack of the required shear reinforcement within the joints. Thus, the use of a high-strength fiber jacket for cases of post-earthquake and pre-earthquake retrofitting of columns and beam-column joints was investigated experimentally. In this paper, the effectiveness of the two jacket styles was also compared.

• Transactions of Materials Processing
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• v.26 no.4
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• pp.246-259
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• 2017

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.52-54
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• 2003

Poly(vinyl alcohol) (PVA) obtained by the saponification of poly(vinyl ester) is a linear semicrystalline polymer; these polymers have been widely used as fibers for clothes and industries, binders, films, membranes, medicines for drug delivery system, and cancer cell-killing embolic materials. PVA fibers have high tensile and compressive strength, tensile modulus, and abrasion resistance because of the highest crystalline lattice modulus. (omitted)

• Transactions of Materials Processing
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• v.13 no.5
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• pp.449-454
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• 2004

The annealing behavior of a 5083 Al alloy deformed at cryogenic temperature was investigated, focusing on the evolution of microstructures and mechanical properties. Especially, the effects of annealing temperature, $150~300^{\circ}C$, and time, 3∼60min., on microstructures and mechanical properties of the sheets received 85% reduction at cryogenic temperature were investigated. The optimization of the annealing conditions resulted in a mixture of equiaxed grains and elongated subgrains, exhibiting a good combination of uniform elongation and high strength.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.48-53
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• 2000

The effects of added elements, such as Co or Nb, on wear properties of high speed steel by powder metallurgy(PM-HSS) had been evaluated in previous paper. The wear properties of materials, in fact, have been a]so influenced by heat-treating conditions. In this paper, the effects of heat-treating conditions on wear properties of PM-HSS have been evaluated. The wear tests have been performed as same conditions as previous paper using PM-HSS(5%Co-1%Nb) heat-treated under different quenching and tempering temperature. The result of this paper shows that wear resistance of PM-HSS is improved with relatively high quenching temperature. However tempering temperature is not sensitve to the wear resistance in range of high quenching temperature. It may be deduced by the fact that the shear strength of matrix by strengthening mechanisms of quenching aging in addition to dispersion-hardening is improved.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.469-476
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• 2003

Despite of considerable research results or uniaxial tension creep available for superalloys, few studies have been made on high temperature creep using the Initial Stram Method (ISM) In this paper, the real-time prediction of high temperature creep strength and creep lift for the nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure static load at the temperatures of 538$^{\circ}C$. 649$^{\circ}C$, and 704$^{\circ}C$. The predictive equation derived from the ISM in creep tests showed better reliability than those from LMP (Larson-Miller Parameter) and LMP-lSM (Larson Miller Parameter-Initial Strain Method) specially for long time creep prediction (10$^3$∼10$\^$5/h).

• Journal of the Korean Ceramic Society
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• v.30 no.9
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• pp.747-753
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• 1993

The investigation was carried out to study the behaviors of the pore size and porosity, the mechanical strength, the resistance to thermal spallings and slag attacks according to particle sizes of starting raw materials in porous high Alumina ceramics. This porous ceramics have been used in processing of the clean steel by the blowing of the inert gas. The required properties in the practice are the suitable pores size, the sharp pores distribution for a uniform blowing of the gas, the strong corrosion resistance to slags and molten metals and the resistance to thermal spalling. The optimized properties in porous high alumina ceramics of the specimen No. 3 was found to be the very low slag intrusion and the superior resistance to thermal spalling because of the suitable pore size of 2.5${\mu}{\textrm}{m}$, the porosity of 30% and the high sinterability.

• Transactions of Materials Processing
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• v.21 no.6
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• pp.354-359
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• 2012

Effects of a nitriding treatment on the tensile and high cycle fatigue properties were investigated by conducting ion-nitriding and gas nitro-caburizing treatments on the spheroidized SCr430B medium-carbon steel and performing tensile and tension-tension high cycle fatigue tests. The nitrided samples showed much lower strength and ductility compared to those in the initial as-spheroidized state and premature fracture occurred at the hardened layers. The micro-voids in the compound layer caused fatigue crack initiation. Thus, the removal of the compound layer with micro-voids remarkably improved the fatigue resistance to even beyond that of the as-spheroidized sample.