• Structural Engineering and Mechanics
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• v.44 no.5
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• pp.601-609
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• 2012

Effect of different crack sizes on fracture criterion of some engineering materials was investigated in this work. Using finite element (FE) method coupled with a newly developed algorithm, J-integral values for different crack sizes were obtained for single-edge notched bend (SENB) and compact type (CT) specimen. Specimens with initial a/W ratio from 0.25 to 0.75 varying in crack size in steps of 0.125 were investigated. Several different materials, like 20MnMoNi55, 42CrMo4 and 50CrMo4, usually used in engineering structure, were investigated. For one of mentioned materials, numerical results were compared with experimental and their compatibility is visible.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.350-355
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• 2005

The running stability and safety of a railway vehicle depends on the design characteristics and the contact condition between wheel and rail. In this paper, numerical simulations using ANSYS and ADAMS were done on the basis of the experimental observations. The results show that 0.6 Hz of the tail car motion is due to the natural mode of car combination of the KTX. The effects of the conicity of wheel and the lateral stiffness of the secondary suspension on the running stability were analyzed numerically using ADAMS/RAIL. The results also show 0.6 Hz as like the experimental observations. And the adoption of the wheel of GV40(${\lambda}=0.025$) brought the sway motion at the tail cars, but XP55(${\lambda}=0.055$) did not when the secondary lateral stiffness of the KTX was greater than 0.3 MN/m.

• Journal of Food Hygiene and Safety
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• v.19 no.2
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• pp.55-59
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• 2004

This study was performed to investigate 172 samples of fried food in fast food store. The free fatty acid value of 22 samples exceeded standard of fried-food. These samples were 10 fried chickens, 6 fried potatoes and 5 fried onions. Fatty acid composition differed from each company. The correlation between free fatty acid value and double bond index was very low. New standard of fried food in fast food store is needed for thorough hygiene management, because of being not existed standard. The fried potato containing many carbohydrate and fat appeared higher calory than fried chicken containing many protein. The fried food had high fat comparatively, so that attention in regard to excess intake is demanded. The trace materials were included Mg, Ca, Mn, Fe, Zn, Cu and Cr in order of quantity, and the harmful heavy metals-Pb, Hg and Cd- were included small quantity.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.48-55
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• 1994

In this experiment, to find optimum brazing conditions for Cu/Stainless Steel brazing using filler metals of Ag-Cu-Zn-Cd system, first of all spreading ratio was tested on 304 stainless Steel and low carbon steel. And then shear test of brazed joint was executed. As the result of that, the shear strengths of brazed joints were the range of 60-90 MPa. Through microstructure analysis for brazed interface layer, We found as follows. Firstly interface layer increased as time increased. Secondly continuous layer of Ag-Cd compound was observed along the side of stainless steel. Also by means of EDS analysis for fracture surface, ductile fracture was occurred and precipitates on the fracture surface were found to include Cr, Mn, Si in Ag-rich phase.

• Transactions of Materials Processing
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• v.26 no.5
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• pp.300-305
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• 2017

In this paper, a design method for an intermediate die was developed to manufacture a hollow linear motion guide rail in mandrel drawing process based on virtual die method and backward tracing scheme. FE simulations and mandrel drawing experiments using Mn55Cr carbon steel were performed to prove the effectiveness of the proposed design method. Results of FE simulations and experiments showed that the proposed design method could lead to drawn products with sound shape and the highest dimensional precision.

• Journal of Powder Materials
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• v.1 no.2
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• pp.135-144
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• 1994

Silicon carbide powder was prepared from mixtures of Sangdong silica sand and carbon black by SHS (Self propagating High temperature Synthesis) method which utilizes magnesiothermic reduction of silica. In the powder preparation process, the reacted powder was leached by chloric acid to remove the magnesium oxide and was subsequently roasted to remove free carbon. The impurities were mostly eliminated by hot acid treatment. The resultant SiC powder showed the mean particle size of 0.22 ${\mu}{\textrm}{m}$ and the specific surface area of $66.55 m^2/g$. The SiC powder was mixed with 1 wt% of boron and of carbon to increase densification rate. The mixed powder was pressed and sintered pressurelessly at $2100^{\circ}C$ for 30 min in argon gas. The sintered body showed the hardness of $2550 kg{\cdot}f/mm^2$ and the fracture toughness, KIC of $3.47 MN/m^{3/2}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.109-117
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• 2004

We synthesized energetic prepolymer(2-nitrato ethyl oxirane, NEO) for plastic-bonded explosive and measured its thermodynamic parameters. 2-Nitrato ethyl oxirane(NEO) as a monomer was synthesized from 4-butene-ol, the first-step was preparation of 1-nitrate-3-butene and second-step was synthesized 2-nitrate-ethyl oxirane from 1nitrate-3-butene and then polymerized by cationic ring opening polymerization. The unreacted monomer concentration was measured by GC. The thermodynamic parameters were obtained from the ceiling temperature(Tc) values of 1 mole monomer at each reaction temperature. We varied feed rate of monomer, concentration of initiator and monomer to control molecular weight and polydispersity of perpolymer(NEO). Number average molecular weight(Mn), polydispersity(PD), and glass transition temperature(Tg), viscosity of prepolymer(NEO) were 2000, 1.07, $-55^{\circ}C$ and 300 poise respectively.

• Korean Journal of Microbiology
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• v.19 no.1
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• pp.31-37
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• 1981

Avicelase, CMCase and salicinase of A.phoenicis K.U. 175 were purified from wheat bran culture by salting out with ammonium sulfate, dialysis and successive column chromatography Sephadex G-100. Optimum pH and temperature of avicelase were pH 3.8-4.8, $35-55^{\circ}C$ and that of CMCase, salicinase were pH4.5-5.5, $45-60^{\circ}C$ and pH 4.5-6.0, $45-60^{\circ}C$ respectively. These enzymes were relatively thermostable, alkali unstable and inhibited by $Ca^{++},\;Mn^{++},\;Cu^{++},\;and\;Hg^{++}$. Km values of avicelase, CMCase and salicinase were calculated to be $1.5{\times}10^{-4}M,\;5.5{\times}10^{-4}M\;and\;2.75{\times}10^{-5}M$ and Vmax values $1.66{\times}10^{-4}mM/min,\;3.33{\times}10^{-4}mM/min\;and\;1.14{\times}10^{-4}mM/min$, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.243-247
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• 1999

Carbon nitride coatings on the substrates of 0.55wt% C - 1.68wt% Mn induction-hardened rolling elements were prepared by ion beam assisted deposition. It was found through metallographic observation that the carbon nitride coatings appeared lamellar-type repeated layers parallel to the surface of substrate. Surface roughness of the coated specimens was improved in comparison with that of the substrates. Wear resistance of the coatings was evaluated using Polymet RCF-1 machine with a constant supply of lubricant followed by Weibull statistical analysis and scanning electron microscopy. the results indicated failure due to old-age wear-out of the coatings was mainly caused by numerous micropits formed on the wear track during repeated rolling contact.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.112.2-112.2
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• 2008