• Journal of Korea Foundry Society
• /
• v.16 no.2
• /
• pp.141-148
• /
• 1996

In high chromium cast iron, the control of matrix microstructure as well as carbide structure is important to the performance as a wear resistant material. In this study, 3.0% C-24.0% Cr white cast irons with various molybdenum contents(residual, 1.0%, 3.0% and 5.0%) were solidified conventionally and unidirectionally for studying their effects on the microstructure and hardness. In the conventional casting, two sets of castings were poured from each melt. One set of the castings consisted of cylindrical bars of 10 and 20mm by 155mm long. The second set of the castings was a cylindrical bar of 30mm by 200mm long. On the other hand, a pep-set mold set on the Cu plate was employed to make the solidification unidirectionally. X-ray diffraction method was used to observe retained austenite and carbides in the high chromium cast iron. The morphology of eutectic $M_7C_3$ carbides changed from needle-like type to nodular type with the increase of Mo content. And, the presence of $M_2C$ carbides was identified in the sample where Mo was added over 3.0 %. Primary and eutectic carbides appeared as rod type and corngrain type, respectively in the unidirectionally solidified samples which were cut to parallel to the solidification direction. In the EDX analysis, Cr concentration was higher in the primary and eutectic $M_7C_3$ carbides, Mo in the $M_2C$ carbides, and Fe in the matrix.

• Textile Coloration and Finishing
• /
• v.27 no.3
• /
• pp.219-227
• /
• 2015

This study aims to propose a method to reduce hair damage after investigating the following: the factors which vary depending on hair treatment conditions; the degree of hair damage in the bleached sample; and an analysis of the effects of a perm on wave formation. To determine the effects of these treatment types, hair bleach was mixed with the hair treatment, and hair damage and formation of permanent waves were examined. Using a scanning electron microscope, in addition, morphological changes were analyzed and the following results were obtained: After mixing natural powder(2.5g) and hair cream(2.5g) and bleaching the mixture, it was compared to the scale structure of untreated hair. When 5g of natural powder was mixed and bleached, a clear layer was observed among cuticle scales, showing the effects of hair treatment. Therefore, this confirms that the effects of hair treatment were most notable when grain powder was mixed with hair cream. Once hair is damaged, it is almost impossible to regain its original state. When chemical agents are used, therefore, it is important to consider the possible hair damage they cause.

• Microbiology and Biotechnology Letters
• /
• v.32 no.4
• /
• pp.366-370
• /
• 2004

Four chitinase producing bacteria, Arthrobacter nicotinae CH4, Arthrobacter nicotinae CHI3, Arthrobacter sp. CH5 and Micrococcus sp. CH3, were isolated from small crabs and shrimps. We investigated the optimum medium condition for the production of enzyme and high cell mass. The preferable medium composition was as follows: colchitin 0.1 %(w/v), glycerol 0.25%(w/v) and yeast extract 0.05%(w/v) in minimal midium ($K_{2}HPO_{4}$ 0.7 g/l, $KH_{2}PO_{4}$ 0.3 g/l, $MgSO_{4}{\cdot}5H_{2}O$ 0.5 g/l, $FeSO_{4}}{\cdot}7H_{2}O$ 0.01 g/l, $ZnSO_{4}$ 0.001 g/l, $MnCI_2$ 0.001 g/l, pH 7.0). This cell culture medium could be used directly as sample for measuring chitinase activity. Because it hardly conreducing sugar such as glucose (blank value=0), the detected reducing sugar can be considered as a chitinase reaction product. The results can be used for easy preparation method for determination of enzyme activity and analysis of enzyme-substrate reaction in step of screening of chitinase producing bacteria.

• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.280-283
• /
• 1997

Human cervical spine has to protect the neural components and vascular structures. Also, it must have the flexibility afforded by an extensive range of motion to integrate the head with the body and environment. Because of these two-sided features, human cervical spine has very complicated shapes and their injury mechanisms are not fully understood yet. We have developed analytical model of human CS by using the finite element method. The model has been verified with in vivo and in vitro experimental results. From the qualitative analysis of simulation results, we were able to explain some of the fundamental mechanisms of neck pain. Further more, this FE model of human CS can be used as an analytical tool or biomechanical design of the clinical device and safety restraints.

• Transactions of Materials Processing
• /
• v.21 no.8
• /
• pp.499-505
• /
• 2012

The fuel cell is a very promising power generation system combining the benefits of extremely low emissions, high efficiency, ease of maintenance and durability. In order to promote the commercialization of fuel cells, a flexible forming process, in which a hyper-elastic rubber is adopted as a medium to transmit forming pressure, is suggested as an efficient and cost effective manufacturing method for fuel cell bipolar plates. In this study, the ability of this flexible forming process to produce the micro channel arrays on metallic bipolar plates was first demonstrated experimentally. Then, a finite element (FE) model was built and validated through comparisons between simulated and experimental results. The effects of key process parameters on the forming performance such as applied load and punch velocity were investigated. As a result, appropriate process parameter values allowing high dimensional accuracy without failure were suggested.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.2
• /
• pp.107-113
• /
• 2006

The torsion beam axle type is widely used in the rear suspension for small passenger cars due to low cost, good performance, etc. To develop the torsion beam axle, it is necessary to estimate the characteristics of rear suspension from the design process. The characteristics estimation of the torsion beam axle is performed using FEM, dynamic simulation and is verified the real test. In this study, the natural frequency and roll stiffness of the torsion beam axle were measured by FEM, and the reliability of the FE model was evaluated according to the comparison of test data. This study presents a unique method for the finite element modeling and analysis of the torsion beam axle. The results of the FEA were verified using test data.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.193-197
• /
• 2002

In this study, the casting/forging process was applied to the Shift-Fork, a manual transmission part of automobiles. In the casting experiments, the effects of additives, Sr, Ti＋B and Mg, on the mechanical properties and the microstructure of a cast preform were investigated. When 0.03% Sr were added into the molten aluminum alloy, the finest silicon-structure was observed in the cast preform and the highest tensile strength and elongation accomplished. And when 0.2% Ti＋B were added into the molten Al-Si alloy, the highest values of tensile strength were obtained. The maximum hardness was in case of 0.2% Mg. In the forging experiment, it was confirmed that the optimal configuration of the cast preform could be predicted by FE analysis. To minimize the cost as the press size, the compact shape of preform was proposed to reduce the volume of flash. The modification of shape in designing preform was performed to attain a satisfactory performance in the areas where the mechanical strength were more required. By using FVM(Finite Volume Method) software, it was verified that a proposed casting design was available. To identify the relationship between effective strain and mechanical properties of the final forged product, the compression test was performed. As the result, the tensile strength and elongation of a cast preform were much higher than before forging. The minimum forging temperature was found 40$0^{\circ}C$ to save heating time.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.36-41
• /
• 2014

Electro-Mechanical Actuator installed on aircraft consists of a decelerator which magnifies the torque to rotate an axis connected with aircraft control surface, a control section which controls the motor assembly through receiving orders from cockpit and a motor assembly which rotates the decelerator. EMA controls aircraft attitued, position, landing, takeoff, etc. It is important part of a aircraft. Aircraft maneuvering make vibration of EMA. Vibration may cause the vibration fatigue. For that reason, it is necessary to analyze the system safety. In this paper, first EMA is modeled in finite element method and analyzed the response from input vibration. second EMA is tested and analyzed from modal experimental data. third EMA Fe model is updated and re analyzed. and EMA is verified safety with $3{\sigma}$ stress and S/N curves.

• Journal of Magnetics
• /
• v.18 no.4
• /
• pp.391-394
• /
• 2013

In this study, nickel-zinc ferrite nanoparticles, with the chemical formula of $Ni_{0.3}Zn_{0.7-x}Cu_xFe_2O_4$ (where x = 0.1- 0.6 by step 0.1), were fabricated by the sol-gel method. The effect of copper substitution on the phase formation and crystal structure of the sample was investigated by X-ray diffraction (XRD), thermo-gravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD result shows that due to the reduction of Zn content,the crystallite size of the sample increased. The results of the vibration sample magnetometer (VSM) exhibit an increase in saturation magnetization value (Ms) for samples with x ${\leq}$ 0.3 and a linear decrease for samples with x > 0.3. The variation of saturation magnetization and coercivity of the samples were then studied.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.565-570
• /
• 2007

Fiber reinforced polymer(FRP) composite decks are new to bridge applications and hence not much literature exists on their structural mechanical behavior. As there are many differences between numerical displacements through static analysis of the primary model and experimental displacements through static load tests, system identification (SI)techniques such as Neural Networks (NN) and support vector machines (SVM) utilized in the optimization of the FE model. During the process of identification, displacements were used as input while stiffness as outputs. Through the comparison of numerical displacements after SI and experimental displacements, it can note that NN and SVM would be effective SI methods in modeling an FRP deck. Moreover, two methods such as response surface method and iteration were proposed to optimize the estimated stiffness. Finally, the results were compared through the mean square error (MSE) of the differences between numerical displacements and experimental displacements at 6 points.