• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.778-781
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• 2002

Durability of rubber dust cover in the ball joint for automotive suspension parts were analyzed by FEM and compared with experimental data. Upper open area of ball joint is sealed by dust cover for preventing outflow of the lubricating oil and intrusion of send, dust, water, etc. This rubber cover undergoes repeated loadings such as tension and compression while the car is running. Analysis about rubber material needs to consider every kinds of nonlinearities arise in finite element analysis, which are geometric nonlinearity due to large displacement and small strain, materially nonlinearity and nonlinear boundary condition such as contact. So in the study, the deformation behavior of dust cover was analysed by using the commercial finite element program MARC. This program could solve these kinds of nonlinear analysis accurately. Finite element model of dust cover is considered as 3-dimensional half model based on 2-dimensional axisymmetric model. Material property of rubber was modeled by Ogden model and input data for calculation takes form uniaxial tension test of rubber specimen, The final object of the study is obtaining the design specification of dust covers and the result of analysis should be a useful data to design of rubber

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.45-52
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• 1999

It is difficult to keep the balance of supply and demand for natural aggregates in recent years, because natural resources have become to be almost exhausted. Crushed stone is already used for coarse aggregate instead of river gravel at present. Now, crushed sand or sea sand should be used for fine aggregate, because natural sand also has been exhausted with a few exceptions around Nakdong River. The sea sand has a lot of problems which are the corrosion of reinforcement bars, the investment of facility for cleansing salt and the cost increase due to the insufficiency of industrial water. Therefore, it is necessary to produce and to utilize the crushed sand very actively, but some material properties which are related to water absorption, strength and chemical durability, prevent from determining the generalized criteria because its rocks make much differences in its physical and chemical characteristics. In this paper, fundamental physical properties of crushed sand, which comes from Daegu Subway construction fields, have been investigated for the usability on basic material of concrete. The optimum replacement ratio and the strength estimation method of crushed sand replacing natural sand also have been presented here through the compressive strength test of ready-mixed concrete cylinders.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.3
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• pp.153-159
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• 2013

The power transmission system has always been considered critical for a human powered boat(or water bike) since it first showed up at Human Powered Vessel Festival. Mechanical problems, such as abrasions and other damages of the gear system for the power transmission, lead to poor durability and low efficiency of a boat. This paper described mechanical problems and a design process of power transmission system and then suggested the method to solve the problems. It is selected a module and a type of gears that are structurally stable thus can transmit the power durable. Especially the lower gear box is applied to CRP(contra rotating propeller) system for improving the structural stability and the propeller efficiency as well. As the results, the upper and lower gear box are designed and manufactured. And from the trial test, it is confirmed that the power transmission system is reliable.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• Elastomers and Composites
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• v.50 no.1
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• pp.55-61
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• 2015

Manufacturing process of OLED contains adsorption-desorption process of glass substrate. There are several adsorption methods of glass substrate such as atmospheric pressure, vacuum and electrostatic adsorption. However, these methods are very complex to connect system. Therefore, the adsorption method using silicone rubber based sticking chuck was proposed in this study. Three types of silicone rubbers having 0, 19.3 and 32.2 wt% of fluorine were used and their mechanical properties, surface energies and adsorption properties were examined. According to the results ${\sigma}_{300}$ and hardness increased with increasing fluorine contents, but elongation was decreased. Also, fluorosilicone rubber containing 32.2 wt% of fluorine showed the lowest surface tension, among three types of rubber and resulted in the highest initial tack with glass substrate. After the adsorption-desorption test of 300,000 cycles was performed, the adsorption force of S-1 (silicone rubber) decreased largely from 2.34 to 0.73 MPa. However, the S-3 (fluorosilicone rubber having 32.2 wt%. of fluorine) decreased only from 3.15 to 2.24 MPa. From this study, we obtained the valuable equations related to long term durability of silicone based sticking chuck. Finally the transfer of silicone rubber to glass substrate with the adsorption-desorption process was not occurred and this phenomenon was examined by UV-Visible spectroscopy.

• Fashion & Textile Research Journal
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• v.16 no.5
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• pp.766-775
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• 2014

This study is aimed to research the actual wearing condition of ballet dancewear of girls aged between 2 and 6 years on its design, size and fit. Survey data were collected from 171 mothers who have a girl learning ballet dance. The questionnaire was composed with ballet education, ballet dancewear purchasing, preference on design, size selection, and fitting. The collected data were analyzed with frequencies statistics, ${\chi}^2$-test, ANOVA using the SPSS WIN 20.0. The results are as follows; High rate of respondents said that the purpose of ballet education was for good body balance, leisure activity, and height growth. The main method of purchase was online shopping. The design, price, size and fit were identified as important ballet dancewear attributes for girls. The most preferred style of ballet dancewear were 'short sleeve skirted leotard' and 'camisole skirted leotard' which look like dress. The respondents reported slight satisfaction with size and fit, price, convenience in action, sewing and durability. The most preferred sizing system was code by height but any ballet dancewear makers don't use code by height. Therefore it is difficult for consumers to select size. Retailers and manufacturers could potentially use the results of this study to improve the sizing system and fit for children's ballet dancewear.

• Biotechnology and Bioprocess Engineering:BBE
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• v.2 no.2
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• pp.77-81
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• 1997

Removal of nitrogen compound from waste water is essential and often accomplished by biological process. To prevent washout and to develop an efficient bioreactor, immobilization of sutibal microorganisms could be sensible approach. Strains and permeabilized cell encapsulated in cellulose nitrate microcapsules and immobilized on polystyrene films were prepared by the method described in the previous study. In the wastewater treatment system, nitrification of ammonia component is generally known as rate controlling step. To enhance the rate of nitrification, firstly nitrifying strains Nitrosomonas europaea(IFO14298), are permeabilized chemically, and immobilized on polystyrene films and secondly oxidation rates of strain system and permeabilized strain system are compared in the same condition. with 30 minute permeabilized cells, it took about 25 hours to oxidize 70% of ammonia in the solution, while it took about 40 hours to treat same amount of ammonia with untreated cells. All the immobilization procedures did not harm to the enzyme activity and no mass transfer resistance through the capsule well was shown. In the durability test of immobilized system, the system showed considerable activity for the repeated operation for 90 days. With these results, the system developed in this study showed the possibility to be used in the actual waste water treatment system.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.77-85
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• 2010

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of a railroad car and vehicles structure.However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weld, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, $({\Delta}{\sigma}_a)_R-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test(ALT) was conducted. From the experimental results, an acceleration model was derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1211-1217
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• 2006

This study is focused on oxidation prevention of STS430, which is generally used as solid oxide fuel cell(SOFC) interconnect at intermediate operating temperatures with oxidation-proof coatings. Inconel, $La_{0.6}Sr_{0.4}CoO_3(LSCo)$ and $La_{0.6}Sr_{0.4}CoO_3(LSCr)$ were chosen as coating materials. Using a radio frequency magnetron sputtering method, each target material was deposited as thin film on STS430 and was analyzed to find out favorable conditions. In this study, LSCr-coated STS430 can reduce electrical resistance to 1/3 level, compared with uncoated STS430. Also, long-term durability test at $700^{\circ}C$ for 1000 hours tells that LSCr thin layer performs an important role to prohibit serious degradations. Superior oxidation-resistant characteristic of LSCr-coated STS430 is attributed to the inhibition of spinel structure formation such as $MnCr_2O_4$.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.294-300
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• 1999

After researching the physical properties of the concrete included Rice Husk Ash(RHA concrete) and workability of fresh concrete admixed RHA, we have tested durability of RHA-concrete against freeaing and thawing in the winter using rapid freezing and thawing test method(KS F 2456) . There aretwo hypotheses to explain the failure mechanism of a freezing and thawing action. First, the hydraulic pressure in the pores of freezing concrete make an internal stress of concrete structures outbreaking micro crack in the face of concrete, Second, Frost action causing damage to cement paste repeatedly come from soil frost action, freezing water in the capillaries. Initial Relative Dynamic Modulus of Elasticity (DME) was biggest in cae of unit binder weight 600kgf/㎥ and relative dynamic modulus of elasticity increased until 300cycles. In general , initial relative DME was proportional to unit binder weight . Relative DME was decreased in proportion to unit binder weight in the case of 300, 400, 500kgf/㎥ , but relative DME fo the others remained more than 90% until 300 cycles. It was not good effect of intermixed RHA to concrete in case of below unit binder weight 300kgf/㎥ and the resistance of freezing and thawing was not good either.