• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.587-598
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• 2008

In the trackbed design using elastic multi-layer model, the stress-dependent resilient modulus is an important input parameter, which reflects substructure performance under repeated traffic loading. The resilient moduli of crushed stone and weathered granite soil were developed using nonlinear dynamic stiffness, which can be measured by in-situ and laboratory seismic tests. The prediction models of resilient modulus varying with the deviatoric or bulk stress were proposed (Park et al., 2008). To investigate the performance of the prediction models proposed herein, the elastic response of the test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of the test sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 1mm, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation. The prediction models proposed for resilient modulus were verified by the comparison of the calculated vertical displacements with measured ones during train passages.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.101-108
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• 2016

Lifting plan in the large spacial structure is an important factor influencing the efficiency and economy of the construction process. The purpose of this study was deriving the requirements for lifting techniques as the basic research in the double spoke wheel roof structure construction. In the lift up erection method, management plan of the interference error in the column and outer-ring was needed that occur during lifting roof structure. In the bent erection method, material usage reduction plan was required by the structural design of the temporary bent. In the hybrid erection method, lifting plan was needed that minimizes weather condition and crane usage. All lifting techniques were required Value Engineering model for reduction of cost and construction period.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1911-1915
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• 2003

Today optical communication industry is developed; demand of optical communication part is increased. ZrO$_2$ ceramic ferrule is very significant part which determines transmission efficiency and quality of information in the optical communication part by connector of optical fibers. Being different from metal grinding, material removal through brittle fracture plays an important role in ZrO$_2$ ceramic grinding. Most of ZrO$_2$ ceramic ferrule processes are grinding which request high processing precision. Particularly, concentricity and cylindricity of inner and outer diameter are very important. The co-axle grinding process of ZrO$_2$ ceramic ferrule is to make its concentricity all of uniform before centerless grinding. Surface integrity of ZrO$_2$ ceramic ferrule is affected by grinding conditions, and equipment. In this study, surface integrity of workpiece according to such as a change of grinding wheel speed, feed rate, regulating wheel speed and grinding force is investigate to improve the concentricity and roundness of ZrO$_2$ ceramic ferrule from many experiments. Thus, if possible be finding highly efficient and quality grinding conditions.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.26-33
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• 2004

Ultra precision grinding technology has been developed from the refinement of the abrasive, the development of high stiffness equipment and grinding skill. The conventional wafering process which consists of lapping, etching, 1 st, 2nd and 3rd polishing has been changed to the new process which consists of precision surface grinding, final polishing and post cleaning. Especially, the ultra precision grinding of wafer improves the flatness of wafer and the efficiency of production. Furthermore, it has been not only used in bare wafer grinding, but also applied to wafer back grinding and SOI wafer grinding. This paper focuses on the flatness of the ground wafer. Generally, the ground wafer has concave pronto because of the difference of wheel path density, grinding temperature and elastic deformation of the equipment. Wafer tilting is applied to avoid non-uniform material removal. Through the geometric analysis of wafer grinding process, the profile of the ground wafer is predicted by the development of profile simulator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.98-101
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• 2003

As the ultra precision grinding can be applied to wafering process by the refinement of the abrasive. the development of high stiffness equipment and grinding skill, the conventional wafering process which consists of lapping, etching, 1st, 2nd and 3rd polishing could be exchanged to the new process which consists of precision surface grinding, final polishing and post cleaning. Especially, the ultra precision grinding of wafer improves the flatness of wafer and the efficiency of production. Futhermore, it has been not only used in bare wafer grinding, but also applied to wafer back grinding and SOI wafer grinding. This paper focused on the flatness of the ground wafer. Generally, the ground wafer has concave profile because of the difference of wheel path density, grinding temperature and elastic deformation of the equiptment. Tilting mathod is applied to avoid such non-uniform material removes. So, in this paper, the geometric analysis on grinding process is carried out, and then, we can predict the profile of th ground wafer by using profile simulation.

• Journal of the Korean Society for Railway
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• v.3 no.3
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• pp.117-124
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• 2000

The rubber wheel-type AGT has two major kinds of bogie; one is the bogie type and the other steering one. Both are important vehicular structure to support the whole running vehicle and passenger loads. This paper deals with the static analysis for the two types of bogie frame subjected to combined external forces, as well as independent ones specified in UIC 515-4. Furthermore, the dynamic analysis is performed under vibrational loading conditions so as to compare dynamic characteristics, Numerical results by using commercial packages, I-DEAS and NASTRAN show that maximum stresses do not exceed the yield strength level of material used for both bogies. From an overall viewpoint of strength, the bogie type turns out to be superior to the steering type except for the case of a lateral loading. It is also observed that the steering type shows a characteristics of low frequency behavior during a course of searching for structurally weak areas to be stiffened. The vibrational fatigue analysis for each bogie frame depends on the loading time history conditions which is applied. Time History Central Database List in the NASTRAN package. Subsequent1y, the fatigue life of bogie type is longer than the steering type.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.3
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• pp.86-92
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• 2002

In this study, experiments were carried out to investigate the characteristics of grinding and wear process of diamond wheel far ceramic materials. Normal component of grinding resistance of $Al_2$O$_3$ was less then that of $Si_3 N_4$ and $ZrO_2$. This seems to be the characteristics of ceramic tools on work pieces both of high hardness. For the case of $Si_3 N_4$ and $ZrO_2$, as the mesh number of wheel increases, the surface roughness decreases. For the case of $Al_2 O_3$, the surface roughness does not decreases. Specific binding energy decreases as the material removal rate per unit time increases. For the case of $Si_3 N_4$ and $ZrO_2$, grinding is carried out by abrasive wear processes. For the case of $Al_2 O_3$, grinding is carried out by grain shedding process due to brittle fracture.

• Tribology and Lubricants
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• v.24 no.6
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• pp.285-290
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• 2008

The purpose of this paper is to present the case study of tribological failure analysis on the gear damages, oil leakage, and sealant sealing in a manual transmission of front engine and front wheel drive vehicle. The manual transmission is to change the speed range and direction of the engines depending on the driving conditions by friction driving forces with input and output gear system. The material property and surface roughness of the gears are strongly related to the gear noise and micro-vibration, oil leakage and wear, which may decrease the real contact area of the gear and the strength of the oil film thickness between the driving gear and driven one. The O-ring damage of speedometer driven gear and bad sealant sealing of oil pan may produce oil leakage through the contact surfaces, which cause the oil shortage and seizure on the sliding surfaces of the transaxle gears. In the failure case study, the proper repair working and good lubrication are very important for the long life of the transaxle without any tribological failures and oil leakage.

• Tribology and Lubricants
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• v.33 no.1
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• pp.31-35
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• 2017

Recently, international attention has been focused on the development of non-traditional energy resources such as shale gas and oil sands, due to the steep increase in the demand for natural resources. The materials incorporated in an oil gas plant module experience extreme environments, and are prone to various problem such as fracture, corrosion and abrasion due to low-temperature brittleness. In order to improve the plant life, it is necessary to perform characteristics study and performance evaluation of the materials. In particular, this paper explains the main set of materials which are most frequently used in oil sands plant project. In order to investigate wear characteristics, the authors carried out abrasive wear tests of TP 316, stainless steel and SS 400, structural rolled steel. For the analysis of the abrasive wear resistance of an oil sands plant, the authors carried out the test according to ASTM G 105 "Standard Test Method for Conducting Wet Sand/Rubber Wheel Abrasion Test" standard guidelines. The authors have derived the results from the data associated with the loss of mass with respect to wear rate. During the test, for a given wear length for 10,000 revolutions, the rotational speed and applied force of the rubber wheel were varied.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.130-143
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• 1993

Engineering ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper, experiments are carried out to obtain the effect of "In-process dressing" to grind the Engineering ceramics with high efficiency. To save running time for dressing process and obtain restraint effect of diamond grain wear, "In-process dressing" system using WA stick type honing stone is proposed. Representative Engineering ceramics, such as AI$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, are ground with diamond wheel. Also bending strength test is carried out to check upward tendancy of mecahnical properties as the result of machining defact restraint through the grinding machining method using "In-process dressing" process. Some results obtained in this study provide useful information to attain the high efficiency grinding and the high mechanical properties of Engineering ceramics.rties of Engineering ceramics.