• Proceedings of the KSME Conference
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• 2001.06a
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• pp.205-210
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• 2001

Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are $200{\mu}m$ and $1000{\mu}m$. For this material, ${\Delta}K_{th}$ is about $8MPa{\sqrt{m}}$ which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low ${\Delta}K$ regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the ${\Delta}K_{eq}$ was represented by narrow band regardless of the stress ratio.

• Transactions of Materials Processing
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• v.22 no.6
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• pp.303-309
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• 2013

Spring-back of MS1470 steel sheets was numerically predicted using a non-linear kinematic hardening material behavior based on the Yoshida-Uemori model. From uniaxial tension and uniaxial tension-compression-tension data as well as the uniaxial tension-unloading-tension data, the parameters of the Yoshida-Uemori model were obtained. For the numerical simulations, the Yoshida-Uemori model was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. The model performance was validated against the measured spring-back from the benchmark problems of NUMISHEET 2008 and NUMISHEET 2011, the 2-D draw bending test and the S-rail forming test, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1210-1216
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• 2003

Recently, as the road capacity reaches the limit and environmental problems becomes serious, there is gradually increased a need for railroad vehicles that are environment-friendly and have time regularity, reliability, and safety. Accordingly, in addition to conventional railroad vehicles, lots of vehicles are being newly developed. We developed the hardware and software of the measurement system for on-line test and evaluation of korean high speed train. The software controls the hardware of the measurement system and acts as interface between users and the system hardware. In this paper, practical experiment are performed to verify mechanical performance of motor and main transformer for Korean high speed rail. The experimental test carried out by using new temperature measurement method and verify the temperature performance of motor and transformer is verified.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.613-618
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• 2020

Exhausting oil resources and increasing pollution around the world are forcing researchers to look for new, renewable, biodegradable materials to lead sustainable development. The use of fiber reinforced composites based on natural fibres has increasingly begun as prospective materials for various engineering applications in the automotive, rail, construction and aerospace industries. The natural fiber chosen to make the composite material is plant-based fibre, e.g. jute fibre, and hemp fibre. Thermosetting polymer based Epoxy (LY556) was utilized as matrix material and The composites were produced using hand lay-up technique. The fabricated composites were tested for acoustic testing, thermo-gravimetric analysis (TGA) and flammability testing to asses sound absorption, thermal decomposition and fire resistivity of the structures. Hemp fibre composites have shown improved thermal stability over Jute fibre composites. However, the fire resistance characteristics of jute fibre composites are better as compared to hemp fibre composites. The sound absorption coefficient of composites was found to enhance with the increase of frequency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.833-841
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• 2013

In the case of composite material, a variety of characteristics were expressed depending on the materials that were composed of. In this study, the materials showing non-linear shear behavior were investigated among FRP composite. Each specimen was designed and analyzed according to ASTM D4255 method: regulations on the 2-rail. The dependent variables included in this experiment were a variety of fiber, fiber volume ratio, fiber array direction, temperature, material homogeneity. For determination of characteristics based on the fiber array, fiber array direction of 0, 30, 45, and 60 degrees were selected for test specimen. Temperature of 25, 40, 60, and $80^{\circ}C$ were considered for investigation of FRP materials'shear behavior based on the external temperature. Nonlinear shear behavior was observed throughout the FRP composite material in this study. Also, using vinyl ester resins, high fiber volume ratio, and fiber array direction of 45 degree appeared to show the most prominent nonlinear shear behavior. As for the findings related to the temperature change, non-linear behavior was decreased as the external temperature increased. For factory manufactured product, non-linear behavior was relatively at parity in comparison to the behavior found in the hand lay-up FRP composite specimen.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.19-28
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• 2014

PURPOSES : This paper evaluates, using LS/DYNA-3D software, the vehicle impact performance of flexible barriers made of steel W-Beam supported by four different types of post configurations. These types include circular post, H-shape post, C-shape post, and square post. METHODS : The post-soil interaction has been investigated according to different impact angles. For this purpose, energy absorption, maximum displacements of post and rail, and occupant risk index of THIV have been compared each other. The three dimensional soil material model, instead of the conventional spring model based on Winkler and p-y curve, has been used to increase the correctness of computational model. RESULTS : It is noted the crash energy absorption has been increased with respect to the increase of impact angle. CONCLUSIONS : In particular, a post with open section(H-shape, C-shape) shows the greater crash energy absorption capability as compared with a post with closed section under the same level of impact conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.338-350
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• 2010

As existing materials for ground reinforcement, chemical grout material using cementitous materials and waterglass was used. But many problems in terms of ground reinforcement effects were implicated. In this study, for development and applicability verification of new materials, viscosity, fluidity, permeability, Self-Leveling, keeping of drilled hole, antiwashout underwater, resistance of water (groundwater dilution and minimize material eluting) and the early strength and long-term strength characteristics of developed materials was confirmed, and material standards, and establishing construction standards for the various model tests were conducted. As a result, high viscosity, flowability, permeability and keeping of drilled hole characteristics are excellent, in addition to the early strength properties, dilution does nat occur to groundwater, including groundwater is available for dealing with environmental issues. Application of basic and reinforcement method by Filler function in addition to structure can also or development of a new concept can be expected. In addition, middle and large-diameter drilled shaft, micropile, ground anchors, soil-nailing, steel pipes multi-grouting reinforcement for cement injection process could be used enough to even be considered.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.7
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• pp.557-561
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• 2016

Recently, in the manufacturing process of flat panel displays, mass production methods of inline system has been emerged. In particular the next generation OLED display manufacturing process, horizontal inline evaporation process has been tried. It is important for the success of OLED inline evaporation process to develop a magnetic levitation transport system capable of transferring a carrier equipped with a mother glass with high accuracy without any physical contact along the rail under vacuum condition. In the case of existing wheel-based transfer system, it is not suitable for OLED evaporation process requiring high cleanliness. On the other hand, the magnetic levitation transport system has an advantage that it does not generate any dust and it is possible to achieve high-precision control because there are not non-linear factors such as friction force. In this paper, we introduce the high-precision magnetic levitation transport system, which is currently under development, for OLED evaporation process.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.377-382
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• 2011

Up to now, process design of multistage profile drawing from initial round material is performed through trial-and-error based on experience of industrial experts. This means the increase in production cost and excessive time consuming. In this study, process design program was developed for multistage profile drawing from initial round material. The program was made using VisualLISP. Therefore, the program can be operated by AutoCAD program. In order to verify the effectiveness of the program, two stage profile drawing process for producing heavy duty guide rail was design by using the program. In addition FE analysis and profile drawing experiment were performed. As a result, the program can be used in order to design profile drawing process design.

• Structural Monitoring and Maintenance
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• v.4 no.3
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• pp.195-220
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• 2017

Nowadays, railway system plays a significant role in transportation, conveying cargo, passengers, minerals, grains, and so forth. Railway ballasted track is a conventional railway track as can be seen all over the world. Ballast, located underneath the sleepers, is the most important elements on ballasted track, which has many functions and requires routine maintenance. Ballast needs to be maintained frequently to prevent rail buckling, settlement, misalignment so that ballast has to be modelled accurately. Continuum model was introduced to model granular material and was extended in ballast. However, ballast is a heterogeneous material with highly nonlinear behaviour. Hence, ballast could not be modelled accurately in continuum model due to the discontinuities nature and material degradation of ballast. Discrete element modelling (DEM) is proposed as an alternative approach that provides insight into constitutive model, realistic particle, and contact algorithm between each particle. DEM has been studied in many recent decades. However, there are limitations due to the high computational time and memory consumption, which cause the lack of using in high range. This paper presents a review of recent ballast modelling with benefits and drawbacks. Ballast particles are illustrated either circular, circular crump, spherical, spherical crump, super-quadric, polygonal and polyhedral. Moreover, the gaps and limitations of previous studies are also summarized. The outcome of this study will help the understanding into different ballast modelling and particle. The insight information can be used to improve ballast modelling and monitoring for condition-based track maintenance.