• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1641-1649
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• 2011

Dynamic response of high-speed railway bridges is important due to the possibility of resonance from continuous and repeated action of high-speed train running. The designer's decision and application affect the result of dynamic analysis significantly, therefore guideline for dynamic analysis is required. On the purpose of the selection of resonable model for dynamic analysis, this study investigated load distribution effect.

• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.948-953
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• 2008

In high dynamic situations, the GPS carrier tracking loop requires a wide bandwidth to track a carrier signal because the Doppler frequency changes more rapidly with time. However, a wide bandwidth allows noises within the bandwidth of the tracking loop to pass through the loop filter. As these noises are used in the numerical controlled oscillator(NCO), the carrier tracking loop of a GPS receiver shows a degraded performance in high dynamic situations. To solve this problem, an adaptive two-stage Kalman filter, which offers the NCO a less noisy phase error, can be used. This filter is based on a carrier phase dynamic model and can adapt to an incomplete dynamic model and a quickly changed Doppler frequency. The performance of the proposed tracking loop is verified by several simulations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.63-66
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• 2001

Recently, as the demand for high efficiency, multi function machine tools is increasing, domestic machine tool industries are investing in research and development for precision machine tools with high speed. This trend is closely correlated with the design technique which is necessary to make new type machine tool compatible with new production system. To achieve high precision, high speed machine tools with reduced chatter, it is needed to develop dynamically rigid structure. In this paper, dynamic optimization of machine structure is presented. At this procedure of dynamic design, dynamic compliance is minimized using Simple Genetic Algorithm(SGA)

• Structural Engineering and Mechanics
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• 제67권1호
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• pp.9-20
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• 2018

In this paper, a framework is proposed for dynamic analysis of train-bridge systems with a damaged pier after barge collision. In simulating the barge-pier collision, the concrete pier is considered to be nonlinear-inelastic, and the barge-bow is modeled as elastic-plastic. The changes of dynamic properties and deformation of the damaged pier, and the additional unevenness of the track induced by the change of deck profile, are analyzed. The dynamic analysis model for train-bridge coupling system with a damaged pier is established. Based on the framework, an illustrative case study is carried out with a $5{\times}32m$ simply-supported PC box-girder bridge and the ICE3 high-speed train, to investigate the dynamic response of the bridge with a damaged pier after barge collision and its influence on the running safety of high-speed train. The results show that after collision by the barge, the vibration properties of the pier and the deck profile of bridge are changed, forming an additional unevenness of the track, by which the dynamic responses of the bridge and the car-body accelerations of the train are increased, and the running safety of high-speed train is affected.

• 항공우주시스템공학회지
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• 제7권2호
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• pp.1-7
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• 2013

Recently, there are a number of studies over dynamic analysis for minimizing vibration of flexible structures such as solar panel for agility of high-agility satellite. The traditional studies perform dynamic analysis of a solar panel assumed as rigid structure since the stiffness of solar panel is higher than the stiffness of solar panel's hinge spring. However, there are vibrations that have modes of bending and torsion when high-agility satellite rotate speedily. This vibrations result in delaying safety time of satellite or degrading image quality. This paper presents dynamic analysis's technique of satellites including the spring hinge of solar panel and flexible structural solar panel's effects described as the linear equation of motion using Lagrange's theorem, and verifies the validity of an established dynamic analysis's technique of satellites by comparing the finite element method. In addition high-agility satellite's dynamic characteristics of a torque profile are analyzed from the established dynamic analysis's technique of satellites.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.849-853
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• 2002

A specific experimental method, the split Hopkinson pressure bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of 103/s~104/s. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading are determined using a Split Hopkinson Pressure Bar technique.

• 한국철도학회논문집
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• 제4권4호
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• pp.131-137
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• 2001

The dynamic behavior of high speed train is very important because of its safety and passengers' ride comfort. The railway vehicle is composed of many suspension components, such as 1st springs, 1st dampers, 2nd springs and 2nd dampers, that have an influence on the dynamic characteristics of high speed train. Also, the wheel/rail shapes and the track geometry affect the dynamic behavior of high speed train. This paper reviews the dynamic behavior of KHST in the KTX test line. The VAMPIRE program is used for this simulation. The simulation results are within the limits of safety criteria. Thus the KHST can operate safely at 350 km/h in the KTX test line.

• 한국철도학회논문집
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• 제9권5호
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• pp.588-593
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• 2006

The catenary system of a high speed train is designed to have a flexibility to ensure the contact with a pantograph during high speed running. The flexibility inevitably entails a vibration. The vibration is transferred to a utility pole through brackets. Therefore, the examination of the dynamic load at the bracket due to the train running is necessary for the design of the bracket. In this research, an equation of motion is derived to calculate the dynamic load at the bracket during high speed running and a computer program is developed. Also, the analyzed results are compared to characterize the dynamic load at the bracket.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.436-447
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• 2002

In this study, the dynamic response of a catenary system that supplies electrical power to high-speed trains is investigated. One of the important problems which is accompanied by increasing the speed of a high-speed rail, is the performance of stable current collection. Another problem which has been encountered, is maintaining continuous contact force between the catenary and the pantograph without loss of panhead. The dynamic analyses of the catenary based on the Finite Element Method (FEM) are performed to develop a pantograph suitable for high speed operation. The static deflection of the catenary, the stiffness variation in contact lines, the dynamic response of the catenary undergoing the force of a constantly moving load and the contact force were calculated. It was confirmed that a catenary model is necessary to study the dynamic characteristics of the pantograph system.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.206-210
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• 2003

Machining of deep holes with conventional boring bars frequently induce chatter vibration because of their low dynamic stiffness which is defined as the product of static stiffness and damping of conventional boring bar materials. In addition, the specific stiffness ($E/{\rho}g$) of boring bars is more important than the static stiffness to increase the fundamental natural frequency of boring bars in high speed machining. Therefore, boring bar materials should have high static stiffness and high damping as well as high specific stiffness. The best way to meet requirements is to employ fiber reinforced composite materials for high speed boring bars because composite materials have high static stiffness, high damping and high specific stiffness compared to conventional boring bar materials. In this study, the dynamic characteristics of carbon fiber epoxy composite boring bars were investigated. From the metal cutting test, it was found that the chatter was not initiated up to the ratio of length to diameter of 10.7 at the rotating speed of 2,500 rpm.