• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.342-348
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• 2014

Contact between wheel and rail leads to the creep phenomenon. Linear creep theory, assuming linear increase in the creep force vs creep, results in a critical speed at which the vibration of a railway vehicle goes to infinity. However, the actual creep force converges to a limited value, so that the vibration of a railway vehicle cannot increase indefinitely. In this study, the dynamics of a railway vehicle is investigated with a 6 DOF bogie model includingthe nonlinear creep curves of Vermeulen, Polach, and a newly calculated creep curve with strip theory. Strip theory considers the profiles of the wheel and rail. The results show that the vibration of a railway vehicle results in a limit-cycle over a specific running speed, and this limit-cycle becomes smaller as the slope of the creep-curve steepens. Moreover, a hunting phenomenon is caused due to flange contact, which restricts the magnitude of the limit-cycle.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.69-77
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• 2018

Launching system is designed to store the payload, withstand the rigors, and prevent it from rusting and damaging. The behavior during initial deployment of the missile is determined by production, assembly and insertion condition of a launching tube and a missile. The purpose of this research is to confirm the safety of a launching tube by statistically analyzing behavior of the missile, during initial deployment stage. Error parameters which effect initial behavior of the missile are selected and analyzed through Monte-Carlo Simulation. Based on the result of simulation, tip-off and stress distribution between rail and shoe is predicted by using the commercial analysis program called Recurdyn. Lastly, the safety factor is calculated based on yield strength of the material and maximum stress of the rail during the process of launching. The safety of the launching system is verified from the result of the safety factors.

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.198-205
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• 2021

For twenty years, in the EU there has been a trend of a lack of maritime infrastructure and a redundance of the road one, which has a negative impact on the economy. The intermodal transport market structure in the EU has not changed over the past ten years. The stability of transport systems due to the lack of changes in the transport market remains under threat, affecting supply chains and networks through the optimization of warehousing and transportation costs. The research methodology is based on a quantitative assessment of cause-and-effect relations between economic growth and transport and logistics in the EU. A statistical analysis of security indicators, intermodal and modal transport, international trade in goods within the EU and in the world trade in goods, the dynamics of GDP of the EU countries, the level of openness of the EU economy, investment and maintenance costs of different modes of transport and infrastructure has been carried out. The results show that in 2000- 2010 there were positive changes in the transport and logistics infrastructure of the EU, which had a positive effect on trade, openness of the economy of the EU, GDP growth. However, at that time, negative effects of environmental impact and the load on road and rail transport were accumulating. Investment in different modes of transport is limited, and technical maintenance and infrastructure maintenance costs form a significant part of GDP of the EU. A slowdown in economic growth leads to budget constraints and infrastructure financing gap. As a result, the freight and passenger intermodal and modal transport market structure remains virtually unchanged. The load on rail and road transport remains stable, despite the reduced level of transport hazards. Transport productivity has declined over the past ten years. Herewith, the intensification of trade and the openness of the EU economies require constant modernization and innovative renewal. The EU policy in this direction remains normative, uncontrolled, which is reflected in investment differences within the EU and maintenance costs.

• Journal of Digital Convergence
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• v.16 no.7
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• pp.199-211
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• 2018

Ever since Korea was geopolitically divided into North and South Korea in the 1940s, South Korea has depended on maritime transportation for global trade and logistics. Now, however, South Korea is preparing to develop a new global route for trans-Eurasia logistics passing through North Korea. Even though there are difficulties to overcome, South Korea expects that a new overland route, shorter than the existing seaways in the Europe-Asia section, will bring more frequent trade with more rapid and cost-effective logistics services in the future. Related to this issue, this study aims to proactively analyze dynamic logistics changes in South Korea when a trans-Korea railway is developed and linked with the trans-China railway and the trans-Siberian railway. This study employed a system dynamics simulation approach to model the logistics system in South Korea. The simulation results indicated that the traffic of the Uiwang inland container depot near the capital area may increase but the traffic of the Port of Busan may decrease. With supplementary research, consequently, follow-up studies on adjusting the traffic capacity in Korea are required to attain successful trans-Eurasia logistics by rail.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.75-80
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• 2011

In the area of wheel on rail vehicle, hunting stability which is generated by lateral motion is one of important characteristics for running safety. It might cause not only oscillation of vehicle but also derailment in an unstable area of the high speed. A Maglev vehicle is usually controlled the voltage to maintain the air gap between electromagnet and track. However, in Maglev system, an occurrence possibility of hunting motion could be high, because Maglev vehicle is not controlled directly lateral force between electromagnet and track in the curved guideway. In this paper, running safety is evaluated when Maglev vehicle run on guideway at high speed according to installment of damper between maglev vehicles and bogies, and to analyze the effect of it. Also, the parametric study is carried out for selecting effective lateral damper properties through the simulation. To accurately predict the running safety, 3d multibody dynamics models which are included air spring, guideway conditions and irregularities profile are used. With the results acquired, suggestions were made whether to adopt the damper and how to optimize the damping characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.164-173
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• 2006

In the electro-hydraulic injector for the common rail Diesel fuel injection system, the injection nozzle is being opened and closed by movement of a injector's needle which is balanced by pressure at the nozzle seat and at the needle control chamber, at the opposite end of the needle. In this study, the piezo actuator was considered as a prime movers in high pressure Diesel injector. Namely a piezo-driven Diesel injector, as a new method driven by piezoelectric energy, has been applied with a purpose to develop the analysis model of the piezo actuator to predict the dynamics characteristics of the hydraulic component(injector) by using the AMESim code. Aimed at simulating the hydraulic behavior of the piezo-driven injector, the circuit model has been developed and verified by comparison with the experimental results. As this research results, we found that the input voltage exerted on piezo stack is the dominant factor which affects on the initial needle behavior of piezo-driven injector than the hydraulic force generated by the constant injection pressure. Also we know the piezo-driven injector has more degrees of freedom in controlling the injection rate with the high pressure than a solenoid-driven injector.

• Structural Engineering and Mechanics
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• v.59 no.4
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• pp.683-701
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• 2016

Safety is the prime concern for a high-speed railway bridge, especially when it is subjected to a collision. In this paper, an analysis framework for the dynamic responses of train-bridge systems under collision load is established. A multi-body dynamics model is employed to represent the moving vehicle, the modal decomposition method is adopted to describe the bridge structure, and the time history of a collision load is used as the external load on the train-bridge system. A (180+216+180) m continuous steel trussed-arch bridge is considered as an illustrative case study. With the vessel collision acting on the pier, the displacements and accelerations at the pier-top and the mid-span of the bridge are calculated when a CRH2 high-speed train running through the bridge, and the influence of bridge vibration on the running safety indices of the train, including derailment factors, offload factors and lateral wheel/rail forces, are analyzed. The results demonstrate that under the vessel collision load, the dynamic responses of the bridge are greatly enlarged, threatening the running safety of high-speed train on the bridge, which is affected by both the collision intensity and the train speed.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.124-132
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• 2010

To predict and analyze the rolling stock's fire growth is considered not only important factor in estimating hazard analysis of rolling stock, but also a primary factor in aspect of a rail load facility. Because it's could be regarded as a ignition source in risk assesment for the facility i.e. tunnel and station. However, currently, standardized method to predict and analyze the fire growth has not been completed yet. it is due to the fact that fire growth is not only depended on thermal property of interior materials, but also is affected dominantly by various factors such as ignition source (characterized by location, duration, and intensity), train running condition and in/exterior ventilation condition. Especially, ventilation condition is one of the most effective factor to affect fire growth in compartment space as noticed by under-ventilation fire condition. In this study, the effect of each ventilation condition on fire growth and load were examined through the numerical method through FDS (Fire Dynamics Simulator).

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.4
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• pp.393-403
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• 1997

In this paper, we proposed an optimal identification method of identifying the membership func¬tions and the fuzzy rules for the stabilization controller of the nonlinear system by RVEGA( Real Variable Elitist Genetic Algo rithm l. Although fuzzy logic controllers have been successfully applied to industrial plants, most of them have been relied heavily on expert's empirical knowl¬edge. So it is very difficult to determine the linguistic state space partitions and parameters of the membership functions and to extract the control rules. Most of conventional approaches have the drastic defects of trapping to a local minima. However, the proposed RVEGA which is similiar to the processes of natural evolution can optimize simulta¬neously the fuzzy rules and the parameters of membership functions. The validity of the RVEGA - based fuzzy controller was proved through applications to the stabi¬lization problems of an inverted pendulum system with highly nonlinear dynamics. The proposed RVEGA - based fuzzy controller has a swing -. up control mode(swing - up controller) and a stabi¬lization one(stabilization controller), moves a pendulum in an initial stable equilibrium point and a cart in an arbitrary position, to an unstable equilibrium point and a center of the rail. The stabi¬lization controller is composed of a hierarchical fuzzy inference structure; that is, the lower level inference for the virtual equilibrium point and the higher level one for position control of the cart according to the firstly inferred virtual equilibrium point. The experimental apparatus was imple¬mented by a DT -- 2801 board with AID, D/A converters and a PC - 586 microprocessor.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.878-884
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• 2012

In this paper, we consider the sway suppression control problem for container cranes with the frictions between the trolley and the rail. If the friction effects in the system can be modelled, there is an improved potential to design controllers that can cancel the effects. The proposed control improves the trolley positioning and sway suppressing against various frictions. The proposed synthesis combines a variable structure control and the adaptive control to cope with various frictions including the unknown constants. First, the variable structure control with the simple switching action is designed, which is based on a class of feedback lineariztion methods for the fast stabilization of the under-actuated sway dynamics of container. Second, the adaptive control with a parameter estimation is designed, which is based on Lyapunov stability methods for suppressing the oscillation of the trolley travelling, especially due to Coulomb friction in the vicinity of the target position. The asymptotic stability of the overall closed-loop system is assured irrespective of variations of rope length. Simulation are shown under initial sway, external wind disturbances, and various frictions.