Earticle

연구목적: 본 연구는 대용량 차량궤적 자료를 이용하여 동적 과속 위험성을 측정하기 위한 방법론을 개 발하고, 개발된 과속 지표의 적용성을 증명하는데 있다. 연구방법: 개별 차량 궤적을 이용하여 차량의 속도 변화를 미시적 시공간으로 분석하고, 사고 위험성 관점에서 과속의 경계(즉, 경계속도)를 결정하 였다. 결정된 경계속도를 이용하여 미시적 시공간 기반 과속 노출도 지표를 개발하였다. 연구결과: 검 증 연구는 대용량 차량 GPS 궤적 자료와 실제 교통사고 자료를 이용하여 수행되었다. 분석결과, 개발된 과속 노출도 지표는 고속도로 교통사고에 대해 우수한 설명력 (R2=0.7)을 보였다. 이는 미시적 시공간 차원에서 과속이 분석되어야 함을 직접적으로 의미한다. 결론: 차량 속도 상태의 시공간적 변화는 매우 가변적이다. 따라서 본 연구에서 제시된 방법론은 차량 궤적 자료를 이용한 미시적인 공간기반 교통사 고 요인 및 사고 위험 노출도 분석에 효과적으로 활용될 수 있을 것으로 판단된다.

Purpose: This study is to develop a method for measuring dynamic speeding risks using vehicle trajectory big data and to demonstrate the feasibility of the devised speeding index. Method: The speed behaviors of vehicles were analysed in microscopic space and time using individual vehicle trajectories, and then the boundary condition of speeding (i.e., boundary speed) was determined from the standpoint of crash risk. A novel index for measuring the risk exposure of speeding was developed in microscopic space and time with the boundary speed. Result: A validation study was conducted with vehicle-GPS trajectory big data and ground-truth vehicle crash data. As a result of the analysis, it turned out that the index of speeding-risk exposure has a strong explanatory power (R2=0.7) for motorway traffic accidents. This directly indicates that speeding behaviors should be analysed at a microscopic spatiotemporal dimension. Conclusion: The spatial and temporal evolution of vehicle velocity is very variable. It is, hence, expected that the method presented in this study could be efficaciously employed to analyse the causal factors of traffic accidents and the crash risk exposure in microscopic space using mobility trajectory data.

본(本) 연구(研究)는 300 km/h 내외의 속도영역(速度領域)에서 운행(運行)되고 있는 고속열차(高速列車)의 불규칙(不規則)한 동적(動的) 윤중변동(輪重變動)을 해석(解析)하여 고속철도궤도(高速鐵道軌道)에서의 대책(對策)과 궤도(軌道) 각(各) 구성요소(構成要素)들의 구조설계(構造設計)를 위하여 종래의 연구(研究)에서 윤중변동(輪重變動)에 관련이 있다고 생각되어 온 차량(車輛)의 스프링하질량(下質量) 및 궤도틀림이외에 레일지지(支持)스프링계수(係數)와 진동감쇠계수(振動減衰係數) 등(等)을 포함하여 보다 정량적(定量的)인 해석(解析)을 시도(試圖)하였다. 특히 차량(車輛)의 동적(動的) 윤중변동(輪重變動)에 대한 궤도부분(軌道部分)의 주(主)된 역할(役割)은 레일지지(支持)스프링계수(係數)와 진동감쇠계수(振動減衰係數)에 있으므로 이에대한 궤도(軌道)의 각(各) 구성요소별(構成要素別) 특성(特性)을 보다 분명(分明)히 하기위하여 충격(衝擊)에 의한 레일지지계(支持系)의 동적(動的) 응답(應踏)을 역학(力學)모델 설정(設定)을 통하여 이론적(理論的)으로 해석(解析)하고 실물궤도(實物軌道)에서의 시험(試驗)에 의하여 종래 확실하게 밝혀지지 않았던 이들 궤도특성치(軌道特性値)를 산출(算出)하였다.

The purpose of this study is to provide the cause and countermeasure for track problems in the high speed railways due to the irregularly increasing dynamic wheel loads running over the speed range of 300 km/h. It has long been recognised that the track problems encountered on high speed railways are associated mainly with vertical dynamic loads which are related to the unsprung mass of vehicles and track irregularities. In addition to these parameters for the estimation of the dynamic wheel load variation, however, the dynamic characteristics of track structures are discussed in this paper with reference to mathematical modelling of the tracks and vehicle. From the results of the more detailed analyses, the effects of track stiffness and damping characteristics are considered to be significant for reducing the dynamic wheel loads. To make this point clear and appraise the overall performance of the track components, the theoretical analysis on the dynamic behavior of the tracks and wheel set impact tests on several track structures are performed. The experimental results from different track components are compared with each other. The track stiffness and damping characteristics are also presented quantatively.

The development of a new railway vehicle is under progress through the Next Generation High-Speed Rail Development Project in Korea. Its aim is to develope fundamental technology of the vehicle that can run over 400km/h. The new distributed traction bogie system, 'HEMU'(High-speed Electric Multiple Unit), will be used and is different from previously developed high speed railway vehicles. Previous vehicles adopted push-pull type system, which means one traction-car drives rest of the vehicle. Due to the difference, investigation on dynamic behavior and its safety evaluation are necessary, as a part of verification of the design specification. In this paper, current progresses of researches are presented. And the High-Speed Railway vehicle system is evaluated for a dynamic characteristic simulation. Proper models including air-suspension system, wheel-rail, bogie and car-body will be developed according to the vehicle simulation scenario. International safety standard will be applied for final verification of the system. This research can propose a better solution when test running shows a problem in the parts and elements. Finally, the vehicle that has excellent performance will be developed, promoting academic achievement and technical development.

This paper analyzes the dynamic behavior of the deck of pergola bridges affected by moving loads, specifically high-speed trains. Due to their characteristic advantages, pergola bridges have become a widely used structural typology on high-speed railways. In spite of such wide-spread use, there are few technical bibliographies published in this field. The first part of this paper develops a simple analytical methodology to study the complex dynamic behavior of these double dimensional structures. The second part compares the results obtained by the proposed formulae and the dynamic response obtained with different and gradually more complex FE models. The results obtained by the analytical model are in close agreement with those obtained by the FE models, demonstrating its potential application in the early design stages of this kind of structure.

The dynamic performance of railway bridges under high-speed trains draws the attention of bridge engineers. The vibration issue for long-span bridges under high-speed trains is still not well understood due to lack of validations through structural health monitoring (SHM) data. This paper investigates the correlation between bridge acceleration and train speed based on structural dynamics theory and SHM system from three foci. Firstly, the calculated formula of acceleration response under a series of moving load is deduced for the situation that train length is near the length of the bridge span, the correlation between train speed and acceleration amplitude is analyzed. Secondly, the correlation scatterplots of the speed-acceleration is presented and discussed based on the transverse and vertical acceleration response data of Dashengguan Yangtze River Bridge SHM system. Thirdly, the warning indexes of the bridge performance for correlation scatterplots of speed-acceleration are established. The main conclusions are: (1) The resonance between trains and the bridge is unlikely to happen for long-span bridge, but a multimodal correlation curve between train speed and acceleration amplitude exists after the resonance speed; (2) Based on SHM data, multimodal correlation scatterplots of speed-acceleration exist and they have similar trends with the calculated formula; (3) An envelope line of polylines can be used as early warning indicators of the changes of bridge performance due to the changes of slope of envelope line and peak speed of amplitude. This work also gives several suggestions which lay a foundation for the better design, maintenance and long-term monitoring of a long-span high-speed bridge.

Dynamic responses of steel composite bridges for the Korean high-speed railway are analyzed by a modal analysis. The bridge is modeled as a simply supported beam structure and a vehicle of TGV-K is modeled using a moving load assumption. When the train is moving on a bridge, its deck shows resonance phenomenon at a critical velocity. However, it is observed that the dynamic response is greatly reduced at a special range of the span length. The results show that the reduction effect should be considered ill designing the railway bridges. A parametric study of tile dynamic response is performed for different span lengths, and specific train speeds train should be considered in designing the high speed railway bridge are suggested.

The dynamic behavior of high speed train is very important because it should be safe and is satisfied with the ride comfort of passengers. The railway is composed of many suspension components-1st springs, 1st dampers, 2nd springs, 2nd dampers etc- that have an influence on the dynamic characteristics of high speed train. Also, the wheel/rail shapes, the track condition and geometry and many environmental factors-rain, snow, wind etc-are affected the dynamic behavior of high speed train. This paper is reviewed the effect of wind(gust) on the dynamic behavior of high speed train. Vampire program is used for this simulation. The result of simulation shows that high speed train should not be operated when the gust speed is beyond 34.5m/sec.

Computer modeling is essential to evaluate possible design of suspension for a railway vehicles. By creating a simulation, the engineers are able to assess the feasibility of a given design and change the design factors to get a better design. But if one wishes to perform complex analysis on the simulation, such as railway vehicle dynamic, the computational time can become overwhelming. Therefore, many researchers have turned to surrogate modeling. A surrogate model is essentially a regression performed on a data sampling of the simulation. In the most general sense, metamodels(surrogate model) take the form $y(x)=f(x)+{\varepsilon}$, where y(x) is the true simulation output, f(x) is the metamodel output, and $\varepsilon$ is the error between the two. In this paper, a second order polynomial equation is partially used as a metamodel to represent the forty-six dynamic performances for high speed train. The number of factors as design variables of the metamodel is twenty-nine, which are composed the dynamic characteristics of suspension. This metamodel is used to search the optimum values of suspension characteristics which minimize the dynamic responses for high speed train. This optimization is a multi-objective problem which have many design variables. This paper shows that the response surface model which is made through the design of analysis of computer experiments method is very efficient to solve this complex optimization problem.

공작기계 응용에 있어서 고속 및 고효율 가공의 추세는 스핀들의 고속화를 지속적으로 요구하고 있다. 내장형 모터를 장착한 스핀들은 가공시스템의 구조를 단순하게 한다. 하지만 로터에는 불평형 질량에 의해 진동이 발생하며, 이를 제거하기 위한 밸런싱 작업은 필수적이다. 이 논문에서는 내장형 모터를 장착한 고속 스핀들의 동적거동을 해석하였다. 불평형 질량, 베어링 강성, 회전 속도의 변화에 따른 휘돌림 궤적을 해석하였고, 이를 저감시키는 방법을 모색하였다. 또한 Timoshenko 빔 요소를 적용하여 스핀들-베어링 시스템을 모델링하고, 영향 계수법을 적용하여 밸런싱 과정을 시뮬레이션 하였다. 스핀들의 경우, 불평형 하중이 작용할 때, 베어링 지지점에서 가장 작은 휘돌림 궤적이 나타났으며, 양단에서 가장 큰 휘돌림 궤적을 나타내었다. 스핀들의 회전속도가 증가함에 따라 스핀들 선단에서의 휘돌림 궤적도 증가하였다. 베어링의 강성이 커짐에 따라 휘돌림 궤적 또한 증가하였다. 밸런싱 전, 후의 휘돌림 궤적 반경은 최대 73%까지 감소함을 확인할 수 있었다. 이러한 연구 결과는 CNC 자동선반의 스핀들 고속화에 중요한 정보를 제공하고 있다.

A spindle with a built-in motor can be used to simplify the structure of a machine tool system, but the rotor inevitably has unbalanced mass. This paper presents an analysis of the dynamic behavior. The spindle was used in a CNC lathe and investigated using the finite element method and transfer matrices. The high-speed spindle can be very sensitive to the rotation of an unbalanced mass, which has a harmful effect on many machine tools. Thus, a balancing procedure was performed with a spindle-bearing system for the CNC lathe by numerical analysis. The balancing was performed through the influence coefficient method, and the whirl orbit radii before and after balancing were compared to evaluate the effects. The results show that the rotational speed of the spindle seriously affects the whirl responses of the spindle. The whirl responses were also affected by other factors, such as the unbalanced mass and bearing stiffness. The balancing of the assembled spindle model significantly reduced the whirl orbit magnitude.

This study have been performed to investigate the dynamic behavior of the Korean High Speed Train(KHST) during the conceptual design process. This study gets a focus on the analysis of the rigid model, for which the yaw damper layout is modified in a nonlinear limit cycle analysis. In this study, influences of the system parameters such as stiffness of suspension and connection elements as well as damping coefficients were studied and an optimized parameter set is achieved. Throughout the dynamic calculation of KHST on the straight and the curved track, vibration accelerations in car body, ride comforts and wheel rail forces are investigated. Finally the vibration characteristics from rigid car body are compared with those due to the influence of elastic car body.

본 연구에서는 고속연속주조의 기초적 연구로서 벌징만을 선택하여 주조속도 의 변화에 의한 주편의 거동을 해석하기 위해 응력을 변형률, 변형률속도, 온도의 함 수로서 잡고 크리프 변형과 탄소성 변형을 동시에 고려한 모델을 도입하여 주편내에서 의 벌징량, 변형률 등의 상태를 밝히며, 고속주조에 있어서 고려해야 할 사항에 대하 여 고찰한다.

This paper shows an deformation behavior of steel cast slabs, which is used to prevent internal cracks of a slab in an unbending zone, in case of hot charge rolling(HCR) and hot direct rolling(HDR). The value of moving strand shell bulging between two supporting rollers under ferrostatic pressure has been computed in terms of creep and elastic-plasticity and for high strand surface temperature and high casting speed V=1.4-2.2m/min. The strain and strain rate distributions in solidified shell undergoes a series of bulging are calculated with boundary condition a very closed to continuous steel cast slabs productions.

The hermetic reciprocating compressor driven by the BLDC motor rotating with variable speeds, is modelled and analyzed for dynamic characteristics. The governing equations of piston, connecting rod and crank-shaft of the reciprocating compression mechanism and characteristics of driving torque of the motor are obtained. Dynamic behavior of the crankshaft supported on 2 journal bearings is analyzed considering compression load and eccentric unbalance for the 4 rotating speeds of crankshaft. And. reaction forces generated from oil film in the journal bearings are analyzed under transient condition using Reynolds' equation. To take into account the dynamic characteristics depending on the variable rotating speeds, comparison on the dynamic behavior of crank-shaft is made for the 4 operating modes of the compressor. Results show that the magnitude of crankshaft locioperating on the lower rotating speeds is more larger than the higher ones due to reduction of inertia force of the reciprocating piston.

A reciprocating compressor unit with variable rotating speed driven by BLDC motor is mounted inside hermetic chamber on an internal suspension composed of 4 coil springs and a discharge pipe. A method for predicting the dynamic behavior of compressor frame is required to reduce the transmitted vibration level. Mechanical characteristics such as mass, spring and discharge pipe stiffness properties are obtained with experimentation. To confirm the vibration model for compressor frame, free vibration analyses are performed with theoretical and experimental methods. Results for analytical and experimental investigations on dynamic behavior of the compressor frame are presented, and the agreement between measured and predicted results are satisfactory.

이 연구에서는 차세대 고속철의 증가하는 주행속도에 따라 600 km/h 까지 10 km/h 간격으로 고속철 PSC 박스 연속교량의 교량받 침에 대한 동적거동을 수치해석하였다. 경부 고속철 구간의 40미터 단경간과 2경간 연속 PSC 박스교를 연구대상으로 프레임모형을 구성하였 으며, 38자유도의 관성질량 차량모형 및 교량과 궤도의 불규칙성을 포함한 상호작용력을 고려하였다. 주행속도별 교량받침의 종방향 변위와 누적이동거리와 변위속도를 산정하여 교량의 동적거동 추이분석과 비교하였다. 또한 마찰판의 내구성능평가를 위한 장기마찰시험 기준을 적 용하였다.

In this study, the dynamic behavior of friction bearings of PSC (Pre-Stressed Concrete) box train continuous bridge was numerically analyzed at 10 km/h intervals up to 600 km/h according to the increasing speed of the next-generation high-speed train. A frame model was generated targeting the 40-meter single-span and two-span continuous PSC box bridges in the Gyeongbu High-Speed Railway section. The interaction forces including the inertial mass vehicle model with 38 degrees of freedom and the irregularities of the bridge and track were considered. It was calculated the longitudinal displacement, cumulative sliding distance and displacement speed of the bridge bearings at each running speed so that compared with the dynamic behavior trend analysis of the bridge. In addition, long-term friction test standards were applied to evaluate the durability of friction plates.

In this study. a computer simulation of the Korean High Speed Prototype Test Train was performed to investigate the dynamic behavior(running stability. safety and comfort) in detail design process. The simulation model which was prepared by ADAMS/Rail V10.l consists of power car and middle car assembly (2 motorized cars ＋ 3 trailer cars). The nonlinear analysis takes into account the full vehicle model including wheel/rail contact and the influence of disturbed track. Throughout the dynamic calculation of KHST on the straight and the curved track. accelerations in car body. ride comforts and wheel rail forces were investigated.

회전체는 질량 중심선이 축의 기하학적 중심선과 일치하지 않을 때 불평형이 발생한다. 윤축은 두 개의 차륜과 한 개의 차축으로 조립되어 철도차량을 주행시키는 회전체 역할을 하고, 차륜 재질의 불균일, 마모, 윤축 조립과정의 오차 등으로 인해 불평형이 발생할 수 있다. 또한 윤축은 축의 직경이 가늘고 고속으로 회전함으로 불평형 질량에 의한 진동의 영향이 더욱 두드러지게 나타나고 이로 인해 철도차량 고속 주행 시 주행안전성 및 주행거동에 영향을 미칠 수 있다. 그러므로 본 연구에서는 차륜 불평형이 고속철도차량의 동적 거동에 미치는 영향을 철도차량 다물체 동역학 해석 도구인 VI-Rail를 이용하여 해석을 수행하였다. 해석결과에서 차륜 불평형량이 증가할수록 철도차량 대차의 임계속도가 감소됨을 확인할 수 있었고, 차륜 불평형량이 주행 중 차량동적거동 악영향을 미침으로 고속주행에서는 반드시 차륜 불평형량에 대한 관리가 필요함을 확인할 수 있었다. 또한 이 연구로 차륜 불평형량의 정적 및 동적 관리 필요성을 국내 철도차량 운영기관에 제시하였다.

This occurs when the unbalanced rotating body is inconsistent with the mass center line axis geometric center line. Wheelsets are assembled by a single axle with two wheels and a rotating body of a running railway vehicle. Owing to non-uniformity of the wheel material, the wear, and error of the wheel and axle assembly may cause an imbalance. Wheelsets will suffer the effects of vibrations due to the unbalanced mass, which becomes more pronounced due to the thin and high-speed rotation compared to the shaft diameter This can affect the driving safety and the running behavior of a rail car during high-speed running. Therefore, this study examined this unbalanced wheel using a railway vehicle multibody dynamics analysis tool to assess the impact of the dynamic VI-Rail movement of high-speed railway vehicles. Increasing the extent of wheel imbalance on the analysis confirmed that the critical speed of a railway vehicle bogie is reduced and the high-speed traveling dropped below the vehicle dynamic behaviour. Therefore, the adverse effects of the amount of a wheel imbalance on travel highlight the need for management of wheel imbalances. In addition, the static and dynamic management needs of a wheel imbalance need to be presented to the national rail vehicles operating agency.

본 연구는 고속열차 시운전 시험과 이에 따른 주행동특성 고찰 및 개선에 관한 것이다. 고속열차 시운전 시험을 통한 선행 연구에서 도출한 요댐퍼 설치 방법에 따른 후미 진동 개선 방안을 실제 고속철도 차량의 시운전시에 적용하여 후미 진동 저감 효과가 있음을 확인하였다. 또한 전체 차량에 대한 진동저감 방안을 동역학 해석 소프트웨어를 사용하여 수치 해석적 방법으로 도출하였으며, 그 효과를 시운전 시험을 통하여 확인하였다. 개선된 설계안은 실제 2층 고속열차 객차에 적용되어 주행동특성 문제없이 시운전을 진행하였다. 차세대 고속열차 임계속도에 영향을 미치는 현가장치 파라미터들에 대한 민감도 분석을 수행하였으며, 임계속도에 크게 영향을 미치는 4개의 설계변수를 도출하였는데, 이는 1차 탄성조인트 열차진행 방향 강성, 2차 요댐퍼 시리즈 강성, 2차 횡댐퍼 댐핑계수, 차간 댐퍼 댐핑계수 순이었다. 이 설계변수에 대한 최적화를 통하여 임계속도를 23.3% 향상시키는 현가장치 파라미터를 제시하였으며, 이는 차세대 고속열차 상용화 모델의 설계에 이용될 수 있다.

This paper describes the dynamic behavior and enhancement of Korean high-speed trains. The tail vibration reduction method of the yaw damper installation method change, which was derived from previous research, was applied to the running test of high-speed train. In addition, the vibration reduction method for the entire vehicle was derived by a numerical method and its effect was confirmed by a running test. The improved design was applied to the double-deck high-speed train coaches and the commissioning proceeded without problems in dynamic behavior. Sensitivity analysis of the suspension parameters affecting the critical speed of Korean next-generation high-speed trains was performed and four design variables that greatly affected the critical speed were derived. These were in the order of the primary elastic joint x-directional stiffness, the secondary yaw damper series stiffness, the secondary lateral damper damping coefficient, and the carbody damper damping coefficient. By optimizing the design variables, the suspension parameter that improves the critical speed by 23.3% can be used in the commercial designs of Korean next-generation high-speed trains.

The visual quality of a fabric is directly connected with the fabric density, i.e., picks/em and ends/em, variations of which are influenced by the weaving process conditions. Any variation in the conditions during a weaving process can lead to a fabric flaw, which implies a deterioration of the fabric quality. The fault that appears frequently in weaving is the stop mark, the variation in fabric density, especially, weft picks per unit length. This research is to set up a model describing the pickspacing dynamics in the weaving process and to simulate the pickspacing changes under given initial conditions, considering the start-up velocity profiles. The results show that initial clothfell position is an important factor affecting the pickspacing unevenness. Thin and harsh-surfaced weft yarns are more sensitive to the pickspacing changes than the thick and even-surfaced, while a velocity profile for a restart, even not considering the dynamics of the machine parts, can bring about a stop mark, if the profile has a quadratic function form with respect to time.

Dynamic behavior of high speed train is very important because the high speed train should be safe and satisfied with the ride comfort. An eddy current brake system is mounted on trailer bogie and wheelset. The eddy current braking force longitudinally exerts on the articulated trailer bogie and the attraction force vertically exerts on the wheelset. Because a frame of eddy current brake system is flexible, these forces generate the vertical vibration at middle point of the frame. Also, the vibration change the vertical clearance between an electromagnet and top of rail which affect the magnitude of braking and attracting forces. Therefore, the dynamic behavior of the eddy current braking system must be predicted for design the dynamic characteristic of its mounting system when normally operate on rail which have irregularity. Vampire program is used for Prediction of the dynamic behavior of an eddy current braking system.