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안정화된 Penalty방법에 의한 접촉력 산정법과 요철부 통과시의 차륜-레일간 접촉분리 현상
정근영(Chung Keun-Young),이성욱(Lee Sung-Uk),이석무(Lee Seok-Mu) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
In this study, to describe vehicle-structure dynamic interaction phenomena, nonlinear Hertzian contact spring and nonlinear damper are adopted. The external loads acting on vehicle model are the self weight of vehicle and the displacement constraint equation of contact point. The displacement constraint is implemented by the Penalty method with stabilization. The penalty force, in the stabilized penalty method, is dependent on not only prescribed displacement but also velocity of contact point. In the time integration of dynamic equations of motion, Newmark time integration scheme is adopted, and the velocity of contact point is estimated by Newmark integration concept. To reduce the error caused by inadequate time step size, adaptive time-stepping technique is also adopted. As the nonlinear Hertzian contact spring is adopted in this study, separation of wheel-rail contact can be described. In numerical it is found that separation of contact between wheel and rail can be occur due to geometric imperfection of the rail to surface. In numerical test, the stabilized penalty method show good accuracy of result and it is expected that more versatile dynamic interaction phenomena can be described more accurately.
궤도지지강성 변화구간에서의 광폭침목 사용에 따른 궤도거동 개선효과 분석
정근영(Chung Keun-Young),이일화(Lee Il-Wha),이진욱(Lee Jin-Wook),최찬용(Choi Chan-Yong) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
To estimate effect of wide sleepers in track transition zone, dynamic analysis of the track with wide sleepers is carried out. The railway line of main concern is tunnel-embankment transition zone. The track in the tunnel is ballastless track with concrete bed on concrete foundation and the track located on embankment is ballasted track. In the transition zone with ballasted track approach slab is installed to reduce abrupt variation of supporting stiffness. It is studied the effect of applying some wide-sleepers in ballasted track located on approach slab is studied. To describe vehicle-track dynamic interaction phenomena nonlinear Hertzian contact spring and nonlinear damper are adopted. The external loads acting on vehicle model are self weight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by the Penalty method with stabilization. To describe the change in stiffness and effective mass due to sleeper size, the ballast modeling technique proposed by Zhai et al is also adopted and modified. Numerical tests show that the use of wide sleeper will decrease settlement of ballast. Thus it is expected that wide sleeper decrease maintenance of track transition zone.
정근영(Chung Keun-Young),김현기(Kim Hyun-Ki),이종득(Lee Jong-Deuk) 한국철도학회 1999 철도저널 Vol.2 No.3
The durability of ballast plays an important role in track behaviour. To estimate the deterioration characteristics of ballast, several tests have been carried out by several scholars. The deterioration characteristics is very important factor in the behaviour of track and its life. In this paper, abrasion/breakage characteristics of ballast is studied to see the effect of physical ballast characteristics on ballast life. To reveal breakage characteristics of ballast, the ballast box test and the MTT field test were carried out. The breakage characteristics studied in this paper is applied to the ballast life prediction in various conditions, such as LA abrasion, annual tonnage, tamping number per year, etc
비선형 헤르쯔 접촉스프링과 변위제한조건식의 적용에 의한 차량 궤도 교량 동적상호작용 수치해석기법
정근영(Chung Keun-Young),이성욱(Lee Sung-Uk),민경주(Min Kyung-Ju) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
In this study, to describe vehicle-track-bridge dynamic interaction phenomena with ¼ vehicle model, nonlinear Hertzian contact spring and nonlinear contact damper are introduced. In this approach external loads acting on ¼ vehicle model are self weight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by Penalty method. Also, to improve the numerical stability and to maintain accuracy of solution, the artificial damper and the reaction from constraint violation are introduced. A nonlinear time integration method, in this study, Newmark method is adopted for both equations of vehicles and structure. And to reduce the error caused by inadequate time step size, adaptive time-stepping technique is partially introduced. As the nonlinear Hertzian contact spring has no resistance to tensile force, the bouncing phenomena of wheelset can be described. Thus, it is expected that more versatile dynamic interaction phenomena can be described by this approach and it can be applied to various railway dynamic problems.
변위제한조건식과 안정화된 Penalty방법에 의한 차량 주행에 따른 구조물의 동적상호작용 해석기법
정근영(Chung Keun Young),이성욱(Lee Sung Uk),민경주(Min Kyung Ju) 대한토목학회 2006 대한토목학회논문집 D Vol.26 No.4D
본 연구에서는 2개의 질량을 갖는 1/4 차량모델을 이용하여 차량-궤도-교량간의 동적상호작용 현상을 표현하기 위해 비선형 헤르츠 접촉스프링(Nonlinear Hertzian Contact Spring)과 비선형 접촉감쇠장치(Nonlinear Contact Damper)를 도입하였다. 또한, 차량에 작용하는 하중은 차량의 중량외에 임의시간단계의 차륜재하위치인 레일답면(즉, 주행로상의 접촉면)에서의 변위가 제한조건식(Constraint Equation)으로 가해졌다. 이 변위제한조건식은 Penalty방법(Penalty Method)에 의해 구현되었으며, 해의 안정화(Stabilization)를 위한 기법과 제한조건오차보정반력(Reaction from Constraint Violation)을 도입하였다. 또 한, 차량의 피칭운동을 표현하고, 다양한 차량/열차를 모형화하기 위해서 1/4 차량모델의 차체 및 대차프레임 간을 강체연결 및 핀이 있는 강체연결조건으로 모형화하였다. 시간적분방법으로는 Newmark계열의 시간적분법이 사용되었으며, 해의 정확성 확보를 위해 국지적 오차평가에 근거한 적응적시간간격기법(Adaptive Time-Stepping Scheme)을 도입하였다. 이러한 적응적시간간격기법을 도입하여 동적해석에서 시간간격의 크기를 자동적으로 결정함으로써 동적해석에서의 해의 정확성을 확보하고 시간적분에 소요되는 계산비용을 감소시킬 수 있을 것으로 기대된다. In this study, to describe vehicle-structure dynamic interaction phenomena with 1/4 vehicle model, nonlinear Hertzian contact spring and nonlinear contact damper are adopted. The external loads acting on 1/4 vehicle model are selfweight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by the Penalty method with stabilization and the reaction from constraint violation. To describe pitching motion of various vehicles two types of the displacement constraint equations are exerted to connect between car bodies and between bogie frames, i.e., the rigid body connection and the rigid body connection with pin, respectively. For the time integration of dynamic equations of vehicles and structure Newmark time integration scheme is adopted. To reduce the error caused by inadequate time step size, adaptive time-stepping technique is also adopted. Thus, it is expected that more versatile dynamic interaction phenomena can be described by this approach and it can be applied to various railway dynamic problems with low computational cost.
요소 세분화를 이용한 비적합 미끄러지는 접촉문제의 개선과 철도 사각암거 문제에의 적용
최찬용,여인호,정근영,이계희,Choi, Chan-Yong,Yeo, In-Ho,Chung, Keun-Young,Lee, Gye-Hee 한국전산구조공학회 2017 한국전산구조공학회논문집 Vol.30 No.5
차량-궤도 구조물 동적 상호작용해석은 차량의 접촉점이 보요소로 모형화된 레일 위를 일정한 속도로 주행하는 미끄러지는 접촉문제로 취급하였다. 하지만 Euler 보와 같은 고차 다항식의 형상함수가 적용된 유한요소를 사용할 경우 미끄러지는 접촉문제에서 적합조건을 만족하지 못한다. 이 연구에서는 유한요소해석프로그램이 미끄러지는 접촉문제에서의 적합조건을 만족시키지 못하는 것에 대한 해결법으로 주행로를 이루는 보요소를 보다 세분화하여 동적상호작용해석에서의 정확성을 확보하고자 하였다. 이를 위해 간단한 예제들을 통해 주행로를 이루는 보요소의 세분화 정도에 따른 동적상호작용해석의 거동을 분석하였으며, 해석 프로그램의 동적상호작용해석에의 적용성을 평가하였다. 마지막으로 사각을 갖는 철도 암거 접속부의 뒷채움재 설치 형식에 따른 차량주행시의 거동을 평가하기 위하여 동적상호작용해석을 수행하고, 접속부 뒷채움재 형식의 변경에 따른 지지강성의 변화에 의한 영향과 노반침하에 따른 궤도틀림의 영향을 비교분석하였다. The vehicle-track structure dynamic interaction analysis problem can be treated as sliding contact problem, and it is assumed that vehicle run at a constant speed over a rail modeled as beam elements. Unfortunately, Salome-Meca can not satisfy the compatibility condition for the beam master elements, which are consist of the elements with higher order polynomial shape function, in sliding contact problem. In this study, it is suggested to use more finer beam master element mesh as the remedy for incompatibility in sliding contact problem, and the accuracy of the solution is secured. For this, the effect of beam element mesh refinement consisting runway is analysed through simple examples, and the applicability to the dynamic interaction analysis is evaluated. Finally, the dynamic interaction analysis of railway skewed culvert transition problem is carried out to evaluate the effect of supporting stiffness due to backfill pattern changes and track irregularity due to uneven subgrade settlement.