초록 ▼

○ 비정상 주행조건에 대한 새로운 탈선 판정 이론 적용
- 차륜과 레일 사이의 마찰계수, 차륜 플랜지의 각도, 윤중감소 등에 따라 탈선 시점과 탈선의 유형이 달라짐.
- 윤축의 탈선거동이 발생할 때, 차륜 플랜지와 레일 접촉부의 마찰력의 작용 방향에 따라 미끄러져오름 또는 타고오름 탈선이 일어남.
- 이와 같이 다양한 물리적 변수를 고려한 새로운 비정상 주행 단일윤축 탈선이론을 탈선 판정에 적용함

○ 시간 단축을 위한 차륜-레일 인터페이스 모델링 방법 개발
- 철도차량의 주행 추진력은 차륜-레일 점

○ 비정상 주행조건에 대한 새로운 탈선 판정 이론 적용
- 차륜과 레일 사이의 마찰계수, 차륜 플랜지의 각도, 윤중감소 등에 따라 탈선 시점과 탈선의 유형이 달라짐.
- 윤축의 탈선거동이 발생할 때, 차륜 플랜지와 레일 접촉부의 마찰력의 작용 방향에 따라 미끄러져오름 또는 타고오름 탈선이 일어남.
- 이와 같이 다양한 물리적 변수를 고려한 새로운 비정상 주행 단일윤축 탈선이론을 탈선 판정에 적용함

○ 시간 단축을 위한 차륜-레일 인터페이스 모델링 방법 개발
- 철도차량의 주행 추진력은 차륜-레일 점착력으로 발생하며 이를 정밀하게 구현하기 위해서는 실제와 동일한 구름접촉 모델이 필요.
- 그러나 구름접촉의 경우, 많은 해석시간이 필요하기 때문에 2점 접촉 모델을 사용한 새로운 차륜-레일 인터페이스 모델을 개발 적용.

○ 동역학적 이론모델을 이용한 지그재깅 및 타고오름의 차간연결부 초기 offset 량 설정 방법 개발
- 타고오름 또는 지그재깅 거동을 시뮬레이션으로 재현하기 위해서는 수많은 시행착오를 통하여 일치시켜야하기 때문에 많은 시간이 소요됨.
- 사고재현 시뮬레이션에서 시행착오를 줄이려면 이론적으로 차간연결부 초기 offset 량을 추정/설정하여 시뮬레이션 하여야, 좀 더 빠르게 실제 거동과 일치하는 결과를 얻을 수 있음.
- 이에 필요한 타고오름과 지그재깅의 초기 offset 량을 추정할 수 있는 이론해를 개발함.

○ 탈선/충돌 복합사고 재현을 위한 1D, 2D, 3D 편성열차 모델링 기술 개발
- 탈선 사고 재현 시뮬레이션에 필요한 다양한 사고유발 원인 모델링 도구(충돌, 궤도, 주행조건 원인 등) 개발.
- 1차원 모델 충돌동역학 해석은 전체적인 관점에서 차체구조의 충돌 에너지흡수량 및 충격감속도를 예측하기 위해 적용.
- 2차원 모델 충돌동역학 해석은 각 단위 차량의 간의 타고오름 현상과 지그재깅 현상을 예측하기 위하여 적용.
- 3차원 모델 충돌동역학 해석은 실제 충돌 시 발생하는 각 단위 차량의 차간 연결기 부품 및 지지 브라켓 구조에서 발생하는 충격력의 크기 등은 예측하기 위하여 적용.
- 결국 사고재현 충돌해석에 필요한 물리량을 도출하려면 편성열차에 대하여 완전 유연체 1차원 모델, 부분 유연체 2차원 및 3차원 모델링 방법을 개발 적용하여야 함.

○ 사고재현 시뮬레이션 및 검증 기술 개발
- 사고재현 시뮬레이션에 필요한 탈선후 차륜-노면 사이의 마찰계수를 각 탈선차량에 대하여 일-운동에너지 법칙과 충격량-운동량 법칙을 이용하여 마찰계수 구하는 방법을 개발.
- KTX 산천 3호 광명역 탈선 사고재현 시뮬레이션 결과와 실제 사고차량의 거동을 비교하여 전체적인 사고거동 비교평가 후, 각 차량의 파손 범위 및 정도를 비교하여 보완 및 검증하는 시뮬레이션 기술을 개발.

○ 손상 예측 및 검증 방안 제시
- 시뮬레이션 결과를 바탕으로 손상부위를 예측하고, 차량의 손상 부위 및 재질에 따라 손상부위 검출을 위한 적절한 검사 방법을 제시.

○ 보수방안 및 추적 유지관리 방안
- 파손 위치와 정도에 따라 재료 및 부재의 특성에 맞는 보수 방안을 제시.
- 보수 방법에 따른 보수 후 결함검사와 추적관리 방법을 제시하고, 동응력 계측을 통한 최종적인 잔존수명 평가 및 관리의 필요성을 제시.

Abstract ▼

Purpose & Contents

Through this research, we aimed at developing the modelling and simulation technologies to reproduce such complicated accidents like train derailments and/or collisions. Using the developed modelling and simulation technologies, we intended to derive the countermeasures to

Purpose & Contents

Through this research, we aimed at developing the modelling and simulation technologies to reproduce such complicated accidents like train derailments and/or collisions. Using the developed modelling and simulation technologies, we intended to derive the countermeasures to repair the damaged car structures and to maintain the repaired structures.
This research will contribute to the development of the world-class technology for crashworthy safety design, repair and maintenance, and finally enhance the structural safety level of the Korean high speed train.

○ Application of the new derailment criteria on a single wheelset under unstable running conditions.

- Due to several mechanical factors like the emergency braking, cross winds, collisions, the overspeed running on the curved or undulated tracks, there occur unstable forces between bodies and carbody. The unstable forces are transmitted to wheelsets through the suspensions.
- The derailment time and patterns caused by those unstable forces will be changed according to the friction coefficient between rail and wheel, the flange angle and the wheel unloading.
- In addition, the derailment patterns can be classified as a lift-up type and a climbing type by the direction of friction forces during derailment occurrence
- In this research, the above-mentioned various physical parameters affecting derailment were considered for the derailments under unstable running conditions using newly developed derailment criteria for a single wheelset.

○ Development of a wheel-rail interface modelling method to reduce simulation time.

- Driving forces of a train are generated by the friction forces resulted from a complicated wheel-rail contact mechanism. If we want to reproduce the complicated wheel-rail contact mechanism in details, we must use the rolling contact models which need an excessive calculation time.
- However, because it is almost impossible to reproduce a train accident with the rolling contact models due to excessive simulation time, we developed a new 2-point contact model for wheel-rail interfaces to simulate the accident reproduction model in a resonable calculation time.

○ Theoretical estimation methods of the intial off-set amounts for zigzagging and overriding derailments.

- After a train derailment or collision, there occur zigzagging and/or overriding derailments in general.
- The intial off-set amounts at the beginning stage of collision between car units are very important for the subsequent zigzagging and overriding derailments. However it would be very difficult and time-consumable to find out the intial off-set amounts by the trial and error method in a full 3-D flexible dynamic model.
- Therefore, it is very important to theoretically estimate the intial off-set amounts for zigzagging and overriding derailments so as to obtain a dramatical reduction of the simulation time.

○ Development of the 1D, 2D, and 3D modelling methods of a full rake train for reproduction of the complicated accidents like train derailments and/or collisions.

- For reproduction of derailment and/or collision accidents, modelling tools for accident induction are essential. So, we developed several accident induction modelling tools for the collisions (train-to-train collision, train-to-a large obstacle, train-to-a small obstacle), for the rail faults (of turn-outs, widening, narrowing, cuts), and for the running conditions (emergency braking, high speed running at curves, strong cross wind and cross running wind).
- Using a 1D collision model of a full rake train, we can simulate and evaluate the energy absorptions of collapsable structural sections, the survival spaces for passengers and the levels of impact decelerations.
- However, although we can easily obtain the above-mentioned performances like the energy absorptions and the impact decelerations from the 1D collision simulation, it is impossible to evaluate the overriding and zigzagging phenomena and the impact forces transferred to the supporting structures of couplers.
- To evaluate the overriding and zigzagging displacements, the couplers and the carbody-bogie links including failure criteria must be modelled using the 2D and/or 3D simulation models for a full rake train.
- Because the 3D model needs a large amount of geometrical and physical data, the 3D simulation can be done in details after the 2D models have been simulated. In these cases, to reduce the simulation time, it is necessary to model the deformation free zones as the rigid bodies.

○ Development of the simulation and evaluation technologies for accident reproductions.

- For accident reproductions after a derailment, it is essential to use the friction coefficient between wheel-track. In this study, we developed a new approach to estimate the friction coefficient from the derailed displacements using the work-kinetic energy law and the impact-momentum laws.
- The 2D and/or 3D models assumed as the rigid bodies for undeformable cars in an accident reproducing simulation can be used to solve the overall behaviors of the full rake train within a reasonable time.
- In this research, we simulated the derailment and collision accident of the KTX Sancheon at Kwang-Myung station and compared its simulated results with the real behaviors in the accident for the overall derailment results. After the two results are confirmed in a good agreement, the positions, ranges and severities of the damaged parts are compared and evaluated with a good confidence.

○ Estimation and verification methods for structural damages.

- For the cracks and faults inscribed in the bodyshell surface, the Visual Inspection and the Penetrating Test are recommended. With the test results along with the simulation results, the damaged spots can be estimated and verified in details.
- For the cracks and faults occurred in inner structures like an ALE body, the Radiation Inspection test, which is most reliable and popularly used, is recommended. With the test results along with the simulation results, the damaged spots can be fixed in details.

○ Suggestions on repair countermeasures and tracking management solutions for maintenance.

- Suggestions on repair solutions in accordance to the characteristics of materials and structures considering the severities and locations of the damages.
- Suggestions on the fault inspections and tracking management solutions after repairs, and the evaluation and control methods of the remaining life of the repaired parts as a final process.

Results

○ Application of the new derailment criteria on a single wheelset under unstable running conditions.

- Excellence of the technological outputs:
● We developed an efficient approach that estimates the derailments caused by unstable running behaviors using the derailment criteria on a new single wheelset where the wheel-rail friction effect, the flange angle and the wheel unloading can be considered.
● In connection with this theoretical derailment criteria, we considered the train accident causal factors, such as the curvature/undulation of tracks, the emergency braking, a strong cross wind and collisions, which occur in a real accidents.

- Published articles:
● 1 SCIE paper,
"Theoretical cross-wind speed against rail vehicle derailment considering the cross-running wind of train and the dynamic wheel-rail effects", Journal of Mechanical Science and Technology, 2016 (Publication in August, 2016)

○ Development of a wheel-rail interface modelling method to reduce simulation time.

- Excellence of the technological outputs:
● We developed a two-point contact algorithm for wheel-rail interactions were developed and applied to simulate the reproduction of train accidents instead of using the time consumable rolling contact models for wheel-rail interfaces.

- Published articles:
● 1 technical document reviewed by the field experts.
"Modelling and application technology of a two-point contact algorithm for wheel-rail interactions of the reproduction of train accidents to reduce the simulation time."

○ Theoretical estimation methods of the intial off-set amounts for zigzagging and overriding derailments.

- Excellence of the technological outputs:
● To reduce some trial and error simulations in an accident reproduction, it is necessary to apply the intial off-set amounts between car units for overriding and zigzagging derailments to the full rake train model. A method using theoretical dynamic models to estimate the intial off-set amounts between units for overriding and zigzagging was developed and verified by numerical simulations.

- Published articles:
● 2 SCOPUS papers,
"A Study on Prediction of overriding for a Loading Vehicle in Train Collision", Trans. Korean Soc. Mech. Eng. A, 2016 (Publication in August, 2016)

"A Study on Prediction of Lateral and Yawing Behaviors for a Leading Vehicle in Train Collision", Trans. Korean Soc. Mech. Eng. A, 2016 (Reviewing after the modification)

○ Development of the 1D, 2D, and 3D modelling methods of a full rake train for reproduction of the complicated accidents like train derailments and/or collisions.

- Excellence of the technological outputs:
● To perform an accident reproduction simulation, we developed the accident induction tools as to the train-to-train, train-to-huge obstacle, and train-to-small obstacle collision models, the faulted turn-out, tract-widening, track-narrowing, and rail cut-out derailment models, the emergency braking model, the high speed running model at curved cracks, and the cross-wind and cross-running wind derailment models.

● In connection with the accident induction tools, we developed three types of simulation models for a full rake train: the 1- dimensional collision model that can be used in quick simulations for energy absorptions and collision decelerations; the 2-dimensional collision model in quick simulations for overriding and zigzagging derailments; the 3-dimensional collision model in sophisticated simulations for impact forces and structural damages in structural components and devices.

- Published articles:
● 2 technical documents reviewed by the field experts.
"The modelling tools to induce train accidents related to derailments or collisions for the reproduction of train accidents."

"The 1D/2D/3D modelling technologies of each unit in a full rake train for the reproduction of train accidents."

● 1 KCI paper,
"A Study on the Effect of Running Vibration Caused by Suspension Stiffness Changes of Subway Vehicles", Journal of the Korean Society of Manufacturing Process Engineers, Vol. 15, No. 2, pp. 57-65, 2016.

○ Development of the simulation and evaluation technologies for accident reproductions.

- Excellence of the technological outputs:
● We performed the reproduction simulation of the Kwangmyung derailment accident using the 3-D collision model made of rigid elements and flexible ones for the full rake train of the Sancheon KTX, and then we compared the simulation results with the accident consequences on the derailed configuration and the damages of some important structures.

- Published articles:
● 1 technical document reviewed by the field experts.
"The derailment and collision simulation model of a full rake train of the Sancheon KTX for the reproduction of the train accident at the Kwangmyung station."

○ Estimation and verification methods for structural damages.

- Excellence of the technological outputs:
● We developed the estimation method for the damaged structural parts using the accident reproduction simulations, and the verification methods by several inspection methods like VT, PT and RT for the positions and severities of the structural damages in the really damaged vehicles.

- Published articles:
● 1 technical document reviewed by the field experts.
"The estimation method for the damaged structural parts using the accident reproduction simulations."

○ Suggestions on repair countermeasures and tracking management solutions for maintenance.

- Excellence of the technological outputs:
● We proposed the repair methods of each damaged structure according to its material and structural function, and the technical maintenance methods on the fault inspection of the repair parts, and the tracking inspection for quality controls.

- Published articles:
● 2 technical documents reviewed by the field experts.
"The application of the PT/RT inspection methods on damaged parts and the repair methods based on the inspected results."

"The tracking inspection on the repaired parts for quality controls"

● 1 SCIE paper,
"A lightweight design approach for an EMU carbody using material selection method and size optimization", Journal of Mechanical Science and Technology, Vol. 30, No. 2, pp. 673-681, 2016.

Expected Contribution
○ In the case of this accident reproduction technology, the reproduction of a specific train accident needs too a very long time in obtaining the simulation results for repairs of structural damages after it occurs. On the other hand, it is also difficult to invest an R&D fund without any train accident. Therefore, this kind of research should be invested as an important fundamental research.

○ After this technology for the modelling and accident reproduction simulation through this research has been developed, the reduction of the repair time and costs can be accomplished and the repair quality will be improved. Consequently, the safety and convenience for users can be improved by far through the development and applications of these field-oriented safety technologies.

○ Hereafter, if a derailment and/or collision accident occurs in the KTX Sancheon, the damaged structural parts can be estimated using these current simulation models within a month. These simulation models can be conveniently used for crashworthiness and derailment researches of the KTX Sancheon.

○ Hereafter, several guidelines on repair, follow-up management, and disposal of a damaged train after a sever accident can be suggested based on the accident reproduction simulations.