• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.800-805
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• 2007

The critical speed of railway bogie is very important in terms of the verification of the vehicle design procedure and safety. The dynamic performance of bogie is tested on the railway roller rig in a laboratory in place of field testing on track. But, the testing on the full scale roller rig caused many problems relating to test costs, test time and has the difficulty in test condition setup. To overcome these problems, scaled models were used in the filed of railway vehicle design and test. In this paper, we have studied the critical speed of scaled bogie model. We have made the 1/5 scaled bogie, the scaled roller rig and analyzed the critical speed of the scaled bogie through the numerical simulation and running test of the scaled bogie. We have confirmed that the analysis results of the critical speed correspond with the test results.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.574-581
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• 1999

비선형 임계속도를 주행시험대를 이용하여 측정하였으며 비선형 임계속도가 관성에 의한 과도 현상이 아님을 확인하기 위하여 주행속도를 연속 그리고 불연속적으로 감가속 하면서 선형 및 비선형 임계속도를 측정하였다. 또한 차량의 안정성을 간편하게 예측할 때 대차모델만을 사용하던 종래의 방법이 타당한지 확인하였으며 차량의 임계속도와 응답주파수를 예측하기 위하여 산업체에서 사용되던 간편 식들의 정확성을 검토한 결과 다음의 결과를 도출할 수 있었다. (중략)

• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.9-16
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• 2012

The dynamic stability of railway vehicle has been one of the important issues in railway safety. The dynamic simulator has been used in the study about the dynamic stability of railway vehicle and wheel/rail interface optimization. Especially, a small scale simulator has been widely used in the fundamental study in the laboratory instead of full scale roller rig which is not cost effective and inconvenient to achieve diverse design parameters. But the technique for the design of the small scale simulator about the dynamic characteristics of the wheel-rail system and the bogie system has not been well developed in Korea. Therefore, the research using the small-scaled derailment simulator and the 1/5 scaled bogie has been conducted. In this paper, we did running stability test of 1/5 scaled bogie using small-scaled derailment simulator. Also, for the operation of the small scaled simulator, it is required to investigate the performance and characteristics of the simulator system. This could be achieved by a comparative study between an analysis and an experiment. This paper presented the analytical model which could be used for verifying the test results and understanding of the physical behavior of the dynamic system comprising the small- scaled derailment simulator and the 1/5 scaled bogie.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.577-587
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• 2017

In the design process of dynamic characteristics of a railway vehicle, demand for analysis, testing and estimation methods of running stability are increasing as railway vehicle speed is increasing. Critical speed tests and estimation have been carried out using computer simulation or special test facilities, like roller rigs, because real track testing at critical speed is very dangerous. This paper introduces a test and assessment method for critical speed and estimates the validity using several roller rig tests. The test results show that it is difficult to estimate the critical speed using safety and instability assessment method in UIC 518, but that there is good agreement between the reduction of the equivalent damping ratio and the critical speed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.86-92
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• 2017

In this study, a running performance evaluation and roller rig test was conducted to evaluate the applicability of a composite bogie frame, which has the role of the primary suspension. The composite bogie frame was made of a GEP224 glass/epoxy prepreg. Vehicle dynamic analysis was carried out on the composite bogie with three different kinds of side beam thicknesses (50 mm, 80 mm, and 150 mm). From the results, the composite bogie with a side beam thickness of 80 mm satisfied all the dynamic design requirements. Although the composite bogie with the side beam thickness of 50mm also met the design requirements, its critical speed was just a 2% margin to the requirement. In contrast, the model of the side beam thickness of 150mm did not meet the ride comfort. In addition, a composite bogie frame with the side beam thickness of 80 mm was fabricated and installed on a complete bogie. Moreover, the roller rig test using the fully equipped bogie was performed to evaluate the critical speed. During the test, the lateral excitation was imposed on the wheelsets to realize the rail irregularity. There was no divergence of the lateral displacement of the wheelsets while increasing the speed. The measured critical speed was similar to the predicted result.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1207-1212
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• 2007

The critical speed of railway bogie related to the stability of the railway rolling-stock is important. Testing of the dynamic performance of bogie is conducted using a roller rig in a laboratory in place of field testing on track. This roller rig is composed of two rollers equivalent to track and used to test the dynamic characteristics of vehicle. But, the geometrical characteristics of the wheel/roller contact on the roller rig are different from those of the wheel/rail contact because the longitudinal radius of roller is not infinite compared with rail. This difference has influence on the wheelset behavior and the critical speed of bogie. Therefore in this paper, we have studied the behavior of wheelset and bogie on the roller rig for railway bogie testing with the purpose of developing the scaled roller rig. As an analysis results, it has been shown that the critical speed of bogie on the roller rig is slightly lower than that of bogie on track.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.218-221
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• 2004

This Research is to test the running stability of the developed bogie with 350km/h of which conventional speed is faster than Korea TGV 300Km/h. The running stability test has been executed in status of a car with the developed bogie on the roller rigger to adjust similar to the actual condition. And the test has been done in the two rail conditions, i.e. excitation and non-excitation, respectively. Running speed of bogie increased by the roller step by step. In consequence, the developed bogie in the non-excitation has run without any unstable point for 400kn0h. Vibration characteristics of carbody also was within the value specified on the UIC 518.

• Journal of KSNVE
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• v.11 no.2
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• pp.265-275
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• 2001

This research has been performed to reveal the hysteresis phenomena of the hunting motion in a railway passenger cars. It is found that there are some factors and its operation region to make the nonlinear critical speed reacts to them more sensitively than the linear critical speed. The simulation results show that a self steering bogie system can be a substitute proposal to improve curving Performance together with the reduction of hysteresis of critical speed. Full scale roller rig test is carried out for the validation of the numerical results. Finally, it is certified that wear of wheel profile and stiffness discontinuities of wheelset suspension caused by deterioration have to be considered in the analysis to predict the hysteresis of critical speed precisely.

• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.618-623
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• 2006

Understanding the contact between wheel and rail is a starting point in railway vehicle dynamic research area and especially analysis for the contact geometry between wheel and rail is important. On the one hand, the critical speed as the natural characteristics of rolling-stock is generally tested on the roller rig. The geometrical characteristics of the wheel/roller contact on the roller rig are different from these of the general wheel/rail contact because the longitudinal radius of roller is not infinite compared with rail. Thus, in this paper we developed the algorithm to analyze the wheel/roller contact geometry of our roller rig which is constructed now and analyzed the difference between whee/roller contact and wheel/rail contact. In conclusion, we found that the yaw motion of wheelset and the roller radius influence the geometrical contact parameters in wheel flange contact area.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.839-844
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• 2002

This research aims to test the running stability of the developed bogie with maximum operating speed of 350km/h, which of Korea TGV was 300km/h. The running stability test has been executed in status of a dummy car with one developed bogie and one dummy bogie on the roller rig to embody similar operation condition. The test has been done in the two rail conditions, i.e. excitation and non-excitation, respectively. Running speed has been increased by the roller step by step. In consequence, the developed bogie was proven to be able to run upto 400 Km/h without any unstable point in the non-excitation. Vibration characteristics of carbody also was within the value specified on the UIC 515.