• International Journal of Railway
• /
• v.3 no.2
• /
• pp.60-67
• /
• 2010

This paper deals with an experimental study on the wheel flange climbing of railway vehicles, which is a major factor leading to derailment. An experiment is carried out on a 1/5-scale model wheelset of a truck used on a standard-gauge track, which is placed on a roller rig. The lateral external force acting on the wheelset is ramped up until derailment occurs under the condition of a fixed attack angle and wheel-load unbalance ratio. Three parameters, the height of wheel lift, the lateral force, and the wheel load acting on the outer rail, are measured until derailment occurs. From these measurements, it is possible to observe the behavior of the wheelset and to elucidate how the attack angle, the wheel-load unbalance ratio and the lateral external force affect flange-climb derailment. Then, a numerical simulation is carried out using an analytical model based on a single wheelset. As a result, the flange-climb behavior observed in the experiment can be explained theoretically on the bases of the analytical results, although further improvement of the model is desired.

• Journal of the Korean Society of Safety
• /
• v.31 no.1
• /
• pp.13-18
• /
• 2016

KTX wheelset bearings have thus far been maintained in accordance with the maintenance system of French national railway company, SNCF. The overhaul cycle time (OCT) of KTX wheelset bearings is now 1.4 million km in mileage. This value, however, has not been validated in Korea that has much different railway environments with France. In fact, it is impossible to validate OCT of wheelset bearings directly because they are disassembled and cleaned only when some faults are detected. In this paper, the accuracy of the current OCT value was evaluated indirectly by investigating the effect of grease lubricants on the bearing life. Five grease samples (one new and four aged greases) were used in this study. Four aged greases of different conditions were obtained from four wheelset bearings whose mileages were about 0.3, 1.2, 1.3, and 1.8 million km, respectively. Each grease sample was then injected into the RCF (Rolling Contact Fatigue) tester and fatigue lifetime was experimentally estimated. In addition, the wt% of Fe in each grease sample was analysed. The experiment results reveal that the bearing lifetime is inversely proportional to the mileage of grease sample while the wt% of Fe increases with the mileage of grease sample. Based on the experimental results, it can be concluded that the current OCT value is appropriate for the first overhaul of wheelset bearings. However, further validation is required to determine the second and third OCT values.

• Journal of the Korean Society for Railway
• /
• v.12 no.4
• /
• pp.465-471
• /
• 2009

In this paper, a relationship between the noise and vibration of a high-speed train's wheelset is examined by using time-varying frequency analysis with random data analysis which together contributes to a reduction in the number of experimental running. The noise and vibration of the wheelset is mainly caused by an interaction between the wheel and railway which shows in non-stationary characteristics. For the analysis, they are measured by some microphones and accelerometers, and those signals are post-processed by time-varying frequency analysis with random data analysis. From the analysis, their methods are useful for analyzing the noise and vibration of high-speed train's wheelset.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.2
• /
• pp.122-130
• /
• 2013

Rail geometries such as cant, grade and curvature can be easily represented by means of a track coordinate system. In this analysis, in order to derive a dynamic and constraint equation of a wheelset, the track coordinate system is used as an intermediate stage. Dynamic and constraint equations of railway vehicle bodies except the wheelset are written in the Cartesian coordinate system as a conventional method. Therefore, whole dynamic equations of a railway vehicle are derived by combining wheelset dynamic equations and dynamic equations of railway vehicle bodies. Constraint equations and constraint Jacobians are newly derived for the track coordinate system. A process for numerical analysis is suggested for the derived dynamic and constraint equations of a railway vehicle. The proposed dynamic analysis of a railway vehicle is validated by comparison against results obtained from VI-RAIL analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.1541-1542
• /
• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.1093-1094
• /
• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.761-762
• /
• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.823-824
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.825-826
• /
• 2007

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