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The dynamic performance of railway vehicle is normally expressed as stability, safety and ride comfort, and is affected by mass properties, suspension characteristics, contact mechanism between a wheel and a rail, etc. This paper describes the procedure of sensitivity analysis between some of the suspension characteristics of the Korean high speed train (KHST) as the design variables and the dynamic performance as the response variables; and it analyzes the results of sensitivity characteristics for the design variables, comparing two different approximated approach processes known as the response surface model formulated in a polynomial equation and neural network model formulated in a processing code. Analyzing the suspension characteristics for KHST, the approximated method creating meta-models consisted of 29 design variables and 46 performance indexes, which are applied in this paper. The models were coded by using the correlation information between the design variables and the performance indexes made by the 66 times iterative simulations according to the design of experimental method. The table consists of the orthogonal array L32 and the D-Optimal design table. The results show that the proposed sensitivity analysis procedure is very efficient and simply applicable for a complex mechanical system such as railway vehicle system. Also they show that the two models applied in this paper have similar tendency in the view of the sensitivity order of the design variables.

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This study describes the dynamic behavior of the HEMU-430X, the Korean next-generation high-speed train. The HEMU-430X was initially analyzed using VAMPIRE, a computer program that is used to examine the dynamics of railway vehicles, based on which it was expected to sway strongly at its tail end. This hunting motion was expected to disappear when the position of the yaw damper was changed. The dynamic behavior of the HEMU-430X was assessed in an on-track test performed using the protocols in the EN14363 standard and measuring the carbody, bogie and axle accelerations; the HEMU-430X was found to satisfy the safety criterion. The hunting motion appeared at speeds of 150, 350 and 387 km/h, and countermeasures such as changing the position of the yaw damper, installing carbody dampers, and increasing the damping coefficient of the yaw damper installed on the motor car containing the driver's cab were taken in order to reduce the vibrations. Ultimately, the highest test speed achieved was 421.4 km/h. Subsequently, it was found that the critical speed tended to decrease with mileage. This was attributed to excessive lateral damping and a revised design was proposed to solve this problem.

The Korean Train Express (KTX) has opened to commercial traffic since 2004 at a maximum speed of 300 km/h. As the train goes faster, it is necessary to inspect and maintain the rail regularly to secure the safety and reliability of the high-speed railway. The track irregularities can affect the running behavior of the train, the riding comfort of passengers, and the safety of the running train. To prevent undesired effects of rail irregularities, it is necessary to inspect the status of the rail regularly. Fast and accurate measurement result is the key role of the rail measurement system. The authors contrived the high-speed rail measurement system with a maximum measurement speed of 320 km/h and installed it into HSR-350x. The Korea High-speed Railway (HSR-350x) was developed and is being tested. The track irregularity inspection module for HSR-350x was designed and constructed over 300 km/h. A real test run on the high-speed rail was then performed. In this paper, we introduce the track irregularity inspection system and the measurement system of HSR-350x. A test run to verify the reliability of the system is performed and the result shows good performance of the track inspection measuring system.