Keywords: railway vehicle, carbody, flexural vibration, experimental modal analysis, natural mode of vibration, ride comfort.

This paper presents the modal properties of carbody flexural vibrations in several types of railway vehicles widely used in Japan. Firstly, the experimental procedure and the modal analysis method used here, which is based on a linear prediction model (LPM), are described. This analysis method is applicable not only of the analysis of single input problems such as the stationary excitation test using an exciter but also of multiple input conditions during running.

Then stationary excitation test results for the following three different types of railway vehicles are presented: a Shinkansen vehicle, an express type vehicle and a commuter type vehicle. These three vehicles have different structural features. The carbody shells of the Shinkansen and express type vehicles are made of extruded hollow aluminum alloy and continuous welding is used to form the carbody. In addition, the Shinkansen carbody shell has an airtight structure to prevent aural discomfort arising from pressure changes during passing through tunnels. On the other hand, the commuter type vehicle carbody is made of stainless steel, and each panel member is connected discretely using spot welding. The sizes of the opening area on the side panel such as side sliding doors and side windows are also different in each of the three vehicles. This paper focuses how those structural differences affect on the modal vibration characteristics of the carbodies.

Moreover, the authors compare the modal vibration properties between the cases for a complete carbody and the carbody shell alone in order to examine the effect of underfloor equipment, inner fixtures and service equipment.

The following results are obtained from this study:

1. Structural features of the carbody shell largely affect the flexural vibration modal properties.
2. Both the Shinkansen and the express vehicle carbodies, whose carbody shells are made of extruded hollow aluminum alloy, have bending modes similar to the first mode of simple elastic free-supported beam. However, they also have many other flexural modes such as the diagonal distortion, different deformation of roof and floor, etc.
3. The bending mode similar to the first mode of simple elastic free-supported beam is not observed in the commuter type vehicle which has a stainless steel carbody shell.
4. A diagonal distortion mode is observed for all of the vehicles tested here.
5. Modal properties can be identified successfully from the measured data in both stationary and running tests by applying the linear prediction model described here.
6. Underfloor and service equipment and inner fixtures of a carbody affect not only as additional mass but also damping and rigidity. In particular, the additional damping effect is large.

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