Higher Vibration Modes in Railway Tracks:
Experimental results

Introduction

The mode shapes of an actual rail have been experimentally examined in the frequency range from 5 kHz to 50 kHz. A scanning vibrometer based on a heterodyne laser interferometer was used to measure the velocity at the surface of the rail (see Figure 4). The laser beam is deflected using two built-in mirrors, thus allowing the vibration measurement at each point of a defined grid. The mode shapes are calculated from the recorded data at user defined bands by performing a standard modal analysis based on the Fast Fourier Transform (FFT).

Figure 4 shows the laser head (2) of the scanning vibrometer standing above the rail (1) on wooden sleepers. The rail is painted with silver color for better laser reflection.

Measurements of the mode shapes on top of the rail head, at the side of the rail head, at the web of the rail and on top of the railfoot were performed at the excitation span and are shown in the section below (excitation at z=0m). The numerically calculated mode shapes are included for comparison. The spatial behavior measured at the running surface over a distance of three sleeper spacings from the excitation at z=0m is also shown for each mode (see Introduction to the behavior of higher vibration modes for definition of type I and type II vibration). The results can be viewed as AVI or animated-GIF animations by pressing the corresponding buttons.

For a detailed discussion of the results please be referred to the online version (PDF, 7840 k, Acrobat Reader 4.0 required) of my thesis.

Index of Modes

• Mode 6, type II vibration
• Mode 7, type II vibration
• Mode 8, type I vibration
• Mode 9, type I vibration
• Mode 10, combination of both types
• Mode 11, type I vibration
• Mode 12
• Mode 13, type II vibration
• Mode 14, combination of both types
• Mode 15, type II vibration
• Mode 17, type I vibration
• Mode 18, type I vibration
• Mode 19, type I vibration
• Mode 20, type I vibration

Mode 6:

Experimental modal analysis:	Numerical simulation:
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Mode 7:

Experimental modal analysis:	Numerical simulation:
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Mode 8:

Experimental modal analysis:	Numerical simulation:
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Mode 9:

Experimental modal analysis:	Numerical simulation:
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Mode 10:

Experimental modal analysis:	Numerical simulation:
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Mode 11:

Experimental modal analysis:	Numerical simulation:
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Mode 12:

Experimental modal analysis:	Numerical simulation:
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Mode 13:

Experimental modal analysis:	Numerical simulation:
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Mode 14:

Experimental modal analysis:	Numerical simulation:
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Mode 15:

Experimental modal analysis:	Numerical simulation:
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Mode 17:

Experimental modal analysis:	Numerical simulation:
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Mode 18:

Experimental modal analysis:	Numerical simulation:
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Mode 19:

Experimental modal analysis:	Numerical simulation:
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Mode 20:

Experimental modal analysis:	Numerical simulation:
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