Manifestation of Flexural Vibration Modes of Rails by the Phase-Based Magnification Method

With the recent development of high performance photography devices, vibration measurements using digital image processing can be utilized for the condition monitoring and the analysis of generation mechanisms. High-quality image recording provides very dense spatial information unlike physical sensors with a limited number of point-oriented measurements and output channels such as accelerometers. Moreover, image acquisition is a non-contact technique and ensures that the installed sensors do not affect the mass or stiffness. In this study, the vibration mode of rails is investigated using the phase-based video magnification method. An extensive amount of information that cannot be detected by human eyes, can be obtained with this imaging motion magnification technique by amplifying and visualising the minute vibrational movements. Flexural vibration modes in rails generate rolling noise, especially at high frequencies where the displacement amplitudes are small. The motion magnification method is applied using a high-speed camera to measure the rail mode shapes. The measured mode shapes are compared to the numerical results obtained from the waveguide finite element method. This method helps in understanding the vibration generation and the transfer mechanisms in the waveguide structures with a uniform cross-section in the lengthwise direction such as a railway track.