Dispersive Modal Characteristics of Guided Waves Propagating in Damaged Rails

Abstract

The dispersive modal characteristics of propagating guided waves are useful for efficiently detecting defects in high-speed railway rails due to their advantages. This paper presents an effective method for directly analyzing the effect of defects in rails on the dispersive modal characteristics of propagating guided waves, which can be utilized for the defect detection in rails. By using the semianalytical finite element method and from the characteristic equations of the guided wave propagation in waveguides, a general perturbation method is developed to provide an exact relationship between the perturbations of structural stiffness caused by damage and the perturbations of dispersive modal characteristics of propagating guided waves. Thus, the phase velocity and group velocity for the damaged waveguide can be accurately predicted. From the obtained propagating guided wave modes, a mode selection index used for selecting effective guided waves for damage detection is introduced by evaluating the nodal displacements and energy concentrations on the rail surfaces. Finally, a numerical study for a high-speed rail is given to demonstrate the effectiveness of the proposed method for rail defect detection and propagating mode selection. The results of the numerical study show that the dispersive modal properties of propagating modes are affected by the location and size of defects in the rail, and the proposed method can give useful information for effective detection of defects in rails.