It is usually difficult to obtain the modal characteristics of the rail fastening clip analytically owing to its complex spatial structure and operating environments. Therefore, experimental modal testing is frequently adopted to identify the modal characteristics of rail fastening clips. This study takes the SKL 15 clip of the Vossloh 300-1 fastening system as the research object to analyse the following three aspects in great detail: (1) Locations of the measurement points are reasonably designed to capture all modes of the clip in the frequency range 0–1000 Hz. (2) The appropriate sensors are selected for the clip in different operating situations by comparing the measured results of three kinds of sensors, namely the accelerometer, laser vibrometer and sound pressure sensor. In addition, the test results suggest that the accelerometer which has a strong anti-disturbance ability in an ambient environment is recommended to be chosen in a noisy environment while the laser vibrometer and sound pressure sensor which have no added mass to the tested structures may be used in an indoor environment with suitable temperature and low noise. (3) In order to eliminate the effect of the additional mass on the modal characteristics of the clip, the accelerometer is recommended to be installed at the rear end of the side leg of the clips in the experimental modal test.

In railway systems, layered structures could be induced in wheel–rail contact interfaces due to several causes, such as head hardening, work hardening, plastic deformation, and mechanical or thermal excursion-induced phase transformation. This study proposes an explicit finite element (FE) method for investigating elastic layer effects in wheel–rail rolling contact. The proposed method is first validated by comparing its solution with that of Kalker’s boundary element method (BEM) when the layer is not present, with a focus on the tractive rolling contact. To investigate general layer effects, the rail is assumed to consist of two layers, i.e., the top layer and the matrix material. The top layer is assumed to have different elastic moduli from the matrix material and then the top elastic layer effects on contact characteristics such as contact stress, contact patch, and subsurface stress are investigated. Different layer thicknesses are also considered. It is observed that a harder layer tends to introduce larger contact pressure and surface shear stress, but a smaller contact patch. A harder layer also produces larger subsurface stresses. A thicker layer may intensify these effects. The results suggest that in engineering applications, the analysis of wheel–rail rolling contact consequences such as wear and rolling contact fatigue (RCF) may need to consider the layered structures using appropriate methods.

Short-pitch rail corrugation is commonly found at curves or resilient track structures of the metro system, causing fatigue failure of key components of the train–track system. Currently, rail corrugation is detected via routine inspections during the possession period, with the compromise between inspection efficiency and data accuracy. A newly proposed indirect diagnosis method for rail corrugation has been proposed. Rail corrugation dynamic characteristics and location can be quantitatively identified by measuring train vehicle interior noise and vibration response of a running train under the normal operation conditions, without requiring track access, together with transfer functions—including receptance and accelerance of the wheel–rail system. This indirect method has been applied to and tested on a rail track section with severe corrugation at curves. Results from the indirect diagnosis method are then compared against direct rail roughness measurement using a standard Corrugation Analysis Trolley. Good agreements of peak magnitudes and corresponding frequency bands have been achieved. The indirect method has been successfully validated and can be used to assist track maintenances.