Narrow Results

This paper uses fractal modeling techniques to effectively depict the roughness characteristics of the rails examined in this study by means of both the structure function and the Weierstrass–Mandelbrot function to capture the intricate nature of the rail roughness. Experimental analysis of the roughness of the railway rails from Faurei Railway Testing Center (RTC Faurei) in Romania proves that the roughness height exhibits distinct mathematical fractal characteristics. The study evaluated and compared 41 classical statistical parameters derived from roughness measurements with simulated fractal parameters. The classical roughness parameters, including the Autocorrelation function, Amplitude Density Function, as well as Bearing Area Curves, and rail acoustic roughness, were determined from a profile obtained using the Weierstrass function and compared to the measured ones, revealing a noticeable congruence between the generated charts. The research findings indicate a strong convergence between experimental measurements and simulated profiles, with most parameters falling within a 10% relative error range. This aspect highlights the approach of fractal potent in assessing rail roughness behavior. Consequently, the simulated parameters could potentially analyze rail roughness quality to maintain and track grinding and mitigate the rolling noise.

Rail defects cause numerous railway accidents. Trains are derailed and serious consequences often occur. Compared to traditional bulk wave testing, ultrasonic guided waves (UGWs) can provide larger monitoring ranges and complete coverage of the waveguide cross-section. These advantages are of significant importance for the non-destructive testing (NDT) of the continuously welded rail, and the technique is therefore widely used in high-speed railways. UGWs in continuous welded rail (CWR) and their propagation characteristics have been discussed in this paper. Finite element methods (FEMs) were used to accomplish a vibration modal analysis, which is extended by a subsequent dispersion analysis. Wave structure features were illustrated by displacement profiles. It was concluded that guided waves have the ability to detect defects in the rail via choice of proper mode and frequency. Additionally, thermal conduction that is caused by temperature variation in the rail is added into modeling and simulation. The results indicated that unbalanced thermal distribution may lead to the attenuation of UGWs in the rail.

Bogie is one of the most major mechanical part of railway train. Its security and reliability are of paramount importance. Since research in this field is still on the early stage, which focus on either mechanical structure without condition or binary coherent systems. A multistate network flow model has been proposed in this paper with consideration of components degradation level and functional interaction between them. Firstly, the structure and function of the bogie for CRH3 were made a detailed introduction. Then transmission paths of three types force on bogie were study to determine the network strcture. Different from other papers, arcs represent the components and nodes are the transitive relation. Arc capacity tends to be confirmed easily with utilization of performance deterioration of elements on bogie involved in force tranferring. Flow rate of each arc depends on both component' health status and the task it undertakes. Furthermore, the minimal paths (MPs) method and the recursive sum of disjoint products (RSDP) with ordering heuristics are used for system reliability calculation; and the relative probability importance of each basic component and system reliability with and without forehead information are given at last. The results show that the network flow model works well on CRH3 bogie, and can support as guidance of bogie system design, daily system operation and predictive maintenance.

Abnormal vibration of Electric Multiple Unit (EMU) carbody underframe was found by the line test, so a three dimensional rigid-flexible coupled vehicle system dynamics model was built to simulate the vibration response of carbody. Due to the excitation frequency was comparatively high, so the rail short wave was considered during the multi-body dynamic simulation. The concerned positions of carbody underframe, which located in center of underframe, was chosen to compare the results from theoretical model with line test. The comparison results illustrate that rigid-flexible coupled model combined with high frequency excitation should be adopted to simulate the high frequency vibration of carbody appropriately.