Study on the Preparation and Performance of Silicone-Modified Phenolic Resin Binder for Rail Grinding Wheels.

A scheme for manufacturing heavy-duty rail grinding wheels with silicone-modified phenolic resin (SMPR) as a binder in the field of rail grinding is presented to improve the performance of grinding wheels. To optimize the heat resistance and mechanical performance of rail grinding wheels, an SMPR for industrial production of rail grinding wheels was prepared in a two-step reaction using methyl-trimethoxy-silane (MTMS) as the organosilicon modifier by guiding the occurrence of the transesterification and addition polymerization reactions. The effect of MTMS concentration on the performance of silicone-modified phenolic resin for application in rail grinding wheels was investigated. The molecular structure, thermal stability, bending strength, and impact strength values of the SMPR were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and mechanical property testing, and the effect of MTMS content on the resin properties was investigated. The results indicated that MTMS successfully improved the performance of the phenolic resin. The thermogravimetric weight loss temperature of the SMPR modified by MTMS with 40% phenol mass at 30% weight loss is 66% higher than that of common phenolic resin (UMPR), exhibiting the best thermal stability; in addition, its bending strength and impact strength were enhanced by approximately 14% and 6%, respectively, compared with those of common UMPR. This study utilized an innovative Bronsted acid as a catalyst and simplified several intermediate reactions in the conventional silicone-modified phenolic resin technology. This new investigation of the synthesis process decreases the manufacturing cost of the SMPR, liberates it from the restrictions of grinding applications, and enables the SMPR to maximize its performance in the rail grinding industry. This study serves as a reference for future work on resin binders for grinding wheels and the development of rail grinding wheel manufacturing technology.

Detection and Classification System for Rail Surface Defects Based on Eddy Current.

The prospect of growth of a railway system impacts both the network size and its occupation. Due to the overloaded infrastructure, it is necessary to increase reliability by adopting fast maintenance services to reach economic and security conditions. In this context, one major problem is the excessive friction caused by the wheels. This contingency may cause ruptures with severe consequences. While eddy's current approaches are adequate to detect superficial damages in metal structures, there are still open challenges concerning automatic identification of rail defects. Herein, we propose an embedded system for online detection and location of rails defects based on eddy current. Moreover, we propose a new method to interpret eddy current signals by analyzing their wavelet transforms through a convolutional neural network. With this approach, the embedded system locates and classifies different types of anomalies, enabling an optimization of the railway maintenance plan. Field tests were performed, in which the rail anomalies were grouped in three classes: squids, weld and joints. The results showed a classification efficiency of ~98%, surpassing the most commonly used methods found in the literature.

Investigating the Effect of Grinding Time on High-Speed Grinding of Rails by a Passive Grinding Test Machine.

High-speed rail grinding is a unique passive grinding maintenance strategy that differs from conventional grinding techniques. Its grinding behavior is dependent on the relative motion between the grinding wheel and rail; hence, it possesses great speed and efficiency. In this study, the effects of the duration of grinding time and the increase in the number of grinding passes on the grinding of high-speed rails were investigated using passive grinding tests with a single grinding time of 10 s and 30 s and grinding passes of once, twice, and three times, respectively. The results show that when the total grinding time was the same, the rail removal, grinding ratio of grinding wheels, rail grinding effect, grinding force, and grinding temperature were better in three passes of 10 s grinding than in one pass of 30 s grinding, indicating that the short-time and multi-pass grinding scheme is not only conducive to improving the grinding efficiency and grinding quality in the high-speed rail grinding but can also extend the service life of the grinding wheels. Moreover, when the single grinding times were 10 s and 30 s, respectively, the grinding removal, grinding efficiency, grinding marks depth, and surface roughness of rail increased with the number of grinding passes, implying that the desired rail grinding objective can be achieved by extending the grinding time via the multi-pass grinding strategy. The results and theoretical analysis of this study will contribute to re-conceptualizing the practical operation of high-speed rail grinding and provide references for the development of the grinding process and grinding technology.

Effects of Grinding Passes and Direction on Material Removal Behaviours in the Rail Grinding Process.

A three-dimensional finite element model of rail grinding was established to explore the effects of grinding passes and grinding direction on the material removal behaviour of grinding rails during the grinding process. The results indicate that as the number of grinding passes increases, a decrease in the grinding force reduces both the amount of removed rail material and the surface roughness. There is a decrease in the grinding ratio caused by the increase in the wear on the grinding wheel and the decreased removal of the rail material. When the grinding direction changes, the wear of the grinding wheel decreases, which is contrary to the increasing trend of the amount of removed rail material, the grinding ratio, the surface roughness and the grinding force.