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Significant increases in rail loads, as well as growing interest in providing higher-speed passenger rail services, is placing new and increasing existing demands on fastening systems and concrete sleepers. Consequently, there is a strong need to better understand the response of fastening systems and concrete sleepers to these significantly increased demands. This paper presents an experimentally validated three-dimensional (3D) finite element (FE) model of a fastening system and concrete sleeper that can be used to study and improve the design and performance of these systems. In this 3D FE model, the following mechanisms that are critical to the performance of fastening systems and concrete sleepers are included: frictional interaction between components of the fastening system; interaction between shoulders and concrete; and the plastic behavior of each component in the system. The FE model is validated using laboratory experimental tests, in which a lateral load is applied to a single concrete sleeper with two sets of fastening systems. The validated FE model is used to analyze the sleeper/fastening system under different loading scenarios involving various vertical and lateral load combinations. Both component stress and system deflection of the model are analyzed to investigate the system performance at the component and system levels. The results of the study show that FE modeling can be used to investigate the complex behavior of fastening systems and concrete sleepers.

Hybrid carbon films composed of graphene film and porous carbon film may give full play to the advantages of both carbon materials, and have great potential for application in energy storage and conversion devices. Unfortunately, there are very few reports on fabrication of hybrid carbon films. Here we demonstrate a simple approach to fabricate free-standing sandwich-structured hybrid carbon film composed of porous amorphous carbon film and multilayer graphene film by chemical vapor deposition in a controllable and scalable way. Hybrid carbon films reveal good electrical conductivity, excellent flexibility, and good compatibility with substrate. Supercapacitors assembled by hybrid carbon films exhibit ultrahigh rate capability, wide frequency range, good capacitance performance, and high-power density. Moreover, this approach may provide a general path for fabrication of hybrid carbon materials with different structures by using different metals with high carbon solubility, and greatly expands the application scope of carbon materials.

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