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Sliding friction pair composed of contact wire and pantograph slide is the key component of train current collection system. Contact temperature is one of the important factors affecting the current-carrying and wear performance of the friction pair. In this article, sliding electrical contact experiments under different experimental conditions were conducted. Based on the measured contour curve of the slide surface, two fractal parameters of the slide surface were calculated by using the structure function method. And the effect of contact current, contact pressure, and sliding speed on the fractal parameters was discussed. A temperature field simulation model of sliding electrical contact considering two rough contact surfaces was established with COMSOL Multiphysics software. The effect of surface roughness and fractal parameters on contact temperature was analyzed by simulation. When other simulation parameters keep constant, the contact temperature first drops and then rises as the average roughness height of the contact surface increases. The average roughness slope of the contact surface has little effect on the contact temperature under high speed and strong current conditions. The contact temperature continuously decreases with the increase of fractal dimension or the decrease of fractal roughness. The conclusions can be used as a basis for further research on the contact temperature characteristics of the friction pair to improve its electrical contact performance. [ABSTRACT FROM AUTHOR]

Tribological tests are adopted to estimate the kinetic friction coefficient (COF) of the material of interest according to the American Society for Testing and Materials (ASTM) standard. Typically, for the measurement process, several replicas, as well as a postprocessing data treatment, are necessary to take into account the observed casual variability of the measurand. This article describes a statistical approach aiming to highlight the running-in phase and the most significant time intervals during the steady-state for each test replica. A two-steps procedure based on the adoption of the bootstrap method allows the automatic detection of the running-in time interval and the outlier filtering of the steady-state. Experimental activity has been carried out by performing multiple tests through the ball-on-flat tribometer in order to verify the improvement allowed by the authors’ proposal about the dry friction COF measurement in terms of both accuracy and repeatability. [ABSTRACT FROM AUTHOR]

We describe an instrument intended to study finger contacts under tangential dynamic loading. This type of loading is relevant to the natural conditions when touch is used to discriminate and identify the properties of the surfaces of objects—it is also crucial during object manipulation. The system comprises a high performance tribometer able to accurately record in vivo the components of the interfacial forces when a finger interacts with arbitrary surfaces which is combined with a high-speed, high-definition imaging apparatus. Broadband skin excitation reproducing the dynamic contact loads previously identified can be effected while imaging the contact through a transparent window, thus closely approximating the condition when the skin interacts with a non-transparent surface during sliding. As a preliminary example of the type of phenomenon that can be identified with this apparatus, we show that traction in the range from 10 to 1000 Hz tends to decrease faster with excitation frequency for dry fingers than for moist fingers. [ABSTRACT FROM PUBLISHER]

A new tape–head design with surface cavities is presented as an alternative to the conventional skiving-edge flat-profile head design. The new head design is referred to as the vacuum head, inspired by the sub-ambient air pressure that develops in the surface cavities during operation. Two prototype head modules, a writer and a reader, were fabricated by modifying commercial tape–head modules and are compared with unmodified reference modules. A finite-element model is presented to simulate the head–tape interface and aid in the surface topography design of the vacuum head prototypes. The modeling results correspond qualitatively with experimental data from interferometer measurements of the shape of tape as it passes over the vacuum heads. The vacuum heads are operated successfully in data read/write experiments, with a slightly reduced signal-to-noise ratio performance compared with the reference heads. An indirect measure of head friction is obtained from tape velocity spectra that show a much reduced friction-induced compressional wave tape resonance for the vacuum modules compared with that for the reference modules. The results presented in this paper show that the new vacuum head design is a promising candidate for future heads with low friction, enabling the use of very smooth media for reduced magnetic spacing and increased areal densities. [ABSTRACT FROM PUBLISHER]

An analytical study has been performed on Cu surfaces rubbed with Rulon, which is a polytetrafluoroethylene (PTFE)-based composite, in order to explain the dramatic reduction in wear of rails and armatures conditioned with Rulon. Electron and optical spectroscopies and microscopies demonstrated that conditioned surfaces were covered by a thin PTFE film, whose thickness was estimated to be no more than 2 nm on average. None of the techniques, however, could demonstrate that the film was uniform across the smooth areas of the surface. Speculations are given to account for the enhanced bore life and antiwear antiarcing behavior of Rulon-conditioned Cu. [ABSTRACT FROM PUBLISHER]