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A low-floor train–turnout coupling dynamic model considering bad alignment irregularity ahead of the turnout was established on the basis of a field test in which the dynamic performances of a low-floor train passing through a no. 6 turnout in a rail transit depot in China had been measured, as well as the line alignment and wheel and rail profiles. There are two types of wheelsets in the low-floor train: integral wheelset and independent wheelset. The model fully considers the coupling effect between the vehicle and the ballast components, and the simulated results are in consistence with measured results in the field test. Based on this, the influences of train speed, the wheel–rail friction coefficient, and the track alignment optimization of the dynamic performance of low-floor trains passing switch in facing direction are analyzed. The main results indicate that eliminating alignment irregularities before the switch can effectively improve the dynamic performance of the integrated wheelset in the switch and the lateral forces of the outer wheels of these two vehicles are reduced by about 80%, the derailment coefficients are reduced by about 70%, the vertical force is reduced by about 10–20% and wheel load is reduced by approximately 30%. [ABSTRACT FROM AUTHOR]

An experimental study on the tribology behavior and mechanism of NBR-Steel pair has been carried out. Abrasive paper was used to polish the NBR surface. The influences of surface topography on the friction coefficient were investigated based on the block-on-ring tribometer. Results show that polishing with abrasive paper is an effective method to reduce the friction coefficient of NBR on steel. Superlubricity was also found in the test. A new method to explain the superlubricity based on the contact angle and surface molecular structure was put forward in this work. Abrasive paper polishing changes the surface asperities, so affects the contact angle, so as to influence the boundary limiting shearing strength, and then causes the superlubricity. During the friction process the microstructure obviously changed, along with mechanical breaking of the molecular chain. [ABSTRACT FROM AUTHOR]

Abstract: The effect of aging in oil on the seal performance of a radial lip seal is investigated in the present study by conducting a constant temperature oil bath test to obtain aged rubber samples and seals, and measuring the changes of material properties and seal performance with the aging time. The change of lip surface micro-morphology with the aging time is also measured by using a 3D white light optical interferometer. The leakage and friction torque are computed in a numerical simulation, utilizing a mixed elastohydrodynamic lubrication (EHL) model, to determine how aging in oil affects the lip seal performance. Finally, the simulation results of the EHL model are verified by a bench test on aged lip seals. [Copyright &y& Elsevier]

Abstract: Since aging is an inevitable phenomenon during storage of a radial lip seal, this study aims to investigate the effect of aging on the seal performance. An air oven aging test is conducted to produce aged rubber samples and seal products. An aging life prediction model is constructed to predict the equivalent material properties at any storage temperature. The material property parameters of aged rubber samples are measured in a uniaxial compression experiment. The pumping rate and friction torque of the seal are calculated through numerical simulation by using a mixed elastohydrodynamic lubrication (EHL) model. A bench test is used to verify the aging life prediction model and the simulation results of the EHL model. Finally, the verified EHL model is used to study how aging during storage affects the lip seal performance, as characterized by the leakage and friction torque. [Copyright &y& Elsevier]

Abstract: This study investigates the effects of structure, material parameters and assembly conditions on the reverse pumping rate and friction torque of the radial lip seal by using a mixed elastohydrodynamic lubrication model. The orthogonal array method is used to make a numerical experiment plan for eight parameters, which are identified as eight control factors. Each factor has five levels. The significance of each parameter on the reverse pumping rate and friction torque of the radial lip seal is evaluated by range analysis and F-test. As a result, optimal values of eight parameters are suggested. The seal with this set of optimal values has a higher reverse pumping rate and lower friction torque than those of a previously-designed seal. [Copyright &y& Elsevier]

The tribological properties of matching pairs at different temperature domain is predicted through friction sound. Two deep learning algorithms respectively by virtue of the Nonlinear Auto-Regressive models with Exogenous Inputs and long short-term memory neural network are adopted to analyze the acoustic features of friction sound to predict tribological properties of polymer surface at five temperatures within a large temperature domain under different working conditions. The deep learning algorithm precisely fits the friction coefficient in accordance with the performance analysis. [Display omitted] • A real-time friction coefficient prediction method based on friction sound. • The mapping relationship between friction sound and friction coefficient with the same random nonlinear characteristics. • The prediction method was widely applicable to the prediction of friction coefficient under wide temperature range. • This method can be used for in-situ monitoring on tribological properties of mating pairs. [ABSTRACT FROM AUTHOR]

Two polymers and five metal pairs were tested at six low temperature points and three constant load speeds. The tribological properties were determined by joint iterative coupling of the temperature, load and friction velocity value. Molecular dynamics simulation was used to study the micro-tribological properties of friction pairs at the atomic scale. The macro-tribological performance test results were similar to the results of the molecular dynamics simulation and exhibited the same trend. Two profound hypothermia points were predicted. The evolution of the tribological mechanism and properties of the polymer interface under different working conditions at low temperature were revealed on the macroscopic and atomic scales. [Display omitted] • A friction mechanism researching method based on a combination of macro and micro research was developed. • The macroscopic and microscopic tribological evolution rules of a polymer interface at low temperature were found. • The simulation was applicable to predicting polymer materials' tribological properties and explaining the test phenomena. • This method can be used for researches under harsher conditions and more extreme environments. [ABSTRACT FROM AUTHOR]

A signal processing method based on friction noise is introduced to predict the tribological properties of polymers in a wide temperature domain. Three different machine learning algorithms, XGBoost, LightGBM and CatBoost are used to establish a mapping relationship between the time–frequency domain features of friction noise and the friction coefficient. The friction coefficients of pairs of four polymers and seven metals are predicted at five temperatures and three load/speed conditions of point contacts in a wide temperature domain from − 120–25 ℃. Performance analysis reveals that the machine learning approach satisfactorily predicts the friction coefficients of different polymer–metal pairs in a wide temperature range from tribological test data. This method can be used for in-situ monitoring on tribological properties. [Display omitted] • A real-time friction coefficient prediction method based on friction noise was developed by using machine learning algorithm. • The following mapping relationship between friction noise and friction coefficient was found. • The prediction method was widely applicable to the prediction of friction coefficient. • This method can be used for in-situ monitoring on tribological properties of mating pairs. [ABSTRACT FROM AUTHOR]