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Applying graphene (Gr) coatings to high-entropy alloys (HEA) is anticipated to enhance their tribological characteristics. The current understanding of the mechanism by which the Gr/HEA is enhanced at the atomic level is still limited. Molecular dynamics simulations revealed the mechanical behavior and strengthening mechanism of the Gr/AlCoCrFeNi HEA during nanoindentation and nanoscratch. The results demonstrate a substantial increase in the indentation hardness of the Gr/AlCoCrFeNi HEA by about 2.4 times. When Gr changed from a single layer to three layers, it further improved (3.2 times for a double layer and 3.9 times for three layers). At the same time, the friction coefficient is effectively reduced. Furthermore, the elevated in-plane stiffness of the Gr coating leads to an expansion of the effective loading area, resulting in increased Shockley dislocation and stair-rod dislocation density within the Gr/AlCoCrFeNi HEA, thereby amplifying the strain hardening effect and reducing subsurface damage. Qualitative experiments confirmed the excellent wear resistance of the Gr/HEA, and coating Gr increased the width of scratches, effectively confirming our simulation results. These findings provide valuable insights for the development and design of Gr/HEA composite coatings with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

At present, metro engineering vehicles rely on visual driving by the driver, and there are safety problems such as rushing cross signals, overspeed and impacting switch in complex operation scenarios. This paper proposes a piece of shunting protection software based on the BeiDou satellite positioning system, and expounds its function design, software interface, mode conversion and protection method in detail. The shunting protection software uses safety computer platform tools, adopts modular design, and makes comprehensive use of the BeiDou satellite positioning system, beacon positioning system, computer-based interlocking system and binary tree theory to realize precise protection of metro engineering vehicles in shunting operation, effectively solve the safety risks in the operation process, and improve the safety of the metro engineering vehicles in shunting operation. At the end of 2020, the shunting protection software was tested in Guangzhou Metro Line 5 and Yuzhu Rolling Stock Depot.The results show that it can timely protect against rushing cross signals, overspeed and impacting switch, and meet the safety protection requirements of users for shunting operation.

Electrochemical descaling devices have been widely used in the industrial field due to their broad applicability, convenience of operation, and cost-effectiveness. However, there are many factors that affect the descaling performance of electrochemical descaling devices, such as the selection of electrode materials, the shape and layout of the anode and cathode, the voltage and current of electrochemical equipment, the flow rate, temperature, and mineral content. Existing research has primarily focused on the influence of electrode materials and current density on descaling efficiency, while neglecting external factors such as water flow rate and temperature. In order to further explore the internal and external factors affecting the descaling performance of descaling machines, this study constructed an experimental platform for a descaling machine fouling device. Different voltages, currents, water flow rates, and temperatures were studied to assess the descaling efficiency of the descaling machine. The results indicated that under the conditions of a temperature of 30 °C, a flow rate of 0.35 m/s, a voltage of 24 V, and a current of 10 A, the fouling resistance effect of the electrochemical descaling device was optimal. This provides a new perspective for further improving the descaling efficiency of descaling machines and conducting parameter optimization. [ABSTRACT FROM AUTHOR]

Micro-hole aerostatic bearings are important components in micro-low-gravity simulation of aerospace equipment, and the accuracy of micro-low-gravity simulation tests is affected by them. In order to eliminate the influence of air resistance on the attitude control accuracy of remote sensing satellites and achieve high fidelity of micro-low-gravity simulation tests, in this study, a design and parameter optimization method was proposed for micro-hole aerostatic bearings for a vacuum environment. Firstly, the theoretical analysis was conducted to investigate the impact of various bearing parameters and external conditions on the bearing load capacity and mass flow. Subsequently, a function model describing the variation in bearing load capacity and mass flow with bearing parameters was obtained utilizing a BP neural network. The parameters of aerostatic bearings in a vacuum environment were optimized using the non-dominated sorting genetic algorithm (NSGA-II) with the objectives of maximizing the load capacity and minimizing the mass flow. Subsequently, experimental tests were conducted on the optimized bearings in both atmospheric and vacuum conditions to evaluate their load capacity and mass flow. The results show that in a vacuum environment, the load capacity and mass flow of aerostatic bearings are increased compared to those in standard atmospheric conditions. Furthermore, it has been determined that the optimal solution for the bearing's load capacity and mass flow occurs when the bearing has an orifice aperture of 0.1 mm, 36 holes, and an orifice distribution diameter of 38.83 mm. The corresponding load capacity and mass flow are 460.644 N and 11.816 L/min, respectively. The experimental and simulated errors are within 10%; thus, the accuracy of the simulation is verified. [ABSTRACT FROM AUTHOR]

The solution of equilibrium positions is a critical component in the calculation of the dynamic characteristic coefficients of aerostatic bearings. The movement of the rotor in one direction leads to bidirectional variations in the air film force, resulting in low efficiency when using conventional calculation methods. It can even lead to iterative divergence if the initial value is improperly selected. This study concentrates on the orifice throttling aerostatic bearings and proposes a novel method called the bivariate interpolation method (BIM) to calculate the equilibrium position. The equilibrium equation for the rotor under the combined influence of air film forces, gravity, and external loads is established. A calculation program based on the finite difference method is developed to determine the equilibrium position. The process of solving the equilibrium position and the convergence is compared with the secant method and the search method. Furthermore, the variation trend of the equilibrium position and stiffness when the external loads changes are studied based on the BIM. Finally, the correctness of the BIM to solve the equilibrium position is proved by comparing it with the experiment results. The calculation results indicate that the BIM successfully resolves the problem of initial value selection and exhibits superior computational efficiency and accuracy. The equilibrium position initially moves away from the direction of the external load as the load increases, and then this gradually approaches the load direction. The main stiffness increases with increases in the external load, while the variation in cross stiffness depends on the direction of the external load. [ABSTRACT FROM AUTHOR]

In order to improve the vibration performance of spindle, the composite surface texture of shell-like shape, shark-like skin shape and cybister bengalensis-like with drag reduction effect was micro-machinated on the high-speed rotating surface of spindle. The vibration performance of double elastic spindle and single elastic spindle before and after increasing the composite surface texture was compared and analyzed under the same conditions. The results showed that the vibration performance of double elastic spindle and single elastic spindle were improved slightly when the composite surface texture of shark-like skin shape was added. The double elastic spindle could work at any speed because its amplitude was small and it was not affected by the critical speed after adding the shell-like shape and the medium size cybister bengalensis-like composite surface texture. The vibration performance of double elastic and single elastic spindle with large and small sizes of composite surface texture cybister bengalensis-like were obviously improved at high speed. [ABSTRACT FROM AUTHOR]

In this study, an extended Reynolds equation incorporating the shape errors and the inertia effects of compressible fluid was formulated. The pressure-solving equation for the gas film was constructed using a second-order finite difference method. By combining the measurement data from the cylindricity of multiple shafts obtained from a cylindricity measuring instrument, the variation of the aerostatic bearing load capacity with the rotation of the shaft was calculated, both with and without considering the inertia effect. An experimental rig was also constructed to measure the error motion data of the corresponding shaft. The results of numerical analysis and experimental validation demonstrated that shafts with larger cylindricity error values exhibit greater deviations in the calculated bearing load capacity, which correspondingly leads to larger radial error motion values measured in the experiment. When the roundness error value of the shaft is small or the shaft speed is low, the influence of inertial effects on the calculation results of the load capacity deviation is minimal and can generally be disregarded. [ABSTRACT FROM AUTHOR]

Intense research efforts are focused on the development of advanced high-entropy alloys intended for premium aerospace components and other applications, where high strength and good formability are crucial. The mechanical properties of these alloys are closely related to the phase transformation, dislocation evolution, and grain size, and these factors are affected by the deformation temperature. The response of the retained austenite to strain-induced martensitic transformation at various temperatures was studied in an advanced Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy via molecular dynamics simulation. It was found that the Ti68Nb7Ta3Zr4Mo18 alloy changes from a single crystal to a polycrystal during the tensile process, and the transition of the Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy from the BCC phase to the FCC phase occurs. At high temperatures and low strain rates, grain boundary slip is the main deformation mechanism, and at low temperatures and high strain rates, dislocation slip replaces grain boundary slip as the dominant deformation mechanism, which improves the strength of the alloy. Moreover, when the grain size is too small, the strength of the alloy decreases, which does not satisfy the fine grain strengthening theory and shows an inverse Hall–Petch relationship. This study offers a new compositional window for the additive manufactured lightweight high-strength material categories for various applications including the aerospace industry. [ABSTRACT FROM AUTHOR]

Ni1/3Co2/3(CO3)1/2(OH)·0.11H2O (NCC) was in situ constructed on the surface of CNTs, which realized the nanoscale recombination of NCC and CNTs. The as-obtained CNTs@NCC composite showed excellent electrochemical performance in both aqueous and all-solid-state electrolyte systems owing to the improvement in the utilization of active materials. This work provides a general duty strategy for improving the combined electrochemical performance of electrode materials for energy storage. [ABSTRACT FROM AUTHOR]