Nanoparticles have as characteristics super sliding, extreme pressure, self-healing, etc., which can improve the friction reduction and anti-wear performance of sliding components, when used as lubricating oil additives. Nano-copper particles have a good synergistic effect with other antifriction agents, anti-wear agents, antioxidants and grease additives because of their low shear strength and grain boundary slip effect, showing a better anti-friction and anti-wear effect. However, nanoparticles are prone to conglomerate, and this causes a bottleneck in the application of dispersant for nano-copper in a lubricating oil system. The regulation of nanosized effect and surface properties has great engineering significance in compensating for the precision in manufacturing accuracy. This paper comprehensively reviews the tribological research progress of nano-copper as a lubricant additive, which provides a reference to the application of nano-copper particles as lubricating oil additives on engineering tribology.

In order to solve the problem of Meshing Efficiency of spur-face gear sliding friction, a method for calculating the Meshing Efficiency of Spur-Face gear is proposed based on Elastohydrodynamic lubrication (EHL) theory. Through the Tooth Contact Analysis (TCA) and Loaded Tooth Contact Analysis technique (LTCA) method, the meshing process of the Spur-Face gear was simulated. The calculation model of Sliding friction coefficient was established by using non Newtonian quasi steady thermal Elastohydrodynamic lubrication (TEHL) theory, and the calculation model of Meshing Efficiency of Spur-Face gear was established. The influence of input torque and rotational speed on Meshing Efficiency is analyzed. The results show that Sliding friction coefficient is an important factor affecting the Meshing Efficiency of gears. Sliding friction coefficient is not the same at different positions of the tooth surface. Sliding friction coefficient is affected by input speed and input torque. This method provides a theoretical basis for further optimization calculation of Spur-Face gear.

The double-helical gear system was widely used in ship transmission. In order to study the influence of backlash on the nonlinear frequency response characteristics of marine double-helical gear system, according to the structural characteristics of double-helical gear transmission, considering the time-varying meshing stiffness, backlash, damping, comprehensive transmission error, external load excitation, and other factors, a three-dimensional bending-torsional-axial-pendular coupling nonlinear dynamic modeling and dynamic differential equation of 24-DOF double-helical gear transmission system were established. The Runge–Kutta numerical method was used to analyze the influence of backlash, time-varying meshing stiffness, damping, error and external load excitation on the amplitude frequency characteristics. The results show that the backlash can cause the runout of the double-helical gear system, and the system has first harmonic and second harmonic response. With the increase of backlash, the amplitude of the system increases and the jumping phenomenon remains unchanged. The amplitude frequency response of the system is stimulated by time-varying meshing stiffness and comprehensive transmission error, and restrained by damping and external load excitation. The vibration displacement amplitude of the system increases with the increase of vibration displacement and has little effect on the state change of the system. The vibration test of double-helical gear is carried out. The frequency response components obtained by numerical simulation are basically consistent with the experimental results, which proves the correctness of the theoretical calculation. It provides a technical basis for the study of vibration and noise reduction performance of double-helical gear.

Accurate analysis of the air gap magnetic field is the focus of research in the field of precision permanent magnet linear synchronous motors. In this paper, the two-dimensional air gap magnetic field of a secondary trapezoidal Halbach permanent magnet array coreless permanent magnet linear synchronous motor (PMLSM) was taken as our research object. On the basis of the equivalent surface current method, we proposed an improved equivalent analytical algorithm with a trapezoidal side length unit. The equivalent analytical model of the magnetic induction vector of the two-dimensional air gap was established, and the air gap magnetic field of the trapezoidal Halbach array coreless PMLSM was calculated. At the same time, we analyzed the influence of the bottom angle α of a trapezoidal permanent magnet equivalent width coefficient α_w, pole height coefficient α_h, and air gap height coefficient α_g on the amplitude (B_peak) and total harmonic distortion (THD_B) of the central magnetic field in the air gap. The results show that α and α_w have a significant influence on the B_peak and THD_B of the central magnetic field air gap. With the synergy of α and α_w, we identified the “flux convergence” effect, which makes the maximum range of B_peak α > 90° and α_w < 0.5. We also found the “equilateral” effect, which causes the minimum region of THD_B to change linearly. The calculation results of the improved equivalent surface current analytical model established in this paper agree with those verified by the finite element method. The calculation is convenient, and the accuracy of the result is high. This research provides a new method for analyzing the air gap magnetic field of a permanent magnet with a nonrectangular cross-section and lays a theoretical foundation for optimizing the PMLSM pole model.

In this article, an aerostatic thrust bearing with annular elastic uniform pressure plate structure was designed. In order to obtain a relationship between bearing capacity and stiffness of aerostatic thrust bearing designed in this article, first, the stress field mechanics model of the gas thrust bearing was established in the static. Second, deformation control equations of the elastic uniform pressure plate and gas lubrication Reynolds equation were established according to the flow continuity principle. Here, finite element mesh of gas flow field was woven using the technology of grid overlapping and grid stitching. Then, gas–solid coupling control equations were solved using the numerical method. Gas film pressure distribution and gas static bearing capacity of thrust bearing were analyzed. Function relationship between bearing capacity and the stiffness and the thickness of gas film was obtained. Finally, the results of theory analysis and experiment were compared. The results of the comparison can be listed as, under the effect of gas pressure, orifice area and the equilibrium pressure groove depth are changed due to elastic deformation of the elastic uniform pressure plate. The static stiffness of aerostatic thrust bearing with elastic equilibrium pressure groove increased by 30% than the static stiffness of aerostatic thrust bearing with rigid equilibrium pressure groove. The maximum carrying capacity occurred in the gas film thickness of 3.5 µm. The maximum static stiffness appeared in the gas film thickness of 5.5 µm. It can be seen from the comparison results of experiments and theoretical analysis that data results of gas film thickness and the bearing capacity are the same. The feasibility of the theoretical analysis method is validated.