The flow state in the flow channel of the control valve directly affects its service life and system stability. In order to explore the three-dimensional flow field information inside the control valve, a series of three-dimensional grid nodes were obtained by shooting different planes with a two-dimensional particle image velocimetry (2D-PIV) device, and the flow field information of unknown nodes was obtained by interpolation, so as to realize the three-dimensional reconstruction of the control valve flow field. The experimental results show that the overall trend of the three-dimensional reconstructed velocity field is consistent with that of the two-dimensional velocity field. The oil at the throttle port of the control valve forms a counter jet due to the throttling effect, and the jet converges to form a high-speed overall jet in the downstream of the valve core head. The combination of impinging jets on both sides in the top area of the valve core will produce a certain amount of oil backflow. The overall flow channel velocity decreases gradually with the moving out of the shooting plane. The velocity distribution of the upstream flow channel decreases steadily at first and then maintains a stable value. The velocity value near the throttle orifice increases first and then decreases, with a large variation. The wall resistance and shear force keep the near-wall velocity stable. The flow velocity in the downstream region is concentric and the flow field changes from turbulent flow to orderly flow. The simulation results show that the overall area of the three-dimensional reconstruction flow field is primarily consistent with the theoretical flow field. The maximum reconstruction error is 9.5%, occurring in the high-speed flow area of the throttle. The experimental reconstruction results is highly similar to the simulation reconstruction results and the reconstruction effect in the smooth flow area is better than that in the violent part. The research can provide a reference for the structural optimization design of the control valve and the improvement of cavitation performance, and is also provides an effective reference for the three-dimensional flow field measurement of the micro-channel.

The recirculating planetary roller screw mechanism, as a derivative of planetary roller screw mechanism, is a transmission mechanism that is engaged by the screw or nut thread and multiple circular groove rollers. To study the random vibration fatigue characteristics of the recirculating planetary roller screw mechanism, this paper established a finite element model of the mechanism based on fatigue failure theory, and conducted the dynamic analysis and fatigue life prediction. Firstly, according to the material stress-number of cycles (S-N) curve and Miner’s linear damage accumulation theory, fatigue analysis was carried out on the recirculating planetary roller screw mechanism using the related software, and fatigue results in the contact area and damage values at each node were obtained. Then, based on the developed four fatigue life prediction models, the obtained analytical solutions were compared with the simulated damage values. The results show that the resonance induced by the recirculating planetary roller screw mechanism at 3 960 Hz causes the most damage to the mechanism. When the excitation frequency is the same, the area of maximum contact stress and minimum fatigue life is the same. Besides, the corresponding frequencies of the peak stress in the harmonic response analysis and that of the peak power spectral density in the fatigue analysis of the recirculating planetary roller screw mechanism are the same. This study can provide a theoretical guidance for the design and fatigue optimization of the recirculating planetary roller screw mechanism.

When the working speed of the low-speed high-torque cam lobe hydraulic motor is developing towards an extremely low speed (up to 0.2 r/min), one of its core friction pairs, the roller-piston pair, is difficult to establish a hydrodynamic lubricating oil film at low speeds, leading to wear fail of the friction pair. Therefore, a three-layer bearing bush structure of steel back-copper powder-self-lubricating material was usually arranged between the roller-piston pair to improve the lubrication ability of friction pair at low speed. However, the cam lobe motors usually need to withstand large loads, and how to design three-layer bearing with high bearing capacity has become a challenge in the design of cam lobe hydraulic motors. The thickness distribution of each layer of the three-layer bearing directly affects the maximum stress of the bearing under load, and then affects the bearing capacity and service life of the cam lobe hydraulic motor. In order to explore the effect of the thickness of each layer of the three-layer bearing bush on the overall bearing capacity of the bearing bush, this paper carried out the force analysis of the three-layer bearing bush, and obtained the mapping law between the thickness of the three-layer material and the maximum von Mises stress of the self-lubricating layer. And this paper also proposed a low-stress three-layer self-lubricating bearing bush thickness distribution scheme suitable for the roller-piston pair of cam lobe motors and designed a three-layer bearing thickness distribution scheme (the self-lubricating layer thickness was 0.2 mm, the copper powder layer thickness was 0.3 mm, and the steel back layer thickness was 1.0 mm) for an cam lobe hydraulic motor with a maximum working pressure of 31.5 MPa.The three-layer bearing using this scheme was installed on the hydraulic motor for motor performance testing. The test results show that the bearing capacity of the bearing under the thickness distribution can meet the requirements of the maximum working pressure of the cam lobe motor.

In applications such as coal mining, food and underwater operations, low speed high torque high water-based hydraulic motors have the advantages of high power-to-weight ratio and medium compatibility. However, the current high-water-based hydraulic motors still maintain the same flow distribution structure as oil motors and only replace the working medium with high-water-based emulsion instead of hydraulic oil. Traditional flow distribution disc structures use spring force to ensure sealing. Under low speed, high pressure, and high water-based conditions, the flow distribution disc wears heavily, resulting in serious leaks. For high-water-based emulsion drive systems, this paper proposed a valve flow distribution mechanism comprising valves, bearings, and a pentagon-wheel. The motor’s intaking and discharging process is controlled by a check valve, and the opening and closing of the valve is controlled by the pentagon-wheel. Then the paper carried out comparative analysis on flow distribution rules, advantages and disadvantages of eccentric-wheel, cam, and pentagon-wheel flow distribution mechanisms. It is found that the pentagon-wheel flow distribution structure can reduce the concentration of push rod stress and solve the phenomenon of push rod self-rotation jamming. Finally, the superiority of the five-star wheel flow distribution structure was verified by using AMESim. The prototype was prepared and the performance experiment was carried out. The results show that the pressure in the plunger cavity can be quickly established under different speed (10~90 r/min) and pressure (5~21 MPa). Compared with traditional disc flow distribution mechanisms, the leak rate of the valve flow distribution mechanism under high-water-based conditions of 21 MPa and 90 r/min is only 0.15 mL/min, significantly improving motor volume efficiency.

The performance of the conductive slip ring brush wires has a vital impact on the lifespan of the satellite in orbit and the overall energy safety. In order to ensure the real-time transmission of signal and current, the brush wire angle needs to be controlled. This study established a three-dimensional model of the brush plate and the brush wire based on the theoretical analysis of the finite element method. The best way for producing the brush wire’s angles was identified by combining the explicit dynamics and implicit statics finite element simulation techniques. The brush wire angle forming and rebound were then fully simulated with these techniques. This paper presented a measurement method based on the rebound process of the brush wire angle, and compared the simulation value with the theoretical value of the brush wire rebound angle. The findings demonstrate that compared to the single-sided deflector plate and the double-sided short clamping plate, the double-sided long clamping plate performs at its finest when forming the brush wire’s angle; the brush wire’s rebound angle is positively correlated to the forming angle; the larger the forming angle of the brush wire, the larger the rebound deformation value of the brush wire after forming; when the brush wire is formed at an angle of 120° or more, the brush wire material is likely to be damaged due to excessive residual stresses. In order to prevent the destruction of the left root of the brush wire during elastic-plastic deformation, the left clamping surface of the clamping plate should be placed as close as possible to the left root of the brush wire to increase the constraints on the root of the brush wire, so as to ensure the quality of the angle forming of the brush wire; the maximum relative error in the angle of rebound of the brush wire is about 2°, but the average rebound inaccuracy is about 1°; the overall rebound trend is generally consistent, so the proposed method can well indicate the variation law of the rebound angle of the brush wire.

The synchronous meshing of threaded pairs and gear pairs is a typical feature of planetary roller screw transmission. To reveal the dynamic load fluctuation law of the screw pair caused by the meshing excitation of the gear pair and the inertia force generated by the roller rotating around the screw axis, this paper proposed a calculation method for the dynamic load distribution of the screw pair considering the inertia force and the meshing excitation of the gear pair. Firstly, based on the cylindrical collision theory, energy method, and time-varying spring model, the meshing excitation and time-varying meshing stiffness excitation of the gear pair were solved, respectively. Based on the spiral surface equation of the planetary roller screw, the static contact forces on the contact side of the roller screw and the roller nut were solved. Then, the force analysis was conducted on the roller, and the dynamic load distribution law of the screw pair considering the meshing excitation of the gear pair was obtained based on the deformation coordination condition of the screw pair and compared with the calculation results of the dynamic contact finite element model of the screw pair, so as to verify the correctness of the theoretical model. Finally, the paper analyzed the impact of inertia force and gear pair meshing excitation on the dynamic contact force and dynamic load distribution of threaded pairs. The results shows that: inertia force leads to a greater dynamic contact force on the roller nut side than on the roller screw side; when considering the meshing excitation of the gear pair, the contact force on the roller screw side decreases with the increase of the number of threads, while the contact force on the roller nut side increases with the increase of the number of threads; the meshing excitation of the gear pair causes the contact force between the roller screw and the roller nut side thread to fluctuate in the same pattern over time.