The purpose of this paper is to study the oil film and friction characteristics of valve plates with a micro-textured surface and to explore the influence of textures of different shapes and sizes on the valve plates. Firstly, on the basis of thermohydrodynamic theory, this paper established the lubrication model of the oil film on the valve plate pair of swashplate axial piston pumps, according to the Reynolds equation. Secondly, the micro-texture was added to the mathematical model of the valve plate pair’s oil film. A combination of the energy equation, oil-film-thickness equation, elastic deformation equation, viscosity–pressure and viscosity–temperature equation, the finite difference method, as well as the relaxation iteration method, was used to solve the problem, and the textured and non-textured valve plate surfaces were simulated. The nephogram of the oil-film-thickness distribution, elastic deformation distribution, oil-film-pressure distribution and oil-film-temperature distribution were generated. Then, the control variable method was used to change the cylinder rotational speed, tilt angle, oil viscosity, initial oil film thickness and other parameters to analyze their effects on oil film characteristics. In addition, the friction characteristics of non-textured surfaces, square textured surfaces, triangular textured surfaces and circular textured surfaces were compared and analyzed. It was found that the textured surface of valve plates can obviously improve friction efficiency under the same operating conditions. The square texture, especially, is the preferable shape, rather than the triangular texture and the circular texture, and the friction performance is at its best when the texture depths are between 20 $\mathsf{\mu }\mathrm{m}$ and 50 $\mathsf{\mu }\mathrm{m}$. The results provide a theoretical basis for the design and improvement of the valve plate.

This article presents a steady-state elastohydrodynamic lubrication model for the contact and sliding interface of an axial piston pump’s port plate pair. The wedge-shaped oil film thickness, pressure, viscosity, and elastic deformation distribution of the port plate pair were investigated by using the finite difference method. The elastohydrodynamic lubrication characteristics for different operating parameters and two materials of the port plate pair were analyzed for comparison. Existing conditions for the EHL were calculated, and variations in leakage and friction coefficients were investigated. The results show that the elastic deformation of the interface greatly influences the oil film’s overall performance, which is related to the material, inlet pressure, velocity, viscosity, and the minimum oil film thickness that determines the EHL. The deformation caused by oil film pressure greatly influences the model leakage and friction coefficient, especially when the deformation is equal to the oil film clearance.

The lubrication properties and friction characteristics of the valve plate pair play a vital role in determining the overall lifespan of the axial piston pump, which makes the analysis of these parameters of significant importance. In this paper, the lubrication model of the cylinder block/valve plate sliding interface of the axial piston pump, considering elastic deformation and cylinder block dynamics, is established. The oil film carrying pressure and asperity microcontact pressure are calculated using the Reynolds equation, Greenwood–Williamson asperity microcontact model, and Hertz contact theory. The dynamic analysis is carried out, and the Newton–Raphson iterative method is introduced to solve the nonlinear equations. The influence of working pressure, cylinder speed, and sealing belt width on the friction characteristics of the valve plate pair is analyzed using the numerical calculation model. The simulation results demonstrate the dynamic changes of the cylinder block and the impact of them on lubrication properties and friction characteristics. The experimental results of the friction coefficient at different cylinder speeds are consistent with the simulation results in trend and accurately reflect the fluctuation of the friction coefficient.

The correlation between geo-acoustic parameters and geotechnical properties provides an effective evaluation of the geophysical investigation of the seafloor. Therefore, this paper describes the design of a multi frequency in-situ sediment acoustic characteristic measurement system consisting of transducers with three frequencies and hydrophones. The system uses two probe rods equipped with sensors. A transducer installed on one probe rod generates sound signals, while two hydrophones installed on the other probe rod receive sound signals propagating from sediment. A matching penetration mechanism was designed to achieve synchronous, continuous, and stable penetration of two probe rods. Three frequency amplifiers were designed for the generation of sound signals. The collection circuits and host computer were designed for sound signal acquisition and real-time analysis. The stress characteristics of two probe rods penetrating sediment were studied using the finite element software ABAQUS. The simulation results guided the design of the probe structure and the penetration mechanism. Finally, a pool test was conducted to calibrate the system, and the average relative error for six hydrophones was less than 0.06 %. The feasibility of the device’s application was further verified through sea trials.

Deep-sea microorganisms are highly abundant and diverse and have potential for engineering applications, medicinal uses, and explaining the origin of life. To obtain many long-term time series samples, an in situ suction filtration sampler was proposed, which can wind more than 360 filter membranes with an effective diameter of 60 mm through rollers. A multilayer filter membrane structure was proposed to avoid interactions between filter membranes and seawater. Based on various test results, multilayer filter membrane structures of PET (polyethylene glycol terephthalate, thickness of 0.2 mm)-PES (polyethersulfone, pore size of 0.45 and 1 μm) and PET (thickness of 0.2 mm)-PTFE (polytetrafluoroethylene, pore size of 0.22 μm) were finally selected. These combinations can ensure not only better water-permeability performance but also better strength. Furthermore, based on the data from the water-permeability test of the filtration membranes, the finite element software ANSYS Fluent was used to study the movement and aggregation laws of suspensions in the filtration chamber. The peak concentration in the suspension increases with increasing particle size and decreasing filter membrane pore size. Finally, the device was successfully operated in a 45 MPa high-pressure chamber. Additionally, in sea trials, the sampler successfully obtained an in situ suspension in a methane leakage area.