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For the ring surface of a hydraulic cylinder, grid and striped textures have been demonstrated in many previous works to easily provide a conductive oil path, which increases the difficulty of generating converging wedges and are harmful to the formation of dynamic pressure lubrication, especially for full lubrication. Moreover, these studies used an orthogonal design method to study the hydrodynamic lubrication effect and friction performance of the surface without considering the comprehensive effect of multiple parameters with simultaneous changes, which may introduce errors into the simulation analysis. In this work, a diamond-like, non-conductive texture, which mimics shark skin, is developed and optimised to determine the optimal texture morphology while simultaneously considering the influence of multiple parameters, including the diamond angle, axial length ratio, and area occupancy, to optimise the surface of the friction pair. The results show that under the same working conditions, the lift of the diamond texture is nine times greater than that of the striped texture, while its friction coefficient is only one-quarter of that of the striped texture, which will greatly improve the friction and responsiveness of the hydraulic cylinder.

Hydraulic servo cylinder is an important component of the hydraulic system. It directly affects the static and dynamic characteristics of the hydraulic system. The first generation of hydraulic cylinder with rubber seals has poor dynamic performance. It is not adapted to the hydraulic system with high frequency. This restricts the development of hydraulic cylinder. So a kind of hydraulic cylinder with variable clearance is proposed on the basis of the research about the second generation of hydraulic cylinder with constant clearance seal. The sealing of this hydraulic cylinder is realized by variable clearance. Theoretical analysis, mathematical modeling, simulation research, experimental verification and applications proved that the third generation of hydraulic cylinders has perfect static and dynamic performance and longer working life. It can be applied to the hydraulic transmission and hydraulic servo system with high frequency response and high-speed. The proposed technology can be extended to hydraulic components with small deformation requirements, and promote the innovation of hydraulic technology.

The dynamic response test to the subgrade plays a very important role in railway construction and a new in-situ test system is proposed. This paper presents the application of non-dominated sorting genetic algorithm-II (NSGA-II) to analyze the stability of the supporting equipment for track subgrade dynamic response in-situ test device. Its stability is related with the extension length of the hydraulic cylinders and the backward condition of the supporting equipment - the hydraulic excavator. The problem is formulated as a multi-objective optimization problem with the objective of maximizing the supporting force for the test device. An 85 tons excavator is picked as the case to study. The first optimal results show the excavator may not support the test system successfully. After redesigning the boom and adding its weight and length as new parameters, the second optimize results indicate the test device can work normally. DOI: http://dx.doi.org/10.11591/telkomnika.v11i12.3986 Full Text: PDF