Abstract:The combined effect of the use of carbon fiber and seawater and the molecular structure on the tribological behavior of various polymer materials under natural seawater lubrication was investigated. After the investigation, the wear morphology of the contact surface was observed by a laser scanning confocal microscope, and the texture of the wear scars and tracks were presented in 3D profiles. Moreover, the mechanism of mixed lubrication and wear resistance was analyzed. The results demonstrated that the friction coefficient of carbon fiber-reinforced polyetheretherketone (CFRPEEK) is the lowest and fluctuates at approximately 0.11. Moreover, the seven polymer materials in ascending order of friction coefficients are CFRPEEK, carbon fiber-reinforced polyamide-imide, polytetrafluoroethylene, polyoxymethylene, polyetheretherketone (PEEK), acrylonitrile butadiene styrene resin, and glass fiber-epoxy resin. More critically, the simultaneous incorporation of deposition, polymeric scrap, hydrophilic groups, and seawater resulted in a decrease in the friction and wear of polymer materials under seawater lubrication. This observation implies that a synergistic friction-reducing and wear-resistant effect exists between carbon fiber, seawater, and the molecular structure of PEEK. As a result, a highly effective polymer material was discovered, CFRPEEK, which has the lowest friction coefficient of 0.11 and lowest wear rate of 2 × 10 -5 mm 3 ·(N·m) −1 among the polymer materials; this validates the selection of dual friction pairs for seawater hydraulic components.

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The variable-speed electrohydraulic drive is a promising drive principle due to its high energy efficiency and large speed-range. However, its slow response and poor low-speed behaviour limit its application. To address these disadvantages, a energy regulation based variable-speed electrohydraulic drive is proposed. This novel drive principle is combined with the advantages of variable-speed drive and valve-control drive. The speed-control of the energy regulation based variable-speed electrohydraulic drive is discussed. The speed-control strategy, which is aimed at the multiple-input multiple-output (MIMO) structure of the proposed drive principle, is analysed. The results of simulations and experiments comparing it with three other drive principle systems show that the proposed drive principle has not only a good speed-control accuracy, but also a perfect energy-saving performance.

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