Cylinder has become an indispensable and important pneumatic actuator in the development of green production technology. The sealing performance of the cylinder directly affects its safety and reliability. Under the service environment of the cylinder, hydrothermal aging of the rubber sealing ring directly affects the dynamic friction performance of the cylinder. So, the dynamic friction model of the cylinder has been developed based on the LuGre friction model, which considers the influence of hydrothermal aging. Here, the influences of the static friction coefficient and Coulomb friction coefficient on the friction model are analyzed. Then, the aging characteristic equation of rubber is embedded in the model for revealing the influence of aging on the friction coefficient of the model. Results show that the aging temperature, aging time, and compressive stress affects the friction coefficient; the variation of the static friction coefficient is larger than that of the Coulomb friction coefficient. The improved cylinder friction model can describe the influence of the aging process on the cylinder friction characteristics, which is of great significance in the design of the cylinder’s dynamic performance.
The friction behavior of cylinder seal greatly affects the dynamic position accuracy of the cylinder execution terminal under hydrothermal aging. So, the hydrothermal aging test, friction test, tensile and compression test, topography analysis and infrared spectroscopy analysis, and multiscale simulation were carried out for studying the effect of the hydrothermal aging on the friction performance of cylinder seal. It was found that when the aging temperature increases from 40 to 80°C, the dynamic friction forces of the cylinder seals increase by more than 15%; the friction force increases with the increasement of the initial mechanical stress. Aging makes rubber to be brittle and more cavities on the fracture surface and reduces the fractured activation energy of the nitrile rubber molecular chain.
As an advanced composite material with a flexible structure, cord-rubber composite has the advantages of high strength, high modulus, and lightweight, widely used in aerospace and other fields. Compared with our previous work, we focus on the effects of three kinds of overlap structures (positive-positive, positive-invert, concave-convex) on the mechanical properties of cord-rubber composites through uniaxial tensile tests and finite element simulation. When the interlaced distance is 5 mm, the concave-convex overlap structure reaches the maximum tensile strength (74.79 MPa). With the increased interlaced distance, the failure form of the cord rubber composite gradually transfers from the overlap end to the interface slip and fixture end. The maximum Von Mises stress distribution of cord-rubber composite flexible support tends to be uniform through rational design by the mechanical characteristics of the three kinds of overlap structures.
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