Influence Of Material Viscoelasticity And Wall-slip On EHL Of Rubber Journal Bearings

Water-lubricated rubber bearings are widely used in marine development machinery such as drainage pumps,submersible pumps,ships and underwater robots because of their irreplaceable superiority but rubber as a viscoelastic polymer material,in the process of bearing operation,whose creep characteristic has a great influence on the lubrication of the bearing.Based on the constitutive equation of rubber material,the elastohydrodynamic lubrication model of rubber bearing is established.The influence of creep properties of rubber on the lubrication state of water-lubricated rubber bearing is studied.Based on the limiting shear stress slip model,the effect of wall-slip on bearing lubrication characteristics is explored.Firstly,considering the unique viscoelasticity of rubber bearing materials,based on the Kelvin model and the three-parameter solid model describing rubber creep,a elastohydrodynamic lubrication model of rubber bearings was established.The center pressure,central film thickness and minimum film thickness of the lubricant were studied.The pressure and thickness variations of the lubricating film in the contact zone are compared at different moments.The similarities and differences of the lubrication characteristics of the rubber bearing under the two creep models are compared.Based on the time-temperature equivalent principle of viscoelastic materials,the effects of temperature on the lubrication of rubber bearings were investigated from three aspects:the central pressure of the lubricating film,the minimum thickness and the lubrication characteristics at different moments.Secondly,based on the three-parameter solid creep model and vibrational load,the analysis of EHL in the rubber bearing is carried out,the maximum pressure and minimum thickness of the rubber bearing lubricating film are calculated and analyzed under the three kinds of vibrational loads such as sine,pulse and decay.The variation is compared with the situation without considering the influence of creep.The variation of the pressure and thickness of the rubber bearing lubricating film under same instantaneous loads at different moments is discussed.Based on the sinusoidal vibrational load,the effect of lubrication characteristics under vibrational amplitude and frequency is explored.Then,based on the limiting shear stress slip model,the slip velocity equation is derived.The various slip types that may occur in the journal bearing are discussed andthe elastohydrodynamic lubrication model with sliding boundary conditions is established.The shear stress of interface lubricant attached the bearing bush and shaft and the limiting shear stress of the corresponding solid interface lubricant are calculated and compared and the judgment basis for slip generation is given.The influence of wall-slip on the pressure and thickness of the lubricant film is analyzed.Finally,the lubrication characteristics of rubber bearings under the coupling of slip and creep are analyzed.Considering the influence of interface modification on interface slip,the whole lubrication area is divided into four areas.The variation of lubricant film thickness and pressure under different slip types is discussed.The influence of interface modification on friction coefficient was analyzed and the variation of friction coefficient with load and speed was studied based on the limiting shear stress model.