Search

In this work, the normal contact stiffness of lubricated rough interface is evaluated theoretically by describing the lubricated rough interface as an equivalent thin layer. Layer parameters, including equivalent thickness and effective Young's modulus, are used to characterize the normal contact stiffness by incorporating the contributions of asperity contact and lubricant contact simultaneously. On the basis of layer parameters, the normal contact stiffness of lubricated rough interface is obtained as a function of interfacial separation, surface topography, and properties of contacting solids and lubricants. Effects of surface topographies and lubricant types on the normal contact stiffness are investigated at varying interfacial separations and contact area fractions. The proportion of solid stiffness and lubricant stiffness from the total normal stiffness is also discussed. Numerical solutions reveal that the normal contact stiffness depends sensitively on the lubricant property at initial contact, whereas the influences of surface topographies become obvious with the decrement of interfacial separation or increment of contact area fraction. Comparisons between the predicted values of normal contact stiffness and experimental data for both dry interface and lubricated interface are presented to validate the rationality of the developed model. [ABSTRACT FROM AUTHOR]

In this paper, a method for evaluating the contact stiffness ratio of the elastic rough interface is proposed. The rough contact interface subjected to normal load is replaced by an equivalent thin layer with isotropic material. The interfacial stiffness ratio is characterized using the material parameters of the thin layer. The shear modulus and Young's modulus of the thin layer are determined by introducing the stuck length coefficient combined with the micro-contact analysis of the deformed asperity. The derived stiffness ratio is related to the surface topography, interfacial separation, material properties of the contacting bodies, and the stuck length coefficient. The implicit solution of the stuck length coefficient is also obtained. Variations of the stiffness ratio with the interfacial separation and the normal force are analyzed for different surface topographies and stuck length coefficients. Comparisons between the interfacial stiffness ratio of the proposed method and the experimental results as well as the calculated values of existing models are performed. [ABSTRACT FROM AUTHOR]

Contact stiffness is an important parameter for describing the interface characteristics in many engineering applications. In this paper, five different statistical micro-models including the Greenwood-Williamson (GW), Zhao-Maietta-Chang (ZMC), Kogut-Etsion (KE), Jackson-Green (JG) and Brake are employed to predict the normal contact stiffness for rough surface contact. It is found that the expressions of contact stiffness obtained using the statistical micro-models are very complex and the direct relationship between the contact stiffness and normal load is not available. Accordingly, an explicit approximated expression for contact stiffness is established in terms of normal load based on the results of numerical simulations. The normal contact stiffness as a function of normal load can be approximated using a power law, in which the coefficient and power are related to surface roughness parameters, material properties as well as nominal contact area. The close agreement between the predicted results and full numerical simulations verify the accuracy of the established explicit expression. The contact stiffness calculated using the predictive expressions are also compared with available experimental results from both ultrasonic method and contact resonance method. Further, the explicit expression of contact resonance frequency for rough surface contact with respect to the normal load is also provided, which can be used to evaluate the contact resonance frequency. The predicted contact resonance frequency is also validated through comparing with experimental results. • Five different statistical micro-models are employed to predict the normal contact stiffness for rough surface contact. • Direct relationship between contact stiffness and normal load is not available using the statistical micro-models. • An explicit approximated expression for contact stiffness is established in terms of normal load. • Predictive contact stiffness values are verified using available experimental results. [ABSTRACT FROM AUTHOR]

• An analytical model is developed to evaluate the interfacial stiffness ratio theoretically considering the interface as an equivalent thin layer. • Effective moduli of the thin layer are derived by a homogenization process of the deformed asperities over the whole rough surface. • The interfacial stiffness ratio depends on surface topographies, interfacial separations, and material properties of contacting bodies. • The interfacial stiffness ratios predicted by the proposed model are basically consistent with experimental results. This work presents a semi-analytical model to evaluate the interfacial stiffness ratio of stationary contacts between rough surfaces. The rough contact interface is described as a homogenized thin layer with effective moduli, which are employed to characterize the ratio of the tangential to normal contact stiffness. In conjunction with the micro-contact analysis of the deformed asperity, effective moduli of the homogenized layer are determined by an ensemble average process of the moduli produced by deformed asperities made over the rough interface. Results show that the sought ratio is related to the surface topography, interfacial separation, and material properties of contacting bodies. Variations of the interfacial stiffness ratio with the applied load for different surface topographies are presented. The proposed model of the stiffness ratio is verified by comparing with the previous models and experimental results eventually. [ABSTRACT FROM AUTHOR]