New analytical model of elastic-plastic contact for three-dimensional rough surfaces considering interaction of asperities

The contact calculation of three-dimensional real rough surfaces is the frontier field of tribology and surface science.In this study,we consider the interaction and elastic-plastic deformation characteristics of asperities and further,propose an analytical contact calculation method for rough surfaces considering the interaction of asperities.Based on the watershed algorithm,the rough surface is segmented and the asperities are reconstructed into ellipsoids.According to the height relationship between the asperities,the definition of the deformation reference height of the matrix between each couple of asperities is provided.Subsequently,the calculation formula of the substrate deformation is provided according to the local contact pressure considering the elastic-plastic deformation of the asperity,and the contact state under a specific load is determined using the iterative correction method.The results correspond with those of finite element numerical calculation and the study reveals the following:(1)compared with the results obtained without considering the asperity interaction,contact area,distance,and stiffness will be reduced by 6.6%,19.6%,and 49.5%,respectively,when the influence of asperity interaction is considered;(2)the interaction of the asperities has the greatest influence on the surface contact distance and stiffness.Under the same load,the existence of asperity interaction will reduce the contact distance,area,and stiffness;(3)considering the interaction of the asperities,the higher asperity will bear more load,but it will simultaneously reduce the contact of the surrounding area and increase that of the distant area.The calculation method proposed in this study has the advantages of high calculation efficiency and accuracy,thus,providing the calculation basis and method for subsequent studies on service performance of rough surfaces,such as the calculation of contact stiffness and fatigue performance analysis of rough surfaces.

Investigation on Normal Dynamic Contact Characteristics of Mechanical Interface of Machine Tools

The dynamic contact characteristics of mechanical interface significantly impact the performance of machine tools.The static contact behaviors of mechanical interface have been studied.However,most mechanical interfaces are exposed to dynamic load.It is necessary to study the dynamic contact characteristics of mechanical interface.A normal dynamic microcosmic contact model is built using the statistical method,and the interactional effects of adjacent asperities are considered.The influences of the normal preload,vibrational frequency and displacement amplitude on normal contact stiffness and damping of mechanical interface are revealed.The predicted contact stiffness and damping of mechanical interface are verified by a series of simulations and experiments.

Analysis of the discrete contact characteristics based on the Greenwood-Williamson model and the localization principle

The contact of a rigid body with nominally flat rough surface and an elastic half-space is considered.To solve the contact problem,the Greenwood-Williamson statistical model and the localization principle are used.The developed contact model allows us to investigate the surface approach and the real contact area with taking into account the asperities interaction.It is shown that the mutual influence of asperities changes not only contact characteristics at the macroscale,but also the contact pressure distribution at the microscale.As follows from the results,the inclusion in the contact model of the effect of the mutual influence of asperities is especially significant for studying the real contact area,as well as the contact characteristics at high applied loads.The results calculated according to the proposed approach are in a good agreement with the experimentally observed effects,i.e.,the real contact area saturation and the additional compliance exhaustion.