A Research On The Contact Characteristics Of Joint Considering The Horizontal Distance Distribution Between Asperities

To enhance the contact reliability of the components and optimize the structure of mechanical equipment at the design phase,it is crucial to investigate the contact characteristics of the joint.In this study,the horizontal distance distribution between asperities on a single rough surface is investigated for the first time,as well as the assumption of contact angle distribution function is replaced by the horizontal distance distribution law between asperities.Following this,a statistical theory-based model of contact characteristics for joints that take side contact between asperities into account is developed,and thus the effect of material parameters and surface topography statistical parameters on contact characteristics of joints is examined.The accuracy and validity of this model are confirmed through a comparing of modal test results with results from a finite element simulation based on virtual material method.The model of this paper overcomes the theoretical bottleneck that the contact angle distribution function must be assumed when modeling the contact of surfaces in side contact.It also lays the foundation for more accurate prediction of the contact characteristics of the joint.The main research work contains the following aspects.1.A Leica microscope DCM3D was employed to measure the three-dimensional surface profile of a steel ground specimen.By hypothesis testing,it was revealed for the first time that the horizontal distance distribution between asperities on a rough surface approximately follows a normal distribution.The side contact between asperities under normal load was divided into three deformation stages deformation,after which a statistical theory-based normal contact stiffness model of the joint was established containing the horizontal distance distribution and interaction between asperities.It was investigated that how the normal contact stiffness and load of the joint were affected by the standard deviation of the horizontal distance distribution,radius of curvature,the interaction between asperities and some material parameters.2.After conducting a mechanical analysis of the asperities in contact on the upper and lower surfaces under normal and tangential load based on the Hertz contact theory and KE model,the side contact model of the joint with the normal and tangential contact stiffness was proposed.The above mechanical analysis included elastic deformation stage,elastic-plastic deformation stage,and plastic deformation stage.The effect of surface mean distance,tangential deformation of the asperities,the ratio of normal load to tangential load,as well as the standard deviation of the horizontal distance distribution between asperities on the nondimensional contact stiffness and load of the joint were evaluated by numerical simulation.3.The horizontal distance distribution between asperities of a single anisotropic surface is investigated for the first time in different texture directions,where it is found that the horizontal distance distribution between asperities in both the texture direction and the inverse texture direction approximately conform to the normal distribution,even though there is a difference in the distribution standard deviation of the two directions.Based on the discovery,a normal contact stiffness model of the orthogonal anisotropic surface was produced,which accounts for the side contact as well as the continuous deformation of asperity.The effect of the statistical parameters for surface morphology as well as some material parameters on the normal contact stiffness and the normal contact load of the anisotropic surface were analyzed.In order to confirm the validity and correctness of this model,it was compared with several classical contact models,including the CEB model,GF model,and WF model.4.Modal tests and finite element simulations containing a virtual material contact layer based on this model are conducted in order to demonstrate its correctness and superiority.The comparison of results from modal tests and finite element simulations demonstrate that this model is more effectively capable of predicting the dynamic properties of the joint.