Study On Combined Surface Contact Stiffness And Friction Modeling And Analysis Based On Fractal Contact Theory

The joint surface known as the joint parts is formed by the assembly of the mechanical parts.Under the influence of complex dynamic loads,microscopic or macroscopic vibration displacement will appear between the joint surface,which aggravate the friction and wear of the joint surface.The influence between them will stimulate joint surface vibration-friction phenomenon and cause the system show the complex dynamic characteristics.Therefore,the study on the dynamic characteristics of the joint surface is of great importance both in theory and in practice.In this paper,the fixed microscopic rough surface is the object of study.From dealing with micro contact fractal parameter prediction model with domain expansion factors considered,visual programming language visual interface design,binding surface finite element dynamic model in this type and experimental aspects,the work are done as following:(1)Through access to a large number of domestic and foreign literature,the research status of the domestic and foreign on joint surface is summarized from three aspects:the research status on the mechanical joint surface contact model,the dynamic characteristics of the mechanical joint surface,and the fractal of Tribology.And the research results and the shortages of the joint surface modeling and its dynamic characteristics are discussed.(2)The fractal model of the contact stiffness of the joint surface considering domain expansion factor is established,and the influence of the parameters of the joint surface to the contact stiffness is discussed by numerical simulation.(3)Based on a pair of contact micro convex body kinematics analysis and contact mechanics analysis,the fractal model of the friction force of non hydrodynamic lubrication is established,which is not limited by surface topography.The dual effects of mechanical deformation and molecular action are considered,and is with the help of the fractal theory in this model.Through numerical simulation,the influence of fractal dimension,fractal parameter and material parameter on sliding friction is studied.The fractal model of static friction coefficient is proposed,and the feasibility of the model for predicting the static friction coefficient of the joint surface is studied.(4)The visual programming language is combined with the fractal prediction model of the contact stiffness of the joint surface,and the complex formula is hidden by visual form.Through inputting the basic parameters of materials,such as elastic modulus,fractal dimension,scale parameters,density and so on.,the contact stiffness can be directly shown in the interface.(5)The HSR25A linear rolling guide of THK Corporations is as the object of study.Firstly,the free state and both ends of the constraint condition of modal analysis are done respectively by the ANSYS software,and the natural frequency and the corresponding formation before the 12 order are obtained.Secondly,the modal experiment of specimen is done.By calculating normal stiffness and tangential stiffness of the rail joint surface,the validity of normal stiffness fractal prediction model and the tangential stiffness fractal prediction model with the domain extension factor considered are verified.Finally,the feasibility of the finite element analysis model is verified by obtaining the first six natural frequencies.