Research On Viscoelastic Friction Mechanism And Experimental Of Servo Cylinder

Research on viscoelastic friction mechanism and experiment of servo cylinder tribology after more than 200 years of research and development,the tribological theoretical system formed at present can support the analysis and calculation of friction force under the condition of plastic body dry friction and complete lubrication,the qualitative analysis of friction force under the condition of elastic body dry friction and boundary lubrication,and the only theoretical achievement for viscoelastic materials is friction force It consists of hysteresis friction and adhesion friction.The viscoelastic friction between O-ring rubber and metal is the bottleneck problem that restricts the development of servo cylinder.The research on the tribological dynamic performance of viscoelastic materials has important theoretical and practical significance for enriching tribological theory and developing pneumatic technology.In this paper,based on the mechanism of viscoelastic material hysteresis and adhesion tribology,the mathematical model of dynamic performance of O-ring rubber tribology of servo cylinder is established.It includes the fitting equation of piecewise polynomials representing the relationship between the energy storage modulus and energy dissipation factor of rubber and the strain and deformation frequency,the calculation equation of the micro back-to-back circular table geometry size on the surface of the inner bore of the cylinder,the relationship equation of the axial length and average contact stress of the micro contact area between rubber and cylinder and the pre compression and the air pressure of the driving cavity,the re contact point position of rubber and the piston transportation under the driving of triangular wave The relation equation between dynamic velocity and natural frequency of rubber vibration.The calculation equation of hysteretic friction is affected by the contact length of rubber and cylinder,average stress,vertical stress,strain,strain rate,energy and rebound lag of rubber in high frequency vibration,and the calculation equation of adhesion friction is affected by the adhesion and shear of rubber and cylinder in a small area of nominal contact area.For the servo cylinder with certain parameters,the simulation model is established on MATLAB,and the calculation of cylinder friction,original variables and state variables is completed.In order to avoid the numerical approximation of the starting point coordinate of the contact line between the O-ring rubber and the micro surface of the cylinder barrel,the simulation curve and data of the starting point coordinate of the contact line changing with the piston speed under 7 kinds of driving cavity air pressure are used,and the fitting equations of the starting point and the ending point coordinate of the contact line in the high-speed section and the low-speed section are synthesized,and the length of the contact line,the driving cavity air pressure and the piston expressed by the subsection basic function are obtained The fitting equation of velocity relation.The original parameters that affect the friction are simulated,and the influence rules of the precompression,the air pressure of the driving cavity and the piston velocity on the friction are obtained.The test-bed of friction force of servo cylinder is set up,and the critical control voltage of charge and exhaust of pneumatic proportional valve is calibrated.The static friction force of servo cylinder is detected when the piston is in different position.The experimental results are in good agreement with the simulation calculation,which shows that the mathematical model of friction force is correct.