| The hydraulic rotary vane actuator(RVA)has the advantages of compact structure,high mechanical efficiency,smooth torque output,good maneuverability,and easy isolation of external dust,etc.It has a wide range of application prospects in applications requiring reciprocating oscillating motion output.The reliability of the seal determines the performance of the RVA.The end seal ring and rotor of the RVA belong to the axisymmetric rotary body,which makes it difficult to form a hydrodynamic lubricating oil film between the friction pairs of the end seal,so that the sealing surface often has relatively serious friction wear and friction heat generation,which greatly affects the performance and life of the end sealing ring.Therefore,it is necessary to carry out the anti-friction research on the end seal of the RVA,so as to provide a theoretical reference for optimizing the friction performance of the end seal,improving the sealing effect,and developing high-performance RVA.From the perspective of improving the friction performance of the end seal of RVA,this paper introduces the surface texture into the friction surface of the end seal.The mathematical models of contact pressure,oil film thickness and friction coefficient of sealing surface were established by comprehensively applying the theories of fluid mechanics,elasticity and contact mechanics.The tribology characteristics of end seal under the action of surface texture were studied,and the analysis results were verified by experiments.It is expected to achieve the goal of reducing the friction coefficient of the end seal,relieving the wear of the seal surface,decreasing the working temperature of the friction pair and improving the lubrication condition of the seal surface.The thesis mainly completes the following aspects:1.The establishment of contact model of micro-convex body on rough surface of end seal.Considering that the surface of the end seal friction pair has a certain roughness,and according to the characteristic that polyurethane(the material of the end seal)is a hyperelastic material,the contact model between the polyurethane micro-convex body and the metal micro-convex body,namely the hyperelastic-rigid model,was deduced again.Furthermore,the virtual rough surface was generated by computer,and the contact pressure and bearing capacity of the whole rough surface can be obtained by combining the contact model of micro-convex body.2.Establishment of lubrication model and friction performance analysis of textured surfaces under rigid-flexible coupling.On the one hand,the average Reynolds equation was used to calculate the oil film pressure on the surface of the friction pair,and the hyperelastic-rigid model was used to calculate the contact pressure of the micro-convex body,the elastic deformation of the end seal ring was calculated by the contact pressure and oil film pressure,and the coupling effect between them was considered,and then the calculation formula of the friction coefficient of the textured surface was obtained.At the same time,the numerical solutions of the average Reynolds equation and the elastic deformation equation were discussed in detail,and the basic ideas of Matlab programming were provided.On the other hand,based on the established textured surface lubrication model,the effects of comprehensive roughness,texture shape,texture depth,texture area ratio and working condition parameters on the friction coefficient of the sealing surface were analyzed.The results show that the friction coefficient increases with the increase of the comprehensive roughness,and the increasing range shows an upward trend.The friction coefficient of different texture shapes is also different.Among the four textures analyzed,the spherical texture has the smallest friction coefficient.The friction coefficient decreases first and then increases with the increase of texture depth,that is,the texture depth should not be too large or too small,but there is an optimal value of texture depth.The influence of area ratio on friction coefficient shows that the larger the area ratio is,the smaller the friction coefficient is and tends to be stable gradually.The effect of operating parameters on the friction coefficient is consistent with the Stribeck curve,and the minimum friction coefficient appears at the transition point of mixed lubrication and fluid lubrication.3.Weight analysis of factors affecting friction performance of textured sealing surface.Based on the established textured surface lubrication model,taking the friction coefficient as the evaluation index,using the range analysis and variance analysis of orthogonal design theory,the primary and secondary order and significance of the influence of texture shape,texture depth,texture area ratio,combined roughness on the friction coefficient of the sealing surface were studied.The results show that the primary and secondary factors affecting the friction coefficient are: combined roughness(29)texture shape(29)area ratio(29)texture depth.Among them,combined roughness,texture shape and area ratio have significant effects on friction coefficient,but texture depth has no significant effect.4.Experimental validation study of lubrication model.The correctness and rationality of the established lubrication model were verified by experiments using UMT-3 friction testing machine.Polyurethane and 45# steel were used as the two materials of friction pair to simulate the end seal ring and rotor respectively,and the45# steel disk sample was textured.The friction coefficient of polyurethane-45# steel friction pair was measured at different rotational speeds and compared with the results of simulation analysis.The experimental results are in good agreement with the calculated results,which proves the effectiveness of the textured surface lubrication model.The research results of this thesis can provide guidance and reference for the application of surface texture in the end seal of RVA and for further research. |
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