Study On Micro-interface And Dynamic Characteristics Of Gear Transmission Under Mixed Lubrication

With the development of the technology and society,the requirements for high precision,high reliability and high efficiency of various types of equipment used on a large scale in production and life have been further improved.And in various mechanical equipment,the transmission of motion and force is a very important part,which often determines its actual service performance.The transmission of motion and force is usually based on interactions between interfaces,which often involve contact and friction.However,the topography of the interfaces vary widely,and their friction and contact properties are affected by a combination of factors.In the case of mixed lubrication,the friction and contact behavior of the real topography interface are more complex,especially the analysis of the three-dimensional line contact interface is insufficiency.At present,the most research on friction and contact characteristics of interface only include one or two aspects,lack of multi-parameter coupling analysis under the cross-integration of multiple disciplines and guiding significance for practical engineering.Therefore,this thesis starts with the micro-topography of the contact surface,with the theory of mixed elastohydrodynamic lubrication(Mixed-EHL),contact mechanics,friction and wear considered,and then studying the friction and contact characteristics of the contact surfaces with different micro-topographies.On this basis,the dynamic characteristics and energy loss due to friction of the transmission system such as gear transmission are analyzed and studied,in order to provide the significance guidance for the performance improvement and energy saving of various precision superior equipment in practical engineering application.In particular,the main research contents of the thesis are listed as follows:(1)An improved surface topography simulation method was proposed.Based on the FFT spectrum method,combined with non-Gaussian transformation and the introduction of asperity distribution orientation,a new method that can simulate machined rough surfaces with typical topography was proposed.On the other hand,according to the classical geometric theory and the biological surface microstructure,the dimple texture and the bionic texture are respectively constructed,and various rough textured surfaces are obtained by compositing the simulated rough surface and the acquired surface texture.By simulating the rough surface,it provides available samples for the subsequent research on friction and contact characteristics of contact surfaces with different micro topography.(2)The optimized mesh density was proposed,and the optimization index of friction characteristics of textured surface was constructed.Based on the mixed elastohydrodynamic lubrication theory and the Achard wear model,a calculation method of transient friction and wear on rough surfaces is given.Through this method,the friction and wear of textured surface and machined rough surface were calculated and analyzed respectively under the condition of line contact.Specifically,the analyzed surfaces are dimple textured surfaces and biomimetic textured surfaces,machined surfaces and surfaces with asperity distribution oritention.The discussion involves the influence of different working conditions,rough surface parameters and texture geometric characteristic parameters on the friction and wears characteristics of rough surface,and the optimization of these parameters is realized.(3)The contact stiffness and damping calculation model of rough surface under mixed lubrication and the contact model of rough surface considering the characteristics of surface topography were constructed.The contact problems of rough surfaces are analyzed from two aspects,and two kinds of methods for calculating surface contact parameters are proposed.Firstly,a method which can calculate the contact stiffness and contact damping of rough surface under mixed lubrication was proposed by combining the mixed elastohydrodynamic lubrication theory,KE model and rough surface unloading theory.Secondly,based on ZMC model,non-Gaussian surface distribution function and elliptical asperity contact theory,the method of calculating anisotropic non-Gaussian surface contact parameters was improved,so as to analyze the influence of surface topography on contact characteristics.Using the above two methods,the effects of shape parameters,operating conditions parameters and lubrication parameters on surface contact parameters were analyzed.(4)Based on the calculation method of contact stiffness and contact damping of rough surface under mixed lubrication state,a calculation model of gear meshing stiffness and meshing damping is established.According to the established model,the contact stiffness and damping as well as meshing stiffness and damping of gears under different parameters are calculated,and the effects of these parameters on stiffness and damping are analyzed.Based on the bending-torsion model of gear meshing,in the case of mixed lubrication,the meshing stiffness and meshing damping of the rough tooth surface and the friction of the tooth surface are all incorporated into a unified tribo-dynamics model of the gear transmission system,and the nonlinear vibration characteristics of the gear are obtained as well as the energy loss caused by friction in the transmission process,then results for different rough tooth surfaces are compared.(5)The rough surface measurement experiment and the dimple texture ring-block friction and wear experiment were carried out to verify the applicability of the proposed method and model.