Study On Lubrication Characteristics And Fatigue Life Of Tripod Universal Coupling Based On Microtexture

The tripod universal coupling is a new type of constant speed universal coupling independently developed by Qingdao University of Science and Technology.It has the advantages of simple structure,low manufacturing cost,good synchronization performance and strong transmission capacity.Due to the influence of alternating load,the main components of the coupling,the slider and sleeve wear seriously,which greatly limits the popularization and application of the coupling.In order to improve the lubrication condition and prolong the service life of the coupling,the lubrication characteristics and fatigue life of the tripod universal coupling were studied in this paper.Firstly,a textured anti-wear structure was proposed based on the surface micro-texture anti-friction lubrication mechanism,and the effects of different design parameters on the lubrication characteristics of a single two-dimensional micro-groove were analyzed.Secondly,a three-dimensional fluid-structure coupling analysis model of the coupling was established to analyze the effects of different working conditions parameters on the stress and deformation of the coupling.Finally,based on the fluid-structure coupling analysis results to analyze the effects of different working conditions parameters on the fatigue life of the coupling,and establish the fatigue life prediction model of the coupling by using the neural network.The main research contents are as follows:（1）The design background of the textured anti-wear structure,the development process of the tripod coupling,the surface texture anti-friction lubrication characteristics and the influence of lubrication on fatigue life at home and abroad are described.On this basis,the main content of this paper is introduced（2）The anti-wear structure of surface micro-groove was designed for the slider which is easy to wear in the coupling.And four texture models of rectangular micro-groove,trapezoidal micro-groove,triangular micro-groove and circular micro-groove were established.Based on cavitation theory,the critical slip velocity of micro-grooves with cavitation effect was investigated,and the lubrication characteristics of four micro-grooves with or without cavitation effect were compared and analyzed.Furthermore,the influence of different cavitation pressures on the lubrication characteristics of micro-grooves was studied.The results show that within a certain slip velocity range,cavitation zone is generated in the inlet area of the micro-groove,and the cavitation area expands towards the outlet area with the increase of slip velocity.Under the same cavitation pressure,compared with the model without cavitation,the oil film pressure and friction of the four micro-grooves all decrease,the oil film bearing capacity increases,and the oil film bearing capacity increases with the increase of cavitation pressure.The trapezoidal micro-groove has the best comprehensive lubrication performance（3）Taking trapezoidal micro-grooves as the research object,the influence of groove depth h₀,width l,inclination AngleΦand depth-to-width ratio on the lubrication characteristics of coupling were investigated.Based on Kriging model and NCGA algorithm,the optimization model of surface texture geometric parameters was established.The results show that with a certain oil film gap,the oil film bearing capacity increases first and then decreases with the increase of the depth and width of micro-grooves respectively,and the friction coefficient decreases first and then increases.With the increase of the inclined Angle of the micro-groove,the oil film bearing capacity increases first and then basically remains unchanged,and the friction coefficient decreases first and then increases.There is an optimal ratio between the depth and width of the micro-groove,which makes the coupling dynamic pressure lubrication effect is the best.The optimal geometric parameters obtained based on NCGA algorithm can significantly increase the oil film bearing capacity,reduce the friction coefficient and improve the lubrication performance of the coupling.（4）Based on the optimal geometric parameters and coupling analysis theory,a three-dimensional fluid-structure coupling model between trapezoidal micro-groove textured slider and grease oil film was established.The pressure distribution of the oil film and the stress and deformation of the slider under different torque M,rotation frequency f and grease viscosityη₀ with or without cavitation effect were investigated.The results show that the oil film pressure,the maximum equivalent stress and deformation of the slider increase with the increase of torque,rotation frequency and grease viscosity.When the cavitation effect is taken into account,the oil film pressure,the stress and the deformation of the slide bar are all reduced.（5）Based on the fatigue life theory,the fatigue life of the coupling at high-speed and high-load,high-speed and low-load,low-speed and high-load was further studied by fluid-structure coupling analysis method.compared with that of the textured slider and the smooth slider under uncoupled condition.Furthermore,the fatigue life prediction model of coupling was established based on BP neural network.The results show that the fatigue life of the coupling increases continuously under the conditions of high-speed and high-load,high-speed and low-load,low-speed and high-load.In the uncoupled condition,the fatigue life of the textured slider decreases significantly compared with that of the high-speed and high-load condition,and the equivalent stress of the smooth slider is larger than that of the textured slider,and the fatigue life of the smooth slider is shorter.The existence of micro-texture reduces the stress concentration and prolongs the service life of the coupling.The BP neural network accurately predicts the fatigue life of the slider,which provides a new method for the prediction of the fatigue life of the coupling.