Study On Film Inertia And System Dynamic Performance Of Deep Groove Ball Bearing

With the increase of rotational speed of the bearing,the high performance of the bearing is needed.In this case,the fluid inertia will increase and the contact stiffness of the bearing may change.Therefore,it is necessary to study the elastohydrodynamic lubrication(EHL)performance of the bearing considering the influence of oil film inertia.In the past year,researches on bearing-rotor system dynamics have not considered the lubrication effect,which leads to the inaccurate analysis of the performance of the bearing-rotor system.Supported by the National Natural Science Foundation of China,“Research on multi-body lubrication and thermal characteristics of high-speed rolling bearings taking into account the influence of rotor dynamic performance”(No.51775067)and the National Key R&D Program of China named “RV reducer digital and efficient precision manufacture”(No.2017YFB1300700),this thesis studies the influence of oil film inertia on the EHL performance of the deep groove bearing,and uses neural network to analyze the dynamic performance of the bearing-rotor system under the consideration of the lubrication,so that references for accurate analysis of the dynamic performance of the bearing-rotor system are provided.The main work of this paper is as follows:First,an EHL model of the elliptical contact considering the film inertia is proposed based on the Navier-Stokes equation and continuity equation,and then effects of film inertia on the EHL performances of the elliptical contact are studied.In doing so,the elastic deformation is calculated with the Fast Fourier Transform(FFT)method,and the film pressure is obtained by the composite direct iteration method.The numerical results show that with the consideration of the film inertia,the secondary spike of the film pressure increases,and the film velocity becomes smaller and the reflow zone of the film expands.The inertia also leads to an increment in the film thickness.Then,in order to validate the above simulation results,an experimental study of oil film thickness is made.The film thickness was measured at the varied load,entrainment velocity and lubricant,and the variation of film thickness with operating parameters is analyzed.The numerical results considering the film inertia are compared with the experimental results.The results show that the film thickness with film inertia considered is larger than that without considering the film inertia,which verifies the correctness of the EHL model considering the film inertia.Next,the film stiffnesses with and without inertia effects under different loads and entrainment velocities are compared.It is found that the film stiffness changes when the film inertia is considered.Therefore,a comprehensive stiffness model of elliptical contact considering film inertia is established.The oil film stiffness considering the inertia effect is obtained based on the EHL model considering the inertia effect of the film.Furthermore,the contact stiffness and oil film stiffness are connected in series,and the elliptical contact stiffness considering the EHL effect is obtained.Finally,a dynamic model of the deep groove ball bearing-rotor system with lubrication is established based on the RBF neural network.The prediction module of oil film force and vibration displacement of deep groove ball bearing is established by using the neural network.The prediction module is coupled to the dynamic performance simulation module of the deep groove ball bearing-rotor system in MATLAB.The simulation results show that the increase of the rotor mass causes the velocity of the inner ring to become lower,the vibration velocity attenuation to become slower,the curve ring formed by the vibration displacement and vibration velocity to become flatter.The increase of the rotor stiffness leads to decreases of the film force and vibration displacement in steady state,and the narrowing of the curve ring formed by the vibration displacement and vibration velocity.The increase of the rotor damping makes the system stable faster.The inner ring vibration displacement is smaller under the consideration of the oil film inertia at the same vibration velocity.