| Magnetic fluid bearing is a new bearing technology using magnetic fluid as lubricant.It has been widely applied in the field of traction motors for high-speed trains because of its excellent self-sealing properties,controllability,high rotation accuracy,and low vibration and noise.The law of lubrication characteristics of magnetic fluid bearing is an important theoretical basis for its design and development.However,a large number of research works at home and abroad are mainly focused on the effect of single effect.In order to more accurately predict the lubrication performance of magnetic fluid bearing under the multiple effects,this paper comprehensively considers the rheological properties of the lubricant itself and the micromorphology of the friction interface,and conducts in-depth research on its lubrication performance.This provides important guidance and reference for the design and development of the magnetic fluid bearing and its engineering applications.First,using the water-based A01 magnetic fluid as lubricant,a generalized Reynolds equation is derived by combining hydrodynamic lubrication theory and magnetohydrodynamic equation,and finite difference method is used to coupling solve the Reynolds equation and film thickness equation.In order to verify the accuracy of numerical results,the magnetic fluid domain simulation was performed by the CFD method.Numerical comparison by the two methods,the results show that the boundary distributions of the positive pressure zone and the cavitation zone are obvious,and the symmetry along the mid-plane ?=0.The increase of magnetic coefficient makes the pressure level increase,and the initial point of cavitation rupture shifts to the right,and the cavitation boundary gradually decreases.The two results have good consistency,indicating the feasibility of the numerical method and the correctness of the theoretical model.Secondly,based on Newton magnetic fluid lubrication theory and the Stokes micro-continuous theory,the mathematical model of non-Newtonian magnetic fluid lubrication introduced by the couple stress is deduced,and then the influence of the lubrication behavior of couple stress magnetic fluids on the bearing performance is discussed in detail and compared with the results of Newtonian magnetic fluids.The results show that the larger the couple stress parameter is,the more obvious the pressure and bearing capacity increase,and the more obvious the effect of magnetic coefficient on pressure,bearing capacity and offset angle.The increase of couple stress parameter and magnetic coefficient can reduce the friction coefficient,while the side leakage flow shows the tendency of rising first and then decreasing with the change of eccentricity,but the overall relative change range is small.Finally,the Monte Carlo method was used to simulate the Gaussian rough surface,and compared with the actual surface morphology under scanning electronic microscope.Then the randomized non-Newtonian dynamic Reynolds equations are deduced by the Christensen stochastic rough principle.The effects of different couple stress parameters,dynamic parameters,and magnetic coefficients on the lubrication state under transverse and longitudinal rough texture were studied comparatively.Studies have shown that the simulated anisotropic surface has similar texture characteristics to the actual machined surface.Compared with smooth surface,when the aspect ratio is relatively small,the longitudinal rough texture can increase the overall pressure level,while the transverse rough texture weakens the pressure,and vice versa.When the dynamic parameters increase,the influence of the two rough textures on the pressure is almost the same;the couple stress parameter and magnetic coefficient increase,the offset angle and friction coefficient decrease,The demarcation point where the dimensionless load capacity changes with the aspect ratio shifts to the right,and the relative change range is also more significant. |
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