Research On Static And Dynamic Characteristics Of Oil-film Bearings Lubricated With Ferrofluid

As the supporting component of steel rolling machinery, oil-film bearing possesses advantages like long lifespan, large carrying capacity and wide speed range ability, etc. In operation, due to various reasons such as the increase of rolling force and temperature rise, the complete lubrication state of oil-film bearing is difficult to guarantee. The incomplete oil film will easily lead to contact friction and wear between roller and bearing, or even bearing failure.To solve the problems above, ferrofluid was introduced to lubricate the oil-film bearing. The viscosity of ferrofluid could be controlled by external magnetic field, thus the integrity of oil film could be ensured, and the load capacity and operation performance of bearing could be improved. Based on ferrofluid lubrication, the external magnetic field was designed, ferrofluid was prepared and the ferrofluid viscosity properties were studied. The mathematical model of static and dynamic characteristics of the oil-film bearing lubricated with ferrofluid was established, based on which the relationship between characteristic parameters with magnetic field intensity was analyzed. The main contents of this thesis are stated briefly as follows:Firstly, based on the self-developed oil-film bearing test rig of Taiyuan University of Science and Technology, three different forms of the external magnetic field were designed, including permanent magnets, toroidal solenoid and Helmholtz coils. The FE models of different magnetic field forms were established and analyzed, according to which the solenoid model was more suitable and practical. The solenoid was designed and manufactured, and the internal magnetic field of solenoid was measured, which provided the basis for the mathematical model of magnetic field. Further, the ferrofluid was prepared and the viscosity-temperature properties and magnetic-viscosity properties of ferrofluid under the external magnetic field were studied, which could provide the basis for establishing the mathematical model of static and dynamic characteristics of the oil-film bearing.Secondly, the mathematical model of static and dynamic characteristics of the oil-film bearing lubricated with ferrofluid was established, including such equations as oil-film thickness, Reynolds equation, stiffness and damping coefficient, the critical mass and critical rotational speed equations,all these will lay a foundation for the study of static and dynamic characteristics of the oil-film bearing lubricated with ferrofluid. The mathematical model was nondimensionalized and dispersed with finite difference methodFinally, based on the mathematical model, the MATLAB language program was applied to solve the relevant parameters of the static and dynamic characteristics, the dimensionless oil-film pressure, oil-film thickness, stiffness and damping coefficient, critical speed distribution curve under the different condition were obtained. The relationship between characteristic parameters with magnetic field intensity was analyzed.