磁流微循环润滑控制理论及其磁膜特性研究

发布时间：2019-02-16 20:37

【摘要】：微循环润滑是指润滑液在摩擦副表面的微循环，以改善界面膜的应力分布和润滑特性。本论文基于磁流体中磁粒子的偶极性可在外磁场作用下定向聚集和运动的功能特性及多孔材料的结构特征，研究了与磁流微循环润滑控制相关的理论问题及其磁性表面润滑膜特性；研究是在国家自然科学基金资助下完成。本文研究了永磁微磁组结构原理及磁流体在外磁场作用下的孔、表效应，构建了磁流微循环润滑作用机理模型，并以此开展了外控梯度磁场结构设计及其分布形态研究；揭示了磁流体的黏度μ、磁性颗粒的百分含量m、磁流体的饱和磁化强度Mg和外磁场磁场强度Hm及其分布(%紿m)对润滑特性（承载力W、摩擦力Fs及其摩擦系数Cf）的影响规律。建立了多孔磁流体输出模型和微磁组优化设计数学模型，并基于模型分析了摩擦系统的孔结构参数分布对其输出的影响；优化设计出可增强磁流输出能力的微磁组结构；试验研究了饱和磁化强度和液体黏度与微磁组结构参数的互耦性；揭示了孔效应对磁流微循环润滑控制及其磁膜特性的影响规律。为了构建摩擦学可控磁极微系统，从理论和试验方法上探讨了磁极（S-S极、N-N极和N-S极）对摩擦表面相互作用的可控性。结果表明：在环形工作表面，磁极的合理分布可提高其磁场强度及其梯度，有利于增强磁流微循环润滑控制及改善其润滑性能。论文在建立的广义磁流微循环润滑模型基础上，通过仿真分析和摩擦学试验，研究了外磁场微磁组体积（数量）及磁距（采用隔磁铜环体积或数量来实现）之间的匹配。研究表明：具有环状永磁组的摩擦表面，其磁场强度随磁组体积的增加而增大，随磁距的增加而减小。通过优化微磁组体积与磁距，可设计出合理的表面磁场强度及磁场梯度，从而获得更稳定的润滑状态；研究还表明：通过摩擦配对副与磁组匹配性设计也可获得具有优良润滑性能的摩擦系统。为了将理论研究成果推广到工程中，本文以多孔材料和滑动轴承为典型例，探讨了其磁流微循环润滑条件下的润滑特性，从以下两方面论证了磁流微循环润滑控制的工程有效性： (1)通过建立具有低弹性模量多孔材料的滑动轴承磁流微循环润滑模型，并以此研究了材料参数和工况参数对其润滑特性的影响规律，论证了其可明显地改善边界混合润滑，并以此绘制出多孔弹性轴承设计图谱；拓宽了经典Stribeck曲线的工程范围。 (2)通过对高速滑动轴承的磁流润滑特性研究，，揭示了外梯度磁场与磁流内聚力的耦合机理；论证了在外梯度磁场作用下磁流润滑可有效地实现轴承旋转项和挤压项的耦合，从而明显地改善了磁性轴承的润滑特性。
[Abstract]:Microcirculation lubrication refers to the microcirculation of lubricating fluid on the surface of friction pair to improve the stress distribution and lubrication characteristics of the interfacial film. This thesis is based on the functional characteristics of directional aggregation and motion of magnetic particles and the structural characteristics of porous materials under the action of external magnetic field. The theoretical problems related to the control of magnetohydrodynamic microcirculation lubrication and the characteristics of magnetic surface lubricating film are studied. The research was completed with the aid of the National Natural Science Foundation of China. In this paper, the structure principle of permanent magnetic micromagnetic group and the pore and surface effect of magnetic fluid under the action of external magnetic field are studied, and the mechanism model of magnetohydrodynamic microcirculation lubrication is constructed, and the structure design and distribution morphology of external control gradient magnetic field are studied. The effects of viscosity 渭, percentage content of magnetic particles, saturation magnetization (Mg) and magnetic field intensity (Hm) of magnetic fluid and its distribution (% m) on the lubricating properties (bearing capacity) of the magnetic fluid are revealed. The influence of friction force Fs and friction coefficient Cf). The output model of porous magnetic fluid and the mathematical model of optimum design of micromagnetic group are established, and the influence of the distribution of pore structure parameters on the output of friction system is analyzed based on the model, and the structure of micromagnetic group which can enhance the output ability of magnetic flow is optimized. The mutual coupling of saturation magnetization and liquid viscosity with the structure parameters of micromagnetic system was studied, and the effect of pore effect on the control of magnetohydrodynamic microcirculation lubrication and the characteristics of magnetic film was revealed. In order to construct tribological controllable magnetic pole microsystem, the controllability of magnetic pole (S-S pole, N-N pole and N-S pole) on friction surface interaction is discussed theoretically and experimentally. The results show that the magnetic field intensity and its gradient can be increased by the rational distribution of the magnetic pole on the annular working surface, which is beneficial to the enhancement of the magnetic flow microcirculation lubrication control and the improvement of its lubricating performance. On the basis of the generalized magnetohydrodynamic microcirculation lubrication model, the matching between the volume (quantity) of the external magnetic field micromagnetic group and the magnetic distance (using the volume or number of magnetic copper ring) is studied by simulation and tribological experiments. The results show that the magnetic field intensity increases with the increase of magnetic volume and decreases with the increase of magnetic distance. By optimizing the volume and the magnetic distance of the micromagnetic group, a reasonable surface magnetic field intensity and magnetic field gradient can be designed to obtain a more stable lubrication state. It is also shown that the friction system with excellent lubricity can be obtained by the design of matching between the pair and the magnetic group. In order to extend the theoretical research results to engineering, the lubrication characteristics of porous materials and sliding bearings under the condition of magnetohydrodynamic microcirculation lubrication are discussed in this paper. The engineering effectiveness of magnetohydrodynamic microcirculation lubrication control is demonstrated from the following two aspects: (1) the magnetohydrodynamic microcirculation lubrication model of sliding bearings with low elastic modulus porous materials is established. The effects of material parameters and operating conditions on the lubrication characteristics are studied, and the boundary mixed lubrication can be improved obviously, and the design diagram of porous elastic bearings is drawn. The engineering scope of classical Stribeck curve is widened. (2) the coupling mechanism between the external gradient magnetic field and the magnetic flow cohesion is revealed through the study of the magnetic flow lubrication characteristics of the high speed sliding bearing. It is proved that the magnetic fluid lubrication under the action of the external gradient magnetic field can effectively realize the coupling of the rotation term and the extrusion term of the bearing, thus obviously improving the lubrication characteristics of the magnetic bearing.
【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH117.2

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