基于6DOF模型及动网格的动静压轴承刚度阻尼数值计算

针对传统雷诺方程求解三维油膜流场特性的局限性,提出基于6DOF模型及动网格的动静压轴承刚度阻尼计算方法.以具有典型结构形式的液体动静压轴承为例,通过加载6DOF自定义程序,采用非线性迭代方法计算外载荷作用下轴心轨迹的瞬态变化过程,得到轴颈在外载荷作用下的静平衡位置;通过嵌入UDF宏程序以动网格更新方法实现对轴颈在静平衡位置的扰动,求解Navier-Stokes方程得到轴颈扰动前后位置变化后的瞬态油膜力,利用差分法求得动静压轴承油膜刚度和阻尼,并分析了不同转速下轴承刚度和阻尼的变化规律.     

转速对内燃机滑动轴承润滑性能的影响

该文主要分析了转速对轴承润滑性能影响的机理,并应用Ricardo轴承设计软件针对某柴油机连杆大头轴承的最大油膜压力、最小油膜厚度以及功率损耗等润滑性能进行了仿真计算,结果表明转速增加将较大地增加轴承功率损耗,但最小油膜厚度呈现先增后减,最大油膜压力呈现先减后增的趋势,而在一个循环内,最小油膜厚度持续时间延长,最大油膜压力多次出现,均加剧了轴承的疲劳.显示在高转速下惯性负荷对轴承润滑性能起主要作用.该文的结果对于高速柴油机设计具有一定的指导意义.     

基于Matlab有限长液体动压滑动轴承压力分布的一种近似解法

采用近似方法模拟径向滑动轴承压力场分布。在轴承径向和周向以三角函数为基函数构造压力P的二维三角级数形式；应用迦辽金法，建立关于系数αij的线性非齐次代数方程组；采用Matlab软件解此方程组，得到各系数，进而得到近似油膜压力分布函数p（φ，z）。计算出各点压力值，绘制压力分布图像。     

混合陶瓷角接触球轴承静力分析

预测复杂工况下陶瓷球轴承的疲劳寿命需要知道轴承接触表面下的应力场,而对轴承进行应力分析须以静力分析为基础.本文通过细化接触区局部网格建立兼顾精度和效率的混合陶瓷角接触球轴承局部有限元模型,分析该轴承受轴向载荷时的应力场,分析不同轴向载荷下该轴承的接触角、轴向趋近量、接触载荷和最大接触应力并与理论值对比.结果显示接触角、轴向趋近量、接触载荷和最大接触应力的有限元分析(FEA)结果与理论计算结果吻合.     

弹性环挤压油膜阻尼器支撑下的柔性转子系统动力学分析

弹性环挤压油膜阻尼器(Elastic ring squeeze film damper, ERSFD)具有良好的支撑作用和减振效果,但由于其结构和流场耦合行为极为复杂,使得已有的物理模型难以完整表现出ERSFD的力学特性.为了进一步探究ERSFD的力学机理,本文借助有限元仿真平台,采用双向流固耦合的计算方法,剖析弹性环与油膜之间的相互作用,获取ERSFD中油膜压力的分布规律.在此基础上,利用最小二乘法进一步拟合出ERSFD等效刚度、等效阻尼与转子轴颈扰动位移的映射关系,并将其分别引入柔性转子系统动力学模型中.通过数值计算研究了ERSFD支撑下柔性转子系统的振动响应,分别给出了不同转速下转子系统的响应分岔图、轴心轨迹等.同时,通过对比分析,进一步揭示了ERSFD所诱发出的转子系统丰富的非线性动力学行为,有助于对ERSFD轴承支撑特性的理解.     

Abaqus在某发动机主轴承螺纹孔强度分析的应用

用AVL/Excite软件对某款发动机主轴承进行EHD分析,选择最危险时刻的主轴承载荷,将主轴承油膜压力结果映射到主轴承壁计算网格表面上,用Abaqus计算全局模型位移,并以此作为边界条件计算主轴承螺栓孔子模型的应力,通过FEMFAT对主轴承孔螺纹进行高周疲劳分析,对结果做出评价,提出结构改进建议.     

基于ABAQUS/CFD的径向滑动轴承参数化数值模拟

针对径向滑动轴承种类多,腔内压力油流动复杂,传统的基于理论编程的方法很难获得其精确模型的问题,采用ABAQUS/CFD软件建立了某径向滑动轴承计算流体动力学参数化仿真模型,分析得到了稳态下油膜压力与油膜流速的分布规律。结果表明,该型滑动轴承稳态特性符合设计要求;参数化的模型还可延用于后续大量的计算与分析,不仅为该系列滑动轴承的设计制造及试验分析提供了仿真依据,同时也开辟了一种新的高效经济的研究方法。     

船用橡胶轴承刚度分析

为进行轴系与船体的耦合结构动力学分析,将船用橡胶轴承与轴颈的相互作用简化为以集中质量和刚度形式表述的动力学缩聚模型,并通过接触非线性有限元分析提取轴承结构的等效质量和等效刚度,准确描述含有超弹性橡胶材料的轴承结构在承受一定轴承压力下的力学行为.计算橡胶轴承结构等效质量、等效径向刚度、等效扭转刚度以及等效转动刚度等,并讨论橡胶压缩性对轴承刚度的影响.结果表明:随着橡胶可压缩性的增强,轴承的等效径向刚度增强,扭转刚度减弱.     

转子-滑动轴承系统支承松动-碰摩故障动力学行为及评估方法

本文针对转子-滑动轴承系统支承松动-碰摩故障动力学行为进行分析,并提出基于动力学行为非线性度量的转子-轴承系统支承松动状态评估方法.应用非线性短轴承油膜力模型、松动刚度模型、Hertz接触理论等建立了带有支座松动故障的转子系统局部碰摩动力学模型,研究并分析松动-碰摩故障转子系统随支承松动间隙变化的动力学行为规律.提出基于动力学行为非线性度量的转子-滑动轴承松动-碰摩故障下支承松动状态评估方法,采取泰勒展开获得线性近似动力学模型,量化比较非线性模型与线性近似模型动力学行为的差异.建立松动间隙与非线性度之间的对应关系,直观反映松动间隙对系统动力学行为的影响程度,实现对转子-滑动轴承系统支承松动状态的评估.本文的研究可为转子-滑动轴承系统支承松动状态评估提供理论基础和支撑.     

微型角接触球轴承特性分析及仿真

在轴承刚性特性的研究中,为了分析微型角接触球轴承的接触特性,建立了轴向载荷作用下轴承的力学模型,以常规尺寸角接触球轴承的理论分析为基础,结合微型轴承的结构特点研究了接触角随负载的变化,并采用Newton-Raphson法编程实现了接触角增量的精确计算.结果表明:微型角接触球轴承在受载后接触角增量远远超过常规尺寸角接触球轴承,可达到50%甚至更多,极大的影响了轴承的力学性能.为了验证上述理论分析,采用有限元法对轴承在轴向载荷作用下的力学性能进行了仿真分析,比较仿真与理论计算结果所得最大误差不超过10%,达到较好的吻合.     

Dynamic characteristics of a coupled journal and thrust hydrodynamic bearing in a HDD spindle system due to its groove location

 This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing (PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT), and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or axial displacement of a rotor, are determined by solving its nonlinear equations of motion with the Runge–Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system. Received: 5 July 2001/Accepted: 17 October 2001     

Prediction of the oil injection time of FDBs in an HDD spindle motor with a tied shaft by utilizing Kirchhoff’s pressure law

We propose a method to predict the oil injection time of fluid dynamic bearings (FDBs) with a tied shaft by applying Kirchhoff’s pressure law. Since the oil is injected by capillary phenomenon, the volume flow rate can be calculated by utilizing Kirchhoff’s pressure law. Then, we calculated the oil injection time of the FDBs with a tied shaft by dividing the volume flow rate by the clearance volumes of the journal bearing, the thrust bearing, and the recirculation channel (RC), respectively. We generated simulation models of the FDBs used in a 2.5″ HDD spindle motor with a tied shaft. The total oil injection times of the FDBs with and without a RC were 0.302 and 0.335 s, respectively. Also, we verified the proposed method by measuring the oil injection time of FDBs with a RC. We applied the proposed method to predict and improve the oil injection time of the FDBs with a tied shaft due to the variation of major parameters affecting the oil injection time.     

Tribological design of a multistep journal bearing

Journal bearings are machine elements with widespread application. The extent of their use, from the automobile engines to gas turbines, gives a significant incentive for improvement of their performance. Various approaches focusing on the journal bearing design have been used in the past in order to reduce power losses and increase load carrying capacity of journal bearings, including artificial texturing, axial and circumferential grooves and bushing specific shapes (e.g. three-lobe bearings). In this paper, the multistep journal bearing is examined. Its performance benefits are quantified. A maximum friction coefficient improvement of 38% is obtained with simultaneous 9.7% improvement of load capacity in comparison to the plain bearing. The specific operating conditions under which these benefits occur are established. The physical mechanism responsible for these improvements is discussed by correlating pressure, shear stress distribution, lubricant thickness and bushing geometry. The ultimate objective of this work is to suggest certain design principles that may adjust the improvement of the desired operating characteristics of the multistep journal bearing. The surface configuration of the bushing is relatively simple and is thus easy to be manufactured.     

多因素耦合下剥落损伤随机分布特性对轴承疲劳寿命的影响

以控制力矩陀螺的角接触球轴承为研究对象,考虑环境温度、摩擦热、对流换热、轴向力和转速等复杂多应力耦合作用及剥落损伤特征,推导其传热模型、接触应力仿真模型和疲劳寿命仿真模型。对比轴承有疲劳剥落损伤和无疲劳剥落损伤2种情况,分别给出典型工况下的温度、应力和疲劳寿命结果,讨论轴向力和转速对温度和应力的影响,总结疲劳损伤的特征尺寸随机分布对应力和疲劳寿命的影响。结果表明：在同样的条件下,剥落损伤引起的应力集中效应很明显,并且会引起区域温度升高;分别改变转速和轴向力,转速对温度和应力影响更明显;随着轴向力和转速增加,损伤轴承的最高温度和最大应力的大小和增长率均大于无损伤轴承;应力和疲劳寿命对剥落区域的直径更敏感,最大应力随直径增大呈先增大后减小的抛物线形关系,并随着深度增加而减小;虽然当剥落区域取最小直径且最大深度、最小深度且最大直径这2种情况下轴承疲劳寿命大于0,但是在剥落区域直径和深度的大部分取值范围内轴承疲劳寿命均为0。     

钢管弯制过程有限元仿真及断裂原因分析

针对某金属结构公司在钢管弯制过程中出现的个别钢管断裂现象进行研究,根据现场钢管弯制工艺和工序的情况描述,采用非线性有限元软件Marc对钢管的多工位弯制过程进行模拟仿真.以最恶劣的情况即曲率最大的胎具进行多工位弯制,仿真结果显示6个工位的连续弯制过程最大应力为552 MPa,没有达到材料的抗拉极限626 MPa,该弯制过程不会引起钢管强度失效.模拟钢管多种曲率胎具弯制下的应力应变分布情况和回弹后残余应力应变情况.仿真结果表明,弯制此种钢管最大曲率的圆弧时,钢管上的最大应力为542 MPa,小于材料的抗拉强度626 MPa;最大塑性应变为0.031,小于材料允许的最大伸长应变0.2.经过模拟仿真分析,该公司采用的弯制工艺不会引起材料强度失效断裂.引起钢管弯制断裂的原因为个别材料夹杂或气孔造成的小概率事件.     

CFD simulation of magnetorheological fluid journal bearings

Magnetorheological fluid journal bearing can be controlled by a steady magnetic field doing that very effective for attenuating and controlling the performance of the rotor bearing systems.An integrated simulation study, of a magnetorheological (MRF) fluid journal bearing, via computational fluid dynamics (CFD) and finite element method (FEM) is presented in this paper. The journal bearing characteristics such as, eccentricity, attitude angle, oil flow and friction coefficients are calculated and presented as functions of the magnetic field, and L/D bearing ratios.A specific procedure in order to simulate an MRF bearing operated in high eccentricity ratios is also presented and the meshing requirements are discussed.     

Sensitivity analysis for the dynamic response of viscoplastic shells of revolution

A computational procedure is presented for evaluating the sensitivity coefficients of the dynamic axisymmetric response of viscoplastic shells of revolution. The analytical formulation is based on Reissner's large deformation shell theory with the effects of transverse shear deformation, rotatory inertia and moments turning around the normal to the middle surface included. The material model is chosen to be isothermal viscoplasticity, and an associated flow rule is used with a von Mises effective stress. A mixed formulation is used with the fundamental unknowns consisting of six stress resultants, three generalized displacements and three velocity components. Spatial discretization is performed using finite elements, with discontinuous stress resultants across element interfaces. The temporal integration is performed by using an explicit central difference scheme (leap-frog method) with an implicit constitutive update. The sensitivity coefficients are evaluated using a direct differentiation approach. Numerical results are presented for a spherical cap subjected to step loading, and a circular plate subjected to impulsive loading. The sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to the thickness, mass density, Young's modulus, and two of the material parameters characterizing the viscoplastic response. Time histories of the response and sensitivity coefficients are presented, along with spatial distributions of these quantities at selected times.