碰摩转子弯扭耦合振动特性分析

在给出单盘转子弯扭耦合振动的一般理论模型后 ,对碰摩转子的弯扭耦合振动动力特性进行了理论分析。在给出几个基本概念和碰摩转子弯扭耦合振动的激振力形式、刚度与阻尼的变化后 ,建立了碰摩转子的非线性弯扭耦合振动微分方程。然后对弯扭耦合振动转子的碰摩特性进行了数值分析 ,得出了若干结论 ,找出了扭转对弯曲的影响特征。     

Jeffcott裂纹转子弯扭耦合振动特性分析

以重力决定的开闭裂纹模型为研究对象，导出了固定坐标系下该模型的刚度扭阵，建立了裂纹转子弯扭耦合振动微分方程，并对转子裂纹的升速瞬态响应和影响因素进行了计算机仿真研究。结果表明：升速过程中，弯振存在1／3阶和1／2阶亚谐共振现象，扭振出现1／2阶亚谐共振；在弯扭左耦合区，出现弯扭耦合共振；在亚临界转速区，存在1X，2X和3X等倍频分量的弯振和扭振；影响弯扭耦合振动特性的因素很多，包括裂纹刚度、裂纹夹角、质量偏心和阻尼等。     

涡轮增压器转子系统三维动力学特性分析

针对涡轮增压器转子系统,考虑陀螺力矩、转子叶轮刚度和转轴抗扭刚度的影响,建立三维分析模型,利用有限元法进行转子系统动力特性分析.开展转子系统临界转速的分析,通过传递矩阵法模型和有限元梁单元模型校验三维模型的有效性,结果表明集总质量法在简化带有较厚轮盘的转子结构时,会减小转子结构的抗弯刚度.开展转子系统不平衡质量动力响应分析,结果显示,转子系统存在着弯扭组合振动,且弯扭组合振动表现为一种非同步的半频激振现象;随着转速的升高,转子系统的弯扭组合振动现象越趋明显;在弯扭组合振动频率附近,转子振动形式为弯扭组合振动;而在其他涡动频率下,转子振动形式为弯曲振动.     

裂纹转子弯扭耦合振动瞬态分析

针对两端刚性支承的Jeffcott转子，导出了固定坐标系中裂纹轴的剐度矩阵，建立了裂纹转子的弯扭耦合振动非线性微分方程。通过数值仿真手段，着重分析了转子升速过程中弯振和扭振的瀑布图、Bode图以及加速度的影响。研究表明，升速过程中，弯振和扭振都出现了1／2阶和1／3阶亚谐共振现象，它们的1X，2X和3X分量共振峰对应转速下的相位角有180。的突变，且在除各分量峰值转速外的其他转速处（如ω0，1／2ω0和1／3ω0）相位角也有一定的波动。弯振响应分别在1／3ω0，1／2ω0，ω0，3／2ω0，2ω0和左右弯扭耦合区处出现共振峰值，而扭振响应则在ωt0和左右弯扭耦合区处出现峰值。有无裂纹情况下的弯振和扭振受加速度的影响大致相同，但在相同加速度下，裂纹转子较无裂纹转子的临界峰值更大，对应的临界转速则更小。     

功率四分支齿轮传动系统的弯扭耦合振动固有特性研究

在轴承-转子系统动力学理论的基础上,考虑齿轮啮合效应和转子弯扭耦合效应,建立了功率四分支齿轮传动系统振动方程,求解自由振动的特征方程,获得了该系统耦合状态下的前14阶固有频率和振型,以及非耦合状态下前8阶固有特性。得出如下结论:1)系统结构的对称性导致部分转子的模态对称;2)系统的模态类型主要表现为两类形态:一类以某一转子振动为主,其他转子的振幅很小;另一类表现为复杂的多转子弯扭耦合振动;3)转子间的弯扭耦合对系统的固有频率和模态产生了很大的影响,在进行功率四分支齿轮传动系统的振动特性研究时,必须同时考虑转子弯扭耦合效应的共同作用。     

功率四分支齿轮传动系统的弯扭耦合振动固有特性研究

在轴承-转子系统动力学理论的基础上,考虑齿轮啮合效应和转子弯扭耦合效应,建立了功率四分支齿轮传动系统振动方程,求解自由振动的特征方程,获得了该系统耦合状态下的前14阶固有频率和振型,以及非耦合状态下前8阶固有特性。得出如下结论:1)系统结构的对称性导致部分转子的模态对称;2)系统的模态类型主要表现为两类形态:一类以某一转子振动为主,其他转子的振幅很小;另一类表现为复杂的多转子弯扭耦合振动;3)转子间的弯扭耦合对系统的固有频率和模态产生了很大的影响,在进行功率四分支齿轮传动系统的振动特性研究时,必须同时考虑转子弯扭耦合效应的共同作用。     

大型水轮发电机组弹性轴系由电磁参数激发的弯扭耦合振动的研究

利用弹性体非线性振动的能量法研究水轮发电机组弹性轴系在电磁参数激发下弯扭耦合振动规律。揭示了弯曲振动能够激发扭振,两者相互耦合。利用奇异性理论在物理参数空间对共振的分叉形式进行分析,找到抑制共振发生的参数区域,为机组工程设计和安全运行提供理论依据。在弯扭耦合情况下,通过数值分析所得弯曲振动响应的理论结果与实测结果相符。     

一种新的转子碰摩故障诊断特征的研究

建立Jeffcott碰摩转子的弯扭耦合振动非线性微分方程，通过数值仿真手段，着重分析转子碰摩故障的扭振时频域特点及其非线性振动特性，并描述动静间隙对碰摩转子扭振非线性特性的影响。研究表明，转子碰摩激起丰富的扭振频谱信息，主要包括N/2X、N/3X等分频成分以及1X、2X等倍频成分，且分频幅值往往比倍频大许多。在一定转速范围内，周期运动与复杂的非线性运动交替出现。而动静间隙对转子扭振特性影响明显，动静间隙越小，转子动静碰摩越严重，频谱成分越丰富，运动形式更趋复杂，相应的各复杂运动区的范围也越宽。文中揭示的扭振特征为转子碰摩的状态识别与诊断提供了一种新方法。     

锥齿轮传动转子系统纵弯扭耦合振动的不平衡响应

研究了在外载荷作用下锥齿轮传动转子系统纵弯扭耦合振动的不平衡响应.建立了锥齿轮传动转子系统纵弯扭耦合振动的力学模型,通过作用在系统上不平衡量和不同外载荷,分析了由于纵弯扭耦合效应对不同转子之间不平衡响应的影响;讨论了外载荷的变化对不平衡响应的影响.结果表明外载荷会引起轴承特性的变化,从而影响系统的不平衡响应.     

多转子系统弯扭耦合振动分析的整体传递矩阵法

介绍了多转子系统弯扭耦合振动分析的整体传递矩阵法,推导了考虑弯扭耦合的齿轮耦合单元的传递矩阵,将整体传递矩阵法推广、应用于包含齿轮啮合效应的齿轮传动转子多轴系统弯扭耦合振动的动力计算问题中。采用整体传递矩阵法对具有齿轮啮合的多转子相互耦合系统的临界转速进行了计算。计算结果表明,这是一种精确度高,简便实用的方法,适于工程技术人员在微机上应用。     

碰摩转子弯扭摆耦合振动非线性动力学特性

为进一步提高旋转轴系的安全性,研究旋转轴系弯扭摆振动耦合振动问题.推导一般意义下,考虑陀螺力矩的单盘转子弯扭摆耦合振动非线性方程,基于该方程推出不平衡转子和碰摩转子的非线性弯扭摆耦合振动方程.应用数值方法研究碰摩转子弯扭摆耦合振动相应的复杂动力学行为,研究转子转速对碰摩转子弯扭摆耦合振动的分岔和混沌行为的影响,以及扭转振动和摆动振动对弯曲振动的影响.分析结果为转子的安全运行和弯扭摆耦合振动故障的判别提供了理论依据.     

Coupled bending and torsional vibration of a rotor system with nonlinear friction

Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating machinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose selfexcited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.     

Stability and dynamics of rotor system with 45° slant crack on shaft

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.     

The effect of root flexibility on the torsional vibration of uniform section blades

Turbomachinery blades are mounted rather loosely in a disc using different root fixing devices. This results in the root offering stiffnesses against bending as well as torsional motions. The effect of root flexibility on the bending vibrations has been studied considerably in the past; the present paper deals with its effect on the torsional vibrations. Solution of the governing differential equation with appropriate boundary conditions is obtained. The proper non-dimensional root flexibility and frequency parameters are derived. The effect on the first three torsional natural frequencies and the corresponding mode shapes is studied for the complete spectrum of root flexibility ranging from a clamped to a free root. An empirical formula is suggested for the value of the correction factor by which the fixed root frequency may be multiplied to obtain the flexible root frequency.     

齿轮-转子系统的振动特性分析

根据转子动力学和齿轮啮合的基本原理,建立了考虑陀螺力矩的齿轮转子系统的动力学模型,以此求得齿轮转子啮合刚度矩阵和阻尼矩阵。探讨了啮合刚度、支承刚度对系统固有频率以及系统稳定性的影响。结果表明齿轮的啮合刚度对弯曲振动以及弯扭耦合振动固有频率的影响不大,而当啮合刚度介于2×105~2×108之间时,对弯扭耦合振动的相对稳定性却有较大的影响;另增大支承刚度,固有频率相应提高;减小跨距可以提高系统的稳定性。分析结果对工程应用具有重要的意义。     

Determination of the principal directions of composite helicopter rotor blades with arbitrary cross sections

Modern helicopter rotor blades with non-homogeneous cross sections, composed of anisotropic material, require highly sophisticated structural analysis because of various cross sectional geometry and material properties. They may be subjected by the combined axial, bending, and torsional loading, and the dynamic and static behaviors of rotor blades are seriously influenced by the structural coupling under rotating condition. To simplify the analysis procedure using one dimensional beam model, it is necessary to determine the principal coordinate of the rotor blade. In this study, a method for the determination of the principal coordinate including elastic and shear centers is presented, based upon continuum mechanics. The scheme is verified by comparing the results with confirmed experimental results.