具有横向裂纹转子的刚度研究

首先计算了含横向裂纹轴转动一周,裂纹处于不同开闭状态下,轴的十六个弯曲刚度的傅氏表达式,分析了诸刚度的特点及影响其变化规律的一些因素。进而,提出了转子空间位置唯一确定裂纹转子弯曲刚度的模型,给出了主要换算公式。     

基于极坐标圆的裂纹转子的振动分析

基于简单铰链裂纹模型,建立含初始弯曲裂纹转子的动力学模型,将裂纹、质量偏心、初始弯曲转化为外部激励,经量纲一化转换可应用于稳态、瞬态、非线性等不同运动状态下、不同系统参数情形下的裂纹转子的振动特性分析中.利用欧拉方程进行解析求解,对比分析无初始弯曲裂纹转子与含初始弯曲裂纹转子频率成分的差异,研究含初始弯曲裂纹转子的亚临界共振特性.定义一种适用于裂纹转子动力学分析的极坐标圆,可全面反映出振动响应幅值的变化关系;数值仿真计算得到不同参数下的极坐标圆,讨论刚度变化、质量偏心与质量偏心角、初始弯曲与初始弯曲角的影响,可为系统优化或抑制振动提供依据;相应的轴心轨迹与频谱分析验证极坐标圆的有效性和可行性.     

考虑切向刚度变化裂纹转子的分叉与混沌

基于不附加任何假设的裂纹模型,考虑切向刚度变化,建立裂纹转子无量纲动力学模型,可适用于瞬态、稳态、非线性等不同运动状态。采用分叉图、Pioncaré映射、轴心轨迹、频谱图、最大Lyapunov指数等,分析裂纹法向刚度变化、切向刚度变化、质量偏心与质量偏心角对裂纹转子分叉与混沌特性的影响,发现:随着裂纹法向刚度变化的增加,裂纹转子在亚临界转速区出现倍周期分叉、拟周期、周期3解等振动形式;考虑裂纹切向刚度变化,裂纹转子在1/2,2/3亚临界转速区出现拟周期、混沌运动,进入混沌的途径与拟周期、周期3解有关;质量偏心的增加或质量偏心角180°时,对裂纹转子的非线性运动具有明显的抑制作用。数值仿真研究可为工程实际中裂纹转子故障诊断提供依据。     

裂纹转子识别中Wigner-Ville分布与小波变换的比较

建立基于简单铰链裂纹模型的裂纹转子瞬态响应的动力学模型，得到裂纹转子与无裂纹转子的数值仿真解，比较裂纹转子与无裂纹转子Wigner-Ville分布和小波变换时频特性的不同。数值仿真进一步对比研究Wigner-Ville分布和小波变换对刚度变化的敏感性，并讨论质量偏心和质量偏心角对Wigner-Ville时频特性与小波时频特性的影响，为工程实际中裂纹转子的识别提供依据。     

含裂纹转子的振动特性计算用于裂纹在线检测的研究

本文研究含裂纹转子的振动特性。文章首先根据裂纹结构的应力强度因子，得到含裂纹单元体的刚度矩阵，进而得到裂纹转子的整体刚度矩阵和质量矩阵，列写出裂纹转子的运动微分方程，导出裂纹引起转子系统刚度变化与系统振动特性参数变化间的关系，从而可由实时在线测得的振动参数判断裂纹的位置。通过对模拟转子的计算和实测，表明本文提出的方法是一种可用于大型旋转机械转子轴裂纹在线检测的极为有效的方法．     

微型涡轮发动机转子系统振动性能研究

以某微型涡轮发动机转子系统为对象,建立了两种不同的有限元模型对转子系统进行了振动性能研究.在考虑轴承径向刚度的基础上,分析了支承刚度对转子系统振动性能的影响.     

含角裂纹剪切型橡胶减振垫的断裂分析

通过非线性有限元方法对橡胶材料分别采用Neo-Hookean及Mooney两种本构模型的橡胶层含角裂纹的剪切型橡胶减振垫进行数值分析.分别给出减振垫切向刚度与撕裂能随不同裂纹尺寸的变化关系,并对两种模型的切向刚度以及撕裂能进行比较.对受剪切载荷作用的减振垫在含不同深度橡胶层斜角裂纹的情况进行了分析.给出含斜角裂纹减振垫的切向刚度和撕裂能随着相对裂纹深度的变化情况.分析了不同载荷以及不同裂纹尺寸的减振垫的撕裂能变化.     

双盘双呼吸型裂纹转子的非线性动力学特性

采用有限元方法建立了双盘双呼吸型裂纹转子系统的动力学方程,利用应变能释放率方法得到了裂纹单元的刚度矩阵,采用应力强度因子为零法模拟裂纹的呼吸效应,研究了双裂纹转子振动响应的特点,以及在一个稳态旋转周期内裂纹轴刚度时变规律,分析了不同裂纹深度和裂纹夹角对转子振动响应的影响。     

含横向裂纹简单转子刚度的计算

以两端简支的 Ｊｅｆｆｃｏｔ 转子为对象,运用断裂力学和材料力学理论推导出含横向弓形裂纹的转子刚度计算公式,并在此基础上研究裂纹位置、裂纹深度和轴细长比 Ｒ／ Ｌ等参数对转子刚度的影响。计算结果表明,裂纹位置距转子中心越近、裂纹深度越深,转子的刚度就越小;转轴细长比越大,裂纹对转子刚度的影响就越大;当裂纹较浅时,可忽略平行于裂纹方向的刚度变化,而当裂纹较深时,应同时考虑与裂纹平行和垂直方向上的刚度变化。     

裂纹拉杆转子尺寸效应机理与动力学特性研究

在利用相似规律设计不同尺寸拉杆转子时,由于尺寸变化,存在明显尺寸效应,含裂纹缺陷的转子尺度律机理尚不明确。本文基于量纲分析法,探究了裂纹扩展的尺寸效应机理。分析了不同尺寸机型,裂纹拉杆应力强度因子的分布规律与刚度变化规律;对比分析了不同尺寸机型对裂纹转子固有频率漂移现象的敏感性;最后提出了一种用拉杆预紧力的下降表征裂纹扩展过程的研究方法,通过实验比较了不同裂纹拉杆分布形式下转子固有频率的漂移现象。研究结论为拉杆转子的系列化设计与设备维护提供了理论基础。     

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.     

Crack detection, localization and estimation of the depth in a turbo rotor

The goal of this paper is to describe an advanced method of a crack detection: a new way to localize position and to estimate depth of a crack on rotating shaft. As a first step, the shaft is physically modelled with a finite element method and the dynamic mathematical model is derived using the Hamilton principle; thus, the system is represented by various subsystems. The equations of motion of the shaft with a crack are established by adapting the local stiffness change through breathing and gaping from the crack to an undamaged shaft. This is the reference system for the given system. Based on a model for transient behavior induced from vibration measured at the bearings, a nonlinear state observer is designed to detect cracks on the shaft. This is the elementary NL-observer (Beo). Using the observer, an Estimator (Observer Bank) is established and arranged at the certain position on the shaft. When a crack position is localized, the procedure for estimating of the depth is engaged.     

The dynamic behavior of a rotor system with a slant crack on the shaft

For a Jeffcott rotor system with a 45° slant crack on the shaft, the motion equations are established with four directions, i.e. two transversal directions, one torsional direction and one longitudinal direction. It can be seen from the deducing process of the stiffness with the strain energy release approach that there are coupling stiffnesses of bending–torsion, bending–tension and torsion–tension for the slant-cracked shaft and only bending–tension for the transverse-cracked one. The paper shows that besides the coupling stiffnesses, there is bending–torsion coupling caused by the eccentricity. All these couplings affect the responses of the slant-cracked shaft and the transverse-cracked one. Comparing responses of a cracked shaft with an open crack model and those with a breathing crack model finds that there are the same prominent characteristic frequencies for these two kinds of shafts, even though the cracked shaft with a breathing crack model behaves much more non-linear than that with an open crack model. Therefore, almost all studies in this paper adopt the open crack model since it needs taking much longer time to compute responses of a breathing cracked shaft than that of an open cracked shaft. Analyses of steady responses indicate that the combined frequencies of the rotating speed and the torsional excitation in the transversal response and the frequency of the torsional excitation in the longitudinal response can be used to detect the slant crack on the shaft of the rotor system.     

基于视觉位感条纹的转轴裂纹缺陷检测

裂纹缺陷是转轴系统中常见的故障形式,裂纹的呼吸效应会改变转轴的动态特性,使转轴的径向振动信号中出现倍频分量。提出一种基于单目视觉位感条纹振动测量原理的转轴裂纹缺陷检测新方法,可实现转轴振动信号的高效测量和裂纹缺陷的快速检测。分析了含裂纹转轴系统的动力学方程,并系统描述了单目相机成像条件下采用位感条纹图案实现转轴径向二维振动测量的原理,建立了成像位感条纹动态编码参数与转轴径向振动位移之间的数学模型。通过与传统基于两路电涡流传感器测量系统的试验对比分析,验证了本方法测量结果的精确性。分析转轴系统在不同转速下径向振动中的频率分量,当转速接近1/2临界转速时,2倍频信号非常明显,且其幅值接近转频幅值,可实现对于转轴系统中裂纹缺陷的有效检测。     

基于ANSYS的大型异步电机转子系统动态特性分析

采用有限元分析软件ANSYS建立了大型异步电机YKS1000-4TH转子系统的集中质量-梁单元有限元模型和三维有限元模型.采用Qr damped法对两种模型进行了模态分析,求得系统的前3阶固有频率和振型,并计算出相应的主轴临界转速.最后改变油膜支承刚度,分析系统临界转速随油膜刚度的变化规律,为大型异步电机转子系统的设计提供了理论依据.     

Simulation on the motion of crankshaft with a slant crack in crankpin

A new model for vibration analysis of a crankshaft with a slant crack in crankpin is proposed, and the influence of crack depth on the transient response of a cracked crankshaft is investigated. A slant cracked shaft element is developed by deducing the local flexibility due to a slant crack. The frequently occurred slant crack in crankpin is studied, and a new finite element model of crankshaft including the slant crack in crankpin, which combines the slant cracked shaft element and Timoshenko beam elements, is derived. The support of engine block and the switching behaviour of the crack are considered, and the non-linear equation of motion for cracked crankshaft-bearing system is set up in a rotating coordinate system. The motion of a crankshaft of a four in-line cylinder engine with and without an initial crack is simulated. The influence of the crack depth on the transient response is investigated. The numerical simulation demonstrates that the current model is valid for simulating the motion of cracked crankshaft system. The results show that a useful foundation is laid for crack detection of crankshaft.     

轴—壳体系统耦合振动控制原理分析及试验

螺旋桨脉动力是引起轴系—壳体振动的主要因素。基于频域模型,研究轴—壳系统耦合振动特性及参数影响,从原理上分析在推进轴系上施加控制力来抑制耦合系统振动的控制方法,并讨论基于自适应前馈控制策略的主动控制方案。采用自适应对消及归一化最小均方算法,在轴上施加纵向控制力,实时抵消脉动推力,降低轴系纵向振动,由此抑制由于轴系振动所引起的壳体振动。仿真结果表明：控制力施加位置对控制效果影响很小,不同轴承刚度对控制力大小的需求不同,刚度较小时误差收敛速度较慢,刚度达到一定程度以后收敛速度不变。通过轴—壳体试验系统对原理分析进行验证,结果也表明推力轴承刚度对轴系纵振频率的影响,所提出的控制方法能够有效地抑制壳体振动。     

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。     

A study on the prevention of cracks on the trepan area of motor bearing

Trepan prevents the wear of the inside part of a bearing when the initial shaft rotates. It continuously contacts with the eccentric part of the shaft in rotation and is loaded repeatedly. Therefore, even if an early crack of a trepan part is small, the crack may progress by the repeated load. If the crack progresses, very small chips come out. This is put in the rotor and prevents the rotation of the compressor. There can be leaks in a microgroove and extreme wear can occur due to lack of oil on the surface contact part. Therefore, this study was carried out to compare and investigate the trepan strength and deflection characteristics between trepan locations and dimension changes using the finite element method and search a motor bearing for a model with bigger stiffness of a trepan part and the same deflection.