转子的热膨胀与横向振动

应用预应力法，采用ANSYS软件分析了转子热膨胀及轴向推力对横向振动的影响，并以某汽轮发电机组模型中汽轮机转子为对象进行了优化设计。     

含旋转运动效应裂纹梁横向振动特性的研究

针对开口裂纹作用下旋转运动欧拉-伯努力梁的振动特性进行了研究.文中使用裂纹梁连续等效刚度模型模拟裂纹效应,将含裂纹旋转运动梁视为弯曲刚度沿梁长度方向连续变化的梁,并应用传递矩阵法推导了求解其振动特性的特征方程.考虑不同裂纹深度和位置、不同旋转速度,分析了梁的一阶和二阶固有频率的变化情况.研究结果表明:旋转运动效应和裂纹效应并非独立影响梁的固有频率,两者间具有耦合作用效应;转速提升使由裂纹导致的频率衰减幅度变小,同时裂纹加深使得由速度升高带来的阶频提升更加显著;相比于二阶频率,耦合作用效应对于一阶频率更加显著.     

椭圆锥动效应对机械抖动激光陀螺振动特性的影响

对机械抖动激光陀螺的振动特性进行了理论分析,得到了水平振动下陀螺测量敏感轴存在椭圆锥动效应,并得出了该锥动效应引起的陀螺输入角速度表达式。利用有限元分析软件ANSYS,对机械抖动激光陀螺进行了随机振动分析,仿真证实了锥动效应的存在,并采用物理方法试验验证了椭圆圆锥运动的存在及其锥动幅角的大小。通过数值仿真与分析,指出了减小锥动效应,提高陀螺振动性能的有效措施是增大抖动偏频机构的横向抗弯刚度。改进设计的试验结果表明,采用大横向抗弯刚度的新型抖动偏频机构使陀螺的抗振性能提高了4倍多。     

小型静电陀螺电极划分方式对转子电位及陀螺精度的影响分析

就小型静电陀螺电极划分方式对转子电位的影响进行了理论分析及仿真,并深入研究了转子的非零电位对陀螺精度的影响,为小型静电陀螺电极结构的设计提供了理论依据。     

振动轮式微机械陀螺动力学方程、振动模态及其灵敏度分析

介绍了一种新的振动轮式微机机械陀螺仪的结构及工作原理,详细推导了该陀螺的动力学方程,分析了其运动规律,并建立了该陀螺的三维有限元模型,给出了前其四阶模态振型,对灵敏度进行了分析模拟。     

裂纹转子的弯扭耦合振动特性分析

研究了裂纹转子的弯扭耦合振动特性,分析了扭转对弯曲振动的影响,数值分析结果表明,在某些情况下扭转振动的耦合使变曲振动转子的裂纹特征消失,对转子水裂纹故障的早期预报与诊断不利,     

旋转Rayleigh梁的自由振动及失稳特性

基于Hamilton原理,采用模态坐标得到了旋转梁在固定参考系及旋转参考系下的时域常微分方程,详细分析了两端简支边界条件下旋转Rayleigh梁自由振动的行波特性及临界转速。讨论了长细比等因素对旋转Rayleigh梁的行波振动频率和临界转速的影响,并给出了不同转速下系统自由振动的典型模态坐标时间曲线。研究发现:旋转Rayleigh梁系统存在一次和二次临界转速,固定参考系中一次临界转速对应于旋转参考系中零特征值失稳点,转速在一次临界转速(低速)附近时系统只发生共振失稳,系统真正的失稳发生在转速超过二次临界转速之后。     

含轴向运动效应的裂纹梁横向振动频率研究

针对含轴向运动效应开口裂纹梁,借助裂纹梁连续等效刚度模型,将裂纹效应引入轴向运动梁的横向振动方程.应用传递矩阵法推导了求解其振动频率的特征方程,计算得到裂纹和运动参数连续变化情况下梁的一阶和二阶固有频率数值解.对裂纹和轴向运动参数对梁的振动频率的联合影响机理进行了分析,研究表明,对于梁的一阶和二阶固有频率,轴向运动速度和裂纹深度具有耦合作用效应.裂纹加深使得由轴向速度带来的频率衰减加速;同时,速度提升导致由裂纹引起的频率衰减变得更加剧烈.相较于二阶频率,耦合作用效应对于一阶频率表现得更加显著.     

推力轴承各耦合动特性系数对转子横向振动状态的贡献

系统地研究了推力轴承各耦合动特性系数对转子横向振动状态的贡献。计算结果表明，推力轴承对转子横向振动状态的影响主要由推力盘摆动而产生的耦合动特性系数所决定，而由平动所产生的耦合动特性系数对转子振动状态影响的贡献很小，可以忽略。     

Transient response of flexible rotor with arbitrarily distributed mass through critical speed

In this paper, the Riccati transfer matrix method and the component theory of forward and backward whirls are used to the eigenproblem of damped free whirling vibration of a flexible rotor with arbitrarily distributed mass on isotropic or anisotropic supports, with the gyroscopic effect taken into account to find out its critical speeds and corresponding vibrational shape functions. The generalized damped mode theory is developed and extended, which is employed in combination with the Bogoliubov-Mitropolskii asymptotic method to deduce two sets of first order differential equations to calculate the transient response of the rotor with limited power supply passing through its critical speeds in forward whirl and backward whirl respectively. The coupling phenomenon of the rotor through two neighboring critical speeds is also analyzed.     

EIGENVALUE PROBLEM OF A LARGE SCALE INDEFINITE GYROSCOPIC DYNAMIC SYSTEM

Gyroscopic dynamic system can be introduced to Hamiltonian system.Based on an adjoint symplectic subspace iteration method of Hamiltonian gyroscopic system, an adjoint symplectic subspace iteration method of indefinite Hamiltonian function gy- roscopic system was proposed to solve the eigenvalue problem of indefinite Hamiltonian function gyroscopic system.The character that the eigenvalues of Hamiltonian gyroscopic system are only pure imaginary or zero was used.The eigenvalues that Hamiltonian function is negative can be separated so that the eigenvalue problem of positive definite Hamiltonian function system was presented,and an adjoint symplectic subspace iteration method of positive definite Hamiltonian function system was used to solve the separated eigenvalue problem.Therefore,the eigenvalue problem of indefinite Hamiltonian function gyroscopic system was solved,and two numerical examples were given to demonstrate that the eigensolutions converge exactly.     

Coupling vibration of vehicle-bridge system

By applying the sinusoidal wave mode to simulate the rugged surface of bridge deck, accounting for vehicle-bridge interaction and using Euler-Bernoulli beam theory, a coupling vibration model of vehicle-bridge system was developed. The model was solved by mode analyzing method and Runge-Kutta method, and the dynamic response and the resonance curve of the bridge were obtained. It is found that there are two resonance regions, one represents the main resonance while the other the minor resonance, in the resonance curve. The influence due to the rugged surface, the vibration mode of bridge, and the interaction between vehicle and bridge on vibration of the system were discussed. Numerical results show that the influence due to these parameters is so significant that the effect of roughness of the bridge deck and the mode shape of the bridge can‘ t be ignored and the vehicle velocity should be kept away from the critical speed of the vehicle_     

Steady-state dynamics of a non-ideal rotor with internal damping and gyroscopic effects

A rotor driven by an ideal source, i.e., a source capable of delivering unlimited amount of power, becomes unstable beyond a certain threshold spin speed due to non-conservative circulatory forces. The circulatory forces considered in this paper arise out of rotating internal damping. If the drive is non-ideal then the rotor spin speed cannot exceed the stability threshold. This phenomenon is a type of the Sommerfeld effect. In this work, a DC motor driving four-degrees-of-freedom rotor with internal damping and gyroscopic effects is considered and the corresponding steady-state spin frequency and the whirl orbit amplitude are analytically derived as functions of the parameters of the drive and the rotor system.     

Analytical solution for axisymmetric problem of thick laminated closed cantilever shells in hamilton system

By giving up any assumptions about displacement models and stress distribution, the mixed state Hamilton equation for the axisymmetric problem of the thick laminated closed cantilever cylindrical shells is established. An identical analytical solution is obtained for the thin, moderately thick and thick laminated closed cantilever cylindrical shells. All equations of elasticity can be satisfied, and all elastic constants can be taken into account. This work is supported by the National Natural Science Foundation of China.     

Study on catastrophic mechanism for rotor drop transient vibration following magnetic bearing failure

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Direct specturm analysis of the state space for random vibration of MDOF linear damped system

This paper proceeds from the general case of the unsymmetric linearized multi-degrees of freedom (MDOF) systems. By adopting the general complex modal theory of the state space, the response analysis for a system subjected to random excitation of the same source is carried out using as a kind of direct spectrum analysis method in frequency domain. With the input of power spectral density function given, the explicit expression of the power spectral density function matrix of the output response can be obtained. By taking Fourier inverse transform, the integrated expressions of the correlation function matrix and of the spectrum moment matrix are obtained. Comparing with the time domain method, this method enjoys the merit of visualization and avoids the procedure of transformation from the obtained response correlation function to be solved for the output spectrum utilizing Fourier transform. This paper has extended the application range of the traditional frequency domain analysis method. The mean square values and variety of statistical values can be obtained conveniently. This method and the time domain method are different in approach but equally satisfactory in their results. The project is supported by National Natural Science Foundation of China and National Education Commission Science Foundation of China     

Research on vibration performance of the nonlinear combined support-flexible rotor system

Nonlinear Dynamics - A finite element model of the cantilever combined support rotor included two discs established in this paper to predict and explain the nonlinear vibration phenomenon. The...     

矩形空腔内Stokes流的状态空间有限元法

基于Hellinger-Reissner二类变分原理,从平面Stokes流问题的平衡方程、连续性要求和边界条件出发,得到相应的Hamilton函数,建立Hamilton正则方程后,采用分离变量法对场变量进行离散求解:在x方向采用有限元插值,在y方向采用状态空间法给出控制坐标方向的解析解。计算过程中的指数矩阵均采用精细积分法求解,使得本文算法具有高效率、高精度、对步长不敏感的优点。通过对侧边自由液面边界条件的单板驱动矩形空腔Stokes流问题的求解,得到与文献相同的结果,从而验证了本文方法的有效性。本文旨在将弹性力学状态空间有限元法的思想引入到低雷诺数流体力学中,为Hamilton体系下研究复杂边界Stokes流问题提供新的途径。     

移动简谐力作用下三维多孔饱和半空间的动力问题

研究了移动荷载作用下多孔饱和地基的动力问题.应用Fourier变换求解该问题的控制偏微分方程,考虑了荷载的移动速度及振动频率对多孔饱和地基动力响应的影响,重点研究了移动速度达地基表面波速时多孔饱和半空间的振动问题(马赫效应),并与相应的弹性介质的解答进行了比较.结果显示当移动速度与多孔饱和半空间的表面波速相近时,地基会产生很大的振动;当移动速度大于表面波速时,多孔饱和半空间的动力响应与弹性半空间的动力响应有较大的差别.