Vibrations of a rotating membrane with unsteady rotations of the axis of rotation

A method and algorithm are developed for numerical calculation of the vibrations of a rotating circular membrane with a rigid central insert. The vibrations are caused by plane rotation of the rotation axis with a variable angular velocity. A system of differential equations is obtained to describe the motion of the membrane in relation to the stress-strain state caused by the rotation. Calculated results are presented for the case when the angular velocity of the membrane is constant, while the angular velocity of the rotation axis changes over time in accordance with a piecewise-linear law.Translated from Problemy Prochnosti, No. 2, pp. 55–60, February, 1990.     

Behavior of a Light Solid in a Rotating Horizontal Cylinder with Liquid Under Vibration

Dynamics of a cylindrical body in a rotating cavity is experimentally studied under transversal translational vibrations of the cavity rotation axis. Experiments are run at high rotation rate, when under the action of centrifugal force the body shifts to the rotation axis (the centrifuged state). In the absence of vibrations, the lagging rotation of the body is observed, due to the body radial shift from the axis of rotation caused by gravity. The body average rotation regime depends on the cavity rotation rate. The vibrations lead to the excitation of different regimes of body differential rotation (leading or lagging) associated with the excitation of its inertial oscillations. The dependence of the differential speed of the body rotation on the vibration frequency is investigated. The body dynamics has a complex character depending on the dimensionless vibration frequency. The analysis of body oscillation trajectory revealed that the body oscillatory motion consists of several modes, which contribute to the averaged dynamics of the body and the flows in the cavity.     

Flow induced vibrations of a triangular tube array in various arrangements of orientation and natural frequency

Abstract

Crossflow induced vibrations of a triangular tube array with a pitch ratio 1.33 were investigated experimentally. The streamwise and cross‐stream displacements of a monitored tube in the array were simultaneously measured by two accelerometers to examine the tube response to the cross flow in a water tunnel. The experiment was aimed to study the effects of the array orientation, and the tube's natural frequency on the flow induced vibration of the tube array. It is shown by amplitude diagrams that fluid elastic vibrations exist when the reduced velocity is above a critical value. The critical reduced velocity is found to be sensitive to the orientation of the test array. Based on the measured data of critical reduced velocity, the tube array in a triangular pattern (at a 30‐deg orientation with respect to the flow direction in the experiment) is found to be more stable than when in a rotated triangular pattern (0‐deg orientation). Furthermore, it is illustrated that the discrepancy in natural frequency of the tubes delays the occurrence of the fluid elastic vibrations of the tube array. With all the tubes in the test array having the same natural frequency, the orbits of the tube that exhibits fluid elastic vibrations are an organized, elliptic shape. The corresponding spectra are line‐dominated with peaks at the natural frequency and its harmonics, suggesting that the tube vibration is an organized oscillator. Without the same natural frequency as the surrounding tubes, the monitored tube exhibits fluid elastic vibration at larger reduced velocity, vibrating in a relatively random orbit.     

拖缆模型涡激振动的影响因素分析

为了考察圆柱型声纳阵拖缆在水下拖曳时,由于尾流中发放旋涡激起的涡激振动情况和有关规律,进行 了试验研究。对不同拖曳速度、拖缆倾角,即拖缆与来流速度之间的夹角和不同直径的拖缆涡激振动进行了测量分析。 结果表明,约化速度、拖缆倾角、拖曳速度等是影响涡激振动的主要因素。试验结果对进一步开展该类课题的研究,对声 纳阵拖缆的设计,提供了技术依据,具有实际价值。     

金马大厦折叠爆破拆除塌落与爆破振动分析

结合大连金马大厦双向折叠爆破拆除工程实例,回归分析了大楼拆除爆破振动和塌落振动的衰减规律,得到了K值和α值。分析了振动波形的时间历程,整个波形主要有2次爆破振动和1次塌落振动。对比分析了这两种振动的速度及频率特征,结果是塌落振动比爆破振动速度更大,是对周边建(构)筑物影响的主要因素;塌落振动比爆破振动的频率更低,更易引起建(构)筑物共振,因此振速和主振频率应作为城市爆破拆除的安全判据。     

The vibration of rotating elastic membrane cylinders

Using membrane theory we first investigate the finite deformation of a right circular cylinder of compressible hyperelastic material rotating about its axis. A necessary and sufficient condition for axial shortening to accompany rotation is given. Secondly we consider small amplitude vibrations propogating on such a finitely deformed cylindrical membrane. The same equations are shown to govern both the compressible and incompressible cases. For axi-symmetric vibrations analytical results are obtained and are used to show that neither pure torsional nor pure longitudinal vibrations can propagate in a rotating cylinder. Numerical results are given for a variety of different forms of vibration for a particular realistic material model.     

复式行星齿轮传动系统综合动力学模型及振动特性研究

建立了复式行星齿轮传动综合动力学模型,模型考虑了各构件的平移和扭转振动及静态传递误差。系统分析了复式行星齿轮传动系统的固有振动特性,研究了其固有频率的带状分布特点,根据中心构件及行星轮的振动特点,将系统振型分为三类,即中心构件平移-行星轮随机振动模式、中心构件扭转-行星轮相同振动模式、中心轮静止-相邻行星轮反向振动模式。     

Calculation of the vibration characteristics of a multi-bearing rotor with a transverse crack and small static strains

A study is made of the flexural vibrations of a heavy multi-section rotor with distributed parameters on elastically damped bearings. The rotor is unbalanced and has a transverse crack as a result of previous loading. The crack is regarded as a notch in the annular cross section of the rotor within the tension region. An examination is made of the first five harmonic components of the crack-induced vibrational displacements in relation to the amplitude of the forced vibrations, the static deflection of the rotor, and the initial orientation and dimensions of the crack. The results that are obtained are compared for cases where the amplitude of the forced vibrations of the rotor is greater or less than its static deflection. It is shown that the initial orientation of the crack has a greater effect on the vibrational displacements in the first case. There can be variants in which the crack is completely open or closed during the period of rotation. Possible signs of the presence of a crack at an early stage of its growth are discussed.Translated from Problemy Prochnosti, No. 2, pp. 92–99, February, 1996.     

钻柱纵向和扭转振动分析

介绍钻柱的振动状态和产生振动的原因。针对钻柱的纵向振动,分别建立了力激励法和位移激励法的数学模型;计算结果表明,力激励法与位移激励法求得的消振转速相反,即力激励法的消振转速恰恰是位移激励法的共振转速,反之亦然;传统多以力激励为边界条件来研究钻柱纵向振动的频率响应,并指导现场消振作业的,这样给出的最佳消振转速,恰恰是共振转速;在钻井作业中,钻头的纵向跳动比纵向受力的变化要稳定得多,钻柱的动负荷比动位移重要得多,应该用位移激励法研究钻柱的纵向振动问题。针对钻柱的扭转振动问题,分别建立了扭矩激励法和转角激励法的钻柱扭转振动数学模型;证明用转角激励法来研究钻柱的扭转振动更符合实际。     

Thermo-mechanical vibration analysis of rotating nonlocal nanoplates applying generalized differential quadrature method

In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines.     

Frequency analysis of rotating truncated circular orthotropic conical shells with different boundary conditions

In this paper, a study is made of the influences of orthotropic properties and boundary conditions on the free vibrations of a rotating, truncated, circular orthotropic conical shell. The study includes the effects of the Coriolis and centrifugal accelerations and the initial hoop tension. It is based on the Love first-approximation theory and Galerkin procedure. Results are obtained for the frequency characteristics of different orthotropic parameters, rotating velocities, cone angles and boundary conditions. Influences of orthotropic properties and boundary conditions on the relationships between frequency parameter and rotation velocity are discussed for different cone angles. To validate the present analysis, comparisons are made with those available in the open literature and very good agreements are obtained.     

79m高烟囱拆除爆破振动与塌落触地振动对比分析

在烟囱南侧近区,沿烟囱倒塌方向布了一条观测线共6个测点,回归分析了烟囱拆除爆破振动及烟囱倒塌触地振动的衰减规律,认为烟囱拆除爆破振动衰减规律中的K值远小于一般土岩小孔径(40mm)爆破振动衰减规律中的K值。分析了振动波形的时间历程,认为记录的整个波形主要含有爆破振动、缺口上唇磕地振动及烟囱塌落触地振动。对比分析了这三种振动的速度及频率特征,认为塌落触地振动的速度最大、频率最低,在烟囱倒塌处保留一定厚度的建筑废碴并敷设沙包墙具有良好的减振效果。     

废旧弹药爆破销毁技术综述

结合多年的废旧弹药销毁经验,总结了废旧弹药的识别方法,阐述了废旧弹药的当量估算与安全距离校核,论述了爆破销毁技术,以及销毁中为防止事故应做到的一般程序。     

Measurement of viscoplastic properties of a liquid in experiments with a torsion viscosimeter

The results of a numerical solution of the problem of vibrations of a torsion viscosimeter filled with an incompressible viscoplastic liquid are presented. It has been shown that in the vicinity of the rotation axis there appears a dead zone, whose boundary changes in the process of vibrations. The influence of plastic properties of the liquid on the characteristics of viscosimeter vibrations has been determined. A method for identifying viscoplastic properties by the observed parameters of vibrations is proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 124–127, January–February, 2007.     

空心管坯电磁离心过程的数值模拟

用有限元法模拟了铸造合金的流动和热量传输过程中瞬态速度场和温度场的分布,研究了电磁场强度和离心机转速对电磁铸造空心管坯的影响.结果表明,电磁搅拌引起的熔体相对运动是凝固过程中晶粒细化的主要原因.最优的电磁搅拌条件:转速1200 r/min,磁场强度为0.08 T,磁场持续加载25 s.在一定的转速和磁场强度条件下电磁离心铸造的温度场和凝固时的温度梯度对凝固组织有重要的的影响.合金液的外层,温度梯度达到最大值,铸件的温度下降得快,容易形成细小的等轴晶.     

Vibration Suppression of Thin-Walled Workpiece Machining Based on Electromagnetic Induction

Thin-walled workpieces are largely manufactured in the aerospace industry. The manufacturing process has been a problem due to its flexibility, and chatter vibrations are apt to occur, which restricts the machining efficiency and quality. A vibration suppression device for thin-walled workpieces is presented based on the electromagnetic induction principle, which utilizes machining vibrations to generate resistant force on the workpiece. The formulated force varies with the workpiece vibration velocity, but in an opposite direction. Excitation tests using the electromagnetic shaker illustrate that the device is effective in vibration attenuation. Finally, machining tests are carried out with applications to two thin-walled structures for further verification. The machining vibrations and surface quality demonstrate the damping promotion of the workpiece assembly, and milling stability limit is increased by more than twofold.     

Vibration mechanisms in the solid phase of a fluidization bed

The phenomenon of periodic vibrations in a fluidization bed is analyzed in the light of two mechanisms of interaction between solid phase particles. Equations are derived for the frequency, the wave velocity, and the wave vector of periodic-bed vibrations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 1, pp. 76–81, July, 1972.     

转速对KDP晶体成帽影响的数值模拟研究

本研究选择有限容积法, 采用Fluent软件对KH₂PO₄(KDP)晶体在不同转速下成帽过程的温度场及速度场分布进行了数值模拟。晶体转速较低(9 r/min)时, 晶体附近温度分布比较均匀, 相应的晶体只出现一个帽区, 但温度较高, 成帽较慢; 晶体转速较高(55和77 r/min)时, 温度分布也比较均匀, 所以晶体也只有一个帽区, 此时温度较低, 成帽较快; 晶体转速介于两者之间时, 温度分布出现扰动, 晶体成帽同时出现两个或多个帽区, 成帽速度介于两者之间。在所模拟晶体转速范围内, 较高转速77 r/min是晶体帽区恢复的最优转速。     

An acoustic method of determination of the coefficient of permeability and the pore velocity of sound in snow

Using an experimental setup that allows one to distinguish resonance frequencies of vibrations of the studied specimen of snow, we showed the possibility of determining the coefficient of permeability of snow and the velocity of sound in the air confined in its pores.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 77, No. 6, pp. 131–140, November–December, 2004.     

基于逐步线性回归的汽轮发电机组振动研究

研究汽轮发电机组运行参数对基础振动的影响对降低振动引起的设备故障具有重要意义。建立汽轮发机组基础振动成因分析试验平台,首先测试不同汽轮机转速、进气压力与载荷工况下基础振动有效值,通过逐步线性回归对振动有效值与运行参数之间的关系进行统计分析,再根据汽轮机降速过程与增压过程中的基础振动时频图对统计分析结论进行验证。结果表明,汽轮发电机组基础的振动与汽轮机转速、载荷呈线性关系,且与汽轮机转速的线性关系更加显著;汽轮机转速对机组基础振动的影响比载荷影响更大,进气压力对基础振动的影响不显著;运用逐步线性回归统计方法可得出汽轮发电机组基础振动的影响因素及各影响因素的重要程度。