Experimental validation of non-contacting measurement method using LED-optical displacement sensors for vibration stress of small-bore piping

There have been many reports of fatigue failures of small-bore piping systems such as drain piping, vent piping and instrumentation piping in nuclear power plants that arise from vibration sources such as pumps. To prevent the failures, integrity evaluation of piping is conducted by measuring and analyzing vibration stress in the piping. But, a more efficient and economical measurement method is desirable to evaluate the vibration fatigue in small-bore piping. In this study, a non-contacting measurement method was proposed that is based on optical displacement sensors using light emission diodes (LEDs) to measure the vibration stress. The applicability of the method was discussed based on the vibration experiments using pipe elements and a mock-up piping system. From the experimental results, the proposed method was clarified to be sufficiently applicable and practically useful for the vibration measurement and stress evaluation in small-bore piping systems.     

A vibration analysis method based on hybrid techniques and its application to rotating machinery

Vibration-based condition monitoring and fault diagnosis technique is a most effective approach to maintain the safe and reliable operation of rotating machinery. Unfortunately, the vibration signal always exhibits non-linear and non-stationary characteristics, which makes vibration signal analysis and fault feature extraction very difficult. To extract the significant fault features, a vibration analysis method based on hybrid techniques is proposed in this paper. Firstly, the raw signals are decomposed into a few product functions (PFs) using local mean decomposition (LMD), and meanwhile instantaneous frequency and instantaneous amplitude also are obtained. Subsequently, Fourier transform is performed on the derived PFs, and then, according to the spectra features, the useful PFs are selected to reconstruct the purified vibration signals. Lastly, several different fault features are fused to illustrate the operating state of the machinery. The experimental results show that the proposed method can accurately extract machine fault features, which proves that the combined application of LMD and other signal processing techniques is a successful scheme for the machine vibration analysis.     

DSC-element method for free vibration analysis of rectangular Mindlin plates

A novel DSC-element method is proposed to investigate the free vibration of moderately thick plates based on the well-known Mindlin first-order shear deformation plate theory. The development of the present approach not only employs the concept of finite element method, but also implements the discrete singular convolution (DSC) delta type wavelet kernel for the transverse vibration analysis. This numerical algorithm is allowed dividing the domain of Mindlin plates into a number of small discrete rectangular elements. As compared with the global numerical techniques i.e. the DSC-Ritz method, the flexibility is increased to treat complex boundary constraints. For validation, a series of numerical experiments for different meshes of Mindlin plates with assorted combinations of edge supports, plate thickness and aspect ratios is carried out. The established natural frequencies are directly compared and discussed with those reported by using the finite element and other numerical and analytical methods from the open literature.     

基于有限元的摩托车振动分析与控制

振动是影响汽车、摩托车等车辆乘坐舒适性和可靠性的重要因素,运用有限元分析和实验模态分析方法对车辆的 振动进行分析,可以将振动问题在设计阶段解决,以缩短产品开发周期,节约开发成本。以摩托车为对象,建立了摩托车 的有限元模型,对模型进行理论模态分析和谐响应分析,并用实验分析对比验证理论模型,通过分析找到摩托车振动的 原因和控制振动的有效方法。     

低压压气机转子叶片振动特性计算与分析

利用优化的八节点超参数单元法对某型发动机低压压气机转子叶片的振动特性进行了计算分析,并结合转子结构和发动机工作状态深入分析了可能发生的危险共振情况,发现第二级转子叶片抗振性能不好,为转子叶片的在线监测与故障预报提供了重要依据。     

Sensitivity analysis of anti-resonance frequency for vibration test control of a fixture

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the undertest, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.     

A new formulation for the torsional vibration analysis of rotating cantilever rods

This paper presents a new modeling method for the analysis of torsional vibration of rotating cantilever rods. The natural frequency and mode shape variations due to the rotational motion could be accurately estimated with the modeling method, and the coefficient for the well-known Southwell equation could be obtained, as well. This method has couple of advantages compared to previous conventional modeling methods. Different from the previous modeling methods, the equations of motion of the rotating cantilever rod were derived with consistent linearization in a rigorous way. An eigenvalue problem to obtain the coefficients of the Southwell equation of rotating rods were derived from the original eigenvalue problem.     

A reverse receptance approach for analysis of vibration of grooved plates

A reverse receptance approach is proposed to solve eigenvalues of a plate with two orthogonally connected through grooves, two parallel through grooves and two parallel internal grooves. The procedure is a modification of the well-known receptance method commonly used to study vibrations of combined structures. In the present paper, vibrations of rectangular plates with grooves in different sizes and boundary conditions are studied analytically to illustrate the approach. A through groove is simulated by a simply supported beam, while an internal groove is simulated by a free–free beam. The accuracy is evaluated by comparing the percent differences between the natural frequencies solved using the reverse receptance method and the standard finite element method.It is verified that the reverse receptance method with both force and moment connections at the interface of each plate–groove pair and with sufficient interaction points is adequate and accurate for solving vibration characteristics of a plate with either through or internal grooves. Parametric study reveals that the percent differences are directly proportional to the length, the width and the depth of the grooves on the plate. It is found that, for good accuracy, the groove width should not exceed 3.6% of the plate width, while the groove depth should not exceed half of the plate thickness. This report demonstrates the potential of reverse receptance concept in the engineering practice of machine design, as a simple numerical or analytical approach to study dynamics of structures with complex geometries.     

Friction-induced vibration for an aircraft brake system—Part 1: Experimental approach and stability analysis

Friction-induced vibrations are a major concern in a wide variety of mechanical systems. This is especially the case in aircraft braking systems where the problem of unstable vibrations in disk brakes has been studied by a number of researchers. Solving potential vibration problems requires experimental and theoretical approaches. A non-linear model for the analysis of mode aircraft brake whirl is presented and developed based on experimental observations. The non-linear contact between the rotors and the stators, and mechanisms between components of the brake system are considered.Stability is analyzed by determining the eigenvalues of the Jacobian matrix of the linearized system at the equilibrium point. Linear stability theory is applied in order to determine the effect of system parameters on stability.     

HSK刀柄不平衡引起振动信号的特征分析

介绍了不平衡振动的机理;分析了HSK刀柄产生不平衡的原因和振动信号的特征;阐述了信号预处理的方法;最后利用小波理论进行小波变换重构信号,更准确的提取了HSK刀柄的振动信号,为今后的科学研究和HSK综合测量系统的开发提供了很好的依据。     

Angular resampling for vibration analysis in wind turbines under non-linear speed fluctuation

This work presents the development of an angular resampling algorithm for applying in conditions of high speed variability, as occurs in wind turbines, and the results obtained when applied to simulated signals, bearings diagnostic test-beds and wind turbines. The results improve the accuracy of similar resampling algorithms offered by the consulted bibliography. This algorithm is part of the wind turbine diagnostic system developed by the authors.     

汽车变速器模态分析及振动噪声测试实验研究

在PRO/E环境下建立SG13 5汽车变速器的 3D实体模型 ,应用I DEAS对变速器箱体进行动力学有限元分析 ,获得动力学参数。设计实验方案 ,测试和分析了箱体不同部位的振动与噪声信号 ,为变速器的减振降噪优化设计奠定了基础。     

复合式振动发电装置电磁发电性能仿真分析

针对微机电系统和无线传感器网络的迅速发展及其对清洁环保新型能源的需求,提出一种复合式振动发电装置,可实现电磁振动发电和压电振动发电。基于Ansoft有限元仿真软件,对复合式振动发电装置的电磁发电性能进行有限元仿真和结构优化。仿真结果显示,通过优化定子槽数和充磁方向,可以获得性能较优的电磁发电性能。     

Thermoelastic and vibration analysis of functionally graded cylindrical shells

The static response and free vibration of metal and ceramic functionally graded shells are analyzed using the element-free kp-Ritz method. The material properties are assumed to vary continuously along the depth direction. The displacement field is expressed in terms of a set of mesh-free kernel particle functions according to Sander's first-order shear deformation shell theory. The effects of the volume fraction, material property, boundary condition, and length-to-thickness ratio on the shell deflection, axial stress, and natural frequency are examined in detail. Convergence studies of node numbers are performed to verify the effectiveness of the proposed method. Comparisons reveal that the numerical results obtained from the proposed method agree well with those from the classical and finite element methods.     

滚动轴承的振动特性分析及典型故障诊断

滚动轴承的固有振动、轴承加工安装引起的振动和在运行时故障引起的振动是它的三种主要振动类型,其振动的频谱结构因此有高频段、中频段和低频段三个部分.通过实验测试滚动轴承的振动特性,并采用功率谱和小波变换对振动信号进行分析,从而识别出滚动轴承的滚动体缺损、内滚道点蚀和外滚道点蚀三种典型故障.     

Detection of stator winding faults in induction machines using flux and vibration analysis

This work aims at presenting the detection and diagnosis of electrical faults in the stator winding of three-phase induction motors using magnetic flux and vibration analysis techniques. A relationship was established between the main electrical faults (inter-turn short circuits and unbalanced voltage supplies) and the signals of magnetic flux and vibration, in order to identify the characteristic frequencies of those faults. The experimental results showed the efficiency of the conjugation of these techniques for detection, diagnosis and monitoring tasks. The results were undoubtedly impressive and can be adapted and used in real predictive maintenance programs in industries.     

轻型小客车车架的振动特性分析及控制

汽车结构模态分析在工程振动中占有重要地位,利用有限元方法对车架进行模态分析,获得车架模态参数-频率、振型等,对存在的问题提出一些改进措施,使得车架结构尽量避免产生共振和噪声,增强了汽车稳定性、舒适性和安全性,同时也为实际试验提供了参考和依据。     

某火箭发动机振动试验装置结构设计及优化

火箭发动机振动试验装置是在做火箭发动机环境振动试验时,用来连接火箭发动机与振动台体的必需工装.对某火箭发动机振动试验装置进行了结构设计,采用了箱体、托架和包带组合的结构形式,并利用ANSYS有限元分析软件对装置的整体结构进行了强度校核和模态分析.根据有限元分析结果,对主要影响装置整体强度和固有频率的结构进行了优化设计,包括在箱体上布置加强筋、加大托架宽度、加大托架与下包带接触面积等措施.优化后振动装置的强度满足试验要求,且其一阶固有频率高于振动试验最高频率,不会发生共振.     

圆柱壳自由振动的有限元分析

以位移模型为基础,用有限元中的分离变量法的理论,求解了圆柱壳自由振动的固有频率,计算结果与壳体解析解相一致。本方法具有节省内存,减少计算工作量的优点,是利用微机解决复杂结构计算的有效途径。     

基于门座式起重机动态称重系统的一种检测方法

本文提出了一种门座式起重机电子秤动态称重的计量要求及检测方法,详细叙述了该方法的具体要求和步骤。