Vibration, Structural Engineering and Measurement II

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Authors: Rui Li, Qi Fen Jia, Shun Zhong
Abstract: Calculation of the induction motor machine modal frequencies of an electrical machine accurately is the base of reducing acoustic noise and vibration. This paper presents a detailed research on the induction motor mode shapes and natural frequencies of induction motor by using 3D finite element technique, based on simplified modal, The influence of and mounting feet and rotor on mode shapes and natural frequencies are investigated systematically. Mounting feet and rotor have a great effect on natural frequencies, the mounting feet and rotor will result in the number of the motor low-vibration mode increases\the frequencies rise obviously, the mounting feet result in motor vibration mode becomes more complicated, rotor modals become an important part of motor mode shapes, the number of the motor low-vibration mode increases. Predictions are validated against experimental results.
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Authors: Hong Qing Lv, Wei Xiao Tang, Qing Hua Song, Shan Shan Sun
Abstract: A review of research on the vibration control technology inspiration from the biological vibration damping mechanisms is described. First the important concept and background of the bionic vibration damping technology are briefly introduced. Then the basic theories and its applications in the engineering fields are elaborated from three aspects: vibration damping mechanisms of the creatures own the good ability to withstand the ambient vibrations, mechanical models of biological prototypes and its application progress in the practical occasions.
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Authors: Wen Qing Zhu, Yang Yong Zhu
Abstract: With the rapid development of high-speed railway in China, the aerodynamic brake is very likely to be an important emergency braking mode of high-speed train in the future. This paper takes aerodynamic braking wing as the object, and uses the finite element software to divide the meshes, then analyses the model influenced by static stress. After simulating the vibratory frequency response of the model in the flow field, it finds that the largest deformation happens in the middle of the upper edge of the wind wing, when the wind speed gets to 500km/h and the load frequency to 4Hz. Some conclusions of this thesis can provide reference for researching the applying the aerodynamic brake in the high-speed trains and laying the foundation for solving the riding and braking safety problems.
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Authors: Jun Chao Zhu, Han Hua Zhu, Xin Ping Yan, Ping Jiang
Abstract: The aft part of large scale vessel propulsion shaft is a cantilever with a propeller. As the shaft doing the lateral vibration, the trail of propeller shaft center-line, which appears together with the movement, is the cone surface with the shaft center as the symmetrical axis, at the same time the propeller will vibrate with the shaft. In order to investigate the influence of propeller effect to shaft lateral vibration, the main work in the paper includes modeling the finite element of a large scale vessel propulsion shaft, studying the factors of water mass adhered to propeller, pin softening and gyroscopic moment to the shaft lateral vibration. The calculation shows that: if the propeller's gyroscopic moment is positive, the free frequency of shaft will increase, while added water mass and spin softening will obviously decrease the free vibration frequency of shaft.
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Authors: Li Hua Chen, Yue Sun, Wei Zhang
Abstract: In this paper, the vibration characteristics of the cantilever rectangular plate with side crack are studied in the way of analysis, which including natural frequency and mode shape. The influences of different parameters of crack, such as the locations and lengths of crack, to the vibration characteristics of the cantilever rectangular plate are investigated. The modal function of the crack plate consists two parts, which are (1) the modal function of intact cantilever rectangular plate from beam functions combination method and (2) corner functions presenting the discontinuity of displacement and slope along the crack. The natural frequencies and modal shapes can be obtained when taking the modal function into the method of Ritz. At last, the effects of the crack location and crack length on the vibration characteristics are investigated, and it could provide the theoretical basis for engineering application and the relevant study.
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Authors: Fang Wang, Ming Chen
Abstract: The swashplate rod is a key component of helicopter control system. The vibration environment of helicopter is quite complex. The natural frequency of the swashplate rod is generally low. So resonance occurs easily. Resonance could reduce control precision or even damage the whole control system. Established dynamic and mathematical model of swashplate rod. Analyzed the vibration characteristics. Obtained the natural frequency and vibration mode function of the rod. In the compression, tension and free state, the natural frequency of the rod is basically the same. Made flight experiment with a developing helicopter as object. Measured the load of the swashplate rod in flight conditions. Make Fourier analysis to the load. Obtained the frequencies of the load on the rod. The frequencies coincide with 1 and 2 times of the rotor speed.
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Authors: Ai Lun Wang, Hui Long, Qiang Huang, Qian Jin Wang
Abstract: The group number and group coupling stiffness are important structural parameters of the grouped blade-disk. This work examines how the group number and group coupling stiffness affect the vibration response localization of tuned grouped blade-disk. The lumped parameter model of the grouped blade-disk was established, and the vibration equation was derived. The vibration response localization factors of tuned grouped blade-disks were obtained at the different group number and group coupling stiffness, and the effects of group number and group coupling stiffness on vibration response localization was analyzed. The results show that the vibration localization appears in the tuned grouped blade-disk and the degree of vibration response localization reduces with the increasing of group number and group coupling stiffness. The results can help to completely reveal the localization mechanism of the grouped blade-disk
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Authors: Xian Bing Li, Gang Wang, Ji Hong Wen, Xi Sen Wen
Abstract: In order to improve the treatment efficiency of the constrained layer damping (CLD), it is meaningful to have a study on its layout optimization. This paper based on current research of Cellular Automata (CA) algorithm for CLD optimization, points out that the current application of CA algorithm is less efficient, considering that adding or deleting a single CLD patch almost does no change to the entire structure, then makes a simplification and modification of CA algorithm. With the aim at improving the structural modal loss factor, this paper uses the current CA algorithm and its modified algorithm to optimize a partial CLD plate. The results have shown that the modified CA algorithm for CLD optimization can not only substantially increase computing efficiency, but to some extent, improve the optimization effectiveness.
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Authors: Zhe Zhang, Guglielmo S. Aglietti, Wei Jia Ren
Abstract: Reaction wheel assemblies are one of the most important microvibration sources on typical modern satellites. In this paper microvibrations induced by a cantilevered reaction wheel assembly are modelled and validated against microvibration test results. The disturbance model is developed using energy method. A microvibration measurement platform is designed to measure its disturbances. Disturbance test results are analyzed in detail. The peculiar dynamic characteristics such as nonlinearity and high damping of harmonic responses in the test results are discussed. Estimations of damping values used in the disturbance model are introduced. A new method developed to model harmonic excitations is discussed. Furthermore, novel methods to identify harmonics and extract model parameters from test results are presented. The empirical modeling method developed for broadband noise excitations are also introduced and validated.
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Authors: Song Lin He, Yan Huang
Abstract: The new rapid series method to solve the differential equation of the periodic vibration of the strongly odd power nonlinear oscillator has been put forward in this paper. By adding the exponentially decaying factor to each harmonic term of the Fourier series of the periodic solution, the high accurate solution can be obtained with a few harmonic terms. The number of truncated terms is determined by the requirement of accuracy. Comparing with other approximate methods, the calculation of rapid series method is very easy and the accurate degrees of solution can be control. By comparing the analytical approximate solutions obtained by this method with numerical solutions of the cubic and fifth power oscillators, it is proven that this method is valid.
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