Papers by Keyword: Vibration Mode

Abstract: The reverberation ray matrix method (MRRM) for analyzing dynamic response of elastic trusses is extended and used to solve the natural frequency and vibration mode of laminated beams. In this study, the MRRM is employed to obtain the frequency response function (FRF) of displacement of a laminated beam under the action of a unit impulse load. The natural frequencies are determined from the peak of the curve of FRF when a resonant frequency is approached. And the mode is retrieved from the ad joint matrix of the coefficient matrix of the governing equations of MRRM. The accuracy of result of MRRM is verified by a simply supported symmetrically laminated beam compared with the analytical solution of classical theory, which is also proved by finite element method (FEM).

Abstract: The damage analysis based on the modal parameters usually need to compare the test data with the computed data by theoretical analysis. In bridge structure damage analysis, it is impossible that the sensors are set at every node. So the test data need to be extended to every node by using interpolation technology. In the paper, three interpolation methods, cubic interpolation method, cubic spline interpolation method and sinc interpolation method, are introduced. Their applications in bridge structure damage analysis are discussed. The experiment results show that the best interpolation method is cubic spline interpolation method. Using the data processed by interpolation technology can well obtain the damage location of bridge.

Abstract: According to the complex damping theory, the formula to calculate equivalent damping ratio of composite structures is derived from damping stiffness matrix by dynamic analysis. The finite element model of a steam turbine foundation is established. The equivalent viscous damping ratio is calculated from natural frequencies, modes and structural stiffness matrix. Due to the vertical stiffness of spring vibration isolator is larger than lateral stiffness of concrete structure, most of free vibration modes of the foundation are movements of concrete structure. Therefore, the equivalent mode damping ratio is close to the one of concrete structure. The dynamic response is overestimated, if the equivalent mode damping ratio is derived from the average of spring vibration isolator and concrete structural ones.

Abstract: Analyze the dynamic characteristics of long tooth height gear transmission system by using transfer-matrix method. Firstly, set up a calculation model of level 2 transmission system for long tooth height gear and master gear and construct the transfer equation and transfer matrix of all components, then calculate the rigidity and rotational inertia of the system and know the natural frequency and dominant mode of the whole system through the computer, at last, analyze and compare two systems and prove the superiority of long tooth height gear for reducing vibration and lowering noise.

Abstract: The rotor under study is a PM rotor of a synchronous machine intended for operation at 60 000 rpm. It is well known that design of high speed permanent magnetic (PM) rotor is quite different from that of a normal PM rotor. The determination of the rotor structure and dimensions must take consideration of the strength, stiffness and the magnetic properties of the PM rotor. Based on the Riccati transfer method, the dynamic model of the rotor-bearing system has been established. Then the supporting stiffness of the magnetic bearing is estimated and the PM rotor’s critical speeds and the corresponding vibration modes have been found. A prototype has been built and some test results proved the correct of the calculation.

Abstract: Vibration and radiated sound of Air Conditioning are harmful to environment and safeness. Air Conditioning Compressor is its major part bringing vibration. To lower noise of a compressor and to improve its sound characteristic, the paper probes into a method indirect measurement of vibration, which both vibration and radiation behavior is represented using acoustic signal and theory of radiation modes. The paper investigates on the basic coupling relationship between structural vibration and acoustic radiation by means of the real modal analysis theory. Besides, the vibration and acoustic radiation characteristics of the rotary compressor are identified through the experiment method. According to the experimental results, between the vibration modes and the acoustic radiation modes have the comparability about the parameters. Therefore, this paper put forward a new method to the Active Structural Acoustic Control (ASAC), and provides the theoretical foundation of indirect measurement of vibration by using acoustic signal.

Abstract: A test bed of closed-end mechanical beveloid gear with intersecting axes is designed to measure various parameters. In order to analyze the reasonableness of the structural design and test the performance of the test bed, a three-dimensional solid simulation model of the test bed is set up first with virtual simulation technology to analyze motion characteristics of test-bed and modal analysis to analyze the vibration characteristics of the key components. Simulation test obtains the vibration mode of the test gear box and drive gear box, providing a useful result for the optimization of the test bed. This solves some problems such as that a common test bed cannot test gear with intersecting axis and must have the same test pair gear, and inaccuracies of measuring transmission efficiency.

Abstract: The uncontrollable factors such as construction errors, material inhomogeneity, etc. will inevitably lead to a certain initial imperfections. It is generally known that the stochastic initial imperfection of the structure is an important factor for affecting structural stability and bearing capacity. Since these imperfections are random in nature, this paper proposes the method mainly based on the standard orthogonal basis to expand the stochastic field, taking into account the decomposition of the stochastic initial imperfections related to structures, which is projected in the buckling mode orthogonal basis. In the end, the article by the stability analysis example shows that this method can use less random variables effectively describing the original stochastic imperfection field, and efficiently search for the most unfavorable initial imperfection distribution form in order to ensure the imperfection sensitivity structures have a higher reliability, so it can be applied to large-scale engineering structure stochastic imperfection analysis.

Abstract: The transverse vibration of a nanobeam subject to initial axial compressive forces based on nonlocal elasticity theory is investigated. The effects of a small nanoscale parameter at molecular level unavailable in classical mechanics theory are presented and analyzed. Explicit solutions for natural frequency, vibration mode shapes are derived through two different methods: separation of variables and multiple scales. The respective numerical solutions are in close agreement. Validity of the models and approaches presented in the work are verified. Unlike the previous studies for a nonlocal nanostructure, this paper adopts the effective nonlocal bending moment instead of the pure traditional nonlocal bending moment. The analysis yields an infinite-order differential equation of motion which governs the vibrational behaviors. For practical analysis and as examples, an eight-order governing differential equation of motion is solved and the results are discussed. The paper presents a complete nonlocal nanobeam model and the results may be helpful for the application and design of various nano-electro-mechanical devices, e.g. nano-drivers, nano-oscillators, nano-sensors, etc., where a nanobeam acts as a basic element.

Abstract: The deformation of the large steel structure truss system, which was subjected to constant loads, variable loads and wind loads, was calculated by using the 3D3S steel structure analysis program. The periods and the vibration mode from the first to the ninth order of the structure were obtained by the earthquake vibration mode period analysis. The dynamic computation of the structure showed that the period difference of the vibration modes is small. The frequencies and the modes of vibration from the first to the ninth order of the same structure mode were calculated by using the ANSYS finite element program. The frequencies and the modes of vibration from the first to the ninth order of the building were obtained by the dynamic analysis of the structure. The dynamic computation of the structure shows that the frequencies difference of the vibration modes is small. The vibration instability is possible for the structure.