Journal of Vibroengineering
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Inherent characteristic analysis of a precast concrete vibrating table based on the Rayleigh-Ritz method
Full text linkTo assess a precast concrete vibrating table, a system mechanics model was established by using the transverse vibration theory of thin plates. The model was then simplified as a stiffened plate structure according to the structural characteristics of a vibration platen. Specifically, the vibration mode functions of the vibration platen were established by utilizing a two-dimensional beam function method in which the maximum kinetic energy and maximum strain energy of the vibration platen were derived. Additionally, the Rayleigh-Ritz method based on the displacement variation principle was utilized to analyze the natural frequency and mode shapes of the vibration platen. A comparison between the theoretical calculation results and the finite element simulation results indicated that the established vibration mode functions can appropriately reflect the mechanical behavior of the vibration platen, which verified the correctness of the analysis method for the inherent characteristic of the vibration platen and provided a preliminarily theoretical basis for the performance improvement of a precast concrete vibrating table
Numerical analysis of the damage mechanics variable and vibration of a viscothermoelastic microbeam with variable thermal conductivity
Full text linkIn the present paper, the analysis for thermoelastic homogeneous isotropic microbeams has been constructed. A generalized viscothermoelasticity theory of one relaxation time with variable thermal conductivity in the context of damage mechanics definition has been applied based on simply supported conditions for aspect ratios. Laplace transform has been applied for the governing differential equations, and its inverse has been carried out by using the Tzou method. Microbeam of silicon nitride has been considered when it is subjected to ramp-type heating and simply supported. The results have been illustrated in figures to stand on the impacts of the viscothermoelastic parameter, the thermal conductivity parameter, the value of the beam thickness, and the ramp-type heating parameter. The influences of the mentioned parameters are significant on all the studied functions, and the ramp-type heating parameter plays a vital role in thermodynamically damping of the energy which has been generated on the beam
Thermoelastic vibration analysis of disc brake based on multi-physical field coupling method
Full text linkThermoelastic vibration is the main cause of brake jitter and noise, including significant fluctuations in temperature, thermal stress, structure size and braking moment. In order to improve the reliability of thermoelastic vibration results, a multi-physical field coupling modeling method is proposed in this paper, which can realize the simultaneous calculation of temperature field, stress field and air flow field. Firstly, the theoretical analysis of the whole braking coupling process and feasibility analysis is carried out. Secondly, ABAQUS solid model and FLUENT fluid model are established respectively, and MPCCI is used to share the parameters of the two models, including temperature, node displacement and heat transfer coefficient. Finally, different paths are constructed to study the fluctuation of thermoelastic parameters in different directions. The research conclusion of thermoelastic vibration can provide important basis for optimization of brake NVH (Noise Vibration and Harshness)
Effect Analysis of dynamic water pressure on dynamic response of offshore wind turbine tower
Full text linkCompared with onshore wind turbine, the offshore wind turbine is more easily destroyed influenced by the complicated conditions at sea. In this study, a refined finite element model of offshore wind turbine in consideration of the soil-structure interaction is built. The dynamic response of the wind turbine tower in different water depths is investigated; then the weak positions of the wind turbine tower under earthquake is determined. We found that the water pressure on one side of the inflow face of pile foundation is the greatest; as the rate of flow increases, the negative water pressure on the contact surface increased more than the positive water pressure. The maximum displacement of the structure influenced by dynamic water pressure is located at the tower top, the maximum equivalent stress strain is located at two-thirds of the tower height, and the maximum bending moment appears at the bottom of the tower. When the water depth increases from 0 m to 5 m, the displacement and bending moment of wind tower structure increased by 29 % and 25 % respectively under the influence of dynamic water pressure; thus the influence of dynamic water pressure on the dynamic response of the structure should be paid attention to. Finally, the shaking table test of the wind turbine is conducted; the test results are compared with the numerical simulation results, and feasibility of the numerical simulation method was verified
Stability analysis of floating raft system under multiexcitation condition
Full text linkA floating raft system is subjected to multiple excitation sources with multiple frequencies for each excitation source. Considering the two characteristics of excitation source, the stability of floating raft system was analyzed. A vibration equation for the floating raft system under multiexcitation condition was established. A multiscale method was then used to solve the equation. The amplitude–frequency response equation and unstable region of solution are discussed. The results show that the vibration of raft frame fits the pattern of soft-spring vibration. This indicates that the excitation of main raft unit with a rigid connection compromises the stability of the system, whereas the excitation of unit with elastic connection increases stability
A noise-resistant Wigner-Vile spectrum analysis method based on cyclostationarity and its application in fault diagnosis of rotating
Full text linkRolling element bearing and gear are the most common used rotating parts in rotating machinery and they are also the fragile mechanical part. Studying the effective method of timely diagnosis of them is very necessary. The Wigner-Vile spectrum (WVS) is an effective time-frequency analysis and common used method for diagnosis of rotating machinery. However, it would not work effectively when the impulsion characteristic fault signal of rotating machinery is buried by strong background noise. To solve the above problem, the property of cyclostationarity of the rotating machinery signal is used, and the cyclic spectral density basing on second order cyclostationarity statistic is combined with the WVS, and the cyclic spectral density Wigner Vile spectrum (CSDWVS) time-frequency method is proposed in the paper. Through the analysis results of simulation and experiment, the CSDWVS method has the advantages of much more noise-resistant than traditional WVS method, and it could extract the fault feature of the vibration signal of rotating machinery buried in strong background noise. Besides, it also has better time frequency aggregation effect
Stress analysis of rotating functionally graded polar orthotropic disk under thermomechanical loading
Full text linkIn this paper, thermo-elastic stress analysis of rotating variable thickness annular disk made of polar orthotropic functionally graded material (FGM) is presented. Elasticity modulus, density and thick-ness of the disk are assumed to vary radially according to a power law function. The material of the disk is assumed to be temperature dependent and different temperature distributions are assumed for variation of the temperature in radial direction. Radial stress and radial deformation of the disk with Clamped- Free (C-F) and Free-Free (F-F) boundary conditions are obtained using the numerical finite difference (FD) method. It is concluded that, by increasing the temperature variation, the radial stress and displacement increase. It is also observed that the radial stress in the rotating FG disk is more than the radial stress in rotating homogeneous disk and by increasing the FG index, the location of maximum stress in the disk shifts toward the outer surface. Also, the effects of temperature variation along the radius and orthotropy of the material on the radial stress and deformation are evaluated and concluded that their effect are significant. The results are compared with the available results in the literature and the good agreement between the present results and results in the literature shows the accuracy of FD method in thermo-elastic analysis of rotating FG orthotropic disk of variable thickness
Numerical analysis of the flow mechanism and axial force characteristics of the cavity in a centrifugal pump with a front inducer
Full text linkAt three flow conditions (0.8Qd, 1.0Qd, and 1.2Qd), the centrifugal pump cavity with front inducer was expanded at 0°, 90°, 180°, and 270°, and a flow path analysis of the axial cross section at the four angles was performed. This revealed that the circumferential and radial velocities of the liquid in the pump cavity along the same angle at different radii follow an axial and radial variation law to different degrees. The pump cavity center axial liquid velocity component along the radial distribution at different angles was analyzed, and liquid pressure in the pump cavity along the radial distribution was numerically analyzed from different points of view. The mean pump cavity pressure was plotted along the radial distribution curve, and a detailed numerical calculation of the axial force of the centrifugal pump and pump cavity was developed. The influence of flow conditions on the liquid flow mechanism and axial force characteristics in the pump cavity was thoroughly discussed. The results showed that liquid flow in the centrifugal pump cavity with the front inducer is mainly restricted by the main flow of the volute. The liquid eddy current in the pump cavity is mainly concentrated near the volute and the hub at 90° and 180° angles, and the higher the flow rate, the larger is the area of the side vortex of the impeller-cover plate, and the smaller is the area of the side vortex of the pump-cover plate. When the flow rate increases, the flow direction of the eddy current at the same angle in the pump cavity remains unchanged, but when the flow rate becomes too high, the flow direction of the eddy current at the same angle in the pump cavity changes. When the range of circumferential and radial partial velocities decreases, the rotational angular velocity increases, and the pressure decreases. At low flow rate, the larger the area of the volute corresponding to the pump cavity, the higher the speed becomes. The axial force in the pump cavity is the most important factor determining the axial force of the centrifugal pump
Partial field decomposition using particle velocity references
Full text linkIn existing partial field decomposition methods, the pressures are generally used as references. This paper is going to use the particle velocities as the references to decompose the sound field radiated by incoherent or partially coherent sources into mutually incoherent partial fields, and evaluate its performance by comparing with the method using pressure references. Both numerical simulations and experiment confirm the effectiveness of the method using particle velocity references for partial field decomposition and demonstrate its superiority over the method using pressure references, and it is also shown through numerical simulations that the particle velocity references almost always perform better than the pressure references as long as the references are located close to the sources and the directions of particle velocity references are perpendicular to the source plane as far as possible
Effect of Coriolis force on vibration localization characteristics of mistuned bladed disk
Full text linkIgnoring the effect of centrifugal force and Coriolis force can increase the vibration localization degree of bladed disk system. In order to address the problem of vibration localization of the mistuned bladed disk of an aeroengine, the finite element reduced order models of bladed disk was established by the component mode synthesis method. The mistuning of the blades were simulated using different mistuned modes. By analyzing the mistuned vibration localization characteristics, it was discussed whether to consider the effect of the centrifugal force and Coriolis force on the vibration localization characteristics on the bladed disk. The effect of the Coriolis force on the vibration localization of the mistuned bladed disk under different engine order of excitation was discussed. The results shows that the centrifugal force and Coriolis force strongly influences the vibration characteristics of both the tuned disk and mistuned bladed disk, in the analysis of the vibration localization characteristics of the mistuned bladed disk, the role of the Coriolis force cannot be ignored