Journal of Vibroengineering
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Optimization and evaluation of three-dimensional high-rise concrete structure equipped by TMD with considering the soil-structure interaction effect
Get PDFDuring the past two decades, countless and valuable studies have been conducted on passive seismic control of structures on two-dimensional shear frame model and a few on three-dimensional shear frames. To simulate the actual behavior of buildings with higher accuracy, it is necessary to use more realistic and more complex models in evaluating the seismic performance and controller design. In this study, two indicators related to the structural damage and efficiency control have been used for the seismic control of the structure considering the soil-structure interaction (SSI) effect. with a detailed and complex three-dimensional finite element model in the OpenSees software, a twenty-story concrete structure is designed by the performance based plastic design (PBPD) method; the optimization process of control system and structure performance under the circumstances taken into account at the design stage have been studied. Seismic performance subjected to three acceleration records of far-field earthquake has been investigated and to consider the effects of SSI, the simplified cone physical model has been used. Results indicate that according to the type of soil for which the structure is designed, Tuned Mass Damper (TMD) cannot be reliably used to reduce lateral displacement of the structure, but TMD shows a proper performance in reducing inter-story drif
Multi-field coupling dynamic response analysis of pipelines with double corrosion defects under seismic loading in cold regions
Get PDFMulti-field coupling system in the paper is composed of the corroded pipelines, fluid, heat preservation layers and frost -heaving soil, and the buried pipelines are inevitable to be affected by earthquakes, but few studies have been done on corroded pipelines in multi-field coupling under seismic loading in cold regions. The paper analyzes the dynamic response of the pipelines under seismic loading. Method by FEM (finite element method), the three-dimensional multi-field coupling mechanics model has been established for analysis, based on a thermal-fluid-solid multi-field coupling analysis theory, considering the actual stress-strain characteristics of the pipeline steel and the frost heaving force of soil. Meanwhile, the influences of fluid pressure, fluid temperature, corrosion defects and seismic waves on the mechanical properties of the pipelines are then discussed. The results show that: the relative corrosion depth, fluid pressure and fluid temperature have obvious influence on the mechanical properties of corroded pipelines; other factors are relatively weak; the properties of corroded pipelines do not change with different seismic loading. For the corroded pipelines in cold regions, the factors which have obvious influence on the mechanical properties of pipelines should be monitored intensely
Effects of axial movements of the ends and aspect ratio of laminated composite beams on their non-dimensional natural frequencies
Get PDFThis study developed to solve the problem of prediction of the natural frequencies of free vibration for laminated beams. The study presented the natural frequencies of composite beams with four layered and different boundary conditions. In each boundary condition, two cases are assumed: movable ends and immovable ends. Numerical results are obtained for the same material to demonstrate the effects of the aspect ratio, fiber orientation, and the beam end-movements on the non-dimensional natural frequencies of beams. Two aspect ratios are given in the numerical results, one is for relatively short-thick beams, while the other is for slender beams. It was found that the results of the non-dimensional frequencies obtained from the short-thick beams are generally much less than those obtained from the other slender beams for same fiber orientation and generally, the frequencies of longitudinal vibration increase as the aspect ratio increased. It was also found the values of the non-dimensional frequencies of the transverse modes are not affected by the longitudinal movements of the ends since these modes are generated by lateral movements only. However, the values of the natural frequencies of longitudinal modes are found to be the same for all beams with movable ends since they are generated by longitudinal movements only
An intelligent fault diagnosis method of rotating machinery based on deep neural networks and time-frequency analysis
Get PDFAs the crucial part of the health management and condition monitoring of mechanical equipment, the fault diagnosis and pattern recognition using vibration signal are essential researching contents. The time-frequency representation method cannot identify the fault patterns from time-frequency representation effectively because of the complex work conditions of rotating machinery parts and the interference of strong background noise. Considering these disadvantages, a new reliable and effective method based on the time-frequency representation and deep convolutional neural networks is presented. In this method, the time-frequency features are calculated by the short time Fourier transform (STFT), and the pseudo-color map as the new identification objects. A novel feature learning method based on the sparse autoencode with linear decode is used to extract these time-frequency features, which is an unsupervised feature learning method with the goal of minimizing the loss function. The convoluting and pooling are applied to establish the hierarchical deep convolutional neural networks and filter the useful features layer by layer from the output of sparse autoencode. And a softmax classifier is used to obtain the faults classification. The experimental datasets from roller bearing and gearbox have been taken to verify the reliability and effectiveness of the proposed method for fault diagnosis and pattern recognition. The results show that the proposed method have excellent performance of the recognized objects
Solar photovoltaic array fed brushless DC motor drive using sensorless technique for reducing vibration with Enhanced DC-DC converter
Get PDFThe proposed research work involves, solar photovoltaic array fed brushless DC motor drive using sensorless technique for reducing vibration with Enhanced DC-DC converter. The purpose of this research is to reduce the vibration in the motor drive and to improve the efficiency of the enhanced converter. The designed model consists of Buck and Boost converter, DC-link unit, state-of-the-art back-EMF sensing methods like terminal voltage, terminal current sensing and also includes third choral voltage amalgamation, back-emf integration and PWM strategies. In addition, reduced number of switches in the proposed research makes the scheme more outlay efficient and the motor speed is synchronized by PI controller. For sensing the vibration during rotation and shock in the brushless DC drive an accelerometer which is an electromechanical device are used, it measures acceleration forces associated to the freefall cause, path of the acceleration is a vector product. The current technique based on evaluation of various parameters are clearly modeled and experimented. A MATLAB platform and a hardware prototype of multioutput buck-boost converter are clearly examined for various effective environment in the proposed research
Stiffness improvement methods and its application on design and optimization of large lens hood for space camera
Get PDFAs an essential part of optical system, lens hoods consisting of shells and plates are designed mainly to protect optical system from unexpected light. Except for such basic function, the hood proposed in this paper has to load several subassemblies and will be applied in high-resolution and wild field-of-view space camera with strict mass limitation, which makes effective mechanical reinforcement and lightweight of hood quite necessary. To meet such requirements, stiffness improvement methods is promoted in this paper to help improve the constraint fundamental frequency and decide the areas where subassemblies can be placed. Subsequently, optimization on key sizes of the hood proceeds to achieve a higher fundamental frequency and a lower weight. Finally, a prototype is fabricated based on the optimal design and a sweep test is held to verify the analytical fundamental frequency. The prototype has large external dimensions (1960×1640×2055 mm) but weighs only 33.5 kg when loading several subassemblies which totally weight 15.95 kg. Sweep test indicates that experimental constraint fundamental frequency is 36.82 Hz. All the parameters coincide with that of theoretical design well. The whole work of this paper provides a worthwhile method to the design of lens hood with large external dimensions and high specific stiffness in space camera. Since the lens hood is a typical plate and shell structure, the method, design and optimization process in this paper may also be helpful to the plate and shell structure in which stiffness and lightweight are highly required
Application of coherence analysis study on identification of vehicle noise sources
Get PDFStructure-Air noise sources in different frequencies were identified based on analysis of frequency and testing of vibration and noise under idling condition, and a method for signal sources priority was developed under identifying the kinds of noise sources. The partial coherence equations of the six input and single output systems were derived based on the theory of coherence. Coefficient of partial coherence of the test data of vibration and noise in vehicle was calculated by using MATLAB. Coherence analysis results show that working engine incentive transferred to the driving cab in low frequency range caused structure noise, engine RH mounting is the main noise source; The noise in middle frequency range is caused by the coupling effects of vibration of engine left mounting and noise of the engine compartment to the driving cab, between which left hanging mount vibration affected more; Engine compartment noise in high frequency leaked through the air to the cab, engine noise is the main source of noise inside
Development of miniature spherical ultrasonic motor using wire stators
Get PDFThe purpose of this study is to develop a miniature motor for directional adjustment of a vascular endoscopic camera. Spherical ultrasonic motor not affected by magnetic fields is used in the miniature motor. The characteristic of spherical ultrasonic motor is that one motor has multi degree of freedom in rotational direction. Wire is used as stator to realize miniaturization of the motor, so it is called miniature spherical ultrasonic motor using wire stators. Firstly, the pressing force between a stator and a spherical rotor is discussed, which is important for developing a miniature spherical ultrasonic motor using wire stators. As a result, it can be clarified that there is an optimum value for the pressing force. Secondly, the starting torque is investigated, which is one characteristic of the miniature spherical ultrasonic motor using wire stators. The relationship between the frequency and amplitude of the applied AC voltage and the starting torque is clarified. Finally, the control method of the rotational direction of a miniature spherical ultrasonic motor using wire stators is discussed. A PWM control method is proposed to control the rotational direction of an ultrasonic motor. In this PWM control, traveling wave and standing wave generated on a wire stator are used. Experimental results show that the proposed method is effective
Vibration mode analysis of multi-degree-of-freedom permanent magnet synchronous motor
Get PDFMulti-degree-of-freedom motors have attracted more and more attentions, and the liquid suspension multi-degree-of-freedom PM motor is regarded as one of the research hotspots of new kind of electrical machine. In order to further optimize the structure of liquid suspension permanent magnet synchronous multi-degree-of-freedom motor and improve the stability of the operation, the mode force analysis of the motor's component is carried out. The characteristics and basic structure of the motor are introduced, and the principle and rules of the motor resonance are expounded in detail. Based on the theory of mechanics, the mode of the motor spherical shell is studied and calculated. By finite element analysis, the modal changes of stator shell under static and energized conditions are calculated and the comparison is made. Then, the 2nd order modal deformation of the spherical shell is monitored by hammering and sensor with the measured data obtained and compared with the finite element simulation. The solid mechanical structure of the claw stator core is analyzed so that the stress distribution and deformation displacement distribution are obtained. The results of the simulation and analysis provide the reference for the optimal design of this kind of motors or actuators
Stability and bifurcation of a flexible rod-fastening rotor bearing system with a transverse open crack
Get PDFThe stability and bifurcation of a flexible rod-fastening rotor bearing system with a transverse open crack in a fastening rod are investigated. The nonlinear dynamic model of a cracked rod-fastening rotor system is established based on the finite element method. A methodology is introduced where shooting method, path-following technique, and Floquet theory are combined for determining the periodic solutions and stability margins of the system. The effects of crack depth and mass eccentricities on the system are studied by numerical simulations. Results show the system stability will reduce due to the presence of crack, two saddlebacks occur on the periodic-doubling borderline whose bottom location corresponds to the two resonant peak of bearing node, and effects of the crack and mass eccentricity play a dominant position in different conditions respectively. Comparisons between the cracked rotor system and the intact ones referred in the literature indicate that some special characteristics of cracked rod-fastening rotor system in motion orbits and frequency components can be used to detect the presence of crack and its depth