Natural Vibration Characteristics Research Articles

Natural vibration characteristics determination of elastic beam with attachments based on a transfer matrix method

The transfer matrix method for multibody system takes into account the accuracy of the equations of motion and the efficiency of the algorithm. Especially if a system is composed of flexible and rigid components, transfer matrix method for multibody system reduces the dynamics problem to an overall transfer equation which only involves boundary state vectors. The state vectors at the boundary are made up of rotation angles, displacements, shear forces, and bending moments, which are normally half known and half unknown. The proposed transfer matrix method for multibody system of multibody system dynamics to determine the vibration characteristics is easy to formulate, systematic to apply, and simple to code. The purpose of this study is to introduce a modeling and simulation idea of beam with attachments based on transfer matrix method for multibody system. Numerical results for several examples of beam with attachments are presented to demonstrate the validity of this method.

An analytical solution to the vibration characteristics for continuous girder bridge-track coupling system and its application

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

Study on natural vibration characteristics and parametric instability vibration under vertical excitation of an upper-opening box structure

Study on natural vibration characteristics and parametric instability vibration under vertical excitation of an upper-opening box structure

Theoretical and experimental study on vibration modal for simply supported bridge

For the highway bridges with small or medium span, a vehicle will stay on the bridge after the excitation. So the measured values of the vibration characteristics of the bridge are related to the vehiclebridge system. In order to analyse the natural vibration characteristics of simply supported bridge and the loaded frequency of vehicle-bridge system, theoretical analysis was carried out firstly, then the simply supported beam calculation model was built based on finite element method, and the results were compared with the measured values. The finite element model of a mass block-simply supported beam system was built by regarding the vehicles as a concentrated mass block attached. Both the vibration modals of the bridge system and the loaded frequencies of the vehicle-bridge system under diffident vehicle positions were obtained by software analysing. As a result, the variation characteristics of the loaded frequency for this simply supported bridge were extracted and discussed through the comparison of the results from both finite element method and the measured.

Evaluation of bearing capacity of reinforced concrete box ribbed arch bridge based on dynamic load test

Dynamic load test is to measure the natural vibration characteristics of the bridge structure or the forced vibration characteristics under dynamic load, and to evaluate the driving performance, driving safety and comfort of the bridge through dynamic load test. In order to evaluate the stress state and working performance of a reinforced concrete box-ribbed arch bridge, the load test of the bridge is carried out. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. Through the experiment with the key parts of the stress (strain) and displacement load and other important data, through analysis and study, the comprehensive analysis of the phenomenon of calculation and test, a comprehensive performance evaluation structure and function whether meet the design requirements, to provide technical basis for the safety of the bridge operation, and provide the original material for the bridge maintenance and management in the future.

In-situ dynamic loading test of a hybrid continuous arch bridge

In this study, the dynamic behavior of a three-span hybrid continuous arch bridge under vehicle loading is investigated. The natural vibration characteristics of the bridge were analyzed through pulsation test. In the dynamic loading test, the vibrations of the bridge under different truck speeds and different pavement conditions were tested, and time histories of deflection and acceleration of the bridge were measured. Based on the dynamic loading test, the impact coefficient was analyzed. The results indicate that the pavement smoothness had more impacts on the vibration of the bridge than the truck's speed. The vertical damping of the bridge under the excitation of the trucks is larger than the transverse damping. Resonance occurs at the side span of the bridge under a truck at 10 km/h.

Free vibration of sigmoid functionally graded plates using the dynamic stiffness method and the Wittrick-Williams algorithm

In this paper, the free vibration characteristics of Sigmoid Functionally Graded Material (S-FGM) Levy-type plates are investigated by developing the Dynamic Stiffness Method (DSM) through the application of the Wittrick-Williams algorithm, as solution technique. Kirchoff-Love Plate Theory (KLPT) and Hamilton principle are utilised to derive the governing equation of motion and associated natural boundary conditions. Based on two power-law distribution functions, the material properties are gradually varied along the thickness direction. Using the proposed theory, a substantial number of numerical examples showing the natural vibration characteristics of plates made of sigmoid functionally graded material are illustrated to demonstrate the accuracy of the method. Some numerical results are compared with published results and found to be in excellent agreement. An extensive investigation is carried out and the results are examined and discussed in detail. The variations of material properties such as the Young’s modulus ratio and density ratio are seen to affect the natural frequencies of S-FGM plates significantly. The proposed method is not only accurate but also, quite simple and straightforward to compute the natural frequencies and mode shapes of S-FGM plates. The results presented can be used as benchmark solution for further investigation of FGM plates.

A Study on the Natural Vibration Characteristics According to the Change of Confluence Geometry of the Dual Exhaust System

A Study on the Natural Vibration Characteristics According to the Change of Confluence Geometry of the Dual Exhaust System

Analysis and suppression of torsional vibration in electromechanical coupling transmission system of high‐speed train

The high-speed train transmission system is a complex electromechanical coupling system. In this study, the torsional vibration of a train transmission system was studied. The centralised mass model of the mechanical structure of the coupling system was established. The natural vibration characteristics of the mechanical mechanism system were analysed. The results show that the natural vibration frequency of the universal shaft was 4.08 Hz, the natural vibration frequency of the pinion was 7.24 Hz, the natural vibration frequency of the big gear was 35.6 Hz, and the natural vibration frequency of the wheelset was 107.48 Hz. The traction motor model was built, and by considering the electromechanical coupling of the system, a torsional vibration suppression strategy for harmonic components in the motor is proposed. The effectiveness of the suppression strategy was verified by MATLAB/Simulink model simulation.

Modal Analysis of Thrust Coupling Based on ANSYS Workbench

Through nx12.0, a solid model of a thrust coupling is established, which is transformed into a finite element model by using workbench 19.0, and modal analysis is carried out. The sixth order natural frequency and critical speed of the thrust coupling are obtained, and the first six order vibration figures are obtained, which clearly shows the natural vibration characteristics of the structure, and at the same time, it is the vibration analysis and structural optimization of the thrust coupling. The design provides a theoretical basis.

Physical Characteristics of Section Coal and Rock Pillars Under Roof Shock Disturbances From Goaf

The stability of rock strata structure is closely related to its response physical characteristics under external shock disturbance. The roof shock disturbance from goaf is usually one of the important factors of causing coal and rock pillars instability. It is necessary to study the dynamic physical characteristics of coal and rock pillars under roof shock disturbance from goaf. The dynamic structural system model of elastic-plastic finite element was established for the formation of surrounding rock and coal pillars in a deep stope. And the response physical characteristics of coal pillars with different widths were analyzed, under the roof shock disturbance intensity and frequency from goaf. The natural vibration characteristics of the stope model were calculated and the first ten orders natural frequencies were extracted. Calculations indicated that the vertical displacement and the plastic zone occupation ratio of the coal pillar increased with the increase of the shock disturbance intensity, decreased with the increase of the shock disturbance frequency, and decreased with the increase of the coal pillar width. The influence of the vertical deformation and the plastic zone occupation ratio of the coal pillar under shock disturbance frequency was more obvious compared with that of shock disturbance intensity, especially at low frequency. The closer the shock disturbance frequency was to the natural frequency of the model, the larger the plastic zone of coal pillars was, which the bearing capacity of coal pillar decreased significantly. It is significant that more attention should be paied to monitoring the frequency of roof shock disturbance signal when design coal pillars width in the coal mine.

Finite element modal analysis and harmonic response analysis of human arm grasping model

Based on CT scan, the finite element models of human arm were constructed. Modal analysis of the arm was performed, and the natural vibration characteristics were evaluated. The dynamic simulation of the vibration transmission process was carried out when grasping the handle, and the vibration response and transmission characteristics were investigated. Resonance was likely to occur in the ranges of 5–10 Hz and 35–40 Hz, which caused fatigue damage to the arm. Vibrations in the ranges should be avoided having direct contact with the handle. The analysis results were found to be consistent with those of modal analysis.

An inverse decaying frequency modulation EMD method for closely spaced modal parameter identification in high precision with Laplace wavelet correlation filtering

Modal parameter identification is a useful tool to reveal natural vibration characteristics in dynamic design and analysis. Due to the influence of closely spaced modes with close frequencies and large dampings, identification accuracy using traditional Hilbert–Huang transform is always unsatisfactory, since the deadline requirement of neighboring intrinsic mode functions cannot be satisfied when the frequency ratio (high frequency versus low frequency) of two adjacent modes is less than two. Therefore, an inverse decaying frequency modulation empirical mode decomposition method is proposed, in order to separate multiple closely spaced modes in high precision, which not only adjusts the frequency ratio by frequency modulation, but also decreases damping by inverse decaying simultaneously. Next, the modal parameters of each separated single mode are picked up by means of Laplace wavelet correlation filtering. The effectiveness of the proposed method is validated by simulated signals in noise and noise-free conditions, and compared with other methods, showing the advantages of high-precision, closely spaced mode identification. In addition, the proposed method is applied to the assembly tightness identification of bolts in an aero-engine rotor, which achieves successful results.

Modal parameters of a transmission tower considering the coupling effects between the tower and lines

The modal parameters of transmission tower-line systems constitute the basis of their wind and seismic design. However, such structures become complicated spatial systems due to the coupling effects between the towers and lines, making it difficult to evaluate the modal parameters of a transmission tower. To study the tower-line coupling effects on the frequencies and mode shapes of a tower, a stochastic subspace identification (SSI) method for identifying modal parameters is first introduced. Then, a finite element model of a transmission tower-line system is established, and the influences of three transmission line parameters, namely, the total span length, span ratio and height difference angle, on the modal parameters are analyzed. An aeroelastic model of the tower-line system is fabricated, and a percussion experiment is performed. The simulated and experimental results both show that the first-order frequency increases with an increase in the total span length but is only slightly affected by changes in the span ratio and the height difference angle. For the wind and seismic design of transmission towers, to obtain reliable natural vibration characteristics, a complete tower-line system model should be established instead of a single tower model.

The Numerical Calculation and Laboratory Model Validation Analysis of Mechanical Noise Based on Benchmark Submarine Model

The mechanical noise analysis of ship structure based on finite element method has been an important means of mechanical noise assessment in the initial design stage of ships. This article is based on the Benchmark standard submarine model, carrying out the numerical simulation of the Benchmark submarine scale model, and obtaining the first-order and second-order natural vibration characteristics of the model. At the same time, we establish a laboratory test system of the Benchmark submarine scale model, and test the natural vibration characteristics of the model under laboratory conditions. We compare numerical simulations and experimental laboratory test results, optimize the numerical modeling method and find the reliability of the numerical simulation calculation. Based on the above research, modeling a true-scale Benchmark standard submarine model, calculate the natural vibration characteristics of the Benchmark submarine model in the ocean flow field environment. Then calculate the value of mechanical radiation noise under the excitation of mechanical equipment based on the natural vibration characteristics results.

Modal Analysis and Experimental Study of Marine Gear Box

In this paper, the finite element model of marine gearbox is established, using Lanczos method performed the modal analysis of the gearbox system mathematical, the modal frequencies and modal shapes of each order of the box were obtained, and the modal experiment of marine gearbox is carried out. The results show that by comparing the data obtained from the experimental modal analysis with the theoretical calculated values, it is verified that the theoretical analysis values and experimental test values are in better agreement, and the maximum frequency error is 4.04%, the fea model is reliable, thus theoretical model could better reflect the natural vibration characteristics of the box on the marine gear box.

Integration of Wavelet Denoising and HHT Applied to the Analysis of Bridge Dynamic Characteristics

When the dynamic characteristics of a bridge structure are analyzed though Hilbert–Huang transform (HHT), the noise contained in the bridge dynamic monitoring data may seriously affect the performance of the first natural frequency identification. A time-frequency analysis method that integrates wavelet threshold denoising and HHT is proposed to overcome this deficiency. The denoising effect of the experimental analysis on the simulated noisy signals proves the effectiveness of the proposed method. This method is used to perform denoising pre-processing on the dynamic monitoring data of Sutong Bridge, and the denoised results of different methods are compared and analyzed. Then, the best denoising data are selected as the input data of Hilbert spectrum analysis to identify the structural first natural frequency of the bridge. The results indicate that the wavelet-empirical mode decomposition (EMD) method effectively reduces the interference of random noise and eliminates useless intrinsic modal function (IMF) components, and the excellent properties of the signal evaluation index after denoising make the method suitable for processing non-stationary signals with noise. When Hilbert spectrum analysis is applied to the denoised data, the first natural frequency of the bridge structure can be identified clearly and is consistent with the theoretical calculation. The proposed method can effectively determine the natural vibration characteristics of the bridge structure.

Resonant frequencies analysis and vibration control of fluid in three-dimensional (3D) moonpool: Analytical modeling and experimental study

Moonpool widely exists in the fields of offshore oil and gas resources drilling, marine energy development and so on, and also has important applications in special ships and surface ships. The aim of this paper is to present an accurate three-dimensional modeling method and analyze resonant frequencies of fluid in three-dimensional moonpool. Based on the three-dimensional potential flow theory, the governing equations and boundary conditions of the fluid in the three-dimensional moonpool are established. According to the characteristics of the governing equations and boundary conditions of the fluid in the moonpool, the velocity potential of the fluid in the moonpool is expanded into the form of the sum of three-dimensional Fourier series and smooth auxiliary functions. Then, the velocity function is introduced into the governing equations and boundary conditions, so that the complex partial differential equations can be transformed into a set of simple linear equations, and the resonance frequency of the fluid vibration in the moonpool can be obtained by solving the linear equations. In order to verify the validity of the three-dimensional accurate model proposed in this paper, numerical examples and experimental verification are carried out, and then the numerical and experimental results show that the proposed solution has good convergence accuracy and calculation accuracy. On this basis, the effects of the length, width and water depth of the moonpool on the resonant frequencies and modes are discussed, and the natural vibration behavior control of the fluid in the three-dimensional moonpool are analyzed in detail. In this work, the three-dimensional analytical solution is proposed for the first time to study the natural vibration characteristics of the fluid in the three-dimensional moonpool, and its correctness is verified by the model experiment. At the same time, some bright research results are also given, which is of great engineering significance for understanding the resonant frequencies and modes of the fluid in the complex moonpool structure.

Seismic behavior of high-rise modular steel constructions with various module layouts

Owing to their superiority in construction speed and quality, modular steel constructions (MSCs) are extensively used in low-rise buildings in non-seismic regions. Even in areas where the lateral load resistance is not demanding, fully modular steel constructions are not applicable unless additional lateral resistant members are introduced, such as cast-in-situ concrete cores or prefabricated steel frames. The primary focus of this research is to study the seismic behavior of high-rise MSCs with various module layouts, thereby enhancing the flexibility and feasibility of high-rise MSCs in regions of high seismicity. Five three-dimensional (3D) high-rise MSCs with various module layouts, i.e., parallel stacked (Configuration 1), one end staggered (Configuration 2), both ends staggered (Configuration 3), intermediately staggered (Configuration 4), and vertically staggered (Configuration 5), were designed. Seismic analyses were carried out in terms of these five models through response spectrum and elastic-plastic time-history analyses. The natural vibration characteristics of various module layouts show that vibration periods of the first three vibration modes are essentially the same (except Configuration 3), which meets the limit requirement. The first two vibration modes are translational deformation along the X and Z directions, and the third mode is torsional, indicating that MSCs can present excellent integrity with Configurations 1, 2, 4, and 5. Structural deformations show that staggered layouts (Configurations 2–5) can solve the problem of inconsistent bidirectional stiffness in Configuration 1. Through discussing the advantages and disadvantages of different module layouts, this paper provides a preliminary knowledge basis for applications of fully high-rise MSCs in seismic regions.

The vibration characteristic and impact analysis of the tunnel lining detection device based on arc rotating multi-section mechanism

In order to overcome the great interference of many ancillary facilities in the process of tunnel lining detection, a vehicle-borne high-speed railway tunnel lining detection device was designed based on the arc rotation mechanism to improve the detection efficiency and quality. The device could automatically maintain the antenna–lining distance and carry three radar antennas at one time, which detected the tunnel from the side of the catenary frame without stopping. Through the establishment of the mechanism three-dimensional finite element model, the simulation and analysis of natural frequency and vibration characteristics were carried out, and the results were confirmed by the field dynamic test. It is concluded that the dynamic characteristics can meet the technical requirements under the radial and the longitudinal vibration at 5 km h−1, but the detection data quality of the three radar antennas under the radial vibration is quite different. After optimizing the bent arm material to carbon fiber, the dynamic stability of the mechanism is significantly improved through simulation analysis and the detection speed can be increased to 10 km h−1 with a substantial leap.