Vibration Transmission Characteristics Research Articles

Vibration transmission and energy dissipation of roll controlled by particle damping absorber

The vibration of rolling mill in rolling process and its harm to rolling equipment have become an international problem in steel rolling industry. The essence of the vibration behavior of a mechanical structure is the transfer of energy in the system. In this work, for a proposed particle damped absorber (PDA) applied to roll vibration control, the influences of the PDA parameters on the vibration transmission characteristics of the system and the energy consumption characteristics of particle groups are studied from the standpoint of energy mechanism. Considering the nonlinearity of rolling interface and particle impact, a non-smooth four-degree-of-freedom vertical vibration model is established. The vibration displacement and velocity of the system are obtained by the incremental harmonic balance method (IHBM). The influence laws of the stiffness coefficients and damping coefficients in the PDA on the power flow are investigated according to the solutions of the system at different excitation frequencies. The effects of particle parameters on the energy consumption behavior of the particle groups are investigated to reveal the energy dissipation mechanism of PDA by using PFC3D software. The results show that the power flow transfer in Roll-PDA system has the targeting performance. This means that the energy loss share of each mechanism in the PDA can be effectively controlled by adjusting the parameters of the PDA. The energy consumption of the particle group increases in step form, which is more obvious in the case of low frequency vibration. In addition, the effects of particle material, particle size, filling rate and particle mixing on vibration suppression of PDA are investigated by experiments. The experimental results are compared with the simulation results to verify the reliability of the established model and the validity of the theoretical analysis. The findings of this study can provide insight into the selection of parameters for PDAs applied to different excitation frequencies.

Vibration Transmission Analysis in FGM Beams with Periodically Arranged Enhanced Multiple Dynamic Vibration Absorbers

Functionally graded material (FGM) beams are widely used in engineering as moving components. Nevertheless, their generated vibrations usually become annoying. To realize multi-broadband vibration reduction of FGM beams, an enhanced multiple dynamic vibration absorber (EMDVA), which utilizes an amplification mechanism, is proposed in this study. The devices are periodically arranged on the FGM beams. The dispersion and vibration transmission characteristics of the structure are investigated using the energy method and nullspace technique. The accuracy of the model is verified using the finite element method. The effects of parameter on its vibration damping performance are also analyzed. Finally, the relationship between the amplification coefficient and the operating performance of the EMDVA is revealed in terms of both the impedance principle and the energy method. The results show that the amplification mechanism can amplify the stiffness, damping, and mass of the MDVA by a factor of square of the amplification coefficient. Therefore, the proposed EMDVA has a wider damping band and stronger attenuation performance compared to the conventional MDVA. This study provides a simple and easy-to-implement solution for multi-band vibration reduction in FGM beams, which is useful for the engineering application of FGM beams in vibration and noise reduction.

Investigation of the Vibration Transmission Characteristics of the Aero-Engine Casing System by Rotating Force Exciter

This work aims to study the dynamic characteristics of an entire aero-engine casing by experiments using a new type of rotating exciter. New vibration sensor layout rules are proposed according to experimental results and vibration transmission characteristics. The vibration response of the aero-engine casing is carried out, and the vibration response of different casing measuring points is also studied. The finite element model of the engine casing’s structure is established to obtain the natural frequency of the whole aero-engine casing, which agrees well with the experimental measurement. We find that the vibration acceleration transmission value of the radial measuring point of bearing No. 1, but not the fan sensor, is more suitable for detecting the running state of the fan rotor. In addition, the sensor in the intermediate casing can detect the vibration of the high-pressure rotor. Bolt loosening of the flange has little effect on the vibration transmission characteristics of the casing. This work aims to provide experimental data of whole aero-engine vibration characteristics with a new rotating exciter for the vibration test, which can help optimize the location of the vibration transducer for the engine and the assembly technology design for the whole engine structure.

In-situ experiment research on environmental vibration transmission characteristics of air-rail combined airport

The rail transit and civil aviation are the important components of the comprehensive transportation system. The development of the air-rail combined transport is an important effective way for China to become a country with strong transportation network. The transportation intersection form of railway under-passing airport transportation hub gradually becomes popular, thus the environmental vibration due to the under-passing railway cannot be ignored. In this paper, a large-scale integrated transportation hub construction project was taken as an example to analyze the transmission rule of environmental vibration due to the high-speed railway at the speed of 350 km/h under-passing airport in terms of the time domain and frequency domain by means of the on-site in-situ wheel-drop test. The research results show that the vertical vibration response of the ground surface along the normal direction of the railway is greater than those of the other two directions within 40 m from the centerline of the track. A vibration amplification zone appears within 5-40 m. The longitudinal vibration response of the ground surface is greater than those of the other two directions within 40-70 m. The local vibration amplification zones appear within 5-20 m and 30-60 m. The lateral vibration level of the ground surface along the normal direction of the railway increase gradually, but attenuates at the distance of 40 m and 10 m with the maximum attenuation rate of 0.67. The vertical vibration level amplifies at the distance of 60 m. The longitudinal vibration level attenuates at the distance of 20 m with the maximum attenuation rate of 0.3, but amplifies at the distance of 40 m with the maximum amplification rate of 1.8.

A fish-skeleton-like metastructure isolator for low-frequency vibration isolation

Vibration isolation for vibration-isolated objects in low-frequency vibration environment has been widely concerned by researchers. In this paper, we designed a local resonant (LR) fish-skeleton-like metastructure isolator with cantilever beam oscillators for low-frequency vibration isolation. Based on the theories of wave dynamics and structural dynamics, we analytically obtained the bandgap characteristics and transmissibility of the metastructure by using the equivalent mass and stiffness method, and carried out simulations through the finite element method (FEM). This metastructure isolator was fabricated by a 3D printing equipment and the vibration isolation test was carried out. Vibration transmissibility characteristics is obtained through the analytical method, FEM and experiment show that the local resonance near the natural frequency of the oscillators can effectively suppress the vibration transmission. The specific performance shows that the vibration transmissibility is as low as 21 % at the center frequency of the bandgap, while the mass of the isolator is only increased by about 2.3 % compared with the ordinary structure which has no oscillators. With the increasing of the mass of vibration-isolated objects (650 g), the transmissibility can be as low as 4 %. In addition, the contribution of different frame bodies and different oscillators of the isolator on the isolation effect and a way of widening the isolation frequency ranges are clarified. The proposed fish-skeleton-like metastructure in the present work provides a new design approach for vibration isolation in engineering applications.

Effects of installing concrete deck on noise radiation of steel box girders: Mechanisms, modeling, and analysis of influential factors

Steel–concrete composite box girder (SCC BG) is widely used in engineering because it can make full use of the tensile properties of steel and the compressive properties of concrete. However, research on the vibrational transmission and vibroacoustic response of the SCC BG is still relatively rare. In this study, a laboratory hammering test was performed to obtain the dynamic characteristics of a scaled specimen of an SCC BG before and after installing a concrete deck. The experimental results revealed that the vibroacoustic response was greatly reduced after the installation of concrete deck due to a reduction in the transmission of on-deck vibrations to the steel box girder. Following this, we introduce a model to predict the structural vibroacoustic response of the SCC BG based on the hybrid finite element–boundary element–statistical energy analysis method, and verify its accuracy through experiments. The accurately calibrated model is then used to study the characteristics of vibration transmission between plates of the SCC BG. The influences of the thickness of the concrete deck, concrete material, and degree of shear connection on vibroacoustic responses of the SCC BG are also discussed.

Vibration transmission characteristic prediction and structure inverse design of acoustic metamaterial beams based on deep learning

In this paper, an intelligent prediction and design method of acoustic metamaterial beams based on deep learning is presented. A theoretical model of acoustic metamaterial beams is derived by using the spectral element method to calculate the band structure and transmission characteristic of beam-type acoustic metamaterial. A high-degree-of-freedom design space dataset of band structure and transmission characteristics is constructed. In addition, the vibration transmission characteristics of acoustic metamaterial beams are predicted and the on-demand inverse design of acoustic metamaterial beams is realized by constructing a fully connected deep learning neural network model. Furthermore, the forward prediction and reverse design network model is verified by using the autoencoder neural network model. Results show that the predicted value of the autoencoder neural network structure is in good agreement with the target value, which indicates the feasibility of the intelligent design method of acoustic metamaterials based on deep learning. The presented intelligent design method could be potentially utilized in the field of fast and efficient acoustic metamaterial design for low frequency vibration isolation in engineering structures.

Analysis and Experimental Research on Dynamic Characteristics of Horizontal Shaft System of Photoelectric Equipment

In order to study the transmission characteristics of vibration in the shafting of optoelectronic equipment, a horizontal shafting test platform for optoelectronic equipment is designed. Firstly, according to the special structure and load conditions of the three-row ball-column combined turntable bearing used in the horizontal shafting, a quasi-static model of the bearing load was established to solve the load distribution of the bearing and further calculate the bearing stiffness. At the same time, the bearing system was established. The dynamic model of the system is used to calculate the frequency response function of the system under the conditions of radial load and axial load and analyze the vibration transmission characteristics of the shaft system. Based on the finite element method, a finite element calculation model is established, the shafting dynamic model established is used to simplify the bearing, the modal parameters of the equipment are analyzed, and the experimental verification is carried out using the Siemens dynamic test system. The results show that the established model is effective and reliable. It provides a reference for studying the dynamic characteristics of the shaft system of optoelectronic equipment.

Free vibration and sound transmission properties of beetle elytron plate: structural parametric analysis

Honeycomb plate (HP), which is a high-strength and lightweight structure, has good vibration characteristics, while beetle elytron plate (BEP) has better mechanical properties. To promote the engineering application of BEPs, the vibration and sound transmission characteristics of aluminium BEPs were investigated in this paper with HP as the comparison object. This paper investigated the effects of the number of trabeculae, the ratio of length and width, skin thickness, core height and core thickness on the first 4 frequencies using finite element method. The results show that (1) the vibration characteristic of BEP is optimal when the number of trabeculae is 6, and its 3rd and 4th modes show mixed mode, i.e., torsion-bending or bending-torsion mode. (2) The frequencies of BEPs are generally lower than those of HPs. Compared with HPs, the ratio of length and width and core thickness have a smaller influence on the mode shapes of BEPs, and the core height has a smaller influence on BEPs’ frequencies. When the skin thickness is small, increasing the thickness can effectively change the natural frequencies of BEPs and HPs. (3) Considering the common frequencies of four applications (aircrafts, unmanned aerial vehicles, high-speed trains and automobiles) of sandwich plates, the effects of the abovementioned parameters including the ratio of length and width, skin thickness, core height and core thickness are analysed. (4) Combined with the theoretical calculation formula, the effect of the above structural parameters on the sound transmission characteristic is explored using the index of sound transmission loss, and targeted recommendations are given. This paper progresses the application in engineering.

Analysis of the Tribological and Dynamic Performance of the Self-Adapting Water-Lubricated Stern Bearing

According to the design requirements of load equalization and vibration reduction for the stern bearing, a water-lubricated stern bearing with self-adaptation capacity is proposed. The bearing is mainly composed of three parts: the bearing bush, the elastic element, and the damping alloy. The elastic element is used to realize static and dynamic load sharing of the stern bearing, reduce the edge effect of the stern bearing, and make the contact pressure evenly distributed in the axial direction, thereby improving the service life of the bearing and reducing the frictional excitation of the bearing. Damping alloy is used to attenuate the shaft vibration transmission from the bearing to the foundation to optimize the vibration transmission characteristics. The revised lubrication models for such bearings are put forward. By analyzing the vibration characteristics of the stern bearing, the results show that the vibration transmission characteristics of the thruster excited to the bearing node are optimized, and the vibration response at the first-order fixed frequency is significantly reduced. A moderate increase in the support stiffness of the foundation can significantly reduce the vibration response of the bearing.

Assessment and mitigation of railway-induced environmental vibrations over underground comprehensive transportation hub

With the development of railway networks, a new infrastructure integrating the underground comprehensive transportation hub and building complex (UCTH&BC) is constructed in many metropolitan cities. However, there is no relevant research to analyse its railway-induced environmental vibrations and propose an appropriate mitigation measure for such a large structure. To have a comprehensive assessment and satisfying control of the potential environmental vibration problem during the life-cycle of UCTH&BC, a numerical study of a newly-built UCTH&BC was carried out through a time-frequency method based on transfer function theory. The ground and building vibrations were firstly evaluated to have a better understanding of vibration transmission and distribution characteristics. Furthermore, rubber mat floating slab tracks (RMFST) were optimised to propose a suitable mitigation measure. Results show that if adopting ordinary track structures, the ground vibrations in the regions where train-induced vibrations transmit directly through columns exceeded the standard limit seriously by more than 5 dB, while the nearby building vibrations were acceptable. The RMFST with the stiffness of 0.011 N/mm3 was recommended to efficiently reduce vibrations by more than 10 dB, ensuring environmental vibrations in the UCTH&BC satisfy the relevant standard requirement and provide a sufficient safety margin to deal with worse track conditions.

Metamaterial beams with graded two-stage inertial amplification and elastic foundation

In this study, a novel local resonant metamaterial (LRM) beam with elastic foundation is proposed by introducing grounded local resonators based on the two-stage inertial amplification structure with adjustable large inertia. The complex band structure is calculated by using the extended plane wave expansion method, and it is found that bandgaps of the novel LRM beam are lower and wider than that of the existing inertant LRM beam. The formation mechanisms of such bandgaps are revealed, and the effects of structural parameters on bandgap characteristics are discussed. Numerical analysis and experimental measurement of vibration transmission characteristics of finite beam structure verify the accuracy of the theoretical results. Furthermore, three kinds of bandgap widening methods based on the structure tunability of local resonator are proposed by setting graded structural parameters. The regularities of bandgap variation with different parameter spacings are given, and the effectiveness of the method is verified by numerical analysis of the finite graded LRM beam under different boundary conditions. These results are expected to provide certain guidance for low and ultra-low frequency broadband flexural waves and vibration control.

Theoretical analysis of 2D meta-structure with inertia amplification

This study proposed a square-grid structure (SGS) attached with inertial amplification mechanisms (IAMs) to obtain a better vibration isolation effect with low frequency and wide band gaps. According to the different stiffness assumptions of the IAM connecting rods, the proposed meta-structure is defined as two different types, 10° of freedom (DOF) elastic system (E-IAM) and 2-DOF rigid system (R-IAM). The motion equations of the two systems are given based on Newton's motion theorem and Lagrange's theorem, respectively. Dispersion relations and motion modes of the infinite system are discussed to obtain lower and wider band gaps. Vibration transmission characteristics of 20 × 20 meta-structures are also conducted. For the E-IAM system, ultra-low frequency vibration isolation can be achieved when the stiffness ratio of the connecting rod is the same in both vertical and horizontal directions and less than the main spring. The approximate analytical expression of the dispersion curve of the R-IAM system is given. Because the denominator is always greater than 1, it is proved that the cut-off frequency of the R-IAM system is always lower than that of the SGS. For finite R-IAM structures, when the longitudinal stiffness is asymmetric in both directions, multiple local resonant band gaps can be obtained in the passband, which is very beneficial to vibration reduction.

A novel rail corrugation suppressor using synergistic mechanism of vibration absorption and damping

Rail corrugation increases the intensity of interaction between the wheel and the rail, make the vehicle and track vibrate more strongly, and increase the rolling noise. Based on the fixed corrugation wavelength mechanism, this paper determines the required corrugation wavelength to be controlled using field investigations. A new type of corrugation suppressor is developed that combines a dynamic vibration absorber and a labyrinth damper. The purpose of the suppressor is to realize wide-band vibration resistance and energy consumption, and to control the vibrations in a specific frequency band. By analyzing the vibration transmission characteristics of a typical small-radius curved subway track, it is verified that the device can flatten the rail dynamic response function, suppress the pinned-pinned resonance of rail, and increase the transmission attenuation rate of rail vibrations. A coupled rigid-flexible model of vehicle and curved track is established. The rail vibration and corrugation growth rate before and after installing the suppressor are compared. The suppressor can reduce the 1000 Hz vibrations by 10.1 dB and decrease the medium and high frequency vibrations of the rail by 5.6 dB. At the same time, it can attenuate the rail corrugation growth rate near 500 Hz and between 700-1000 Hz. A field tracking test showed that the suppressor can effectively inhibit the initiation of 15-30 mm wavelength corrugation.

Test analysis and numerical simulation of noise from forage crushers

To identify the exact noise source and accurately predict the coupled noise from forage crushers, the multipoint synchronous measurement method based on sensor arrays is used, and the collected data are analyzed using auto-spectrum and wavelet analysis. The vibration transmission characteristics of the unbalanced rotor, the airflow–material coupling flow field, and the shell are calculated and analyzed based on the analysis results. The acoustic-solid coupling method is then used to numerically predict the coupled noise of the forage crusher's air noise and mechanical noise. The primary source of noise in forage crushers is aerodynamic noise. Mechanical noise from unbalanced rotor excitation, as well as material and mechanical structure collisions, play important roles in coupled noise distribution. The noise energy around the excitation fundamental frequency generated by the rotor hammer disturbing the airflow accounts for 58.32% of the total energy, the noise energy around the third harmonic frequency accounts for 9.15%, the noise energy caused by the unbalanced rotor excitation accounts for 7.05%, and the noise energy around the second harmonic frequency accounts for 4.34%. The overall change trends of the simulated sound pressure levels (SPLs) are similar to those of the measured values, and the maximum SPLs of the measured and simulated results appear at the same location near the inlet. The total SPLs of the measured values are slightly higher than those of the simulated values, and the maximum difference is 1.6 dB(A). The numerical prediction method for the coupled noise of forage crushers is feasible, and the prediction results are credible. This study provides the basis for the low-noise design of forage crushers.

Analysis of the similarity design and vibration transmission characteristics of typical support structures of an aero-engine

In the vibration test of an entire aero-engine, the magnitude and phase of the unbalanced vector of the internal rotor must be identified based on the vibration signal of the measuring point on the casing. Therefore, in addition to understanding the vibration transmission law between the high- and low-pressure rotors under unbalanced excitation, the vibration transmission law of the support structure must be studied urgently. However, few studies have investigated the vibration transfer characteristics of typical support structures. In this study, the similarity design of typical support structures was first performed, and the structural parameters of the core member squirrel cage were determined using theoretical calculations. Subsequently, the bush and spring elements were used to establish the connection between the inner and outer rings of the bearing to realise the equivalent simulation of the bearing stiffness. Using this method, refined finite element models of elastic and rigid support structures were established, and the accuracy of the model was verified based on low-speed rotating vibration and hammering tests. Furthermore, the unbalanced vibration transmission law of typical support structures was studied, and the vertical vibration transmission law from an aero-engine bearing pedestal to the panel was established with the vibration transmission rate as the quantitative index. Finally, considering the vital role of the squirrel cage, the influence of the local stiffness degradation of the squirrel cage on the unbalanced vibration transmission of the elastic support structure was studied. The research methods and results of this study can provide a basis for aero-engine assembly as well as manufacturing and structural performance evaluation.

Enhanced suppression of vibrational wave transmission in structures with periodically attached absorbers exploiting amplitude magnification mechanisms

Large-span spatial structures can exhibit excessive vibrations caused by dynamic loads. Different types of vibration suppression devices have been proposed and there has been much research on the optimization and improvement of traditional dynamic vibration absorbers. Nevertheless, it is still of great significance to develop ways of comprehensively improving the working capacity of vibration suppression devices. This article proposes a design idea where an amplitude magnification mechanism is used to enhance significantly the working capacity of the vibration suppression device. The proposed amplification of the amplitude can not only strengthen the inertia of the vibration suppression device, but also simultaneously enhance its damping and stiffness characteristics. In-depth analysis is carried out, revealing the relationship between the amplitude magnification factor and the working capacity of the vibration suppression device, and providing important design guidelines of the vibration suppression device. From the perspective of controlling the propagation characteristics of bending vibration waves in structures, a beam attached with the proposed periodically arranged vibration suppression devices with amplitude magnification effect is taken as an example. The energy band structure and vibration transmission characteristics are investigated using the energy method, and the reliability of the proposed model is verified from the energy band structure perspective through the finite element method. The results reveal that the working capacity of the vibration suppression device is increased by α2 times when the amplitude is amplified by α times. Consequently, the attenuation ability of the vibration wave in the bandgap is significantly enhanced. On this basis, the principles of anti-resonance and dynamic vibration absorption are combined to design a new type of vibration suppression device with an amplitude magnification effect, achieving ultra-wideband vibration reduction.

Comparative Research on Vibration Characteristics of Cast-In-Place Steel-Spring-Floating Slab Track under Different Subway Line Conditions

Purpose: Steel-spring-floating slab tracks are widely used in subway lines. It is necessary to analyze and study the vibration damping and transmission characteristics of the steel-spring-floating slab track in various frequency bands under the action of train loads. Method: A steel-spring-floating slab track and ordinary monolithic track tunnel sites with similar line conditions on straight and curved segments were selected. The vibration signals of rail, track bed, and tunnel walls were collected and the analysis results of vibration damping and vibration transmission between the steel-spring-floating slab track and the ordinary monolithic track were compared. Results: The dynamic responses of the rail in the four working conditions are relatively close, and the acceleration of the steel-spring-floating slab track bed is significantly larger than that of the ordinary monolithic track. The vibration response generated in the curved segment is significantly greater, and each frequency band will generate more peak points, and the high-frequency vibration will be more severe. Conclusions: The steel-spring-floating slab track can significantly reduce the acceleration response of the tunnel wall; the bottom constraint of the steel-spring-floating slab track is less, and the vibration response of the track bed is more severe.

Research on the vibration transmission characteristics of quasi-periodic impedance layered structure constructed by magnetorheological fluid

In this work, the theoretical and experimental study on vibration transmission in quasi-periodic impedance layered structures built by magnetorheological (MR) fluid is conducted. Based on the MR effect of MR fluid, the quasi-periodic layered structures formed by low and high impedance layers following Fibonacci, Thue–Morse and multiperiodic sequences are constructed, respectively. These different quasi-periodic patterns can be flexibly obtained by controlling the arrangement style and magnetic field strength of electromagnets outside the MR fluid. The vibration transfer model is established based on the transfer matrix method and the trends of vibration level difference with different parameters are analyzed. Furthermore, experiments are performed to estimate the vibration transmissivity of the proposed structures. It indicates that the developed quasi-periodic impedance layered structures can exhibit greater damping effect on vibrations by appropriately increasing the magnetic field strength and thickness ratio of low to high impedance layers. Moreover, there exist quasi-periodic impedance patterns whose attenuation effect on vibration is better than that of periodic pattern in the frequency range studied in this paper (20–200 Hz). This means that the introducing of the particular quasi-periodicity increases the transmission loss of vibrations in a certain frequency range. This investigation is conducive to further expand the application of MR materials and quasi-periodic structures in the field of vibration control.

Effects of the duct on the vibro-acoustic characteristics of the pump-jet–shaft–submarine system under pump-jet excitation

The characteristics of the distributed pressure on duct induced by rotor and its effects on the vibro-acoustic response of the coupled pump-jet – shaft – submarine system are investigated. Firstly, the pulsating pressure on the duct and the rotor of the pump-jet is computed by numerical approaches of computational fluid dynamics (CFD). Then, the pulsating pressures on CFD mesh are mapped to structural mesh based upon radical basis function to apply them on the pump-jet to calculate the vibro-acoustic responses of the coupled pump-jet – shaft – submarine system by coupled finite element method (FEM) and direct boundary element method (BEM). Finally, the effects of the duct (including the distributed pressure on it as well as the vibration transmission characteristics) on sound radiation are investigated. The results show that the distributed pressure on the inner surface of the duct near rotor disk is a kind of traveling wave pressure, which is tonal at blade passing frequency and its harmonics. The main contribution of the unsteady distributed pressure on the duct to the underwater sound radiation mainly reflects at blade passing frequency (BPF), as well as the duct modes and the hull bending modes that exhibit large deformation at the locations for the stator blades attached to.