Structural Vibration Reduction Research Articles

Dynamic Analysis and Optimization on Passive/Active Vibration Reduction of a Beam Structure with Distributed Smart Foams

A smart foam is a vibration absorption structure integrated with piezoelectric material and shows promise for a highly efficient structural vibration reduction both passively and actively. The arrangement of the smart foams on the primary structure is a key issue in practical engineering. In this work, the vibration reduction performances of distributed smart foams attached to a simply supported beam are investigated, and the distribution scheme is optimized. The dynamic equations of the vibration system are established for passive and active vibration reduction, respectively. The frequency responses are analyzed based on a Newmark-[Formula: see text] method, and the accuracy is verified by a finite element analysis. An optimization method based on the genetic algorithm is proposed for the smart foams’ quantity and locations. The study reveals that, with the same total attached mass (1% of the beam mass), a limited distribution of smart foams achieves a larger vibration reduction ratio than a single smart foam or uniformly distributed smart foams. For the passive reduction mode, the optimal scheme is to arrange four smart foams at the middle of the beam, and a reduction ratio of 38% is achieved. It is related to both the first-order modal shape of the beam and the mass distribution of smart foams. For the active reduction mode, the optimal scheme is to arrange two smart foams separately, and 98% of the vibration is reduced. The optimal location is no longer at the middle of the beam, because the active moment of the piezoelectric beam makes the main contribution, rather than the passive vibration absorption. This research provides an optimization method and instructions for both passive and active vibration reductions of smart foams.

A study on low-frequency vibration mitigation by using the metamaterial-tailored composite concrete-filled steel tube column

The bandgap properties exhibited by local resonant metamaterials provide a potential approach for structural vibration reduction. In this work, we introduce the local resonance mechanism into the composite structure for the first time and propose a novel metamaterial column with 33.8–47.2 Hz low-frequency vibration mitigation based on practical engineering materials and utilizing material shear deformation. By vertically arranging metamaterials, the metamaterial concrete-filled steel tube column with low-frequency vibration reduction bandgap is designed. Its equivalent bandgap model is proposed by combining the Timoshenko beam and Bloch theorem. The bandgap formation mechanism and vibration mitigation effect of the metamaterial are clarified by finite element analysis. It is revealed that the bandgap generation depends on the contrary motion between the resonator and the substrate, thus the reaction force from the relative motion can cancel the external excitation. Then, the bandgap vibration mitigation effect of the metamaterial column is proved by shaking table tests at different amplitudes. This also supplies a feasible solution for vibration mitigation control and even earthquake protection for buildings, bridges, and major infrastructures. Finally, the theoretical, numerical, and experimental results are discussed to verify the validity of the theoretical approach and numerical model, and the rubber damping is found to widen the bandgap but weaken the vibration reduction capacity.

Design and Optical Performance Analysis of Large-Aperture Optical Windows for Structural Vibration Reduction

In order to address the issue of large-aperture optical windows operating in wind tunnel environments with dynamic responses, the damping ratio between the vibration isolation device and the mass of the system was calculated by the passive vibration isolation principle. Two isolation models using circular rubber pads and rectangular rubber pads were proposed, and it was proven that the stiffness value of the circular rubber pad is superior to that of the rectangular rubber pad. A three-dimensional model of the optical window was established using finite element analysis software to simulate the working vibration environment of the optical window. Modal analysis and harmonic response analysis were carried out on the optical system with the isolation device installed, and the nodal data of the optical glass surface changes in the optical window were input into the Zemax 19.4 optical design software in the form of Zernike coefficients to calculate imaging quality evaluation indicators. Through finite element structural analysis of the optical window and evaluation of optical performance indicators, it was demonstrated that under the background of the wind tunnel working environment, the isolation performance of the circular rubber pad in the isolation device of the optical window is superior to that of the rectangular rubber pad. This study can provide a design basis for the isolation analysis methods and isolation measures of optical windows in wind tunnel working environments. These research results have implications for the development of large-aperture optical windows in high-speed wind tunnel applications.

Structural vibration reduction achieved by lightweight porous layers through the near-field damping effect: A technical summary

Properly designed porous materials can provide damping equivalent to conventional viscoelastic dampers by the dissipation of the evanescent wave energy in the vibrating structure's acoustical near-field. At the same time, these materials possess advantages such as light weight and effective sound absorption. Thus, there are potential benefits with respect to cost and weight saving in automotive and aerospace applications by using porous layers as multi-functional noise and vibration control solutions. The intention in this article is to provide a concise summary of the methods and major findings previously presented in an extensive set of publications and conference presentations. In that work, porous media, such as fibers and foams, were designed to serve as treatments for various vibrating structures to examine their damping effectiveness. Both analytical modeling and numerical simulation based on finite element methods were involved depending on the complexity of the structure. Specifically, a Fourier transform-based computational method was introduced as the key step to allow accurate prediction of a panel's spatial response. The analytical model was further developed into an efficient software toolbox, so that parametric studies could be conducted to identify the optimal properties for a porous layer to provide the maximum damping within a target frequency region, based on which near-field damping design concepts are summarized. Key findings include the observation that the addition of bulk elasticity to the solid phase of the porous medium improves damping performance compared to equivalent limp treatments.

Dynamic Response and Parameter Analysis of Electromagnetic Railguns under Time Varying Moving Loads

During the launch process of an electromagnetic railgun, the armature is subjected to the ampere force and moves along the rail with variable acceleration. In this period, the rail is excited by time varying moving loads and generates lateral vibration. For analysis, the rail is simplified as an Euler–Bernoulli beam, and the nonlinear dynamic equation of the beam under time varying moving loads is established. The electromagnetic repulsive force between rails, the contact pressure between the armature and the rail, and the thermal expansion pressure acting on the rail are taken into account. The lateral vibration response of the rail is achieved by using the analytical method combined with numerical integration. The variable motion of the armature during launch is also illustrated. Furthermore, the study of the effects of structure parameters on the vibration amplitude of the rail is performed. The research results can provide a theoretical basis for the structural optimization and vibration reduction of electromagnetic railguns.

Developments in the Use of Hinfinity Control and μ-Analysis for Reducing Vibration in Intelligent Structures

During the past few years, there has been a notable surge of interest in the field of smart structures. An intelligent structure is one that automatically responds to mechanical disturbances by minimizing oscillations after intelligently detecting them. In this study, a smart design that contains integrated actuators and sensors that can dampen oscillations is shown. A finite element analysis is used in conjunction with the application of dynamic loads such as wind force. The dynamic-loading-induced vibration of the intelligent piezoelectric structure is aimed to be mitigated using a μ-controller. The controller’s robustness against uncertainties in the parameters to address vibration-related concerns is showcased. This article offers a thorough depiction of the benefits stemming from μ-analysis and active vibration control in the behavior of intelligent structures. The gradual surmounting of these challenges is attributed to the increasing affordability and enhanced capability of electronic components used for control implementation. The advancement of μ-analysis and robust control for vibration reduction in intelligent structures is amply demonstrated in this study.

Research on identification of the hydraulic and structural vibration sources in a tubular pumping station

The hydraulic and structural vibration sources of pumping station are investigated in current research. Based on a vertical shaft tubular pumping station project in an eastern province of China, a three-dimensional fluid-solid coupling model of the pumping station is established, including the fluid in the flow channel, concrete structure, and hydraulic machinery. Two-way fluid-structure interaction (FSI) method is used to calculate the coupled vibration responses of the pumping station. Based on the FSI simulation results, the hydraulic and structural vibration sources of the pumping station are explored from the frequency perspective based on the Fourier transform theory and the vibration energy transmission perspective based on the time-delayed transfer entropy method. Research results show that the fluid pulsation generated by the rotation of the impeller is the main hydraulic vibration source, and the rotating impeller is the main structural vibration source that causes the vibration of the unit and the concrete structure. This research could provide a scientific basis for structural vibration control, vibration reduction, and isolation design of the pumping station.

Effect of polyurethane addition on the dynamic mechanical properties of cement emulsified asphalt

As widely used in railway construction, cement emulsified asphalt (CA) is mainly composed of cement hydrate and emulsified asphalt, playing a key role in supporting structure and track vibration reduction. This work explored the effect of polyurethane (PU) addition on the dynamic mechanical properties of CA. It showed a nonmonotonic variation of 0 ∼ 20 wt% PU loading to the cement on the dynamic stiffness of CA, while 5% and 10% PU could improve both the dynamic stiffness and damping capacity. As for the fatigue life measured by dynamic mechanical analysis (DMA), it is found that the addition of PU can prolong the fatigue life of CA, and this effect is most prominent when the PU loading is 10 wt%. Microstructures and chemical composition were studied by scanning electron microscope (SEM) and Fourier Transform Infrared Spectrometer (FTIR) to explore the original reason for the enhanced dynamic mechanical properties of CA modified by PU. A core–shell structure composed of anionic PU covered on the surface of cationic emulsified asphalt was found, and this PU induced inorganic–organic transition layer between asphalt and cement may play an important role in the enhancement of dynamic mechanical properties of CA.

Flexnertia: A novel dissipation mechanism for structural vibration reduction through coupling of flexural motion with an inerter

This paper presents a novel Flexnertia metastructure concept to perform vibration suppression through coupling rotational inertia to structural flexural motion. Theoretical analysis and experimental test of the proposed metastructure with emphasis on dissipating structural flexural motion is exhibited, showing vibration control performance. The experimental and numerical results are in good agreement, both confirming that the average overall response of the metastructure is significantly reduced. The attenuation becomes most pronounced in the low-frequency range where structures tend to suffer most due to high response around the regime of the first flexural modes.

Solidification microstructure evolution and its correlations with mechanical properties and damping capacities of Mg-Al-based alloy fabricated using wire and arc additive manufacturing

Magnesium (Mg) alloys, as the lightest metal structural material with good damping capacities, have important application prospects in realizing structural lightweight and vibration reduction. However, their engineering application is greatly limited by poor plastic formability. Wire and arc additive manufacturing (WAAM) provides a potential approach for fabricating large-scale Mg alloy components with high manufacturing flexibility. In this study, the evolution of the solidification microstructure of a WAAM-processed Mg-Al-based alloy was quantitatively analyzed based on the analytical models; then, the correlations between the solidification microstructure and mechanical properties/damping capacities were investigated. The results revealed that the WAAM-processed Mg-Al-based alloy with an equiaxed-grain-dominated microstructure displayed a simultaneous enhancement in mechanical properties and damping capacities compared to those of the cast Mg-Al-based alloy. The good combination of mechanical properties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basal <a> slip, the twinning-induced plasticity (TWIP) effect associated with the profuse {10-12} tensile twinning, and the relatively high dislocation density caused by the thermal stress during the WAAM process.

Design and modeling of a novel triple-magnet magnetic dynamic vibration absorber

A novel Triple-magnet Magnetic Dynamic Vibration Absorber (TMDVA) with Eddy Current Damping (ECD) and Coulomb damping is proposed in this paper. A multi-storey structure is selected as the vibration reduction object. First, the equivalent dynamics model of the TMDVA multi-storey structure vibration reduction system is established. Then the nonlinear magnetic force model is built according to the magnetizing current theory. Next, an ECD accurate calculation model is developed and derived based on Faraday’s law of electromagnetic induction. Because of the model, the ECD coefficient can be designed and adjusted arbitrarily. The full text indicates that adjusting the ECD coefficient properly can not only improve the vibration reduction effect of the TMDVA, but also reduce the sensitivity of the vibration reduction effect to the excitation amplitude as well as enhance the broadband vibration reduction performance and the robustness of the TMDVA. With its simple structure, the TMDVA is easy to be implemented and miniaturized. And the low frequency vibration reduction effect of the TMDVA is better than other existing magnetic dynamic vibration absorbers. Taken together, the TMDVA has potential application value in passive vibration reduction of engineering structures.

Application of vibroacoustic metamaterials for structural vibration reduction in space structures

This contribution presents research activities on vibroacoustic metamaterials (VAMM) based on the resonance effect for application in space structures to reduce structural vibrations. The focus of this work is the development of a design process for conception, numerical simulation, and manufacturing of vibroacoustic metamaterials as well as an experimental demonstration of the vibration reduction effect. The technology of VAMM is applied to representative scaled down launcher and satellite components. The vibration reduction behavior is tailored to each component, dependant on requirements on additional mass, manufacturing considerations and frequency range. A high potential is shown for all demonstrators, giving a bright outlook for further development and implementation of VAMM components for launcher and space components.

A novel residual improved deep learning indirect measurement algorithm (RIDLA) for nonlinear dynamic responses

Accurately measuring points-of-concern in nonlinear structures is of great importance for structural optimization analysis, vibration reduction and isolation design, and structural health assessment. For complicated structures with strong nonlinear characteristics, it can be challenging to directly measure the strain, displacement, and other responses at points-of-concern, so sometimes measurements can only be indirectly deduced using data from measurable points. To address the disadvantages of traditional dynamic response analysis and prediction methods, such as their time-consumption and low accuracy, this study made full use of the ability of deep learning to capture nonlinear features. A novel residual improved deep learning indirection measurement algorithm (RIDLA) for predicting dynamic responses of nonlinear structures is proposed. The long short-term memory (LSTM) neural network with time-series feature prediction feedback was selected as the basic algorithm, and a multi-level residual improving deep learning model was constructed using interactive iterations between measurable point responses and calculated residuals, which effectively acquired the dynamic responses of the point-of-concern with improved accuracy. The performance of the RIDLA method in nonlinear response regression was evaluated using a simulation analysis of a six-degree-of-freedom mass-damping-spring nonlinear system and by using random vibration test data of a satellite structure. The results showed that the proposed RIDLA method can achieve high measurement accuracy and is suitable for indirect measurements of dynamic responses in complex nonlinear systems.

Investigation on Distributed Vibration Damping of Bridge Based on Energy Harvesting Technique and Finite Element Analysis

Based on the vibration control method and energy harvesting principle in the bridge field, this paper proposes a distributed vibration reduction and energy harvesting method for bridges. Firstly, the analytical solutions of the induced electromotive force, output power and magnetic damping generated by a coil in a magnetic field were deduced through an electromagnetic theory analysis. In addition, the structural vibration equation under the magnetic damping was deduced. Then, a new method of joint simulation and modeling analysis of vibration and energy output was proposed. Finally, the structural vibration reduction and energy output power were analyzed and calculated. The main research results are as follows: by calculating the instantaneous power of the energy collection of the designed circuit, the average instantaneous power collected by the design method is 1.093 × 10−9 W; the initial vibration signal of the target node is obtained through analysis, and the vibration signal of the node before and after applying the electromagnetic damping force is transformed. For the energy analysis, the energy of the acceleration curve before and after the node was calculated to be 3.1048 × 108 and 3.1044 × 108, respectively, and the reduction rate of the node vibration energy was 0.01% and 0.02%, respectively. Thus, the feasibility and vibration reduction effect of the designed bridge distributed vibration reduction and energy harvesting method is verified when the electromagnetic damping force is small. This method can provide new ideas for bridge structure vibration reduction and energy harvesting research and is of great significance to the infrastructure construction and utilization of renewable energy.

Computer-Aided Analysis of Small Clear Space Intersection Tunnel and Heavy Load Railway Surrounding Rock Structure Dynamic Response Characteristics Analysis under Intelligent Manufacturing

Among many tunnel construction projects, small clear tunnels have been the focus of urban rail transit construction in recent years. The purpose of this research work is to study the dynamic response characteristics of the surrounding rock structure of a heavy-duty railway with a small clearance crossing tunnel. It is proposed to analyze the dynamic response characteristics of the surrounding rock structure through the frequency response function. The vertical acceleration, tensile force, stress, and internal strength of the pipe section are specifically analyzed. The influence of the pipe joint and the assembly method on the dynamic response is also analyzed. The influencing factors of stability are analyzed from buried depth, clear distance, and surrounding rock grade. Studies have shown that the minimum clear distance of crossing tunnels increases nonlinearly with the increase of tunnel depth and gravity, and decreases nonlinearly with the increase of cohesion, internal friction angle, calculated internal friction angle, and lateral pressure coefficient. When other parameters are the same and when the side pressure coefficient is less than 1, the minimum clear distance is larger than that of the side pressure coefficient when it is equal to 1. When the vibration frequency exceeds 100 Hz, the coherence coefficient is basically close to 1, indicating that the frequency response function response result of this section is the most reliable. It is hoped that it can provide a reference for the dynamic stability analysis of the surrounding rock structure of the heavy-duty railway surrounding rock structure and the surrounding stratum and the research of structural vibration reduction technology for the small clearance crossing tunnel in the future.

Vibration Measurement and Numerical Modeling Analysis of Transformer Windings and Iron Cores Based on Voltage and Current Harmonics

The operating condition and structural state of the converter transformer are closely related to vibration. Abundant harmonics aggravate the vibration of windings and iron cores, resulting in frequent mechanical structural failures, which seriously affect the stable operation of the power system. Traditional research mainly focuses on the vibration of AC transformers without harmonics and there is no in-depth discussion of the vibration mechanism and the numerical calculation model of windings and iron cores under harmonics. In addition, the influence of harmonics, winding connection method and other factors on the vibration characteristics are not clear. Therefore, this paper analyzes the voltage and current harmonic components and contents, establishes a harmonic-vibration numerical model and compares the vibration time-frequency characteristics with or without harmonics and different valve side winding connections through vibration measurement experiments. Finally, a combined simulation analysis reveals the contribution of the windings and core to the tank. The results show that the tank vibration amplitude and dominant frequency will increase under harmonica and the valve side current will affect the dominant frequency. Among these results, when there are harmonics, the amplitude increases by three times, the vibration dominant frequency changes from 100 Hz to 400 Hz and the frequency spectrum widens to 2000 Hz. In particular, the contribution of the winding vibration under the harmonic current will exceed the iron core. The research results reveal the influence of converter transformer harmonics on vibration, which can provide a theoretical basis for numerical calculation of vibration and monitoring of operating conditions and guide the design of structural vibration reduction to reduce mechanical failures caused by vibration.

Study on the Bandgap Characteristics and Vibration-Reduction Mechanism of Symmetric Power-Exponent Prismatic Phononic Crystal Plates

In this paper, a symmetric power-exponent prismatic phononic crystal configuration was proposed for the vibration reduction of thin plate structures, and the mechanism of bandgap generation and the influencing factors of the band gaps were analyzed. The results showed that the proposed symmetric power-exponent prismatic phononic crystal structure has three complete band gaps of bending waves, where the width of the second band gap can go up to 1639 Hz. The band gaps of bending waves of the phononic crystal were verified using a combination of numerical simulations and experimental methods, and subsequently, the bandgap characteristics and energy-focusing effect of the phononic crystals were effectively used to suppress the bending vibration of the thin plate. With the increase in prismoid height of the structure, the width of the first band gap expanded, while the bandwidths of the other two band gaps narrowed down. It was observed that an increase in the power of the power-exponent prismoid would reduce the starting and ending frequencies of the band gaps, whereas an increase in the prismoid edge thickness would weaken the energy-focusing effect and narrow the band gaps gradually. Our research results provide a new technique and a pathway to realize vibration reduction in thin plate structures.

Study on Vibration-Transmission-Path Identification Method for Hydropower Houses Based on CEEMDAN-SVD-TE

The analysis of the vibration-transmission path is one of the keys to the vibration control and safety monitoring of a hydropower house, and the vibration source of the hydropower house is complex, making it more difficult to analyze the vibration-transmission path. In order to accurately identify the transmission path of the vibration in a hydropower house, an identification method for the vibration-transmission path based on CEEMDAN-SVD-TE is presented in this paper. First of all, this paper verifies that the CEEMDAN-SVD-TE method has higher effectiveness and is superior to the single transfer-entropy (TE) algorithm in information-transmission-direction identification; secondly, based on the measured field-vibration data, CEEMDAN-SVD noise-reduction technology is used to adaptively decompose the characteristics according to the signal energy; finally, the transfer-entropy theory and the information-transmission rate are used to determine the vibration-transmission path of the hydropower house. The results show that the main transmission path of the vibration caused by tailwater fluctuation is tailwater pipe (top cover measurement point)→turbine pier (stator foundation measurement point, lower frame foundation measurement point)→generator floor (generator floor measurement point). This research can offer a reference for vibration control and safety monitoring of hydropower houses, and provide a new idea for structural vibration reduction.

Hierarchical model predictive vibration control for high‐rise structures using semi‐active tuned liquid column damper

Vibration control for high-rise structures has become more important as buildings become more lightweight. Tuned liquid column dampers are an established approach for this problem, as they do not consume high amounts of energy while achieving high damping forces. The natural frequency of tuned liquid column dampers (TLCDs) can be changed semi-actively by modifying their column geometry. As shown by previous studies, this approach increases the control performance of the damper and allows a larger application field. However, this modification simultaneously provokes strong nonlinearities, which need to be addressed for controller design. In this contribution a model-based controller for such TLCDs is proposed, which explicitly accounts for the nonlinear dynamics of the coupled system consisting of a multi-storey structure with a semi-active TLCD. To account for various system dynamics of the structure, a hierarchical nonlinear model predictive controller (NMPC) in combination with a multi-start strategy is formulated. In addition, an extrapolation algorithm is developed to determine an approximation of the future trajectory of the structure's induced excitation load. The excitation trajectory is then incorporated in the NMPC framework. For validation, a frequency response analysis and a case study are conducted on a 20-storey benchmark structure, which is equipped with a semi-active TLCD. The study is carried out in simulation, and the results are compared with passive vibration control. With the proposed hierarchical control, a significant improvement is shown in the reduction of structural vibrations over the relevant spectrum of excitation frequencies up to a mean of 50%.

Research on Structural Vibration Reduction Technology of Rotating Machinery Based on Dynamic Vibration Absorption

Rotating machinery such as steam turbines, generators, and fans are generally composed of rotating parts and stator parts. The structural vibration that occurs on the stator parts often seriously affects the safe and stable operation of the equipment. Usually, a part of the structural vibration failure can be solved by dynamic balancing. However, due to the complexity of the system, another part of the structural vibration failure cannot be completely solved by dynamic balancing. For solving structural vibration faults, a vibration reduction technology based on the dynamic vibration absorption is proposed. This method designs a dynamic vibration absorber so that its natural frequency is equal to the excitation force frequency. The vibration of the stator is transferred to the absorber, so as to achieve the purpose of vibration reduction. Then, a rotor system test bench was built, and the vibration absorption device parameters were designed according to the vibration data of the test bench. Through experiments, it is proved that this method has a good vibration reduction effect.