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In order to investigate the effect of passenger load on the vibration of rail vehicles, a modal experiment was conducted on a certain type of high-speed train under empty-load, rice counterweight, and passenger-carrying conditions. The influence of different load configurations on the modal vibration of the vehicle was examined and analyzed using multi-point excitation and sine sweep frequency methods. The differences between the impact of passenger and rice loads on vehicle vibration were elucidated. Subsequently, the human–vehicle coupling mathematical model was modified based on the experimental results, and the differences in the effect of different loads on vehicle vibrations were simulated and analyzed. Finally, the attenuation mechanism of passenger loads on vehicle vibration was analyzed. The research has established that the modal parameters of the vehicle are greatly influenced by different loads. Numerical calculations demonstrate that the vertical bending mode of the car body in the middle experiences a maximum vibration attenuation of 60% when carrying passengers compared to the same mass of mass loaded. The natural frequencies and damping ratio of passengers can significantly affect the vertical bending mode vibration. The findings of this research can serve as a theoretical foundation and technical assistance for implementing vehicle vibration reduction techniques. [ABSTRACT FROM AUTHOR]

In this study the optimum topology distribution of the magnetorheological elastomer (MRE) layer in an adaptive sandwich plate is investigated. The adaptive sandwich plate consists of an MR elastomer layer embedded between two thin elastic plates. A finite element model has been first formulated to derive the governing equations of motion. A design optimization methodology incorporating the developed finite element model has been subsequently developed to identify the optimum topology treatment of the MR layer to enhance the vibration control in wide-band frequency range. For this purpose, the dynamic compliance and density of each element are defined as the objective function and design variables in the optimization problem, respectively. The method of the solid isotropic material with penalization (SIMP), is extended for material properties interpolation leading to a new MRE-based penalization (MREP) model. Method of moving asymptotes (MMA) has been subsequently utilized to solve the optimization problem. The developed finite element model and design optimization method are first validated using benchmark problems. The proposed design optimization methodology is then effectively utilized to investigate the optimal topologies of the magnetorheological elastomer (MRE) core layer in MRE-based sandwich plates under various boundary and loading conditions. Results show the effectiveness of the proposed design optimization methodology for topology optimization of MRE-based sandwich panels to mitigate the vibration in wide range of frequencies. [ABSTRACT FROM AUTHOR]

This study investigates the design and optimization of a 3D periodic structure to minimize vibrations in helicopter rotor blade systems. The research focuses on nonlinear models for rotating beams using a hybrid formulation of finite element methods and variational asymptotic beam sectional analysis. The periodic structure attenuates vibration transmitted from the blades to the rotor shaft. Dimension optimization was performed using particle swarm and gradient search algorithms, showing a minimal average difference of 2.37 %. Performance simulations at 190 rpm revealed that a 5.4 % reduction in reaction forces in the X and Y directions and a 3.2 % reduction in Z direction forces of main rotor shaft occur in comparison with conventional damper system. As a result of the study, it was concluded that 3D periodic structures can form a suitable passive damping system and mass reduction solution for helicopter blades. [ABSTRACT FROM AUTHOR]

Planetary gearboxes play a crucial role in altering rotary speed and transmitting power in large machines like wind turbines and sophisticated vehicles. There are many nonlinear interfaces, such as splines, bearings, and gear pairs, in planetary gearboxes, and the resulting vibration signal transmission and attenuation mechanisms are still unknown. In this study, a novel method for quantitatively analyzing the transmission and attenuation of vibration signals is proposed. A multibody dynamic model of the planetary gearbox considering nonlinear gear meshing is presented and experimentally validated. To avoid the interference of foundation vibration on the transmission of the fault signal, the fault impact factor (FIF) is used to describe the intensity of the failure, which aligns well with the experimental signals. Based on the FIF, the vibration signal attenuation of nonlinear interfaces such as splines, bearings, and gear meshing interfaces is quantitatively evaluated. To clarify the transfer paths of fault vibration signals inside the gearbox, the transfer path area method (TPAM) based on FIF is proposed. According to the simulated results, the primary transfer paths of fault vibration signals within the gearbox have been identified, which is of great help in understanding the transmission and attenuation of vibration signals in planetary gearboxes. [ABSTRACT FROM AUTHOR]

The focus of this research is on designing a longitudinally excited lightweight metastructure that consists of external units distributed periodically, each enhanced with internal oscillators to serve as vibration absorbers. The metastructure initially exhibits uniformity, with all absorbers being identical to each other, being comprised of a cantilever that is integrated into the external parts of the metastructure, with each cantilever containing a concentrated mass block at its tip. Despite its simplicity and suitability for 3D printing, the design of the absorbers could not be kept in the original form when previous theoretical attempts were made with a view to achieving maximal vibration attenuation efficiency around the second resonance. To overcome this shortcoming and keep the absorbers in the original shape, this study undertakes a machine learning methodology to mitigate vibrations near the second resonant frequencies itself, as well as around the first and second resonant frequencies simultaneously. The newly designed metastructure is manufactured, and its advantageous vibration mitigation capabilities are experimentally verified qualitatively. Additionally, physical insight into the configuration and arrangement of the redesigned absorbers in the newly designed metastructure is provided. [ABSTRACT FROM AUTHOR]

Abstract The acoustic black hole (ABH) structure exhibits remarkable energy focalization above a given cut-on frequency, offering potential for broadband vibration suppression in structures. However, its energy focusing properties diminish significantly below this cut-on frequency. Therefore, it is crucial to enhance the vibration attenuation capabilities of ABH structures within the low frequency range. This study presents a numerical investigation into the impact of thin-walled structures with embedded ABHs and distributed dynamic vibration absorbers (DVAs) on low frequency broadband vibration reduction. Initially, the focusing characteristics of the ABH thin-walled structure is analyzed, aiding in the attached position of DVAs. Furthermore, the influence of the design parameters and attached position of DVA on the broadband damping effect of the structure is explored. The findings indicate that DVAs designed for low frequencies can achieve significant vibration attenuation across the entire frequency spectrum, including low frequencies, when installed at specific focusing positions. When compared to the position with the maximum vibration response, while the attenuation of the low frequency common amplitude value is slightly reduced, greater vibration attenuation across the entire frequency band is achieved. This research offers valuable insights into optimizing the integration of DVAs with ABHs in thin-walled structures for enhanced broadband vibration attenuation.

In this work, a semi-active quasi-zero-stiffness (QZS) vibration isolation system with controllable lateral springs was proposed and its practical vibration isolation effectiveness was demonstrated through theoretical and experimental studies. A semi-active control strategy was developed to allow for the regulation of the lateral spring length to address the large resonant responses in the low-frequency range of the QZS system, while maintaining QZS benefits of increasing the control bandwidth with sufficiently low transmissibility and satisfactory static stiffness. The effect of the length of the lateral springs on the negative stiffness of the system under static conditions was investigated, and the stability of the system was analyzed to ensure the system's stability during its operation. Moreover, by employing the semi-active control strategy with the resonance-detuning approach, the dynamic characteristics of the QZS system could be altered from linear to nonlinear through the highly-responsive adjustment of the lateral spring stiffness. As a result, the excitation of low-frequency resonance could be avoided while simultaneously obtaining an increase of control bandwidth with low transmissibility. Specifically, experimental results showed that the developed QZS vibration isolation system could achieve a reduction of transmissibility peaks by 9.68 dB and 15.59 dB, compared to the linear isolation system and the QZS vibration isolation system without control, respectively. The QZS vibration isolation system also achieved an overall reduction in vibration transmissibility with its low-frequency 0-dB bandwidth reduced by 11.8% (from 3.64 to 3.21 Hz) when compared to the linear system, demonstrating an improved vibration isolation effectiveness. [ABSTRACT FROM AUTHOR]

The acoustic black hole (ABH) structure exhibits remarkable energy focalization above a given cut-on frequency, offering potential for broadband vibration suppression in structures. However, its energy focusing properties diminish significantly below this cut-on frequency. Therefore, it is crucial to enhance the vibration attenuation capabilities of ABH structures within the low frequency range. This study presents a numerical investigation into the impact of thin-walled structures with embedded ABHs and distributed dynamic vibration absorbers (DVAs) on low frequency broadband vibration reduction. Initially, the focusing characteristics of the ABH thin-walled structure is analyzed, aiding in the attached position of DVAs. Furthermore, the influence of the design parameters and attached position of DVA on the broadband damping effect of the structure is explored. The findings indicate that DVAs designed for low frequencies can achieve significant vibration attenuation across the entire frequency spectrum, including low frequencies, when installed at specific focusing positions. When compared to the position with the maximum vibration response, while the attenuation of the low frequency common amplitude value is slightly reduced, greater vibration attenuation across the entire frequency band is achieved. This research offers valuable insights into optimizing the integration of DVAs with ABHs in thin-walled structures for enhanced broadband vibration attenuation. [ABSTRACT FROM AUTHOR]

In the process of the on–board transportation of liquid hydrogen storage and transportation tanks, apart from considering the support strength and adiabatic performance, it is imperative to take into account the vibration characteristics of the carrying platform. The present work introduces a versatile support structure comprising a damping module and a ball contact insulation structure, enabling effective isolation of external vibrations while simultaneously providing support and insulation. The first step involves describing the principle of a flexible support structure and designing the mechanical structure. Subsequently, a damping analysis is conducted based on dynamic theory to establish the relationship between the spring and damping. Finally, the structural parameters of the dual–function strut are determined, followed by simulation of heat transfer performance. The results demonstrate that the dual–function strut exhibits exceptional vibration damping performance by reducing the amplitude of external vibrations greater than 5 Hz to less than 6%. Moreover, owing to the compact linear diameter spring structure of the vibration damping module and its ball contact effect, the thermal resistance of the dual–function strut is significantly enhanced, resulting in a mere heat leakage of only 22 W/m2 in a single rod section. [ABSTRACT FROM AUTHOR]

The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design, in which the band gaps play a paramount role. Aiming at providing better designs for these foundations, this study first proposes and validates the analytical formulas to approximate the bounds of the first few band gaps. In addition, the mapping relations linking the frequencies of different band gaps are presented. Furthermore, an optimal design method for these foundations is developed, which is validated through an engineering example. It is demonstrated that ensuring the superstructure's resonance zones are completely covered by the corresponding periodic foundation's band gaps can achieve satisfactory vibration attenuation effects, which is a good strategy for the design of rubber concrete layered periodic foundations. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of vibration suppression systems with desired efficiency and low cost is one of the significant challenges in engineering. In this study, a parametric lattice model is considered to analyze the wave mitigation features in the metamaterial based on a tetra-chiral topology of the periodic cell equipped with internal resonators. Bloch wave theorem and finite element method are employed to explore the bandgap of the structure and its wave mitigation features. Since the unit cell geometry can be designed to open and shift bandgaps, particle swarm optimization algorithm is used to find the largest possible gap in the desired frequency range. The optimization method is programmed using MATLAB combined with an in-house finite element solver, considering the parameters' ranges to ensure geometric compatibility. In all studied cases, the optimized geometry leads to superior vibration suppression and larger complete bandgaps. [ABSTRACT FROM AUTHOR]

ABSTRACTBased on the principle of local resonance and the strategy of hybrid design, in this paper we propose three truss-plate hybrid multifunctional lattice metamaterials featured by the cubic cell topology with a central truss-plate unit connected by the elastic beams to the eight corners. Finite element (FE) simulations were validated by experimental tests on specimens made of TPU substrate material through SLS additive manufacturing technique. At the relative density of 0.31, the specific energy absorption reaches 2.71 J/g, the bandgap width reaches 2.624 KHz, and the elastic wave transmission attenuation at 1400 Hz frequency reaches – 270 dB. Parametric analyses were carried out to investigate the effects of different geometric parameters on the performance indicators. These results highlight the proposed truss-plate hybrid metamaterial as an intriguing multifunctional material with excellent performances in both energy absorption and vibration attenuation, that can be applied to scenarios with multiple engineering requirements.

In this study, a novel dynamic model of a ball bearing based on rigid–elastic–liquid (REL) coupling structure considering external load excitation is established, and the dynamic response of its outer ring under external load excitation is examined. First, the differential equation of the journal motion (i.e. the outer ring) is derived based on Newton’s law, and the oil film force induced by the REL coupling structure is determined by using the central finite difference method, planar bending theory of thin ring, and Simpson’s rule. Further, the fourth and fifth-order variable step length Runge–Kutta method is used to solve the kinematic differential equation. Second, the dynamic characteristics of the outer ring of the bearing under different speeds and elastic support structural parameters are examined. Finally, the feasibility of the theoretical model is verified through experiments. The results show that compared with the traditional squeeze film damper (SFD) system, the ball bearing with REL coupling structure is more stable, and the vibration damping effect is better under higher bearing speed, lower squirrel cage stiffness, and smaller elastic ring flexibility coefficient. The above findings provide useful insights into the dynamic characteristics of REL coupled ball bearings under unbalanced excitation, which can serve as a reference for the optimization design of such ball bearings. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to suppress the low-frequency ultrasound vibration in the broadband range of 20 kHze100 kHz, this paper proposes and discusses an acoustic metamaterial with low-frequency ultrasound vibration attenuation properties, which is configured by hybrid arc and sharp-angle convergent star-shaped lattices. The effect of the dispersion relation and the bandgap characteristic for the scatterers in star-shaped are simulated and analyzed. The target bandgap width is extended by optimizing the geometry parameters of arc and sharp-angle convergent lattices. The proposed metamaterial configured by optimized hybrid lattices exhibits remarkable broad bandgap characteristics by bandgap complementarity, and the simulation results verify a 99% vibration attenuation amplitude can be obtained in the frequency of 20 kHze100 kHz. After the fabrication of the proposed hybrid configurational star-shaped metamaterial by 3D printing technique, the transmission loss experiments are performed, and the experimental results indicate that the fabricated metamaterial has the characteristics of broadband vibration attenuation and an amplitude greater than 85% attenuation for the target frequency. These results demonstrate that the hybrid configurational star-shaped metamaterials can effectively widen the bandgap and realize high efficiency attenuation, which has capability for the vibration attenuation in the application of highprecise equipment. [ABSTRACT FROM AUTHOR]

Purpose: Particle dampers are dynamic vibration absorbers that can be attached or inserted into a vibrating structure for broadband vibration attenuation. The particle damping technique is widely used across various industries for vibration attenuation because of its conceptual simplicity, cost-effectiveness, and suitability for harsh environments (Gagnon et al. in J Sound Vib, 2019. https://doi.org/10.1016/j.jsv.2019.114865; Lu et al. in Struct Control Health Monit, 2018. https://doi.org/10.1002/stc.2058). However, designing a particle damper for real-world applications is significantly challenging primarily due to the interaction among the numerous parameters that influence the damping effectiveness of a particle damper. Therefore, this contribution aims to experimentally investigate the particle dampers performance in the context of their designs. Methods: We introduce three different design variants, namely thin-walled cavity (TWC), thin-walled cavity with additional sheets (TWC-AS), and ring cavity (RC). Different strategies are detailed and evaluated in the current paper. Following the comprehensive study of various design variants at the laboratory scale, several tests were conducted on a real-scale wind turbine generator, subjected to real-world loading conditions. Additionally, the effect of particle damper size and its location for the structure on vibration attenuation has been studied. Results: Based on the experimental investigation, all these variants are effective in reducing the vibration amplitude of a structure. Furthermore, it has been found that for practical applications, particularly in the case of large-scale mechanical structures such as wind turbines, it is advisable to combine the most successful variants to design a particle damper. This approach can achieve significant vibration attenuation, and also minimize the additional mass of the granular material compared to a conventional particle damper. Conclusion: The findings from our experimental studies offer valuable insight into the design of particle dampers for large-scale hollow mechanical structures. [ABSTRACT FROM AUTHOR]

This study systematically introduces a floating slab track (FST) with rubber vibration isolator (RVI) and investigates its behavior in urban rail transit. The FEM is used for modal analysis to clarify the modal parameters of the FST system. A vehicle–slab track coupling sub-model and a tunnel–soil coupling sub-model were established and the propagation law was analyzed by calculating the vertical vibration accelerations beneath the shield wall as well as the vertical vibratory acceleration levels of the surrounding soil. A wheel-set drop test was carried out to verify the actual vibration isolation effect compared with the numerical models. The results reveal that the vibratory acceleration levels at the distance of 20 m from the tunnel center-line basically meet the requirements for vibration in most areas of a city. The variation trend of the vibratory acceleration level measured in laboratory tests agrees well with the calculated values from the numerical simulation. The attenuation amplitude of the levels reaches 19.33 dB with the German high disturbance irregularity and 20.05 dB with the short-wave irregularity in the simulation, and the levels are reduced by 45–58 dB in laboratory tests which demonstrate the FST with RVI performs well in vibration isolation. [ABSTRACT FROM AUTHOR]

AbstractSandwich plates are extensively utilized across various fields, encompassing building engineering, mechanical engineering, and aerospace engineering, owing to their exceptional stiffness-to-weight ratio. However, effectively attenuating the low-frequency and broadband vibrations of these plates poses a significant challenge. This paper proposes a new type of metamaterial sandwich plate that incorporates two-degree of freedom inertial amplified resonators (IA-MSPDF2), to attain two low-frequency band gaps (BGs) and achieve broadband vibration attenuation. The dispersion relation of the IA-MSPDF2 is calculated based on the Bloch-Floquet theorem, and the generation mechanism of two low-frequency BGs is analyzed through eigenmodes. Both numerical and experimental studies are conducted to substantiate the advantages associated with the presence of two BGs in the IA-MSPDF2 design. The results show that the enhanced coupling effect between the primary and secondary resonators of the IA-MSPDF2 leads to the band associated with the local resonance that shifts to lower frequencies, resulting in a Bragg scattering BG that arises above the locally resonant BG. Compared to the metamaterial sandwich plate with one-degree of freedom inertial amplified resonators (IA-MSPDF1) of equal mass, the IA-MSPDF2 exhibits an increased relative bandwidth of BG by 15%. Increasing the damping of the inertial amplified resonator causes two attenuation zones to widen and merge into a wider attenuation zone. The proposed IA-MSPDF2 can robustly and effectively attenuate the low-frequency and broadband vibration with a small mass cost, contributing to the further exploration and utilization of metamaterial sandwich plates in engineering applications. [ABSTRACT FROM AUTHOR]

AbstractIntelligent controllers represent a class of advanced control systems designed to adapt, learn, and make decisions based on changing environments and dynamic conditions. These controllers leverage artificial intelligence and computational techniques to enhance traditional control methods, providing a level of adaptability and sophistication that is particularly valuable in complex and uncertain systems. In this work for the first time, the Proportional–integral–derivative (PID) controller the intelligent controller is used to speed up vibration attenuation of a sandwich smart structure subjected to external excitation. The sandwich smart structure is made of a composite core and sensor and actuator patches. Using shear deformation theory, Hamilton’s principle, and compatibility equations, the governing equations of the sandwich smart structure under external excitations are obtained. After that using numerical solver and time-dependent solution procedure, the equations are solved. After obtaining the datasets via mathematical modeling, this kind of dataset is used as the input and output data to train, validate, and test the machine learning method to use it with low computational cost. After that, using this kind of machine learning method, future researchers can use it to estimate a control vibration of the sandwich structure after mechanical excitation. The results suggest some applicable recommendations to speed up the vibration attenuation of a sandwich smart structure subjected to external excitation. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new type of local resonance sandwich metastructure beam is proposed in this paper. The structure consists of the corrugated sandwich beam matrix and local resonance units which is composed of mass blocks wrapped by soft materials. The band gap distribution and vibration transmission characteristics of the structure are calculated by transfer matrix method and finite element method respectively. The vibration transmission test platform of the sandwich metastructure beam was built, and the test data were obtained and compared with the calculation results. Finally, the regulation strategy of the structural parameters on the band gap characteristics of the structure was studied. The results show that: there are two flexure wave band gaps in the low frequency range, and the band gap frequencies are 196. 1 ~ 339. 0 Hz and 377. 2 ~ 655. 6 Hz, respectively; a full band gap is shown in the flexure wave band gaps, and the frequency range is 380. 0 ~ 423. 6 Hz. Within these two band gap ranges, significant suppression of flexure vibration transmission occurs. The structural parameters of corrugated sandwich beams have great influence on the characteristics of the band gaps. The low frequency and high bandwidth vibration reduction requirements of the local resonance sandwich metastructure beam can be realized by selecting proper structural parameters. [ABSTRACT FROM AUTHOR]

Vibration, in most cases, is an undesirable phenomenon in electro-mechanical systems. The adverse effects of vibration in a system are noise, loss of energy, compromise on comfort, and reduced life span of mechanical systems. The current study focuses on vibration damping of a Flexible Cantilever beam (FCB) by utilizing a differential type of electromagnetic actuator. The electromagnetic forces of both actuators are controlled by Pulse Width Modulation (PWM) using a current controller designed in the lab. The electromagnets are mounted above and below the FCB by maintaining a distance along the same vertical axis. The non-contact active vibration attenuation study is carried out by varying the PWM values of upper and lower electromagnets to produce different electromagnetic forces. The current research work compares different combinations of forces on upper and lower electromagnets experimentally and, based on the analysis, provides the best combination of forces on both actuators to damp the vibrations as swiftly as possible. The study is divided into three cases where case I study the vibration damping with the same PWM on both electromagnets; in case II and case III, one of the electromagnets has fixed PWM while the PWM on other electromagnet is varied. [ABSTRACT FROM AUTHOR]

For the squirrel cage in aero-engine, a metamaterial attenuation structure is presented to control its vibration. Considering the characteristic rotating speeds of rotor system, several types of metamaterial cells are designed. According to the shape of squirrel cage, a structure composed of the metamaterial belts is designed to realize vibration attenuation. For each cell, the dispersion analysis is carried out. The results prove that the bandgap could cover the characteristic frequency of the rotor system. For the squirrel cage equipped with the metamaterial belts, corresponding Finite Element Method (FEM) model is established and simulations are carried out. The results prove that the metamaterial belts could attenuate the cage's vibration effectively. The validation experiments were carried out. The results of sweeping frequency prove that the metamaterial structure could attenuate the vibration amplitude significantly. Especially, at the resonance frequency, the squirrel cage with metamaterial belts could reach a 96% reduction in amplitude compared to the squirrel cage without it. The responses for harmonic excitations prove that at the characteristic rotating speed the vibration amplitude of squirrel cage can be reduced greatly. The results may provide a guidance for the design of vibration attenuation of squirrel cage. [ABSTRACT FROM AUTHOR]

Minimum weight along with low vibration level of structures are main desires of engineers in various industries such as aerospace, automobile, and electronics. The metastructures are a kind of nontraditional structures with distributed vibration absorbers without any change in their general shape. In this article, transverse vibration suppression of a proposed metastructure cantilever beam (MSCB) was considered by a lumped mass-spring model. A prismatic cantilever beam with hollow square cross-section, carrying five uniformly distributed absorbers was investigated. Effects of combination of the absorbers' first natural frequency on vibration suppression of the whole structure were examined. Results were validated by finite element method (FEM). Frequency response functions of the MSCB were compared by those of simple prismatic cantilever beams with the same mass. The results showed that the transverse vibration does not always decrease by increasing the number of absorbers. Also, linear combination of the first natural frequencies of absorbers leads to more vibration suppression for the MSCB. [ABSTRACT FROM AUTHOR]

To reduce the structural vibration of the duct structure in pump-jet propulsors (PJPs) and lower the induced vibration noise, this study learned from the "processor box" in an aero-engine and set a certain number of axial slots in the PJP. First, using finite element analysis, both dry and wet modes of the PJP ducts with and without an axial slot structure were simulated for analysis. Next, with the two-way fluid–solid coupling calculation method, the vibration performances of the PJP ducts with and without axial slots were contrasted and studied. The differences in calculation results under different duct structures were compared from three aspects—the vibration displacement, velocity, and acceleration of the duct and mesh nodes. According to the present results, after the addition of axial slots, the vibration displacement, the vibration velocity, and the vibration acceleration can be significantly reduced, especially in the back segment of the duct. Meanwhile, it can be concluded that it is quite important to select vibration acceleration for structural analysis in evaluating the PJP vibration. This study can provide a reference for further designs of low-noise PJPs. [ABSTRACT FROM AUTHOR]

Investigating pulley wireway systems equipped with friction dampers as alternatives to traditional exposed raceway light fixtures, this study adheres to the ICC-ES AC156 standard and evaluates the impact of system mass and connector types on seismic behavior using shaking table tests. The key findings indicate that an increased system mass variably affects the fundamental frequency of the system, depending on the type of connectors. In terms of earthquake performance, direct connectors outperformed pole connectors in the original system configuration, and the addition of dummy masses significantly reduced seismic energy while stabilizing acceleration responses in pole connector systems. Moreover, the study underscores the critical importance of minimizing pole length in systems using pole connectors and adopting a lower mounting height in systems with direct connectors to improve seismic performance.

In the process of the on–board transportation of liquid hydrogen storage and transportation tanks, apart from considering the support strength and adiabatic performance, it is imperative to take into account the vibration characteristics of the carrying platform. The present work introduces a versatile support structure comprising a damping module and a ball contact insulation structure, enabling effective isolation of external vibrations while simultaneously providing support and insulation. The first step involves describing the principle of a flexible support structure and designing the mechanical structure. Subsequently, a damping analysis is conducted based on dynamic theory to establish the relationship between the spring and damping. Finally, the structural parameters of the dual–function strut are determined, followed by simulation of heat transfer performance. The results demonstrate that the dual–function strut exhibits exceptional vibration damping performance by reducing the amplitude of external vibrations greater than 5 Hz to less than 6%. Moreover, owing to the compact linear diameter spring structure of the vibration damping module and its ball contact effect, the thermal resistance of the dual–function strut is significantly enhanced, resulting in a mere heat leakage of only 22 W/m2 in a single rod section.

This paper proposes an optimization procedure to achieve the best configuration of multiple degrees of freedom Tuned Mass Dampers (TMDs) to mitigate the pointing error of Very-Long-Baseline Interferometry (VLBI) Earth-based radio antennae operating under aerodynamic gust conditions. In order to determine the optimum sets of TMDs, a Multi-Objective design optimization employing a genetic algorithm is implemented. A case study is presented where fourteen operational scenarios of wind gust are considered, employing two models of atmospheric disturbances, namely the Power Spectral Density (PSD) function with a statistical profile presented by the Davenport Spectrum (DS) and a Tuned Discrete Gust (TDG) modeled as a one-minus cosine signal. It is found that the optimal configurations of TMDs are capable of reducing the pointing error of the antenna by an average of 66% and 50% for the PSD and TDG gust excitation scenarios, respectively, with a mass inclusion of 1% of the total mass of the antenna structure. The optimal TMD parameters determined herein can be utilized for design and field implementation in antenna systems, such that their structural efficiency can be enhanced for radio astronomy applications.

Structures with variable stiffness during deformation are of great importance in many fields. The solid-liquid transformation method using low melting point alloys (LMPA) is a promising method to control structural deformation. In this study, a coaxial filamentary feature consisting of pure LMPA surrounded by thermoplastic polymer (TP) is three-dimensionally printed and deformable structure can be constructed. The Polymer/LMPA structure can reveal special and valuable performances: The flexural modulus of the printed TPU/LMPA unit is about 1152 MPa, which is almost 330 times that of TPU and it can achieve large-scale stiffness changes by regulating temperature. Due to its reversibility and variable stiffness, the structure can achieve drive response perturbations under large bias loads. The maximum output force of the TPU/LMPA composite structure is 8.5 N and the maximum driving displacement is 18.5 mm. The fundamental frequency variation of the structure is achieved during the heating of the structure and the change of temperature can change the damping effect according to adjusting the frequency. This study has an important role in the future design of controllable stiffness structures. [ABSTRACT FROM AUTHOR]

Abstract Metamaterials have received extensive attention due to their special properties in the fields of wave attenuation and acoustic engineering. Many researchers have designed metamaterials with different band gap frequency ranges. In this paper, a star shaped metamaterial structure with triangular characteristics is proposed to attenuate mid and low frequency elastic waves in practical applications. The band gap and dispersion characteristics of the structure are numerically studied. The results show that the structure generates ultra-wide band gaps in the frequency range of 6000 Hz, accounting for up to 69.14%. Interestingly, by adding a support structure to the original structural unit, the bandwidth of the improved structure reached 73.89%, and multiple band gaps were opened within 2000 Hz. Finally, the vibration transmission loss of the structure is analyzed by finite element method, and the control performance of vibration transmission in periodic structures is simulated, demonstrating its potential in practical applications. [ABSTRACT FROM AUTHOR]

Dynamic vibration absorbers array (DVAA) is a newly developed and promising technique for vibration attenuation of integrally bladed disk (blisk) by mounting underneath the disk. In this paper, the vibration attenuation characteristics and energy dissipation mechanism of DVAA for tuned and mistuned blisk are parametrically studied, where the viscous and frictional damping are both considered. The lumped parameter model of a blisk is employed for the convenience of parametrical study. Analytical power flow formulas within the blisk-DVAA system are derived to characterize the dynamic interaction between blisk and DVAA. Four typical modes of a blisk with different nodal diameters and deformation characteristics are selected to evaluate the performance of DVAA. Then, the effects of the mass ratio, the frequency ratio and the damping ratio of DVAA on the vibration of tuned and mistuned blisk are addressed. Numerical results show that a light DVAA can significantly mitigate the resonant amplitudes of the tuned and mistuned blisk. Such damper is effective for the modes with different modal characteristics and can provide robust vibration attenuation performance against random mistuning. [ABSTRACT FROM AUTHOR]

This paper proposes an optimization procedure to achieve the best configuration of multiple degrees of freedom Tuned Mass Dampers (TMDs) to mitigate the pointing error of Very-Long-Baseline Interferometry (VLBI) Earth-based radio antennae operating under aerodynamic gust conditions. In order to determine the optimum sets of TMDs, a Multi-Objective design optimization employing a genetic algorithm is implemented. A case study is presented where fourteen operational scenarios of wind gust are considered, employing two models of atmospheric disturbances, namely the Power Spectral Density (PSD) function with a statistical profile presented by the Davenport Spectrum (DS) and a Tuned Discrete Gust (TDG) modeled as a one-minus cosine signal. It is found that the optimal configurations of TMDs are capable of reducing the pointing error of the antenna by an average of 66% and 50% for the PSD and TDG gust excitation scenarios, respectively, with a mass inclusion of 1% of the total mass of the antenna structure. The optimal TMD parameters determined herein can be utilized for design and field implementation in antenna systems, such that their structural efficiency can be enhanced for radio astronomy applications. [ABSTRACT FROM AUTHOR]