Vibration Reduction Properties Research Articles

Effect of MoS2 particle size on tribological and vibration reduction properties of thermoplastic polyurethane

The incorporation of lubricating filler can improve the self-lubricating properties of polymers and mitigate friction-induced vibration under harsh conditions. However, filler performances significantly vary depending on its size. In this study, molybdenum bisulfide (MoS2) particles of various sizes were utilized as lubricating additives to reinforce thermoplastic polyurethane (TPU). The results showed that an appropriate decrease in the particle size of MoS2 facilitated more efficient stress transfer from the polymer to the particle due to strengthened interfacial interaction, resulting in improved mechanical properties of the reinforced TPU composites. Additionally, the adsorption property of the MoS2 particle improved, extending the duration of the MoS2 tribo-film. These beneficial phenomena endow TPU composites with excellent tribological and frictional vibration reduction properties, with the 500 nm MoS2 presenting the best reinforcing effect. However, further reduction in particle size caused particle agglomeration, which adversely affected the mechanical and self-lubricating properties of the composite and eventually reduced the frictional vibration reduction properties. The findings obtained herein provide a valuable reference for developing a novel polymer with excellent friction and vibration reduction properties.

Application and Vibration Reduction Properties of Prefabricated and Cast-in-Place Phononic-Like Crystal Polymer Concrete Track Bed in Subway Engineering

Application and Vibration Reduction Properties of Prefabricated and Cast-in-Place Phononic-Like Crystal Polymer Concrete Track Bed in Subway Engineering

Multi-source uncertainty propagation and sensitivity analysis of turbine blades with underplatform dampers

Underplatform dampers (UPDs) mitigate turbine blade vibrations in aeroengines through friction dissipation generated by the contact interface. However, in UPD design, uncertainties are often overlooked, including manufacturing discrepancies, excitation forces, and wear factors, leading to suboptimal predictions of structural dynamic responses. This study presents a dynamic model for the blade-UPD system with cyclic symmetric attributes, which simulates uncertainties using statistical methods. An efficient algorithm using adaptive techniques is proposed to construct polynomial chaos expansions (PCE) for precise and efficient uncertainty quantification (UQ) in turbine blades with UPDs. Further, the influence of single/multiple parameter uncertainties on the dynamic characteristics of the blade-UPD is explored. Sobol' indices are then employed to assess the sensitivity of uncertain factors to the vibration reduction properties of UPDs. The findings suggest that the new approach, which offers precise UQ at minimal computational cost, outperforms traditional methods like Ordinary Least Squares (OLS) and Sparse Least Angle Regression (LARS). Observations reveal a significant impact of parameter uncertainties on blade-UPD dynamic responses, which manifest as "resonance bands" and "frequency shifts" in some cases. Sensitivity analysis indicates noticeable variations in Sobol' indices for each uncertainty parameter as the excitation frequency changes. Specifically, the uncertainty in the friction coefficient demonstrates pronounced sensitivity to amplitude when slip occurs at the contact interface. Furthermore, the observed "drop" phenomenon in Sobol' indices is explained.

Double-order coupling bandgap design of metamaterial beams and broadband vibration reduction properties

<sec>Local-resonance bandgap and Bragg bandgap can coexist in a metamaterial beam, and their coupling effect can be used to realize ultra-wide bandgap, which has great potential applications in the field of wide-band vibration reduction. Previous studies usually considered the single-order coupling between the local-resonance bandgap and Bragg bandgap in metamaterial beams with a single array of local resonators, which can only achieve the single-order ultra-wide coupling bandgap and cannot meet the wide-band vibration reduction requirements of double/multiple target frequency bands. In this paper, metamaterial beams with double arrays of local resonators are considered, and the regulation design and analysis of double-order coupling of local-resonance and Bragg bandgaps are carried out based on an analytical model of bending wave dispersion relation. Moreover, the vibration reduction characteristics of the double-frequency-resonator metamaterial beams with double-order coupling bandgaps are studied by using spectral element method and the finite element method. The main conclusions are as follows.</sec><sec>1) A design method is proposed for realizing double-order coupling wide bandgap in a metamaterial beam with double arrays of local resonators. By using this method, the resonance frequencies of the local resonators can be quickly designed on conditions that host beam parameters, lattice constant and added mass ratio of the local resonators are given.</sec><sec>2) The double-order coupling bandgaps in a metamaterial beam carrying double arrays of local resonators are compared with the single-order coupling bandgaps in metamaterial beams with a single array of local resonators. It is found that through proper design, the total normalized width of the double-order coupling bandgap can be much broader than that of the single-order coupling bandgap, so the double-order coupling bandgap is more beneficial to wide-band vibration reduction.</sec><sec>3) It is found that for a given total added mass ratio of the double arrays of local resonators, it is necessary to optimize the mass distribution ratio of the double resonators to maximize the total normalized width of double-order coupling bandgap. An approximate formula for designing the optimal mass distribution ratio of the double resonators is further established.</sec><sec>4) The spectral element method is used to study the vibration reduction characteristics of the metamaterial beams carrying double arrays of local resonators designed based on double-order bandgap coupling. The accuracy of the spectral element method is verified by comparing with the finite element method. The results show that significant vibration reduction can be achieved in two wide frequency bands corresponding to the double-order coupling bandgaps. The influences of number of unit cells and resonator damping on the vibration reduction characteristics of the metamaterial beam are further analyzed. It is shown that the increase of number of unit cells can enhance the vibration reduction performance in the bandgap, and the increase of resonator damping can effectively broaden the vibration reduction frequency band.</sec>

Design of Kagome lattice composite sandwich metastructures with high load bearing and low frequency vibration reduction properties

Design of Kagome lattice composite sandwich metastructures with high load bearing and low frequency vibration reduction properties

Enhancing friction and vibration reduction properties of a polymer using h-BN particles

The unstable contact state of the water-lubricated bearings can induce severe friction and vibration behavior in extreme conditions, posing a threat to the reliability and stability of ship propulsion systems. Enhancing the self-lubrication and reducing the frictional excitation forces are crucial for eliminating or suppressing the friction-induced vibration behavior during the frictional processes. This study developed a new composite material by incorporating hexagonal boron nitride (h-BN) particles into a thermoplastic polyurethane (TPU) matrix. Frictional vibration experiments were conducted to investigate the influence of h-BN particles on frictional vibration behavior. Comprehensive evaluations were performed on the coefficient of friction (COF), wear mass loss, vibration behavior, morphology, and element distribution to elucidate the influences of h-BN particles. The findings demonstrated that adding h-BN imparted excellent self-lubricating properties to TPU and significantly reduced the deformation on the worn surface. It effectively reduced COF behavior as well as its fluctuation amplitude, thereby enhancing the wear resistance and attenuating the vibration behaviors of the friction system. TPU modified by 6 wt.% h-BN exhibited the lowest COF with minimal fluctuation amplitude and the best vibration reduction properties, particularly at higher frequencies. The knowledge obtained herein will aid in a better understanding of the influences of h-BN on friction and vibration reduction, facilitating the design of water-lubricated TPU matrix composite bearings with promising self-lubrication and frictional vibration reduction performances.

Novel Wood-Based Functional Material with Vibration and Noise Reduction.

As a kind of typical green material, natural materials tend to exhibit excellent performance in the engineering field because of their structure and special functions. The homogeneous vessels of red willow (RW) are potentially unique structures to store lubricants or reinforcing agents to present special functions for engineering applications. A series of novel red willow wood-based composites, which were infused with nano-MoS2 and then reinforced by the epoxy, were developed. Their self-lubricating, mechanical vibration and noise reduction performances were investigated, and the friction, vibration, and noise reduction mechanisms were disclosed. The infusion MoS2 treatment was very beneficial for improving the tribological properties of MoS2-curing epoxy/red willow (MCW), and the coefficient of friction (COF) was reduced by 65.8% under water-lubricated friction after infusing 24 times. Meanwhile, the mechanical performances of MCW were obviously enhanced through the curing treatment of the epoxy. The synergistic effects of the infusion and curing treatments significantly decreased the wear phenomena on the friction surfaces of MCW and weakened the COF and its fluctuation amplitudes, which resulted in the presented excellent vibration and noise reduction performance. The knowledge gained herein could not only develop a novel wood-based composite with low COF and good vibration reduction properties in the engineering field but also provide a new methodology for the design of artificial porous materials with stable and smooth friction processes.

Nonlinear dynamic analysis and vibration suppression on the composite laminated plates with general boundary conditions in supersonic airflow

This paper performs the nonlinear dynamic analysis and vibration reduction of the panel structures subjected to supersonic airflow. The negative capacitance piezoelectric shunt damping circuit (PSDC) which contains bonded piezoelectric element and external negative capacitance is adopted. Based on the modified Ritz approach and energy approach, the formulations of the nonlinear panel structure with attached piezoelectric element are derived. A unified mathematical model for the nonlinear dynamic analysis of composite panels subjected to general edge boundaries in supersonic airflow is formulated. Furthermore, the Newmark approach and Newton iteration approach are utilized to calculate time domain responses of panel structures under aerodynamic pressure. Several numerical cases are further performed to verify the present formulations. Finally, impacts of several factors on the flutter characteristics of panel structures are investigated and the comparisons concerning the vibration responses of panels having and without PSDC are performed to verify vibration reduction properties of the present method. The numerical results show that the vibration and flutter of panels in supersonic airflow can be sufficiently suppressed by the present simple vibration reduction strategy.

Bandgap mechanisms and wave characteristics analysis of a three-dimensional elastic metastructure

PurposeIn order to investigate the vibration reduction properties of a three-dimensional elastic metastructure with spherical cavities at low frequencies.Design/methodology/approachThe bandgap characteristics of a three-dimensional elastic metastructure with spherical cavities are studied based on analytical and numerical approaches.FindingsThe results of both method revealed that the vibration of the vertexes masses is important for opening bandgaps. The fact that the big sphere cavity radius or short side length of the cube unit leads to a wider bandgap, is noteworthy.Originality/valueThis research provides theoretical guidance for realizing the vibration attenuation application of EMs in practical engineering.

Frictional vibration behaviors of a new piezo-damping composite under water-lubricated friction

Water-lubricated bearings have become an important component of marine propulsion systems due to the requirements of environmental friendliness and concealability. However, water-lubricated bearings are often subjected to bending stress, additional stress, frictional resistance and other multi-factor effects, resulting in boundary friction or even dry friction on the friction interfaces when encountering unique working conditions such as engine start-stop, steering, low-speed, and heavy-load. The severe frictional processes often induce vibration behaviors and generate frictional noise, which seriously weakens the sound concealment performance and service life of marine propulsion systems. Therefore, it is urgent to improve the vibration and sound pressure behaviors of the composite bearings under water-lubricated conditions. In this study, novel barium titanate/carbon black/polyurethane composites (BaTiO3/CB/PU) are fabricated and then explored the damping capacities and tribological properties of the new polymers. The results showed that the BaTiO3 concentrated on transforming the mechanical energy generated by frictional vibration into electrical energy which generates the thermal energy. The water cooled the frictional heat and the piezo-damping heat. This energy dissipation method increased the damping capacity to reduce the vibration and noise behaviors induced by friction. The composite with 3.0 wt% BaTiO3 performed the highest loss factor under the operating temperatures and presented the best frictional vibration reduction properties. The knowledge obtained in this study is useful not only to explore a new piezo-damping composite, but also to provide a theoretical basis for developing higher performance polymer-based water-lubricated bearing.

The roles of T-ZnOw and MoS2 particles in the friction-induced vibration reducing the process of polymer

A novel thermoplastic polyurethane (TPU) matrix composite was combined with tetra-needle zinc oxide whisker (T-ZnOw) and molybdenum disulfide (MoS2) particles. Frictional vibration experiments were conducted to study the effect of T-ZnOw and MoS2 particles on frictional vibration behaviors. The tribological properties and vibration behaviors of TPU composites were synthetically analyzed to reveal the effects of T-ZnOw and MoS2 on the friction excitation force and vibration reduction properties. The results showed that T-ZnOw enhanced anti-deformation property, and MoS2 weakened the friction excitation force in the friction process, which resulted in a lower coefficient of friction (COF) with a small amplitude, and eliminated the high-frequency vibration amplitude. In addition, the particle composition of 6% T-ZnOw and 9% MoS2 was controlled to obtain a low COF and the best vibration reduction properties. The knowledge obtained herein contributes to the understanding of the synergistic effects of T-ZnOw and MoS2 on COF and vibration reduction behaviors, and the development of a water-lubricated TPU composite stern tube bearing with low COF and good vibration reduction properties.

Synthetical vibration reduction of the nonlinear acoustic metamaterial honeycomb sandwich plate

Light-weight and high-stiffness honeycomb sandwich plates are widely used in high- speed vehicles. Suppressing their low-frequency and broadband vibration is significant for improving safety and reducing noise, but remains challenging with limited mass cost. Bandgaps and chaotic band in nonlinear acoustic metamaterials (NAMs) offer an effective way for vibration reduction. This paper conceives a NAM sandwich plate and studies its vibration reduction properties based on numerical and experimental methods. We establish its nonlinear finite element model based on the equivalent homogeneous model and experiments. The influences of the resonator distribution, nonlinear stiffness, resonant frequencies, mass, amplitude and structural plate parameters on its vibration are thoroughly analyzed to achieve the best performance. Then, we manufacture an optimized NAM plate and experimentally demonstrate that all resonances of the high-stiffness NAM plate below 800 Hz are greatly reduced with only 17.7 % attached mass; particularly, the first low-frequency resonance at 93 Hz is reduced by 20 dB. This shows that the NAM strategy can robustly and effectively suppress the low-frequency and broadband vibration of the light-weight and high-stiffness plates with small mass cost, a synthetical performance desired for broad potential applications. The models, regularities, designs and experiments can also enlighten more studies on relate topics.

An integrated nonlinear passive vibration control system and its vibration reduction properties

A novel integrated nonlinear passive vibration control system with the function of vibration isolation and absorption is proposed by applying a bio-inspired isolator and a nonlinear energy sink (NES). The designed integrated system has excellent vibration isolation capability in the low-frequency bands and can decrease the resonance amplitude simultaneously. The nonlinear dynamic model of the integrated passive vibration control system is established. The displacement transmissibility is employed to evaluate the vibration reduction performance of the integrated system by the harmonic balance method. The coupling mechanism of vibration isolation and absorption is revealed through studying the effects of the parameters on the vibration isolation and absorption performance. It is found that due to the nonlinear weak coupling between the bio-inspired isolator and the NES, they can promote each other in the vibration isolation and absorption. Experiments are conducted to validate the advantageous vibration reduction properties of the system. And the design methodology of the integrated passive vibration control system is also elaborated for practical applications. The integrated nonlinear passive vibration control system would provide an innovative method for vibration control in various engineering practice.

Multi-objective optimal design of periodically stiffened panels for vibration control using data-driven optimization method

Vibration reduction properties of the periodically stiffened panels are studied using the data-driven optimization method and are verified using the 3D printing techniques. The dynamic responses and band gaps of periodically stiffened panels are calculated using the finite element method and periodic boundary conditions. To further develop the potential in vibration mitigation, a data-driven method is used to study the multi-objective structural optimization problem for minimizing the weight and mean square velocity simultaneously. The layout, thickness, and height of the stiffeners are taken as design variables. Numerical results show that the data-driven method is efficient in the optimal design of stiffened panels, and the optimized panels have targeted band gaps for different engineering demands. Moreover, two 3D printed panels are fabricated to study band gap properties of periodically stiffened panels experimentally.

Friction-induced vibration and noise behaviors of a composite material modified by graphene nano-sheets

Due to the weak hydrodynamic lubrication effect under low speed and heavy load in the starting or stopping state of ship propeller stern shafts, it is very difficult to form the effective lubricating films between water-lubricated polymer stern tube bearings and shafts. Under these extreme conditions, friction and wear usually are severe problems, which can induce frictional vibration and noise. In this study, graphene nano-sheets (GNS) were chosen to modify the polymer which was often made into the ship water-lubricated stern tube bearing. The friction-induced vibration and noise behaviors of the modified polymer materials were carried out using a wear test apparatus with precision vibration and noise sensors under the water-lubricated condition. The results showed that friction-induced vibration and noise behaviors of modified polymer materials strongly depended on the content of graphene nano-sheets and wear processes. GNS endowed the modified polymers with a limited excellent self-lubricating to reduce the vibration and noise behaviors. The modified polymer materials with GNS exhibited good friction-induced vibration and noise reduction properties. The knowledge gained in this study aimed at further comprehensively understanding the friction-induced vibration and noise behaviors of the polymer materials and designing a composite material with good self-lubricating and vibration reduction properties.

Band Gap and Vibration Reduction Properties of Damped Rail with Two-Dimensional Honeycomb Phononic Crystals

The prevention of environmental vibration pollution induced by train operation is one of the inevitable problems in the construction of urban rail transit. With the advantage of flexible adjustment, phononic crystals (PCs) have a broad application prospect in suppressing elastic wave propagation of rail transit. In this paper, a damped rail with two-dimensional honeycomb PCs was proposed, and its band structure was analysed with FEM. Then, a parametric study was used to investigate the influences of design parameters of the honeycomb PCs on its band gap property. Furthermore, with a 3D half-track model, the vibration reduction property of the damped rail with honeycomb PCs was discussed. The results show that the damped rail with honeycomb PCs has an absolute band gap in the frequency range of 877.3–1501.7 Hz, which includes the pinned-pinned resonance frequency of the rail internally. Reducing the filling fraction and elastic modulus of the matrix can obtain an absolute band gap in a lower frequency range but also bring a narrower bandwidth. The decrease of scatterer density leads to higher boundary frequencies of the absolute band gap and descends the bandwidth. In order to obtain an absolute band gap which can suppress the pinned-pinned resonance of the rail and keep a wider bandwidth, the filling fraction is suitable to be about 0.5, and the elastic modulus of the matrix is proposed to be not more than 0.6 MPa. Metals with heavy density can be used as the scatterer to obtain a better vibration reduction effect. It is hoped that the research results can provide a reference for the application of PCs in track vibration reduction.

Vibration properties and optimized design of a nonlinear acoustic metamaterial beam

Lightweight, low-frequency, broadband and highly efficient vibration reduction is widely desired in various devices. Nonlinear acoustic metamaterial (NAM) is a new type of metamaterial that may possess these vibration reduction features. However, the laws governing the manipulation of the NAM vibration response and its optimized design have not been addressed. This paper numerically and experimentally studies the manipulation laws and optimized design of the NAM beam reported in [Nature Comm., 8: 1288(2017)]. The strongly nonlinear metacell consists of three bridging-coupled resonators: A Duffing oscillator, a flexural resonator and a vibro-impact resonator. Both time-domain and frequency-domain finite element models are established to calculate the vibrations of the beam. We systematically study the influences of the amplitude, nonlinear stiffness coefficients, resonance frequencies, mass and beam thickness on the bandwidth and efficiency of its vibration reduction properties. Moreover, based on these laws, we present an optimized lightweight NAM beam to realize the low-frequency, broadband and highly efficient vibration reduction with the greatly reduced attached mass. Finally, different NAM samples are fabricated to verify the efficient reduction effect. This work could support the study, creation and application of NAMs in the future.

Bandgap enhancement of periodic nonuniform metamaterial beams with inertial amplification mechanisms

The aim of this study was to obtain bandgaps that are much better, that is at lower frequencies and in broader frequency ranges. Novel nonuniform metamaterial beams with periodically variable cross sections and inertial amplification mechanisms are designed and investigated by numerical and experimental methods. Flexural vibration equations of the nonuniform metamaterial beams are established, and the enhanced bandgap and vibration reduction properties are achieved by combining Bragg scattering and the inertial amplification mechanisms. Numerical results of the bandgaps for the periodic elastic beams with and without the inertial amplification mechanisms are validated by comparing them with the results of vibration experiments. Effects of the amplification mass and angle on the bandgap properties are investigated. Larger amplification mass and angle lead to much enhanced bandgap performances of the nonuniform metamaterial beams in lower to higher frequency ranges.

A 2D Daubechies wavelet model on the vibration of rectangular plates containing strip indentations with a parabolic thickness profile

This paper presents a 2-D semi-analytical model for the vibration analyses of a plate with a power-law-profiled thickness variation, referred to as an Acoustic Black Hole (ABH) plate. The proposed model, along with the associated wavelet-based solution procedure, is intended to overcome major technical difficulties which are specific to ABH structures: the non-uniform wavelength distribution and ABH-induced wave compressions at the high frequency range in a realistic structure of finite size. Under the general Rayleigh-Ritz framework, Daubechies wavelet (DW) scaling functions are chosen as the admissible functions to decompose the transverse displacement of the plate with ABH indentations featuring a thickness variation along one direction of the panel. Modal and forced vibration analyses are carried out with results compared with those obtained by the FEM. It is shown that the model allows an accurate prediction of various vibration parameters and a realistic description of the typical ABH phenomena. Meanwhile, the use of Daubechies wavelet functions allows enhancing the effectiveness of the Rayleigh-Ritz method to reach the high frequency range, where systematic Acoustic Black Hole (ABH) effects are expected. Numerical analyses also reveal the potential of using strip ABH indentations in a plate to achieve a light-weight design with appealing vibration reduction properties. Analyses on the ABH-induced damping enhancement demonstrate the dominant effect of the local structural modes within indented area, which exhibit lower-order deformations (containing typically half and one wave along the direction in which the thickness is tailored).

Flexural wave band gaps and vibration reduction properties of a locally resonant stiffened plate

A locally resonant stiffened plate is constructed by attaching a two-dimensional periodic array of spring-mass resonators to a traditional periodic stiffened plate. A method based on the finite element method and Bloch theorem is presented for calculating the flexural wave dispersion relation and forced vibration response of the proposed locally resonant stiffened plate. The method is validated by comparing the predictions with simulations by FEM software COMSOL. The effects of the spring-stiffness and mass ratio of local resonators on the flexural wave band gap and vibration reduction performance are analysed, which can facilitate the design of the locally resonant stiffened plate for vibration-reduction applications in engineering. The main findings of this work are as follows. 1) The local resonator can have a significant effect on the propagation of flexural wave in stiffened plate. On the one hand, the local resonator is able to create a low-frequency local resonance band gap; on the other hand, it can enhance the high-frequency Bragg band gap. Within the band gap frequency range, the vibration of the locally resonant stiffened plate can be reduced remarkably. 2) The spring-stiffness of local resonators shows a notable influence on the band gap and vibration reduction performance of the locally resonant stiffened plate. As the spring-stiffness gradually increases, the nature frequency of local resonator is gradually tuned to higher frequency, and the phenomenon of band-gap transition and band-gap near-coupling may arise. Under the near-coupling condition, the pass band between two band gaps turns narrow, and it seems that these two band gaps form a super-wide pseudo-gap (within which only a very narrow pass band exists). This behaviour is of great interest for the broad band vibration reduction applications. Moreover, the complete band gap will disappear if the nature frequency of local resonator is tuned to a higher value than a threshold frequency, which is dependent on the geometrical and material parameters. 3) The influence of the additional mass ratio of local resonator on the band gap behavior is highly relevant to the nature frequency of local resonator. If the nature frequency of resonator is lower than the band-gap near-coupling frequency, both the local resonance band gap and Bragg band gap are broadened with increasing the additional mass ratio of resonator. When the nature frequency of resonator is close to the band-gap near-coupling frequency, the phenomenon of band-gap near coupling and band-gap transition may arise or disappear as the additional mass ratio of resonator gradually changes. When the nature frequency of resonator is higher than the band-gap near-coupling frequency, on the one hand, the lower frequency band gap will disappear rapidly with increasing the mass ratio of resonator. However, it will be present again if the mass ratio of resonator increases up to a large enough value. On the other hand, the higher frequency band gap is broadened with increasing the mass ratio, but if the mass ratio is tuned to a larger value than a specific value, this band gap will transform from local resonance band gap to Bragg band gap, and the normalized gap width of this band gap will be narrowed with increasing the mass ratio.