The layered van der Waals(vdW)ferroelectric CuInP2S6(CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced application...The layered van der Waals(vdW)ferroelectric CuInP2S6(CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced applications in nanoelectronics.However,an explicit analysis of its lattice dynamics and vibrational symmetries,pivotal for understanding the material’s peculiar ferroelectric and ferroionic behaviors,remains incomplete.Here,we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic lattice vibrations of CIPS single crystals.By analyzing the polarization-dependent Raman intensities,we determine the symmetry assignments and Raman tensors of all major vibrational modes,revealing good agreement with theoretical predictions.Furthermore,we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order evolution by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS.Our findings establish a foundational framework for correlating lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics.展开更多
Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identi...Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy （SFG-VS） system. This system is able to measure the spectra with two polarization combinations （ssp and ppp, or psp and ssp） simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.展开更多
Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are si...Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and particle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations, Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.展开更多
Based on electromagnetics and mechanics, electromechanical coupled dynamic equations for the drive were developed. Using method of perturbation, free vibrations of the mechanical system under electric disturbance were...Based on electromagnetics and mechanics, electromechanical coupled dynamic equations for the drive were developed. Using method of perturbation, free vibrations of the mechanical system under electric disturbance were investigated. The forced responses of the mechanical system to mechanical excitation under electric disturbance were also presented. It is known that for the system with electric disturbance, as time grows, beat occurs. When electric disturbing frequency is near to the natural frequencies of the mechanical system or their integer multiple, resonance vibrations occur. The forced responses of the mechanical system to mechanical excitation under electric disturbance are compound vibrations decided by mechanical excitation, electric disturbance and parameters of the system. The coupled resonance vibration caused by electric disturbance and mechanical excitation was discussed as well. The conditions under which above coupled resonance occurs were presented. The results show that when the difference of the excitation frequency and the perturbation frequency is equal to some order of natural frequency, coupled resonance vibrations occur.展开更多
We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed ...We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed the relationships between the active control force of the actuator and the parameters of the passive isolators by studying the dynamics of two-stage active vibration isolation for the actuator at the foregoing two positions in turn. With the actuator installed beside the upper mount, a small active force can achieve a very good isolating effect when the frequency of the stimulating force is much larger than the natural frequency of the upper mount; a larger active force is required in the low-frequency domain; and the active force equals the stimulating force when the upper mount works within the resonance region, suggesting an approach to reducing wobble and ensuring desirable installation accuracy by increasing the upper-mount stiffness. In either the low or the high frequency region far away from the resonance region, the active force is smaller when the actuator is beside the lower mount than beside the upper mount.展开更多
We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material（VGM）. The dynamical behavior of the sphere is influenced by the external energy input fro...We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material（VGM）. The dynamical behavior of the sphere is influenced by the external energy input from an electromagnetic shaker which is proportional to ε,where ε is equal to the ratio between the square of the dimensionless acceleration Γ and the square of the vibration frequency f of the container. Empirical results reveal that as the VGM transits from local-to-global convection,an increase in ε generally corresponds to an increase in the magnitudes of the rotational ω（RS） and translational v（CM） velocities of the sphere, an increase in the observed tilting angle θ（bed） of the VGM bed, and a decrease in the time t（wall） it takes the sphere to roll down the tilted VGM bed and hit the container wall. During unstable convection, an increase in ε results in a sharp decrease in the sphere＇s peak and mean ω（RS）,and a slight increase in t（wall）.For the range of ε values covered in this study, the sphere may execute persistent rotation, wobbling or jamming, depending on the vibration parameters and the resulting convective flow in the system.展开更多
This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system...This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system.The most fantastic feature of the proposed torsion harvester-absorber system(HAS)is the quasi-zero-stiffness(QZS)characteristic for suppressing and har-vesting low-frequency vibration energy.The QZS characteristic is realized by combining negative stiffness magnet couplings(NSMC)in parallel connection with a pair torsion coil spring.A theoretical model of the NSMC is established based on the equivalent magnetic charge method,and parametric studies are conducted to provide a guideline for the design of the NSMC.Furthermore,the dynamic model of the host oscillator with a torsion QZS HAS is established based on Lagrange’s equation,and then the dynamic amplification factor is obtained using the harmonic balance method.The effects of geometric parameters on both the performances of vibration mitigation and energy harvesting are investigated.Finally,the parameters of the torsion QZS HAS are optimized using H_(∞)optimization method and genetic algorithm,respectively.This enables the torsion QZS HAS to effectively suppress low-frequency vibrations of the rotor system while simultaneously harvesting energy over a wide frequency band.展开更多
In this study,we consider a single-link flexible manipulator in the presence of an unknown Bouc-Wen type of hysteresis and intermittent actuator faults.First,an inverse hysteresis dynamics model is introduced,and then...In this study,we consider a single-link flexible manipulator in the presence of an unknown Bouc-Wen type of hysteresis and intermittent actuator faults.First,an inverse hysteresis dynamics model is introduced,and then the control input is divided into an expected input and an error compensator.Second,a novel adaptive neural network-based control scheme is proposed to cancel the unknown input hysteresis.Subsequently,by modifying the adaptive laws and local control laws,a fault-tolerant control strategy is applied to address uncertain intermittent actuator faults in a flexible manipulator system.Through the direct Lyapunov theory,the proposed scheme allows the state errors to asymptotically converge to a specified interval.Finally,the effectiveness of the proposed scheme is verified through numerical simulations and experiments.展开更多
A variable mass tuned particle absorber is designed for the nonlinear vertical vibration control of the corrugated rolling mill in the composite plate rolling process.Considering the nonlinear damping and nonlinear st...A variable mass tuned particle absorber is designed for the nonlinear vertical vibration control of the corrugated rolling mill in the composite plate rolling process.Considering the nonlinear damping and nonlinear stiffness between the corrugated interface,a three-degree-of-freedom nonlinear vertical vibration mathematical model of corrugated rolling mill based on dynamic vibration absorber control is established.The multi-scale method is used to solve the amplitude–frequency characteristic curve equation of the installed dynamic vibration absorber(DVA)system.The effects of stiffness coefficient and damping coefficient on the amplitude–frequency characteristic curve are analyzed.The expressions of the dynamic developed factor of the corrugated roll are derived,and the influence laws of mass ratio,frequency ratio and damping ratio on the dynamic amplification factor are analyzed.The optimal parameters of the DVA are obtained by adaptive genetic algorithm.The control effect of the DVA on the nonlinear vertical vibration is studied by numerical simulation.The feasibility of the designed dynamic absorber is verified through experiments.The results show that the designed dynamic absorber can effectively suppress the vertical vibration of the corrugated roller.展开更多
This paper investigates the feasibility of using an active dynamic vibration absorber(ADVA) for active vibration control of a flexible missile system through simulation.Based on the principles of a dynamic vibration a...This paper investigates the feasibility of using an active dynamic vibration absorber(ADVA) for active vibration control of a flexible missile system through simulation.Based on the principles of a dynamic vibration absorber(DVA),a ring-type ADVA is first designed to attenuate the elastic vibration of the flexible missile,and the design of the active controller adopts the proportional-integral-derivative(PID)control algorithm.The motion equations of a flexible missile with an ADVA,which is subjected to follower thrust at its aft end,are derived using the Lagrangian approach.Taking the minimum of the root mean square(RMS) of the lateral displacement response of the center of mass as the objective function,a genetic algorithm(GA) is used to optimize the parameter of the DVA and PID controller.The numerical calculations show that the ADVA and DVA are effective in suppressing the vibration and provide approximately 41.2% and 17.6% improvement,respectively,compa red with the case of no DVA,The ADVA has better performance than the DVA,When the missile is subjected to follower thrust,the effect of vibration reduction is more effective than the case without follower thrust.It is feasible to reduce vibration and improve the stability of flexible missiles by means of the ADVA.展开更多
Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantil...Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.展开更多
Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates wa...Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates waves.It offers efficient energy focalization and broad-spectrum vibration suppression,making it highly promising for applications in large equipment such as aircraft,trains,and ships.Despite previous advancements in ABH-DVA development,certain challenges remain,particularly in ensuring effective coupling with host structures during control.To address these issues,this study proposes a partitioned ABH-featured dynamic vibration absorber(PABH-DVA)with partitions in the radial direction of the disc.By employing a plate as the host structure,simulations and experiments were conducted,demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance.The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping.Simulation results revealed that the PABH-DVA exhibits more coupled modes,occasionally with lower coupling coefficients than the symmetric ABH-DVA.The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance.Additionally,the study discussed the impact of the number of slits and their orientation.This research further explains the coupling mechanism between the ABH-DVA and the controlled structure,and provides new ideas for the further application of ABH in engineering.展开更多
High-static-low-dynamic-stiffness(HSLDS)vibration isolators with buckling beams have been widely used to isolate external vibrations.An active adjustable device composed of proportion integration(PI)active controllers...High-static-low-dynamic-stiffness(HSLDS)vibration isolators with buckling beams have been widely used to isolate external vibrations.An active adjustable device composed of proportion integration(PI)active controllers and piezoelectric actuators is proposed for improving the negative stiffness stroke of buckling beams.A nonlinear output frequency response function is used to analyze the effect of the vibration reduction.The prototype of the active HSLDS device is built,and the verification experiment is conducted.The results show that compared with the traditional HSLDS vibration isolator,the active HSLDS device can broaden the isolation frequency bandwidth,and effectively reduce the resonant amplitude by adjusting the active control parameters.The maximum vibration reduction rate of the active HSLDS vibration isolator can attain 89.9%,and the resonant frequency can be reduced from 31.08 Hz to 13.28 Hz.Therefore,this paper devotes to providing a new design scheme for enhanced HSLDS vibration isolators.展开更多
In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radi...In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.展开更多
Structure-borne sound attenuation at corner interface of two plates with dynamic vibration absorber attached is investigated by wave approach.Equations governing transmission and reflection coefficients are deduced by...Structure-borne sound attenuation at corner interface of two plates with dynamic vibration absorber attached is investigated by wave approach.Equations governing transmission and reflection coefficients are deduced by introducing some non-dimensional coefficients,which help to reveal the physical sense inside and to simplify the analysis.Numerical investigation on vibration energy transmission of bending wave is carried out as well.The results from measurement and prediction show almost the same trends in the simplified experiment.It is found that energy transmission at corner interface depends greatly on whether the dynamic vibration absorber attached acts at resonance and is relatively lower right after the nature frequency of dynamic vibration absorber.Furthermore,the dynamic vibration absorber attached provides less energy transmission of bending wave than blocking mass at the end of "passing band".展开更多
As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address thes...As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.展开更多
An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain th...An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation.A classic simply supported manipulator is selected as the controlled system.The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA.An experimental platform is set up to verify the theoretical results.It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs.The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA.Finally,based on the short-time Fourier transformation(STFT),a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure.Through the above steps,the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.展开更多
Following a small-scale wedge failure at Yukon Zinc＇s Wolverine Mine in Yukon, Canada, a vibration monitoring program was added to the existing rockbolt pull testing regime. The failure in the 1150 drift occurred aft...Following a small-scale wedge failure at Yukon Zinc＇s Wolverine Mine in Yukon, Canada, a vibration monitoring program was added to the existing rockbolt pull testing regime. The failure in the 1150 drift occurred after numerous successive blasts in an adjacent tunnel had loosened friction bolts passing through an unmapped fault. Analysis of blasting vibration revealed that support integrity is not compromised unless there is a geological structure to act as a failure plane. The peak particle velocity（PPV） rarely exceeded 250 mm/s with a frequency larger than 50 Hz. As expected, blasting more competent rock resulted in higher PPVs. In such cases, reducing the round length from 3.5 m to 2.0 m was an effective means of limiting potential rock mass and support damage.展开更多
A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were c...A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.展开更多
Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated an...Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12474089,12574102 for L.Y.and L.F.,and 12404102 for J.Z.)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions(for L.Y.and L.F.)+2 种基金the Natural Science Foundation of the Jiangsu Province(Grant No.BK20230806 for J.Z.)Southeast University Interdisciplinary Research Program for Young Scholars(Grant No.2024FGC1008 for J.Z.)the support by the State Key Laboratory of Solid State Microstructures(Nanjing University)(No.M37067)。
文摘The layered van der Waals(vdW)ferroelectric CuInP2S6(CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced applications in nanoelectronics.However,an explicit analysis of its lattice dynamics and vibrational symmetries,pivotal for understanding the material’s peculiar ferroelectric and ferroionic behaviors,remains incomplete.Here,we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic lattice vibrations of CIPS single crystals.By analyzing the polarization-dependent Raman intensities,we determine the symmetry assignments and Raman tensors of all major vibrational modes,revealing good agreement with theoretical predictions.Furthermore,we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order evolution by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS.Our findings establish a foundational framework for correlating lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics.
文摘Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy （SFG-VS） system. This system is able to measure the spectra with two polarization combinations （ssp and ppp, or psp and ssp） simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.
基金This project is supported by National Natural Science Foundation of China (No.50375029)Provincial Natural Science Foundation of Guangdong,China(No.4009486).
文摘Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and particle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations, Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.
基金Project(51075350)supported by the National Natural Science Foundation of China
文摘Based on electromagnetics and mechanics, electromechanical coupled dynamic equations for the drive were developed. Using method of perturbation, free vibrations of the mechanical system under electric disturbance were investigated. The forced responses of the mechanical system to mechanical excitation under electric disturbance were also presented. It is known that for the system with electric disturbance, as time grows, beat occurs. When electric disturbing frequency is near to the natural frequencies of the mechanical system or their integer multiple, resonance vibrations occur. The forced responses of the mechanical system to mechanical excitation under electric disturbance are compound vibrations decided by mechanical excitation, electric disturbance and parameters of the system. The coupled resonance vibration caused by electric disturbance and mechanical excitation was discussed as well. The conditions under which above coupled resonance occurs were presented. The results show that when the difference of the excitation frequency and the perturbation frequency is equal to some order of natural frequency, coupled resonance vibrations occur.
基金the Natural Science Foundation of China under Grant No. 50075029
文摘We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed the relationships between the active control force of the actuator and the parameters of the passive isolators by studying the dynamics of two-stage active vibration isolation for the actuator at the foregoing two positions in turn. With the actuator installed beside the upper mount, a small active force can achieve a very good isolating effect when the frequency of the stimulating force is much larger than the natural frequency of the upper mount; a larger active force is required in the low-frequency domain; and the active force equals the stimulating force when the upper mount works within the resonance region, suggesting an approach to reducing wobble and ensuring desirable installation accuracy by increasing the upper-mount stiffness. In either the low or the high frequency region far away from the resonance region, the active force is smaller when the actuator is beside the lower mount than beside the upper mount.
基金Supported by the CHED-FDP II Program of the Commission on Higher Education of the Philippines
文摘We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material（VGM）. The dynamical behavior of the sphere is influenced by the external energy input from an electromagnetic shaker which is proportional to ε,where ε is equal to the ratio between the square of the dimensionless acceleration Γ and the square of the vibration frequency f of the container. Empirical results reveal that as the VGM transits from local-to-global convection,an increase in ε generally corresponds to an increase in the magnitudes of the rotational ω（RS） and translational v（CM） velocities of the sphere, an increase in the observed tilting angle θ（bed） of the VGM bed, and a decrease in the time t（wall） it takes the sphere to roll down the tilted VGM bed and hit the container wall. During unstable convection, an increase in ε results in a sharp decrease in the sphere＇s peak and mean ω（RS）,and a slight increase in t（wall）.For the range of ε values covered in this study, the sphere may execute persistent rotation, wobbling or jamming, depending on the vibration parameters and the resulting convective flow in the system.
基金supported by National Natural Science Foundation of China(Grant Nos.12122206,11972152,12272129)Postgraduate Scientific Research Innovation Project of Hunan Province and the Hong Kong Scholars Program(Grant No.XJ2022012).
文摘This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system.The most fantastic feature of the proposed torsion harvester-absorber system(HAS)is the quasi-zero-stiffness(QZS)characteristic for suppressing and har-vesting low-frequency vibration energy.The QZS characteristic is realized by combining negative stiffness magnet couplings(NSMC)in parallel connection with a pair torsion coil spring.A theoretical model of the NSMC is established based on the equivalent magnetic charge method,and parametric studies are conducted to provide a guideline for the design of the NSMC.Furthermore,the dynamic model of the host oscillator with a torsion QZS HAS is established based on Lagrange’s equation,and then the dynamic amplification factor is obtained using the harmonic balance method.The effects of geometric parameters on both the performances of vibration mitigation and energy harvesting are investigated.Finally,the parameters of the torsion QZS HAS are optimized using H_(∞)optimization method and genetic algorithm,respectively.This enables the torsion QZS HAS to effectively suppress low-frequency vibrations of the rotor system while simultaneously harvesting energy over a wide frequency band.
基金supported in part by the National Key Research and Development Program of China(2023YFB4706400)the National Natural Science Foundation of China(62273112,62073030,62203161)+6 种基金the Guangdong Basic and Applied Basic Research Foundation(2023B1515120018,2023B1515120019)the Open Project of Xiangjiang Laboratory(23XJ03012)the Natural Science Foundation of Hunan Province(2024JJ5087)the Natural Science Foundation of Jiangxi Province(20232BAB212024)the National Research Foundation of Korea funded by the Ministry of Science and ICT,South Korea(IRIS-2023-00207954)the Science and Technology Planning Project of Guangzhou,China(2023A03J0120)the Guangzhou University Research Project(RC2023037)
文摘In this study,we consider a single-link flexible manipulator in the presence of an unknown Bouc-Wen type of hysteresis and intermittent actuator faults.First,an inverse hysteresis dynamics model is introduced,and then the control input is divided into an expected input and an error compensator.Second,a novel adaptive neural network-based control scheme is proposed to cancel the unknown input hysteresis.Subsequently,by modifying the adaptive laws and local control laws,a fault-tolerant control strategy is applied to address uncertain intermittent actuator faults in a flexible manipulator system.Through the direct Lyapunov theory,the proposed scheme allows the state errors to asymptotically converge to a specified interval.Finally,the effectiveness of the proposed scheme is verified through numerical simulations and experiments.
基金National Key Research and Development Project(2018YFA0707300)National Natural Science Foundation of China(52205404)Fundamental Research Program of Shanxi Province(202203021212293).
文摘A variable mass tuned particle absorber is designed for the nonlinear vertical vibration control of the corrugated rolling mill in the composite plate rolling process.Considering the nonlinear damping and nonlinear stiffness between the corrugated interface,a three-degree-of-freedom nonlinear vertical vibration mathematical model of corrugated rolling mill based on dynamic vibration absorber control is established.The multi-scale method is used to solve the amplitude–frequency characteristic curve equation of the installed dynamic vibration absorber(DVA)system.The effects of stiffness coefficient and damping coefficient on the amplitude–frequency characteristic curve are analyzed.The expressions of the dynamic developed factor of the corrugated roll are derived,and the influence laws of mass ratio,frequency ratio and damping ratio on the dynamic amplification factor are analyzed.The optimal parameters of the DVA are obtained by adaptive genetic algorithm.The control effect of the DVA on the nonlinear vertical vibration is studied by numerical simulation.The feasibility of the designed dynamic absorber is verified through experiments.The results show that the designed dynamic absorber can effectively suppress the vertical vibration of the corrugated roller.
基金supported by the National Natural Science Foundation of China(10972033)。
文摘This paper investigates the feasibility of using an active dynamic vibration absorber(ADVA) for active vibration control of a flexible missile system through simulation.Based on the principles of a dynamic vibration absorber(DVA),a ring-type ADVA is first designed to attenuate the elastic vibration of the flexible missile,and the design of the active controller adopts the proportional-integral-derivative(PID)control algorithm.The motion equations of a flexible missile with an ADVA,which is subjected to follower thrust at its aft end,are derived using the Lagrangian approach.Taking the minimum of the root mean square(RMS) of the lateral displacement response of the center of mass as the objective function,a genetic algorithm(GA) is used to optimize the parameter of the DVA and PID controller.The numerical calculations show that the ADVA and DVA are effective in suppressing the vibration and provide approximately 41.2% and 17.6% improvement,respectively,compa red with the case of no DVA,The ADVA has better performance than the DVA,When the missile is subjected to follower thrust,the effect of vibration reduction is more effective than the case without follower thrust.It is feasible to reduce vibration and improve the stability of flexible missiles by means of the ADVA.
基金The authors gratefully acknowledge the support provided by the National Natural Science Foundation of China(Nos.11622216,11672115 and 11972167).
文摘Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.
基金Supported by National Key Research and Development Program of China (Grant No.2021YFB3400100)National Natural Science Foundation of China (Grant Nos.52241103,U2241261,52022039)。
文摘Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates waves.It offers efficient energy focalization and broad-spectrum vibration suppression,making it highly promising for applications in large equipment such as aircraft,trains,and ships.Despite previous advancements in ABH-DVA development,certain challenges remain,particularly in ensuring effective coupling with host structures during control.To address these issues,this study proposes a partitioned ABH-featured dynamic vibration absorber(PABH-DVA)with partitions in the radial direction of the disc.By employing a plate as the host structure,simulations and experiments were conducted,demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance.The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping.Simulation results revealed that the PABH-DVA exhibits more coupled modes,occasionally with lower coupling coefficients than the symmetric ABH-DVA.The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance.Additionally,the study discussed the impact of the number of slits and their orientation.This research further explains the coupling mechanism between the ABH-DVA and the controlled structure,and provides new ideas for the further application of ABH in engineering.
基金Project supported by the National Natural Science Foundation of China(Nos.62188101,12272103,12022213)。
文摘High-static-low-dynamic-stiffness(HSLDS)vibration isolators with buckling beams have been widely used to isolate external vibrations.An active adjustable device composed of proportion integration(PI)active controllers and piezoelectric actuators is proposed for improving the negative stiffness stroke of buckling beams.A nonlinear output frequency response function is used to analyze the effect of the vibration reduction.The prototype of the active HSLDS device is built,and the verification experiment is conducted.The results show that compared with the traditional HSLDS vibration isolator,the active HSLDS device can broaden the isolation frequency bandwidth,and effectively reduce the resonant amplitude by adjusting the active control parameters.The maximum vibration reduction rate of the active HSLDS vibration isolator can attain 89.9%,and the resonant frequency can be reduced from 31.08 Hz to 13.28 Hz.Therefore,this paper devotes to providing a new design scheme for enhanced HSLDS vibration isolators.
基金The Scientific Innovation Research of Graduate Students in Jiangsu Province(No.KYLX16-0186)the National Science and Technology M ajor Project(No.2013ZX04012032)
文摘In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.
基金the Special Foundation of State Key Laboratory of Ocean Engineering of Shanghai Jiaotong Universitythe Foundation of the Education Department of Shandong Province (No.J10LG60)
文摘Structure-borne sound attenuation at corner interface of two plates with dynamic vibration absorber attached is investigated by wave approach.Equations governing transmission and reflection coefficients are deduced by introducing some non-dimensional coefficients,which help to reveal the physical sense inside and to simplify the analysis.Numerical investigation on vibration energy transmission of bending wave is carried out as well.The results from measurement and prediction show almost the same trends in the simplified experiment.It is found that energy transmission at corner interface depends greatly on whether the dynamic vibration absorber attached acts at resonance and is relatively lower right after the nature frequency of dynamic vibration absorber.Furthermore,the dynamic vibration absorber attached provides less energy transmission of bending wave than blocking mass at the end of "passing band".
基金Project supported by the National Natural Science Foundation of China(Nos.12172248,12021002,12302022,and 12132010)the Tianjin Research Program of Application Foundation and Advanced Technology of China(No.22JCQNJC00780)IoT Standards and Application Key Laboratory of the Ministry of Industry and Information Technology of China(No.202306)。
文摘As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.
基金supported by the National Natural Science Foundation of China(Nos.11772010 and 11832002)the State Key Laboratory of Mechanical System and Vibration of China(No.MSV202004)。
文摘An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation.A classic simply supported manipulator is selected as the controlled system.The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA.An experimental platform is set up to verify the theoretical results.It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs.The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA.Finally,based on the short-time Fourier transformation(STFT),a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure.Through the above steps,the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.
文摘Following a small-scale wedge failure at Yukon Zinc＇s Wolverine Mine in Yukon, Canada, a vibration monitoring program was added to the existing rockbolt pull testing regime. The failure in the 1150 drift occurred after numerous successive blasts in an adjacent tunnel had loosened friction bolts passing through an unmapped fault. Analysis of blasting vibration revealed that support integrity is not compromised unless there is a geological structure to act as a failure plane. The peak particle velocity（PPV） rarely exceeded 250 mm/s with a frequency larger than 50 Hz. As expected, blasting more competent rock resulted in higher PPVs. In such cases, reducing the round length from 3.5 m to 2.0 m was an effective means of limiting potential rock mass and support damage.
基金Project(51221462)supported by the National Natural Science Foundation of China for Innovative Research GroupProject(20120095110001)supported by the Doctoral Fund of Ministry of Education of China+1 种基金Project supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,ChinaProject(CXJJ201303)supported by the Innovation Foundation of Xuyi Research and Development Center of Mining Equipment and Materials,China University of Mining and Technology,China
文摘A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.
基金Supported by National Natural Science Foundation of China(Grant No.51105025)International Science & Technology Cooperation Program of China(Grant No.2013DFB70110)
文摘Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.
