Search

Nonlinear vibration absorbers have been widely used for vibration suppression of elastic structures, but they were usually placed within the structures. However, designing such a vibration damping device within an engineering structure is possibly difficult. In this paper, an inertial nonlinear energy sinks (NES) is mounted on the boundaries of the elastic beam to suppress its vibration. Although this vibration suppression approach is more in line with engineering requirements, it introduces nonlinear oscillators at boundaries. This brings certain difficulties to the structural vibration analysis and the optimal absorber design. An approximate analytical approach for the steady-state response is developed in this work and verified by numerical solutions. The comparison with the uncontrolled system demonstrates the high-efficiency vibration suppression of the inertial NES installed on the boundary. Besides, the optimization of the NES parameters is performed. Resonance amplitude of the elastic structure can be reduced by 98% with the optimized NES. In summary, this paper proposes a novel approach to suppress the bending vibration of elastic structures through boundary NESs. The vibration reduction effect is very significant, and it is more feasible to implement. Therefore, this work is helpful to study the vibration of elastic structures with nonlinear boundaries and to promote the application of nonlinear vibration absorbers. A boundary damping strategy is proposed to solve the problem of the difficulty of installing the vibration absorber in engineering. Introduce an inertial nonlinear energy sinks (NES) to reduce the weight of the shock absorber. The nonlinear boundary is separated and merged into the elastic beam vibration control equation to realize the decoupling of the continuum model. Resonance peak of the elastic structure can be reduced by 98% with the optimized NES. This work is helpful to study the vibration of elastic structures with nonlinear boundaries and to promote the application of nonlinear vibration absorbers.

NiTiNOL-steel wire rope (NiTi-ST) is a new vibration absorber with nonlinear stiffness and hysteretic damping. Although there are many studies on NiTi-ST nonlinear identification, there are few studies on vibration suppression for laminated structures with NiTi-ST. In the present work, the NiTi-ST is integrated with a composite laminated beam for structural vibration suppression for the first time. A coupling model of the composite laminated beam embedded with NiTi-ST is proposed. The nonlinear restoring force and hysteretic damping force of NiTi-ST are processed into polynomial form. The responses of the beam embedded with different NiTi-ST are investigated by the Galerkin discretization together with the harmonic balance method (HBM). The terms of the polynomial model are discussed. Two numerical methods are utilized for steady-state responses and numerical validations. Simulation results demonstrate the effectiveness of NiTi-ST. This vibration suppression method can be popularized for other laminated structures and contribute to vibration control in engineering fields.

Purpose When a manipulator captures an unknown space object, inertia parameters of endpoint payload should be timely obtained to handle possible unexpected parameter variations and monitor the system’s operating conditions. Therefore, this study aims to present an identification method for estimating the inertia parameter of the payload carried by a flexible two-link space manipulator. Design/methodology/approach The original nonlinear dynamics model of the manipulator is linearized at a selected working point. Subsequently, the system modal frequencies with and without payload are determined using the subspace identification algorithm, and the difference of these frequencies is computed. Furthermore, by adjusting the structural configuration of the manipulator, multiple sets of frequency differences are obtained. Therefore, the inertia parameters of the payload, i.e. the mass and the moment of inertia, can be derived from the frequency differences by solving a least-squares problem. Findings The proposed method can effectively estimate the payload parameters and has satisfactory identification accuracy. Practical implications The approach’s implementation provides a practical reference for determining inertia parameters of an unknown space target in the capture process. Originality/value The study proposes a novel method for identifying the inertia parameters of the payload of a flexible two-link space manipulator using the estimated system frequencies.

Quasi-zero stiffness system has been widely used to isolate structural vibrations. However, its small dynamic stiffness may result in drastic low-frequency vibration. This is a curse of employing quasi-zero stiffness systems in engineering. In this paper, a nonlinear energy sink (NES) is used to overcome this difficulty. In order to reduce the additional weight of the NES, the mass of the NES is replaced by an inerter. By superposing the quasi-zero stiffness system and the inertial NES together, a combined vibration control technique is proposed. The equations of the motion of the primary structure and the combined control system are established. The steady-state response of the system is solved by the harmonic balance method and verified numerically. The suppression performance is evaluated based on the resonance suppression efficiency and the effective vibration isolation bandwidth. In addition, the parameters of the inertial NES are optimized. The results show that the combined control system has a better vibration control effect than the quasi-zero stiffness isolator. Specifically, the combined control system provides a smaller resonance amplitude and a wider vibration isolation band. In summary, the combined control scheme has both effects of the nonlinear isolation and the nonlinear absorption. Therefore, this paper proposes a vibration control technique that can achieve a wide band of vibration isolation and small vibration amplitude with a very little additional mass.

Nonlinear vibration absorption of a laminated composite beam is investigated with the account of complex environment (moisture and temperature). A passive efficient nonlinear energy sink (NES) vibration absorber is used to control the transverse vibration. The generalized Hamilton principle is applied to derive a dynamic model of the laminated composite beam coupled with the NES. Numerical simulations reveal the effects of temperature, moisture, and laying angle on natural frequencies. It is numerically found that the NES can rapidly reduce the vibration amplitude. Then, approximate analytical solutions are sought via the harmonic balance method. The approximate analytical solutions are confirmed by the numerical solutions. Amplitude–frequency response curves show that the NES can reduce the amplitude to very low values for various temperatures, moisture levels, and laying angles. In a certain ranges of the NES parameters, different control effects are determined via an approximate analysis. It is demonstrated that the NES is a promising approach to control vibration of a laminated composite beam in complex environment.

The nonlinear behaviors and vibration reduction of a linear system with nonlinear energy sink (NES) are investigated. The linear system is excited by a harmonic and random base excitation, consisting of a mass block, a linear spring, and a linear viscous damper. The NES is composed of a mass block, a linear viscous damper, and a spring with ideal cubic nonlinear stiffness. Based on the generalized harmonic function method, the steady-state Fokker-Planck-Kolmogorov equation is presented to reveal the response of the system. The path integral method based on the Gauss-Legendre polynomial is used to achieve the numerical solutions. The performance of vibration reduction is evaluated by the displacement and velocity transition probability densities, the transmissibility transition probability density, and the percentage of the energy absorption transition probability density of the linear oscillator. The sensitivity of the parameters is analyzed for varying the nonlinear stiffness coefficient and the damper ratio. The investigation illustrates that a linear system with NES can also realize great vibration reduction under harmonic and random base excitations and random bifurcation may appear under different parameters, which will affect the stability of the system.

When introduces nonlinearity into the system, there may be closed detached frequency response due to the bifurcation. This paper aims to provide the dynamical behaviors of a structure combined with a lever-type nonlinear energy sink (LNES). The structure subjected to periodic excitation is modeled as linear to stress the dynamical complexity driven only by the LNES. Depended on the numerical results, the global bifurcation analysis is proposed to expose the existence of periodic and aperiodic motion. The aperiodic motions are numerically identified via time history response, phase trajectories, Poincare maps, and power spectra. Besides, to trace the frequency response of the system, especially the closed detached response curves, the harmonic balance method is covered with the arc-length tracking continuation. The Floquet theory is utilized to settle the stability of frequency response and discovers the saddle-node (SN) bifurcation and the Neimark–Sacker (NS) bifurcation under the resonance response interaction. The investigation demonstrates that when SN bifurcation and NS bifurcation occur concurrently, it is a predictor that the closed detached frequency response may appear.

A novel archetype of nonlinear energy sink (NES) enhanced by an inerter is proposed for vibration reduction of vibrating systems. The proposed NES-inerter suppressed vibration more effectively than a convenient NES measured by both energy dissipation and amplitude frequency responses. Complexification-averaging technique is applied to analyze a coupled system to find steady-state periodic solutions, and the analytical results are confirmed by numerical simulations. The analytical solutions are used to bifurcation analysis, and the results show that the saddle node and the Hopf bifurcations occur under a series of parameters in the steady-state responses. The effects of parameters, such as inertance, cubic stiffness, viscous damping, and amplitude of the external excitation, on the performance of the proposed NES are examined based on the analytical solutions. The investigation reveals that the optimal value of the inerter exists in a certain range.

A generalized transmissibility is proposed to evaluate nonlinear vibration absorbers. Due to possible existence of higher order harmonics and aperiodic motion, the root mean square is employed to define the transmissibility. The transmissibility beyond harmonic motion is applied to measure vibration reduction of a structure coupled with a nonlinear energy sink. Periodic steady-state responses of the coupled system are analytically predicted by the method of harmonic balance, and the stabilities of the responses are determined. The effects of parameters of the nonlinear energy sink on the transmissibility are explored based on harmonic balance solutions and numerical simulations. Phase portraits, Poincare map and frequency spectrum reveal that quasi-periodic motions occur when periodic responses are unstable. Finally, two evaluation approaches based on the energetics and the transmissibility are compared. The investigation demonstrates the quasi-periodic motion is an indication of the optimal transmissibility. The performance of nonlinear energy sink absorbers may be extremely sensitive to parameter variations.

The power flow analysis approach is applied for quantitatively evaluating the dynamic performance of a nonlinear energy sink in the frequency domain. A two-degree-of-freedom model of the whole-spacecraft coupled to a nonlinear energy sink is considered. Analytical approximations and numerical integrations are performed for the integrated system. The time-averaged input and dissipated and absorbed powers of the system are formulated. Power absorption ratio is proposed as the vibration reduction performance indicator of the nonlinear energy sink and is compared with kinetic energy of the oscillator. Results show that the power absorption ratio of nonlinear energy sink is high at all frequencies except at an antiresonance region. The effects of varying nonlinear energy sink parameters on its vibration absorption performance are discussed. As observed, the nonlinear energy sink performs well with the increase in viscous damping of nonlinear energy sink in the high-frequency range. However, the nonlinear energy sink performs poorly in the low-frequency range in the same case. Therefore, power flow analysis can provide great insight for nonlinear energy sink design in frequency domain and is suitable for practical engineering application.

A novel type of a nonlinear energy sink is proposed by introducing a lever to reduce the necessary mass. The lever-type nonlinear energy sink is attached to a two-degree-of-freedom simplified model of whole-spacecraft subjected a harmonic excitation. The transmissibility is used to evaluate the performance of vibration reduction. The harmonic balance method with an alternating frequency time is applied to predict the variation of the transmissibility with the excitation frequency. The harmonic balance solutions are supported by the numerical results. It is found that the disappearance of closed detached resonance response may dramatically decrease the transmissibility. Besides, the quasi-periodic motion may be a predictor to generate the closed detached resonance. The harmonic balance solutions are used to examine the effects of the mass, the nonlinear stiffness and the fulcrum location. With a suitable fulcrum location, the lever-type nonlinear energy sink outperform a conventional nonlinear energy sink with same mass, damping and nonlinear stiffness.

In order to improve the harsh dynamic environment experienced by heavy rockets during different external excitations, this study presents a novel active variable stiffness vibration isolator (AVS-VI) used as the vibration isolation device to reduce excessive vibration of the whole-spacecraft isolation system. The AVS-VI is composed of horizontal stiffness spring, positive stiffness spring, parallelogram linkage mechanism, piezoelectric actuator, acceleration sensor, viscoelastic damping, and PID active controller. Based on the AVS-VI, the generalized vibration transmissibility determined by the nonlinear output frequency response functions and the energy absorption rate is applied to analyze the isolation performance of the whole-spacecraft system with AVS-VI. The AVS-VI can conduct adaptive vibration suppression with variable stiffness to the whole-spacecraft system, and the analysis results indicate that the AVS-VI is effective in reducing the extravagant vibration of the whole-spacecraft system, where the vibration isolation is decreased up to above 65% under different acceleration excitations. Finally, different parameters of AVS-VI are considered to optimize the whole-spacecraft system based on the generalized vibration transmissibility and the energy absorption rate.

The present study describes a method of using a nonlinear energy sink (NES) to realize vibration reduction of the flywheel system, and integrates the NES with the flywheel support structure consisting of a simply supported plate and the flywheels to achieve vibration control. In the micro-vibration environment of the laser communication satellite, the device is proposed on the vibration attenuation of the momentum wheel system. In the system, the external excitation consists of a superposition of several discrete sinusoidal harmonics generated by the radial micro-vibration of the flywheel. A finite-element model is developed and then verified by the equivalent model results. The governing equations of the plate are discretized via the Galerkin method. The complexification-averaging (CX-A) method is employed to obtain approximate solutions. The amplitude-frequency responses of the system are obtained. The vibration suppression of the system is analyzed, and the approximate solutions are verified by numerical results. To systematically analyze the dynamic behaviors of the designed nonlinear vibration absorber, different parameters are selected for NES, and saddle-node bifurcations and Hopf bifurcations are obtained by selecting some specific parameters. The RMS ratio of the transmitted force to the excitation force is used to calculate the transmissibility of the system equipped with the NES. A parametric study is conducted for further optimization. Results illustrate that NES has a good vibration reduction effect on the micro-vibration of the system.

This paper focuses on the free and forced nonlinear vibration of a viscoelastic transporting belt supported by pulleys for the first time. The transporting belt boundary conditions are usually specified as simply supported or fixed. Therefore, the static equilibrium of the belt is supposed to remain straight. However, the belt wraps around two pulleys in most practical mechanical systems. The round support of the pulleys causes nonhomogeneous terms in the boundary condition. A nonlinear dynamic model is established to describe the transverse vibration of the transporting belt. The static equilibrium configuration caused by the nonhomogeneous boundary conditions is determined by developing a numerical iteration scheme. By means of coordinate transformation, the influence of nonhomogeneous boundary conditions is eliminated. Then, the natural frequencies of transverse vibration of the belt around the equilibrium configuration are obtained by adopting the differential quadrature method. Furthermore, the inertia excitation of the belt system is taken from the periodic motion of the foundation. In dynamic mechanical systems, this kind of fluctuation induced by the engine is very common. By applying the differential quadrature method and the Runge–Kutta time discretization, the time histories of the forced vibration are numerically calculated. Resonance areas of the belt are studied by using the frequency sweep. Moreover, parametric studies are carried out to understand the influences of the system parameters. It is concluded that pulley support ends cause nonhomogeneous boundaries and the static equilibrium configuration, and consequences are exacerbated by transmission speed.

Giant magnetostrictive material (GMM) is integrated into a nonlinear energy sink (NES) to construct a NES-GMM device for vibration control and energy harvesting. The NES-GMM device is experimentally embedded in a scaled model of a whole-spacecraft system. LMS Test.Lab software and an oscilloscope are used to collect vibration and energy signals of the whole-spacecraft system with and without the NES-GMM device under sine sweeping frequency excitations. The transmissibility amplitudes, resonant frequencies, and voltage values demonstrate the effeteness of vibration control and energy harvesting of the NES-GMM device under different various conditions. The experimental system is modeled as a two-degrees-of-freedom (2DOF) linear primary system with a nonlinear NES-GMM additional subsystem. The complexification-averaging (CX-A) method verified with numerical verifications is developed to investigate analytically the vibration reduction and energy harvesting of the NES-GMM device for the whole-spacecraft system. The experimental and theoretical results show that the NES-GMM device reduces the vibration and produces the electricity and that the device hardly changes the resonance frequencies of the original whole-spacecraft system. The saddle-node (SN) bifurcation is detected in the steady-state periodic response of the system. The performance of the NES-GMM device is examined for its varying parameters.

This paper investigates a highly efficient and promising control method for forced vibration control of an axially moving beam with an attached nonlinear energy sink (NES). Because of the axial velocity, external force and external excitation frequency, the beam undergoes a high-amplitude vibration. The Galerkin method is applied to discretize the dynamic equations of the beam–NES system. The steady-state responses of the beams with an attached NES and with nothing attached are acquired by numerical simulation. Furthermore, the fast Fourier transform (FFT) is applied to get the amplitude–frequency responses. From the perspective of frequency domain analysis, it is explained that the NES has little effect on the natural frequency of the beam. Results confirm that NES has a great potential to control the excessive vibration.

Herein, a novel pyramid lattice sandwich structure with the active variable stiffness (AVS) is proposed, which consists of a proportion integration (PI) active controller, a piezoelectric actuator, and a variable stiffness device. The principle of AVS is to process the real-time vibration feedback signal of the lattice sandwich beam by using the PI controller and the piezoelectric actuator to change structural stiffness continuously. The structure has excellent self-adjusting and active vibration reduction effect. Based on the supersonic piston theory, Hamilton's principle, and the assumed modes method, the dynamics equations of the whole structure are established. The vibration reduction and energy dissipation of lattice sandwich beams with AVS and without AVS are analyzed by using the Runge-Kutta algorithm. Moreover, the relevant parameters of PI controller, positive stiffness, negative stiffness, incoming flow velocity, damping coefficient, and installation position are compared and analyzed, respectively. The results indicate that the novel lattice sandwich structure with AVS can achieve ideal vibration reduction effect, and the efficiency can be improved by adjusting the parameters appropriately.

A closed detached response due to the resonance response interaction has a critical effect on vibration isolation and energy harvesting. In this paper, a promising novel approach by integrating a lever-type nonlinear energy sink (LNES) and a giant magnetostrictive-piezoelectric (GMP) energy harvester (LNES-GMP) for vibration isolation and energy harvesting is investigated. The method of harmonic balance is applied to trace the response and voltage of the system, and numerical results support the harmonic solutions. It can be noted that the occurrence of closed detached resonance response could dramatically increase the voltage of the system. Moreover, the structure of the LNES-GMP, such as the mass, nonlinear stiffness, and fulcrum location may influence the efficiency of vibration isolation and energy harvesting. Lastly, with an appropriate fulcrum location, the performance of the LNES-GMP, which contains less attached mass, is more improved than the traditional NES-GMP.

A mechanical-piezoelectric system is explored to reduce vibration and to harvest energy. The system consists of a piezoelectric device and a nonlinear energy sink (NES), which is a nonlinear oscillator without linear stiffness. The NES-piezoelectric system is attached to a 2-degree-of-freedom primary system subjected to a shock load. This mechanical-piezoelectric system is investigated based on the concepts of the percentages of energy transition and energy transition measure. The strong target energy transfer occurs for some certain transient excitation amplitude and NES nonlinear stiffness. The plots of wavelet transforms are used to indicate that the nonlinear beats initiate energy transitions between the NES-piezoelectric system and the primary system in the transient vibration, and a 1:1 transient resonance capture occurs between two subsystems. The investigation demonstrates that the integrated NES-piezoelectric mechanism can reduce vibration and harvest some vibration energy.

This paper explores a promising novel approach by integrating nonlinear energy sink (NES) and giant magnetostrictive material (GMM) to realize vibration control and energy harvesting. The vibration-based apparatus consisting of a NES, a Terfenol-D rod, and a linear oscillator (the primary system) is proposed. The mathematical model of the prototype under displacement driven has been established and simulated by utilizing the Runge-Kutta algorithm. The exhibited responses and the obtained electric energy are computed. Furthermore, the Fast Fourier Transform (FFT) of the resonant responses is performed. The distribution of the input energy is calculated to evaluate the designed structure. The instantaneous transaction of the energy is then examined by considering the energy transaction measure (ETM). Lastly, a parametric study is conducted for further optimization. The numerical simulations demonstrate that the nonlinear pumping phenomena occur, that is, the target energy transfer (TET) that leads to a very efficient vibration suppression. In addition, the results also illustrate that the localized vibration energy can be converted into magnetic field energy due to the Villari effect and then transformed into electric energy.

For the first time, a new representation of transmissibility based on nonlinear output frequency-response functions (NOFRFs) is proposed in the present study. Furthermore, the transmissibility is applied to evaluate the vibration isolation performance of a nonlinear energy sink (NES) in frequency domain. A two-degree-of-freedom (2-DOF) structure with the NES attached system is adopted. Numerical simulations have been performed for the 2-DOF structure. Moreover, the effects of NES parameters on the transmissibility of the nonlinear system are evaluated. By increasing the viscous damping and mass, as well as decreasing the cubic nonlinear stiffness of the NES, the analytical results show that the transmissibility of the 2-DOF structure with NES is reduced over all resonance regions. Therefore, the present paper produces a novel method for NES design in frequency domain.

This paper presents a novel design by integrating geometrical and material nonlinear energy sink (NES) with a piezoelectric-based vibration energy harvester under shock excitation, which can realize vibration control and energy harvesting. The nonlinear spring and hysteresis behavior of the NES could reflect geometrical and material nonlinearity, respectively. Two configurations of the piezoelectric device, including the piezoelectric element embedded between the NES mass and the single-degree-of-freedom system or ground, are utilised to examine the energy dissipated by damper and hysteresis behavior of NES and the energy harvested by the piezoelectric element. Similar numerical research methods of Runge-Kutta algorithm are used to investigate the two configurations. The energy transaction measure (ETM) is adopted to examine the instantaneous energy transaction between the primary and the NES-piezoelectricity system. And it demonstrates that the dissipated and harvested energy transaction is transferred from the primary system to the NES-piezoelectricity system and the instantaneous transaction of mechanical energy occupies a major part of the energy of transaction. Both figurations could realize vibration control efficiently.

Thermal shock-induced vibration suppression of an axially moving beam with a nonlinear energy sink (NES) is investigated. Owing to thermal shock on the beam, the beam is subjected to excessive vibrations. The equation for the transverse vibration of the beam with thermal shock is established using Hamilton’s principle, and the equation for the beam with NES is approximated by the Galerkin method. A numerical algorithm is used to obtain the displacement responses of the beam with and without NES attached under thermal shock. The NES efficiencies at different positions are obtained. Results show the NES can absorb a large number of vibrational energy.

Parts energy of nonlinear system such as the closed detached response (CDR), primary response (PR), closed detached voltage (CDV), and primary voltage (PV) are resultant of the resonance response interaction and represent their corresponding dynamic characteristics. In this paper, we proposed a promising novel device by integrating a lever-type nonlinear energy sink (LNES) and a levitation magnetoelectric energy harvester (LMEH), to discover the effects of CDR, PR, CDV, and PV on the vibration isolation and energy harvesting. In nonlinear energy harvesting, the weight of the system plays a vital role in improving the accuracy, and hence it cannot be neglected. The root mean square is used to evaluate vibration control and energy harvesting. We used the method of harmonic balance to trace the CDR, PR, CDV, and PV of the system, and numerical results support the harmonic solutions. Specifically, the CDV dramatically increases the voltage of the system. The performance of vibration isolation and energy harvesting has been discussed in terms of the attached mass, nonlinear stiffness, and fulcrum location. Finally, with an appropriate fulcrum location, the performance of LNES-LMEH is compared with the traditional NES-LMEH.

The composite laminated plate is widely used in supersonic aircraft. So, there are many researches about the vibration suppression of composite laminated plate. In this paper, nonlinear energy sink (NES) as an effective method to suppress vibration is studied. The coupled partial differential governing equations of the composite laminated plate with the nonlinear energy sink (NES) are established by using the Hamilton principle. The fourth-order Galerkin discrete method is used to truncate the partial differential equations, which are solved by numerical integration method. Meanwhile study about the precise effectiveness of the nonlinear energy sink (NES) by discussing the different installation location of the nonlinear energy sink (NES) at the same speed. The results indicate that the nonlinear energy sink (NES) can significantly suppress the severe vibration of the composite laminated plate with speed wind loadings in to protect the composite laminated plate from excessive vibration.

Given its essential nonlinearity, nonlinear energy sink (NES) has been extensively studied as a promising vibration energy harvesting device. Internal resonance, which is due to strong energy exchange between modes, also provides a valuable idea for vibration energy harvesting. Combining these two advantages, we put forward a 3:1 internal resonance system, which consists of an NES and a coupled linear oscillator, as an enhanced method for vibration energy harvesting. The multiscale method is applied to derive the relationship between amplitude and frequency response. Simulations are carried out to evaluate the performance of the proposed method. Results show that the internal resonance system can remarkably improve the vibration energy harvesting performance. The numerical solutions verify the accuracy of the analytical solutions. The results demonstrate that the internal resonance system with NES for energy harvesting has better output power and bandwidth compared with noninternal resonance system. Overall, the comprehensive design improves the performance of NES for vibration energy harvesting.

In this paper, A novel idea is put forward. The nonlinear output frequency response functions(NOFRFs) is the first used in analyzing the dynamical equation of the model of Electro-Mechanical to achieve vibration control and energy collection. The controlling system consisting of a nonlinear energy sink(NES), gaint magnetostrictive material(GMM), 2-DOF is proposed. According to the dynamics model, setting up corresponding kinetic control equations. The nonlinear output frequency response function(NOFRFs) is devoted to calculate the kinetic equations of the 2-DOF with NES and GMM. Results prove that the NOFRFs is used for well calculating and resolving the dynamical equation of the model of 2-DOF with NES and GMM. The NES can control the excessive vibration of the model of 2-DOF obviously and suppress the vibration more effective with GMM. An reasonable designed NES-GMM can efficiently assimilate and dissipate broad band-frequency energy. GMM can collect energy form NES targeting delivery and transform the mechanical energy into the voltage and power through corresponding device.

The present study aims to investigate the steady-state response regimes of a device comprising a nonlinear energy sink (NES) and a giant magnetostrictive energy harvester utilizing analytical approximation. The complexification-averaging (CX-A) technique is generalized to systems defined by differential algebraic equations (DAEs). The amplitude-frequency responses are compared with numerical simulations for validation purposes. The tensile and compressive stresses of giant magnetostrictive material (GMM) are checked to ensure that the material functions properly. The energy harvested is calculated and the comparison of transmissibility of the apparatus with and without NES–GMM is exhibited to reveal the performance of vibration mitigation. Then, the stability and bifurcations are examined. The outcome demonstrates that the steady-state periodic solutions of the system undergo saddle-node (SN) bifurcation at a certain set of parameters. In the meantime, no Hopf bifurcation is observed. The introduction of NES and GMM for vibration reduction and energy harvesting brings about geometric nonlinearity and material nonlinearity. By computing both the responses of the primary system equipped with the NES only and the NES–GMM, it is indicated that the added GMM can dramatically modify the steady-state dynamics. A further optimization with respect to the cubic stiffness, the damper of NES, and the amplitude of excitation is conducted, respectively. The boundary where the giant magnetostrictive energy harvester is out of work is pointed out as well during the process of optimizing.

A nonlinear energy sink (NES) approach is proposed for whole-spacecraft vibration reduction. Frequency sweeping tests are conducted on a scaled whole-spacecraft structure without or with a NES attached. The experimental transmissibility results demonstrate the significant reduction of the whole-spacecraft structure vibration over a broad spectrum of excitation frequency. The NES attachment hardly changes the natural frequencies of the structure. A finite element model is developed, and the model is verified by the experimental results. A two degrees-of-freedom (DOF) equivalent model of the scaled whole-spacecraft is proposed with the two same natural frequencies as those obtained via the finite element model. The experiment, the finite element model, and the equivalent model predict the same trends that the NES vibration reduction performance becomes better for the increasing NES mass, the increasing NES viscous damping, and the decreasing nonlinear stiffness. The energy absorption measure and the energy transition measure calculated based on the equivalent model reveals that an appropriately designed NES can efficiently absorb and dissipate broadband-frequency energy via nonlinear beats, irreversible targeted energy transfer (TET), or both for different parameters.

In this paper, the vibration suppression mechanism of a nonlinear fluid pipe via nonlinear energy sink (NES) is studied for the first time. The fluid pipe is simply supported under harmonic foundation excitation. The complexification-averaging method combined with the arc-length continuation method is used to predict the response of the system. The analytical solution is supported by the numerical result. The trend of interaction between liquid speed and NES parameters are investigated by comparison of parameters optimization. It is especially pointed out that the change of stiffness has a very complicated influence on the response. The parameters optimization is investigated at the resonance frequency. It is noted that the liquid speed has an important effect on the vibration suppression of the fluid pipe. Besides, the system is evaluated from the point of view of energy. The distribution of the input energy is calculated and the instantaneous transaction of the energy is examined by considering the energy transaction measure (ETM). The numerical simulations demonstrate that the target energy transfer (TET) leads to a very efficient vibration suppression.

Acoustic metamaterials with specifically designed lattices can manipulate acoustic/elastic waves in unprecedented ways. Whereas there are many studies that focus on passive linear lattice, with non-reconfigurable structures. In this letter, we present the design, theory and experimental demonstration of an active nonlinear acoustic metamaterial, the dynamic properties of which can be modified instantaneously with reversibility. By incorporating active and nonlinear elements in a single unit cell, a real-time tunability and switchability of the band gap is achieved. In addition, we demonstrate a dynamic “editing” capability for shaping transmission spectra, which can be used to create the desired band gap and resonance. This feature is impossible to achieve in passive metamaterials. These advantages demonstrate the versatility of the proposed device, paving the way toward smart acoustic devices, such as logic elements, diode and transistor.

In the present paper, free vibration of a rotating ring supported by an elastic foundation is studied by analytical method, finite element (FE) simulation and experiment. By adopting the ring analogy of Timoshenko beam theory, the nonlinear vibration of the rotating ring on an elastic foundation is modeled based on Hamilton’s principle. Radial and tangential deformation are considered. By solving the generalized eigenvalue problem, natural frequencies and flexural modes are obtained. Furthermore, the Euler–Bernoulli (E–B) theory is also employed to investigate the free vibration. For determining the necessity of the Timoshenko theory, the flexural vibration frequencies from two theories are compared. Specifically, the effects of the radius and the radial height (the thickness) of the ring on the difference between the two models are studied. In order to confirm the analytical results, finite element analysis and experiments on three test specimens are used to verify the natural frequency and flexural mode predictions. Overall, this work shows the necessity of the Timoshenko theory for studying free vibration of an elastic ring.