Vibration Isolation Capability Research Articles

Natural Mechanism of Superexcellent Vibration Isolation of the Chicken Neck

No matter how the chicken's body shakes, its head can always remain relatively motionless, leading to the intuitive impression that the S-configuration of the chicken neck possesses an unparalleled vibration isolation capability. However, this viewpoint has not been rigorously substantiated. To unravel the vibration isolation mechanism inherent in the chicken neck, this study introduces a multi-modular S-configurational model inspired by its biological structure. Utilizing Newton's law and Lagrange's equations, both the static and dynamic models for the S-configurational model are formulated. Furthermore, we incorporate actuators into the model and develop a bionic attitude control method. Surprisingly, numerical simulations reveal that the S-configuration of the chicken neck does not exhibit any passive vibration isolation function, challenging the intuitive impression. Instead, the motionless of a chicken head results from active control implemented by the corresponding chicken neck. This study may contribute to a better understanding of the vibration attenuation function of the neck of birds.

Stair‐Stepping Mechanical Metamaterials with Programmable Load Plateaus

AbstractMaterials with target load plateaus offer the potential for developing innovative vibration suppression and isolation systems for applications such as satellite platforms, submarines, and electric vehicles. However, implementing these materials can pose significant challenges. In this study, stair‐stepping mechanical metamaterials with programmable load plateaus are presented, which are created via a three‐level (unit, module, and 3D object) construction strategy. The strategy inspired by the inverse design concept achieves tunability in the number and properties of load plateaus within the force–displacement profiles of the metamaterials. This approach even yields appealing stair‐stepping response patterns, as validated by experiments and finite element simulations. Promisingly, programming the unit from its initial configuration to a “zero stiffness” configuration enables these metamaterials excellent vibration isolation performance. Furthermore, two reversible methods are proposed for switching among various unit configurations, namely shape memory programming and supporting payload. This innovative design strategy for programmable load plateaus opens up new possibilities for creating metamaterials with customized force–displacement responses. It also provides opportunities to incorporate multimodal vibration isolation capabilities into precision devices.

Topology optimization of programable quasi-zero-stiffness metastructures for low-frequency vibration isolation

Quasi-zero-stiffness (QZS) isolators have been demonstrated to realize low-frequency vibration isolation without loss of static stiffness. However, most previous designs are based on spring-driven links, cam-roller structures, or two-phased network structures resorting to complex assembling components, other than compact and integrative single-phased solid structures. In this paper, we propose a topology optimization scheme to inversely design QZS metastructures with smooth boundaries for customized nonlinear force-displacement curves. The optimization model is established based on the distinguishing features of the QZS force-displacement curve. The boundary smoothing procedure is introduced in the genetic algorithm to improve the convergence and stability of topology optimization. The designed metastructures are verified to have robust QZS feature. A linear relationship between the platform force and the initial modulus of the base material is obtained. We numerically show the high-static-low-dynamic performance, the load bearing, and even full band vibration isolation capabilities of the designed QZS metastructures. In addition, experiments are performed to verify the QZS feature of the designed metastructure. The inverse design scheme developed in this paper can efficiently design QZS isolators suitable for different scenarios with great flexibility. The metastructures with smooth boundaries are obtained so that postprocessing is not required before manufacture. The proposed inverse-design methodology paves the way for low-frequency vibration isolation using compact solid structures without any positive or negative stiffness units.

Machine Learning-Driven Design Optimization of Buckling-Induced Quasi-Zero Stiffness Metastructures for Low-Frequency Vibration Isolation.

Metastructures, artificial arrangements of micro/macrostructures, possess unique properties and are of significant interest in aerospace, stealth technology, and various other applications. Recent studies have focused on quasi-zero stiffness metastructures, providing an outstanding vibration isolation capability. However, existing methods are constrained to low preloads and lack the consideration of structural analysis, despite their intended use in practical structures. This study introduces metastructures with quasi-zero stiffness characteristics under high preloads by inducing local buckling. An optimization framework combining deep reinforcement learning and finite-element analysis is employed to derive an optimal model that considers both structural safety and quasi-zero stiffness characteristics. To validate the optimization results, quasi-zero stiffness metastructures are fabricated via 3D printing, and compression and vibration experiments are conducted. The fabricated metastructures exhibit quasi-zero stiffness characteristics under a high target preload along with outstanding vibration reduction performance, even in the low-frequency range.

Optimization of Load Distribution Method for Hydropower Units Based on Output Fluctuation Constraint and Double-Layer Nested Model

During the load distribution of hydropower units, the frequent crossing of vibration zones as well as large output fluctuations affect the stability of the power station. A multi-objective double-layer intelligent nesting model that considers the constraint of the output fluctuation of units is proposed to address these problems. The nonlinear constraint unit commitment optimization model layer is built based on outer dynamic programming, and the load distribution optimization model layer is constructed based on the improved biogeography-based optimization algorithm. Simultaneously, the unit output fluctuation constraint is established based on whether the unit combination changes in order to limit the unit output fluctuation. The results of this model indicate that compared with traditional load allocation models, the application of the method proposed in this paper can reduce the fluctuation range of unit output by 85.01%. In addition, except for the inevitable vibration zone crossings during startup and shutdown processes, the unit does not cross the vibration zone during operation, which greatly improves the unit’s vibration isolation and optimization capabilities. The multi-objective double-layer intelligent nested model proposed in this paper has significant advantages in the field of load allocation for hydropower units. It effectively improves the stability and reliability of unit operation, and this method can be applied to practical load allocation processes. It is of great significance for the research on load allocation optimization of hydropower units.

Adaptive optimal fault-tolerant vibration control and sensitivity analysis of semi-active suspension based on a self-powered magneto-rheological damper

To reuse the energy dissipated by vehicle suspension, a semi-active suspension with a self-powered magneto-rheological damper is proposed. An electromechanical coupling model of self-powered semi-active suspension is established. The energy conversion efficiency is defined and investigated by changing the electrical parameters. By considering unmodeled dynamics and perturbation values, an adaptive optimal fault-tolerant control algorithm is proposed to ensure the vibration-isolation performance. The robust index of the adaptive optimal fault-tolerant control algorithm is constructed using the Lyapunov equation and evaluated by changing the key parameters. The sensitivity of the key parameters to the damping force is investigated using a grey relation analysis approach. Furthermore, multi-objective optimization between the vibration-isolation capability and energy harvesting is conducted. Via analysis, the proposed suspension can harvest more energy near the second resonance range. Compared to passive control and self-powered mode, the adaptive optimal control algorithm mitigates vibration more significantly in the time and frequency domains, respectively, under stochastic excitation. The robust index is most sensitive to inductance and the diameter of the magnetism cylinder. The length of the damping channel and the diameter of the magnetism cylinder influence the sensitivity of key parameters to the damping force most obviously.

Nonlinear dynamics analysis of the attachment system and design of variable stiffness connecting bracket based on the complete aero-engine system

During the operation of the aero-engine, the attachment and brackets are subjected to various complex internal and external loads, which can pose risks to the structural integrity of the engine. To address this issue, this paper introduces a variable stiffness bracket designed for vibration reduction in the attachment system. Firstly, a finite element model (FEM) of the aero-engine was established using the Lagrangian method, incorporating the dual rotor-bearing system and bracket-attachment system. Subsequently, the vibration response of the system was solved using the Runge-Kutta method. The sources and propagation paths of vibration within the system were identified. Lastly, leveraging the material properties of Shape Memory Alloy (SMA), a stiffness-adjustable bracket for the aircraft engine was proposed to achieve active vibration reduction in the system. The results demonstrate that the variable stiffness bracket effectively reduces the resonance amplitude and frequency in the attachment system, exhibiting excellent vibration reduction and isolation capabilities.

4D printing of customizable and reconfigurable mechanical metamaterials

Customizable and reconfigurable mechanical behavior is critical for self-adaptive low-frequency vibration isolators operating in dynamic environments. Herein, the mechanical metamaterials with customizable and configurable geometries, material stiffnesses, cushioning properties, and vibration isolation capabilities are fabricated using a 4D printed multi-material system. The metastructure is characterized by the connection of a flexural beam structure and a collapsible straw structure. At the unit level, the stiffness characteristics are analyzed by geometric and theoretical mechanical models. The effect of geometric parameters and material composition on the stiffness behavior of multi-material metamaterials is investigated. Metamaterials' customizable and configurable characteristics are examined by the quasi-static compression mechanical properties, cushion performances, and vibration isolation capabilities under varying geometric parameters and material compositions. Finally, the reprogrammable stiffness of the metamaterial is demonstrated through the modification of geometric parameters utilizing the shape memory properties in 4D printing. The customizable and configurable metamaterials inspire the next generation of cushioning and vibration isolators, holding significant promise for applications demanding superior vibration isolation performances in dynamic environments.

The Adjustable Bandgap of Novel Local Resonance Sandwich-Like Metamaterial Plates with Buckling Beam Oscillators

Sandwich structures possess a high stiffness-to-mass ratio, which facilitates flexural wave propagation at lower frequencies and enhances their vibration isolation and sound insulation capabilities, therefore, sandwich-like metamaterial plates with the nonlinear local oscillator is constructed in this paper to obtain adjustable bandgap in low-frequency. The buckling beam oscillator consists of a small mass, linear support spring, and buckling elastic elements for nonlinear stiffness. First, governing equations of flexural vibrations of plates are deduced based on the Hamilton principle. By utilizing the harmonic balance method (HBM), the dispersion relation of a sandwich-like plate can be determined. Theoretical analysis reveals the presence of structural bandgap ranges at lower frequencies, which are subject to the excitation amplitudes. And in order to validate the theoretical findings, the finite element method (FEM) is employed. Moreover, the influence of structural parameters, including oscillator mass, linear spring stiffness, buckling beam angle, and Young’s modulus, are conducted to enhance the vibration control in the low-frequency. Interestingly, it is observed that the effectiveness of low-frequency suppression in the nonlinear metamaterial plate varies significantly across different boundary conditions. Therefore, the sandwich structures with nonlinear local oscillators can provide an effective way to suppress low-frequency vibration and maintain dynamic stability.

Compression behavior of 4D printed metamaterials with various Poisson's ratios

In this study, three types of cellular metamaterials with negative/zero/positive Poisson's ratio and vibration isolation effects were devised and fabricated based on 4D printing of shape memory polymers. The compressive properties and energy absorption capacity of three cellular metamaterials at variable temperatures were evaluated by finite element simulations and compression experiments. To explore the application possibilities of 4D printed cellular metamaterials in deformable structures, shape recovery experiments were carried out, and the results showed that the three types of cellular metamaterials exhibited a high shape recovery rate. The vibration modes and vibration isolation capabilities of 4D printed cellular metamaterials were investigated for three types of cellular metamaterials with negative/zero/positive Poisson's ratio. In addition, based on the deformation reversible capability of the structure, the vibration isolation capability of three cellular metamaterial structures was investigated under different deformation stages. The results demonstrate that the cellular metamaterials with zero Poisson's ratio possess superior vibration isolation capability compared to negative or positive Poisson's ratio cellular metamaterials at different deformation stages by a comprehensive analysis. The methods and conclusions presented in this study will guide the design of functionalized cellular metamaterials with high energy absorption, strong vibration isolation, and autonomous deformation ability.

A tunable metamaterial using a single beam element with quasi-zero-stiffness characteristics for low-frequency vibration isolation

Quasi-zero-stiffness (QZS) isolators exhibit high-static and low-dynamic stiffness without sacrificing the load-bearing capacity and with the ability to shield the vibration in low-frequency ranges. Most of the current designs possess QZS property using a combination of positive stiffness element with negative stiffness element, increasing the complexity of the model. In the present research, a single-element mechanical metamaterial is tailored to obtain the QZS property. The building block consists of a single elastically-deformed beam, and the static results of the 3D-printed metastructure demonstrate QZS behavior. A mathematical model is developed for studying the nonlinear behavior of the proposed model, and the dynamic equation is solved using Harmonic-Balance method. Further, an experiment is performed to confirm the vibration isolation capability of the proposed model in low-frequency ranges. Stability analysis is performed mathematically using the perturbation analysis. The QZS mechanism obtained here solely depends on the flexible beam’s geometrical configuration, hence making the design strategy material independent.

Investigation of broadband damping and damping mechanism of quadrangular star-shaped ligament heterostructure

In this paper, a single-phase quadrangular star-shaped ligamentous heterostructure is constructed, and a two-phase structure is formed by attaching a resonator at the center of the structure. The lattice theory and finite element modeling are combined to analyze the band structure of the two structures, and the additional resonator at the center of the structure improves the bandgap range. Based on this, the bandgap can be widened and reduced by adjusting the resonator size. In the structural vibration modal analysis, it is explained that the coupling of traveling wave and vibration can open the omnidirectional bandgap, which provides guidance for the subsequent structural optimization. In addition, the relationship between bandgap opening and directional propagation of elastic waves is verified by a comprehensive analysis of group velocity, phase velocity, and other means. Finally, the transmission characteristics and stress distribution of the structure within the finite period structure are investigated, and it is further verified that the structure has a strong attenuation capability to vibration. This structure has good vibration isolation capability in a wide frequency range and has potential for application in complex vibration control.

Quasi-zero stiffness vibration isolators with slender Euler beams as positive stiffness elements

Based on the combination of the high bearing capacity of a slender Euler beam before buckling and low stiffness in the postbuckling range near the critical condition after loading, a novel quasi-zero stiffness (NQZS) isolator with enhanced vibration isolation capability is proposed using slender beams as positive stiffness elements. The proposed NQZS isolator can obtain a much large range with ultralow system stiffness maintaining the bearing capacity. Its vibration isolation performance was robust to equilibrium position deviation, which is essential for engineering practice. The correctness of the theoretical analysis was confirmed by the agreement between the experimental and theoretical results.

Hierarchical re-entrant honeycomb metamaterial for energy absorption and vibration insulation

A novel hierarchical re-entrant honeycomb metamaterial is proposed by integrating the re-entrant honeycomb (RH) with square unit cell and named as square re-entrant honeycomb (SRH). The novel hierarchical re-entrant honeycomb can not only improve energy absorption capacity but also present better vibration insulation compared with traditional RH structure. Dynamic crushing behaviors of the SRH structures are investigated theoretically and numerically. The theoretical plateau stress is in good agreement with the numerical plateau stress. Meanwhile, the deformation modes and energy absorption capacity of RH and square re-entrant honeycombs (SRHs) are compared under different impact velocities. The results show that the plateau stress and the specific energy absorption (SEA) of SRHs is higher than RH. Moreover, the vibration isolation capability of the SRHs is studied using finite element analysis. In particular, the introduction of square unit cells expand the band gap, especially in the low frequency range. By adjusting the size of oscillators, the starting and stopping frequencies of band gaps are lower effectively and the number of band gaps is increased. The results indicate that the introduction of the mass inclusions can improve the band gap characteristics of the SRH, which produce local resonance effect and the local resonance type band gap. It also appears multiple band gaps at the same time. In addition, the introduction of the mass inclusions also improves the SEA of the SRH under high-velocity crushing. This work may benefit structural vibration isolation and protection design, which provides a new thought for design and development of advanced multi-functional composite structures and materials in the engineering.

Vibration characteristics of multi-dimensional isolator based on 4-PUU parallel mechanism with joint clearance

For isolating multi-dimensional vibration experienced by vehicle-mounted precise facility, a multi-dimensional vibration isolator based on parallel mechanism with joint clearance is designed and analyzed. The main thrust of this work is establishing kinematic and dynamic equations of the isolator and exploring vibration isolation capability with joint clearance. Firstly, type synthesis of the parallel mechanism with three translations and one rotation is performed. The kinematic and dynamic equations of the isolator with joint clearance are deduced. Subsequently, vibration isolation performance is simulated with different values of joint clearance under harmonic and stochastic excitations in time and frequency domain, respectively. The simulating results demonstrate the proposed isolator with joint clearance inhibit multi-dimensional vibration effectively. The first-order resonance peak is sensitive to the increment in joint clearance. Finally, the proposed multi-dimensional vibration isolator is fabricated. The vibration isolation experiment is conducted. Through experimental results, the isolator reduces multi-dimensional vibration effectively in time and frequency domain. The vibration isolation capability degenerates as the counterweight of moving platform increases.

On the displacement transferability of variable stiffness multi-directional low frequency vibration isolation joint

In this paper, the proposed variable stiffness vibration isolation joint (VSJ) is refined, and the effects of structural damping and friction are considered and systematically investigated. The VSJ is provided with positive stiffness by the disk spring and negative stiffness by a combination of opposing buckled Euler beams with adjustable lengths to form a quasi-zero stiffness vibration isolation system. The force balance equations of VSJ in horizontal and vertical directions are presented, and the stiffness regulation capability of the structure is discussed. The vibration equations of VSJ are established and the vibration transmission rate under displacement excitation is determined using Taylor expansion and harmonic balance method. Parametric analysis shows that the reasonable configuration of slider position, spring size and stacking form can ensure the low-frequency vibration isolation capability of VSJ under heavy load, and has the ability to adjust the stiffness for different working conditions and loads. The excellent load-bearing capacity, small space footprint, and high customizability and flexibility of the performance of the VSJ give it the potential for a wide range of applications in engineering. We have investigated its adjustable stiffness and vibration isolation performance in the vertical direction by conducting experiments on the prototype to verify the correctness of the theoretical model.

New floating slab track isolator for vibration reduction using particle damping vibration absorption and bandgap vibration resistance

• A new floating slab track vibration isolator is developed using particle damping vibration absorption and bandgap vibration resistance. • Using the low-frequency vibration reduction effect of non-obstructive particle damping (NOPD), the attenuation of resonance peaks in the begin of bandgap frequency range is realized. • A coupled train-floating slab track-bridge dynamic model is established to investigate the vibration isolation capability. The environmental vibrations caused by rail transit continue to increase in importance. Even though there are a variety of efficient vibration reduction measures, there is still room for further improvement by trying new, effective vibration control mechanisms. In this paper, a new floating slab track vibration isolator is developed using particle damping vibration absorption and bandgap vibration resistance. Using the low-frequency vibration reduction effect of non-obstructive particle damping (NOPD), the particulate material is added to the outer ring vibrator to participate in vibrations, and the attenuation of resonance peaks in the begin of bandgap frequency range is realized. The energy loss factor and damping ratio of particle damping for different particle sizes are analyzed using a discrete element model. A finite element model with integrated particle damping effect is also formulated and the bandgap behavior of phononic crystal vibration isolator (PCVI) with additional particle damping is analyzed. The effect of particle damping is assessed by calculating the force transmission spectrum. In order to the investigate vibration isolation performance of the combined NOPD-PCVI when subjected to excitation from trains running at different speeds, a coupled train-floating slab track-bridge dynamic model is established. The results show that the NOPD-PCVI offers better vibration isolation than a steel-spring vibration isolator and the traditional PCVI (T-PCVI) in the frequency band of 50–150 Hz. The energy dissipation provided by particle damping and the bandgap damping of phononic crystals reduce the vertical accelerations of the bridge deck in the bandgap frequency band. Specifically, the total vertical accelerations of the bridge deck equipped with NOPD-PCVIs is reduced by 15.3 dB compared to steel springs, and 5.6 dB compared to T-PCVIs, respectively.

Development of a Performance-Enhanced Hybrid Magnetorheological Elastomer-Fluid for Semi-Active Vibration Isolation: Static and Dynamic Experimental Characterization.

Magnetorheological elastomers (MREs) are a class of emerging smart materials in which their mechanical and rheological properties can be immediately and reversibly altered upon the application of a magnetic field. The change in the MRE properties under the magnetic field is widely known as the magnetorheological (MR) effect. Despite their inherent viscoelastic property-change characteristics, there are disadvantages incorporated with MREs, such as slow response time and the suspension of the magnetic particles in the elastomer matrix, which depress their MR effect. This study investigates the feasibility of a hybrid magnetorheological elastomer-fluid (MRE-F) for longitudinal vibration isolation. The hybrid MRE-F is fabricated by encapsulating MR fluid inside the elastomer matrix. The inclusion of the MR fluid can enhance the MR effect of the elastomer by providing a better response to the magnetic field and, hence, can improve the vibration isolation capabilities. For this purpose, an MRE-based coupling is developed, and isolation performance is investigated in terms of the linear transmissibility factor. The performance of the hybrid MRE-F was compared against two different MRE samples. The results show that further enhancement of MR-effect in MREs is possible by including MR fluid inside the elastomer. The hybrid MRE-F exhibited better stiffness change with the current increase and recorded the highest value of . The transmissivity curves revealed that the MRE-F contributed to a broader shift in the natural frequency with a overall shift at . The damping characteristics are higher in MRE-F, recording the highest percentage increase in damping with . Overall, the results reveal the promising potential of hybrid MRE-F in developing MRE-based coupling for longitudinal vibration isolation.

Study on Electrical Parameter Matching of Piezoelectric Stack Periodic Strut for Helicopter Cabin Noise Control

The gear meshing noise generated by the helicopter main reducer is one of the important sources of noise in the helicopter cabin. By improving the isolation performance of the struts supporting reducer to the gear meshing vibration, the purpose of reducing the gear meshing noise in the helicopter cabin can be achieved. Piezoelectric stack periodic strut (PSPS) composed of piezoelectric stacks and passive materials periodically arranged is an original type of strut with active and passive hybrid isolation characteristics. Piezoelectric stacks and passive materials form a periodic structure, which makes PSPS have a unique stopband characteristic. The propagation of elastic waves in the stopband frequency range is attenuated, which can improve the broadband passive vibration isolation capability of the PSPS; The piezoelectric stacks can adjust the elastic wave propagation in the PSPS and improve the single-frequency or multifrequency active isolation performance of the PSPS. Since the driving voltage and current range of the piezoelectric stacks significantly affect the isolation performance of the PSPS, this article focuses on the relationship between the isolation performance of the PSPS and the voltage and current required by the piezoelectric stacks. Firstly, based on the passive material periodic structure transfer matrix model, the driving voltage and current of the piezoelectric stacks are introduced into the model, and a PSPS electromechanical coupling model based on the transfer matrix form is established. Secondly, the correctness of the model is verified by the finite element software. Based on the model, the design process of PSPS parameters is proposed. The optimal isolation performance of PSPS is predicted under the limitation of maximum driving voltage and current. The effects of damping loss factor, exciting force, period number and passive material on the requirements of electrical parameters for active control are studied. A three-period PSPS strut composed of piezoelectric stack actuator and PV strut is used for experimental research, and the matching of electrical parameters of this PSPS in the test is analyzed.

Implementation and Experiment of a Novel Molecular Spring Isolator

A molecular spring isolator comprising ZIF-8 with hydrophobic micropores, water, and a cylinder/piston unit is introduced. Liquid water can be intruded into the micropores of ZIF-8 under critical pressure. In the meantime, mechanical energy is stored. And once the external pressure is withdrawn, spontaneous capillary evaporation will occur. The stored energy, meanwhile, is released. This behavior is similar to a coil spring. The Laplace–Washburn equation is used to describe the force equilibrium of a single water column in a micropore. After that, the result of water infiltrating a great deal of hydrophobic pores is revealed by theoretical analysis and an experiment. An averaging method is devoted to computing the primary resonance response and its accuracy is proved by the fourth-order Runge–Kutta method. Furthermore, the energy transmissibility is used to estimate its vibration isolation capability. Finally, a vibration isolation test indicated that the inherent frequency of the isolator is as low as 1.3 Hz.