Vibration Isolation Research Articles

An Effective Alternative to the Open Trench Method for Mitigating Ground-Borne Environmental Body Waves: Corrugated Cardboard Boxes Reinforced with Balsa Wood

This research develops and evaluates a recyclable corrugated cardboard vibration isolation box reinforced with balsa wood as an alternative to traditional open trench methods for mitigating ground-borne environmental body waves. This study includes designing and testing scaled prototypes, laboratory analyses, prototype fabrication, and full-scale field experiments. In soft ground conditions, ensuring slope stability during deep excavations is a key engineering challenge for open trenches. For this purpose, scaled prototypes were subjected to laboratory tests to assess the resistance of the wave barrier’s wall surface. Numerical analyses were also conducted to evaluate the strength of the internal lattice structure under various loads. A prototype was fabricated for on-site experiments simulating real-world conditions. Field experiments evaluated the vibration isolation performance of the proposed barrier. Accelerometer sensors were strategically placed to gather data, analyzing ground surface vibrations for free field motions to assess the vibration shielding efficiency of both the open trench method and the corrugated vibration isolation box, with and without Styrofoam infill. This study concludes that the recyclable corrugated vibration isolation box is a viable alternative, offering comparable or improved vibration isolation efficiency in soft soil conditions while promoting environmental sustainability using recyclable materials.

Study on Bandgap of Two‐Dimensional Square Lattice Acoustic Metamaterial with Multiembedded Cores

Acoustic metamaterials have been widely studied for their excellent ability of vibration isolation. In this article, a 2D square lattice acoustic metamaterial structure with multiembedded cores is proposed. Based on Bloch's theorem and finite element method, the band structures and bandgap properties of the structure are calculated and analyzed, and the vibration isolation ability of the structure is investigated. The effects of structural parameters on the bandgap property are analyzed. Thus, the anisotropy of the structure is also analyzed by the contours of phased velocity and group velocity. The results show that the structure has significant bandgap properties and vibration isolation. The second‐order similarity ratio has significant effects on the bandgap property. Via increasing the second‐order similarity ratio, the total bandgap width and low‐frequency bandgap width are widened. In addition, the structure has significant anisotropy, and the energy of elastic wave propagates at the direction of 45° and 135°. The research in this article supplements the design and research of 2D lattice acoustic metamaterials and makes a beneficial exploration for future engineering applications.

Vibration isolation performance analysis of a nonlinear fluid inerter-based hydro-pneumatic suspension

Vibration isolation performance analysis of a nonlinear fluid inerter-based hydro-pneumatic suspension

3D-printed multifunctional chiral metamaterial with invariant sound absorption under large deformation and low-frequency vibration control

ABSTRACT Acoustic metamaterials provide a distinctive route for reducing low-frequency noise and vibration; however, most are characterised by their singular functionality, e.g. sound absorption or vibration suppression. We present a 3D-printed multifunctional chiral metamaterial (MCM) with double helix structures inspired by cochlea and DNA for excellent acoustic, mechanical, vibration isolation and mitigation properties. By employing impedance matching, nearly perfect sound absorption can be obtained and kept invariably in the low-frequency range under strain from +25% to −25%, as confirmed by the standard impedance tube tests. The double helix structure provides versatile mechanical properties, including compressibility, stretchability, and recoverability. Excellent vibration isolation ability from 94 Hz and strong elastic wave attenuation performance between 199 and 254 Hz based on bandgap strategy are demonstrated by isolation and mitigation vibration tests and simulations. This 3D printed structure presents a promising solution for multipath noise control, setting a paradigm for biologically inspired multifunctional materials.

An analytical method for the vibration characteristics of double panel structures with uniform elastic boundary supports

ABSTRACT In this paper, the methods for solving the free vibration and forced vibration of double panel structures under arbitrary boundaries are studied. Based on the Mindlin plate theory, the natural boundary between plates and plates is constrained by artificial springs, and the theoretical model of the structure is derived. The displacement function of in-plane vibration and bending vibration is expressed by a modified Fourier series expansion. The effectiveness and reliability of this method are verified by a series of numerical calculations and comparison with those of the finite element method. Through the parameter analysis, it can be seen that the vibration isolation effect can be increased by properly increasing the coupling height or making the connecting plate closer to the boundary of the bottom plate. The method presented in this paper can be used in vibration absorption and structural design of such structures.

Experimental Evaluation of Under Slab Mats (USMs) Made from End-of-Life Tires for Ballastless Tram Track Applications.

The growing population of urban areas results in the need to deal with the noise pollution from the transportation system. This study presents experimental test results of static and dynamic elastic characteristics of under slab mats (USMs) according to the procedure of DIN 45673-7. Prototype USMs based on recycled elastomeric materials, i.e., SBR granules and fibres produced from waste car tires, are analysed. Vibration isolation mats with different thicknesses (10, 15, 20, 25, 30, and 40 mm), densities (500 and 600 kg/m3), and different degrees of space filling (no holes, medium holes, large holes) are considered. Moreover, a practical application of the laboratory test results of USMs in the design of ballastless track structures of two different types (with a concrete slab and longitudinal beams) is presented. Deflections of the rail and the floating slab system, as well as stresses acting on the mat, are determined according to EN 16432-2. The use of shredded rubber from recycled car tires as a material component of sustainable and environmentally friendly tram track structures may be one of the most effective ways to manage rubber waste within the current trend toward a circular economy, and this study intends to introduce methods for experimental identification and analytical selection of basic static and dynamic parameters of prototype USMs.

Reducing low-frequency noise radiation from a concrete box girder bridge using acoustic short circuits

Low-frequency noise (20–200 Hz) radiated from concrete box girder bridges on urban viaduct railway lines is a significant source of disturbance to nearby residents. Many researchers have investigated methods which can be used to effectively reduce this bridge noise. Currently, most of the methods are based on the principles of vibration isolation and/or absorption. This paper, after modelling and analysing the contributions of various parts of a concrete box girder bridge to the total noise radiated from the bridge, presents a study on the potential in bridge noise control of making holes to create acoustic short circuits on the bridge wings. It is found that by this means the bridge noise can be reduced by up to 6.8 dB at standard-specified measurement points. Additionally, a 3dB-effectiveness distance ratio design method for acoustic short-circuiting is proposed, which effectively reduces bridge noise and achieves stable noise reduction outcomes.

Ultra-low frequency and broadband flexural wave attenuation using an inertant nonlinear metamaterial beam

Attenuation of elastic waves in the extremely low frequency range is a considerable challenge. While linear acoustic metamaterials can manipulate elastic waves, their effectiveness is often limited to a narrow frequency range. The present paper proposes a novel inertant nonlinear metamaterial beam to address the challenging problem of the ultra-low frequency broadband flexural wave attenuation. The amplitude-frequency response and dispersion relations of the flexural waves are obtained using the first-order harmonic balance method, where four different resonant units are investigated and the resulting band gaps are compared. Finite element (FE) simulations are also conducted to evaluate the transmission spectra of the flexural vibration through a finite metamaterial beam. The good consistency between the band gaps predicted by the analytical model and the FE simulation verifies the correctness and effectiveness of the developed analytical approach. The results of this study demonstrate that introducing the inertance and softening nonlinearity into the resonant units can significantly widen the flexural wave band gaps within the low-frequency range. This finding provides a viable solution for engineering applications that require low-frequency vibration suppression and isolation.

SH‐waves in a complex fluid composite structure with spring membrane imperfect interfaces

AbstractComplex fluids are of nobleness due to their unique mechanical responses to applied stress, which are different from simple fluids. Therefore, the current study encapsulated the behavior of SH‐wave in a complex fluid layer overlying a fiber‐reinforced half‐space with six different cases considered at the common interface. These cases involve various interface conditions, including perfect bonding, a spring layer, an infinitely thin membrane layer, loose bonding, a combined spring‐membrane layer, and a membrane layer with loose bonding. Precisely, the effect of loose bonding, membrane strength, and spring stiffness at the common interface on the propagation of SH (Shear Horizontal) wave is studied in detail. The problem is mathematically formulated for all the aforementioned six models followed by their solution with the aid of appropriate boundary conditions. Numerical computations are performed with a view to study the effect of stiffness of spring and membrane, as well as loose bonding at the common interface of the media. It is demonstrated that membrane strength impedes wave propagation, while increased spring stiffness supports it. Notably, the combined spring‐membrane interface has a more pronounced effect than a spring layer alone. The findings of this study may be utilized in the development of membrane technology, including the study of fluid membranes and it has significant importance in seismic engineering and vibration isolation systems.

A new inerter-based acoustic metamaterial MRE isolator with low-frequency bandgap

Abstract Acoustic metamaterials are capable of generating vibration bandgaps at specific frequency ranges, which makes them have good applications in the field of vibration isolation. To further broaden the vibration bandgaps, both magnetorheological elastomer (MRE) and graded stiffness are employed to enhance the bandgap properties. However, lowering the vibration bandgap is usually accompanied with excessive reduction of the structure stiffness. Except for reducing the stiffness, increasing the mass of the acoustic metamaterial can also lower the bandgap. In this research, a novel inerter-based acoustic metamaterial MRE isolator (IAM-MREI) was designed and prototyped. Inerters not only can generate large equivalent mass, but also are discovered to be able to greatly lower and broaden the vibration bandgap of the IAM-MREI with a brand-new mechanism, which cannot be achieved only with extra equivalent mass. The effects of the inerters on the overall performance of the IAM-MREI was thoroughly investigated and validated both theoretically and experimentally. The evaluation experiments confirmed that the IAM-MREI possesses a low frequency vibration bandgap and can provide great vibration isolation performance.

Bandgap characteristics of four component periodic pile barriers in passive vibration isolation

Based on the local resonance theory, the vibration isolation performance of four-component periodic pile barriers consisting of a matrix, an outer pipe, an inner pipe, and a pile core was investigated using the finite element method (FEM). This configuration is contrasted with traditional three-component periodic pile barriers, which are composed of a matrix, a pipe, and a pile core. The four-component systems demonstrate significantly broader bandgaps compared to three-component systems. To validate the efficiency of the FEM, model test on pile barriers were conducted, facilitating a comparison between the FEM and experimental observations of bandgap characteristics. Additionally, the effects of the outer pipe’s density, elastic modulus, and thickness on the complete bandgap characteristics were comprehensively studied within the four-component structure. It is found that the broadest vibration isolation band gaps occur under hexagonal arrangement pattern. In square and hexagonal lattice configurations, the density, elastic modulus, and thickness of the outer pipe pile’s pile have predominantly influenced the upper bound frequency (UBF). There has been a positive correlation between the elastic modulus and the UBF, while the density and thickness have shown inverse relationships. Moreover, there exists a elastic modulus threshold, marking a transition in the displacement mode of the UBF, from the outer irreducible Brillouin zone (M or X) to the inner zone (Γ). Once the threshold is exceeded, both the vibration displacement mode and the width of bandgap remain substantially unchanged. The results obtained in the present paper are very useful for the design and application of periodic pile barriers in ambient vibration reduction.

Research of Reducing Liquid Damping of Liquid Inertia Vibration Eliminator

The liquid inertia vibration eliminator (LIVE) is a type of dynamic anti-resonance vibration isolation (DAVI) devices with compact structure and light weight, which is mainly used in vibration control in the main transmission of helicopters. To investigate the influence of damping generated by the internal liquid flow on the vibration isolation performance, a model and the equations of motion of the LIVE system are established. The friction head loss, local resistance loss and damping coefficient caused by liquid movement in the tuning port of LIVE are calculated. The factors affecting the damping coefficient of the liquid are analyzed. Parameter sensitivity analyses are carried out to reveal the order of importance and interaction of the parameters. Results show that the damping of the LIVE has a negative impact on the vibration isolation performance. The liquid damping is affected by many parameters and the model has a high degree of non-linearity and complexity. The liquid damping can be effectively reduced through the selection of appropriate liquid properties and the design of the structural parameters of the LIVE.

Accelerated inverse design of vibration isolators with customizable low dynamic stiffness characteristics via deep neural network

Accelerated inverse design of vibration isolators with customizable low dynamic stiffness characteristics via deep neural network

Ultra-low frequency active vibration isolation system with quasi-zero stiffness characteristic using self-tuning filter-based feedforward control

Ultra-low frequency active vibration isolation system with quasi-zero stiffness characteristic using self-tuning filter-based feedforward control

Novel Active–Passive Piezoelectric Hybrid Constrained-Layer Damping Technique for Vibration Isolation in a Whole Spacecraft

Novel Active–Passive Piezoelectric Hybrid Constrained-Layer Damping Technique for Vibration Isolation in a Whole Spacecraft

Theoretical characteristics of a three-point Roberts linkage.

The Roberts linkage is recognized for enabling long-period pendulum motion in a compact format. Utilizing this characteristic, we are developing a three-point Roberts linkage for vibration isolation systems, with an eye toward its potential contribution to the development of next-generation interferometric gravitational wave antennas. In this article, we derived the equations to determine the essential parameters when using this linkage as a vibration isolation system, namely, the equivalent pendulum length and the relationship between translational motion of the center of mass and rigid body rotation, from size parameters. In addition, we analyzed the behavior in response to various errors.

Ground vibration isolation using mass scatters: A comparative study with trench barriers and wave‐impeding blocks

AbstractTraffic‐induced ground vibrations cause significant problems for residents and nearby structures. Reducing the effect of these vibrations on the neighboring environment is a key challenge, particularly in urban areas. This study presents both numerical and experimental investigations of the performance of mass scatters for screening ground vibrations. A three‐dimensional numerical model is validated and extended to conduct a comparative study on the efficiency of three geotechnical methods of isolation. These methods include trench barriers, wave‐impeding blocks (WIBs), and mass scatters. The results showed that mass scatters represent an efficient way of scattering ground vibrations, and their efficiency is mainly related to the weights of mass scatters and their natural frequency, which control the dynamic soil response in the frequency domain. Rigid trench barriers are less effective than soft ones, and their efficiency is more pronounced regarding the WIB. Soft barriers with a depth of an order of half of the wavelength can decrease the vibration levels by up to 50%, which is comparable to the performance of enormous mass scatters. The dimensions of WIBs must be chosen according to the wavelength of incident waves and the cutoff frequency of the topsoil layer. Considering the significant wavelength of traffic‐induced vibration, the use of trench barriers or WIBs becomes impractical and expensive; therefore, mass scatters appear to be an efficient and practical solution.

Advancements in Key Technologies for Vibration Isolators Utilizing Electromagnetic Levitation

With the advancement of manufacturing, the precision requirements for various high-precision processing equipment and instruments have further increased. Due to its noncontact nature, simple structure, and controllable performance, electromagnetic levitation has broad application prospects in ultra-precision instruments and ground testing of aerospace equipment. Research on vibration isolation technology using electromagnetic levitation is imperative. This paper reviews the latest research achievements of three types of passive isolators and five active isolation actuators. It also summarizes the current research status of analytical methods for passive isolators and the impact of isolator layout. This study explores current isolators’ achievements, such as the development of passive isolators that generate negative stiffness and require mechanical springs for uniaxial translational vibrations, single-function actuators, and control systems focused on position and motion vibration control. Based on the current isolators’ characteristics, this review highlights future developments, including focusing on passive isolators for heavy loads and multi-axis isolation, addressing complex vibrations, including rotational ones, and developing methods to calculate forces and torques for arbitrary six-DOF movements while improving speed. Additionally, it emphasizes the importance of multifunctional actuators to simplify system structures and comprehensive control systems that consider more environmental factors. This provides significant reference value for vibration isolation technology using electromagnetic levitation.

Developing Programs for Converting MIDAS GEN to ANSYS Models Based on Python

The reasonableness and accuracy of engineering design are often assessed through the use of a variety of structural design analysis software, which are then compared and verified. However, it is challenging for a single analysis software to meet the diverse and complex design requirements. In order to meet the specific engineering requirements, it is necessary to convert the MIDAS result model into an ANSYS structural model and conduct a nonlinear analysis and simulation in ANSYS. Nevertheless, the existing interface is unable to facilitate direct conversion of the model. Accordingly, this paper presents a Python-based ANSYS APDL program that enables the complete conversion of MIDAS GEN structural models to ANSYS finite element models. The program is capable of converting a range of data, including material, section, element, connection, load, node mass, constraint, time history function, and so forth. The program is capable of converting specific connection units, including elastic and general connection units. Additionally, the beam-column section direction, beam end freedom release, rigid element, and special anti-rocking structure of the structure can be considered. Ultimately, the theatre model is transformed. Following a comparison of the analysis results, it was found that the mass and mode of the model before and after the transformation were essentially identical. The maximum error of the first six orders of the structure is 2.95%, with the structural displacement under gravity load remaining essentially unchanged. The research and analysis demonstrate the accuracy and reliability of the MIDAS GEN conversion ANSYS program. The conversion program significantly reduces the time required for direct modeling in ANSYS, enhancing work efficiency. The study has considerable practical significance for the seismic sway design and analysis of buildings based on vibration isolation design.

Semi-Active Suspension Control Strategy Based on Negative Stiffness Characteristics

This paper investigates the potential of negative stiffness suspensions for enhanced vehicle vibration isolation. By analyzing and improving traditional control algorithms, we propose and experimentally validate novel skyhook, groundhook, and hybrid control strategies for suspensions with negative stiffness characteristics. We establish pavement models, incorporate negative stiffness into suspension modeling, and develop a performance evaluation index. Our research identifies shortcomings of classical semi-active control algorithms and introduces a new band selector to combine improved control methods. Simulation results demonstrate that the proposed semi-active suspension control strategy based on negative stiffness effectively reduces body vibration and enhances vehicle ride performance.