Vibration Transmission Research Articles

Dual-nozzle 3D printing of fiber composites for fabrication of compliant lever-type vibration isolators with wide stopband

This study proposes fiber-composite lever-type vibration isolators with a wide stopband around the antiresonance frequency. The proposed mechanisms were 3D-printed monolithic structures with compliant butterfly hinges that mimic an ideal pinned support for the lever. Continuous carbon fiber and short carbon fiber regions were combined to achieve a wide low-frequency stopband. A rigid link model was developed to derive analytical solutions for the resonance and antiresonance frequencies of the proposed mechanisms. Frequency response analysis and modal analysis were performed to examine designs for widening the stopband using the finite element method. The print path-dependent anisotropy of short fiber-reinforced plastic was reflected in the finite element model. A dual-nozzle fiber-composite 3D printer was used to fabricate the proposed lever-type mechanisms. The measured vibration transmissibilities of the 3D-printed samples showed a similar improvement of the stopband width to the numerical analysis results, demonstrating that suitable designs of continuous fiber placement and hinge shape widened the stopband.

Study on Vibration Damping Characteristics of Mounting Structure Based on the High Damping Alloy Material

Abstract: The high damping alloy materials, by virtue of the excellent mechanical properties and damping performance generated by the material’s properties and internal friction mechanism, can be employed directly in the reduction of structural vibrations. On the basis of summarising the current research progress and application status of existing damping alloy materials, the damping characteristics of Fe-12Cr-3Al ferromagnetic high damping alloy material were tested and applied to the vibration reduction of an aero-engine lubricating oil tank. Subsequent to this, vibration characteristics simulation analysis and tests were conducted. The results show that the amplitude reduction rate of mounting structures utilising the Fe-12Cr-3Al ferromagnetic high damping alloy is 30% in comparison to Q235 carbon steel. Additionally, the vibration transmission rate can be diminished by 40%. The utilisation of the Fe-12Cr-3Al ferromagnetic high damping alloy in the aero-engine mounting structure has been observed to result in a discernible reduction in vibration.

Analyzing vibration transmission through cantilever systems using biomechanical and impact-responsive metamaterial structures

Vibration control in cantilever systems is a critical challenge in various engineering applications, where unwanted vibrations can lead to structural fatigue, reduced performance, and potential failure. This study investigates the effects of integrating biomechanical and impact-responsive metamaterials into cantilever systems to mitigate vibration transmission. The metamaterials, characterized by their adaptive stiffness and energy-absorbing properties, are strategically embedded in key structural components such as the arms, joints, and base. Through experimental analysis, this work assesses the reduction in vibration amplitude, shifts in natural frequency, enhanced damping capacity, energy absorption during impact, and strain reduction at critical points. The results show that the metamaterial-enhanced system achieves significant reductions in vibration amplitude, up to 40%, and increases in natural frequency by over 30%, minimizing the risk of resonance. Additionally, the damping ratio is improved by as much as 53%, while the energy absorption during impact is increased by up to 26%. Strain reduction at critical points reaches 24%, contributing to improved mechanical resilience. These findings demonstrate the potential of biomechanical and impact-responsive metamaterials in enhancing the dynamic performance of cantilever systems, offering a new approach to vibration mitigation in engineering applications.

Creating bandgaps in active piezoelectric slender beams through positive position feedback control

Abstract Bandgaps - frequency ranges with reduced vibration transmissibility in elastic structures, are an opportunity for vibration control originating from the research on elastic metamaterials. In this paper, we study the design for bandgap in slender beams with collocated piezoelectric patch transducers. While creating bandgaps using shunted transducers is a well-established research field, using structures with piezoelectric sensors, actuators, and feedback controllers for the same application has not been thoroughly explored. This paper aims to study the use of the tools originating from the active vibration control (AVC) field for bandgap generation in finite beams with collocated piezoelectric sensors and actuators. Lightly damped second-order low-pass filters are used as controllers in the same configuration as positive position feedback (PPF), widely used for active damping. To facilitate the understanding of systems behaviour, we propose a simplified model based on the Euler-Bernoulli beam theory. A modal analysis approach and an assumption of an infinite number of transducers of infinitesimal length distributed along the structure are used to predict the frequency range of the locally resonant bandgap in closed form. The experimental part of the work demonstrates the feasibility of the proposed approach for creating bandgaps in practice. Thanks to the insights from AVC, the control system can be designed purely based on experimental frequency response data without the need for a parametric model of the system. We also show that the uniform distribution of actuators is not necessary for creating bandgap, which can be achieved in a structure with a relatively small number of sparsely placed actuators and compare the obtained results with analytical predictions for ideal metastructure. Low-frequency bandgaps placed between 10 and 320 Hz are obtained in experiments.

Contribution of remote Pacinian corpuscles to flutter-range frequency discrimination in humans

Among the various classes of fast-adapting (FA) tactile afferents found in hairy and glabrous skin, FA2 afferents, associated with Pacinian corpuscles (PC), preferentially signal high-frequency sinusoidal events corresponding with vibration percepts, in contrast to other classes associated with lower frequency flutter percepts. The FA2-PC complex is also uniquely sensitive to distant sources of vibration mechanically transmitted through anatomical structures. In the present study, we used a pulsatile waveform to assess the contribution of FA2 afferents to the perception of flutter-range frequency stimuli (~ 20 Hz) in combination with two methods to abolish local FA inputs and force a dependence on FA2 via transmission from adjacent structures. Firstly, we examined frequency discrimination and perception of vibration applied to the hairy skin overlying the ulnar styloid before and during the blockade of intradermal receptors by local anaesthesia. Secondly, we tested frequency discrimination on the digital glabrous skin before and during the blockade of myelinated fibres by ulnar nerve compression. Despite reliance on vibration transmission to activate remote PCs, we found that flutter-range frequency discrimination was unimpeded across both skin types. Comparisons with stimuli applied to the contralateral side also indicated that perceived frequency was unaffected. This confirms that flutter-range frequency perception can be encoded by the FA2-PC system. Our results demonstrate that input from receptors specialised for low-frequency signalling is not mandatory for flutter-range frequency perception. This explains how the constancy of frequency perception might be achieved across different skin regions, irrespective of the afferent type activated for transmitting these signals.

Influence of the variation of concrete properties in determining the vibration transmission index Kij

In this work, the influence of the modulus of elasticity, the loss factor and the density of reinforced concrete on the vibration transmission index ([Formula: see text]) of a reduced concrete bench was evaluated. An experimental modal analysis based on the Operating Deflection Shape (ODS) methodology is carried out on a reinforced concrete slab (1.20 × 0.80 × 0.20 m) supported on four concrete pillars, applying four sources of distinct impacts: mallets of 1 and 4 kg, impact machine and one person jumping. The experimental results served to validate the finite element bench model (FEM) considering both the first four modes of slab vibration and the adjustment of the elasticity and shear modulus, the loss factor and the density of the concrete using the NSGA genetic algorithm-II. The [Formula: see text] index between the slab and the columns was determined experimentally, numerically and analytically, according to the Gerretsen model. The FEM model showed a percentage difference in the frequencies of the vibration modes less than 10% concerning the tests for the [Formula: see text] index. The influence of density and the modulus of elasticity mainly in the direction perpendicular to the plane of the structure modify the values of the frequencies of the vibration modes by up to 10% without interfering in the modal forms of the structure. In addition, the internal loss factor alters the amplitude of the [Formula: see text] results by an average of 10 dB. Finally, it is shown that the stiffness varies according to the orthotropy of the material. It was possible to conclude that the computational model showed good convergence in results ([Formula: see text]%) when compared with the [Formula: see text] experiments, with the same varying along the frequency, different from what is proposed in the analytical and normative models. This fact proves the hypothesis raised that structural couplings in practice generate significant interference in the results, as happens in residential buildings, with the test bench being an important experiment for initial predictions with little interference from energy transmission to the environment.

An efficient Volterra series approach for identifying nonlinear system vibration responses to an excitation

This paper focuses on the issue of nonlinear vibration responses identification of nonlinear systems. An efficient algorithm is presented, in which the nonlinear vibration system under studied is decomposed into a multiple-input/single-output (MISO) linear system with a series of power characterized inputs based on Volterra series, and the nonlinear output responses of different orders are identified by taking power spectra operation to the input and output data, revealing the contributions of each order nonlinearity to the output of the system. Compared to the existing method, the input signal of the system required in the presented approach need not remain unchanged in waveform and adjustable in magnitude. To verify the approach, a classic Duffing–Van der Pol oscillator was simulated, obtaining results very close to the fourth order Runge–Kutta method. Finally, an experiment analysis was carried out, in which the vibration transmission properties of a bolt connection were tested when the bolt was tight and loose, respectively. The results proved that the approach is effective in identifying nonlinear vibration frequency responses.

Attenuation of bulk waves using locally resonant soil-coupled metabarriers

Abstract Low frequency ground-borne vibrations generated by transport infrastructure are one of the most serious causes of disturbance to the general population. One possibility to reduce this problem is to use the wave filtering properties of elastic metamaterials. However, their integration in the soil complicates the prediction of their response, and the influence of soil-structure interaction needs to be correctly evaluated for an efficient design. The aim of this work is to experimentally evaluate the efficiency of metamaterial trench barriers set in soil in attenuating vibrations, using low-frequency local resonance mechanisms. A lab scale model is proposed comprising different resonating structures and a cylindrical encasement is adopted to couple the structure to the soil. The influence of various parameters is evaluated, such as metamaterial structure, geometrical characteristics of the resonator, and constituent materials. Finite Element simulations are used to develop a suitable design, analysing mode shapes and resonance frequencies of structures with and without the surrounding encasement. Experimental modal analysis is then performed on the corresponding fabricated samples, providing both model validation and out-of-soil mechanical characterization. Finally, vibration transmission loss measurements are performed in a setup in which different resonant metamaterial barriers are embedded into the soil sample, allowing the evaluation of barrier performance. Results indicate that the metamaterial structures provide good attenuation of vibrations in selected intervals in the low to high frequency range (1–5 kHz), demonstrating the feasibility of the approach in a scaled sample. Preliminary data regarding the structures providing preferable design characteristics is also obtained. These results can be useful for the design of trench barriers scaled to large dimensions in more realistic applicative settings.

Design and Application of a Lightweight Plate-Type Acoustic Metamaterial for Vehicle Interior Low-Frequency Noise Reduction

To reduce the low-frequency noise inside automobiles, a lightweight plate-type locally resonant acoustic metamaterial (LRAM) is proposed. The design method for the low-frequency bending wave bandgap of the LRAM panel was derived. Prototype LRAM panels were fabricated and tested, and the effectiveness of the bandgap design was verified by measuring the vibration transmission characteristics of the steel panels with the installed LRAM. Based on the bandgap design method, the influence of geometric and material parameters on the bandgap of the LRAM panel was investigated. The LRAM panel was installed on the inner side of the tailgate of a traditional SUV, which effectively reduced the low-frequency noise (around 34 Hz) during acceleration and constant-speed driving, improving the subjective perception of the low-frequency noise from “very unsatisfactory” to “basically satisfactory”. Furthermore, the noise reduction performance of the LRAM panel was compared with that of traditional damping panels. It was found that, with a similar installation area and lighter weight than the traditional damping panels, the LRAM panel still achieved significantly better low-frequency noise reduction, exhibiting the advantages of lightweight, superior low-frequency performance, designable bandgap and shape, and high environmental reliability, which suggests its great potential for low-frequency noise reduction in vehicles.

Nonlinear vibration analysis of multi-support oil-tank system in aero-engine based on asymptotic methods

This article is primarily focused on the complicated nonlinear vibration behavior of an aero-engine lubricating oil-tank system with multiple nonlinear pedestals. First, the rubber damping ring’s nonlinear factors are introduced into a cubic nonlinear dynamic model of lubricating oil-tank system. The nonlinear system parameters are identified by testing a simplified aero-engine lubricating oil-tank structure. Then, the nonlinear dynamic model is solved via asymptotic approach, and results are confirmed using Runge-Kutta numerical analysis approach. The system’s vibration responses and amplitude-frequency curves are also acquired, and influence of system parameters on nonlinearity is analyzed. Finally, an experimental investigation on the simplified oil-tank is performed. The nonlinear vibration characteristics of the rubber damping ring and its vibration reduction mechanism are verified using vibration transmissibility. The experimental results are consistent with numerical results. This paper’s recommended analysis approach has engineering significance for vibration and noise reduction design of aero-engine components.

Influence of Spatially Varied Soil Property on Train-Induced Soil-to-Column Vibration Transmission

The proximity of residential areas to traffic corridors has raised concerns among researchers regarding train-induced vibrations. Experimental studies have consistently shown variations in train-induced vibrations, which can be attributed to uncertainties and randomness in both the vibration source and propagation path. This study aims to investigate the influence factors and quantify their contributions to train-induced vibration variations through a comprehensive field measurement campaign and numerical simulations using random finite element models. During the field measurements, vibrations were recorded at the ground surface and the column base for a total of 53 passbys of the same type of metro train on parallel rail lines. Variations in train-induced vibrations caused by the source-to-receiver distance and spatially varied soil properties were analyzed and compared. Specifically, the investigation focused on the spatial variation of soil properties including elastic modulus, density and damping ratio in the topsoil and the second layer of clay, while simultaneously considering the influence of spatial variations of all three soil properties on the transmission of train-induced vibrations from the surface soil to the structural columns. Understanding these variations is crucial for the probabilistic assessment of building serviceability during train passbys. The findings of this research provide valuable insights for probabilistic prediction and evaluation of building vibration comfort.

Distributed annular diffuse vibration isolator: Isolating shaft vibration of guide roller in printing machine

The operating stability of guide roller in the printing machine is an important factor to affect the paper tape transmission, and the severe vibration of guide roller can becomes erratic the printing quality. In this paper, a novel distributed annular diffuse vibration isolator is proposed to suppress the shaft vibration of the guide roller and improve the printing performance. For discussing isolation performance, dynamic stiffness method is used for establishing the theoretical model of the proposed isolator, and calculate the vibration transmission ratio and normalized modal displacement. The results indicate that three vibration isolation frequency bands, which are 86–140, 182–224, and 236–2000 Hz, can effectively block vibration energy transmission; the normalized modal displacement decreases less between 0 and 50 Hz, decreases significantly between 50 and 1000 Hz. Finally, the experimental platform on vibration isolator of guide roller is set up to verify the vib-isolating performance. These experiment results confirm the vibration transmission ratios obtained from the experiments consistently align with the trends predicted by the theoretical model, and show that vibration acceleration RMS reaches the maximum when the driving frequency is 50 Hz, the maximal RMS before isolator is 122.7 dB; When the driving frequency is 20 Hz, the RMS reaches the minimum, and the minimum is 94 dB. Thus it indicted that the proposed vibration-isolator has excellent vibration isolation performance, can isolate the vibration of the guide roller effectively in a wide frequency range.

Reconfigurable topological gradient metamaterials and potential applications

Elastic topological metamaterials are innovative fields of the fusion of physics and mechanics. Through novel microstructural designs, elastic topological metamaterials provide a pioneering approach to precisely manipulate elastic waves, maintaining robustness and efficiency in wave propagation even within complex environments. Recent advancements in reconfigurability and gradient features have significantly enriched the mechanical phenomena of wave manipulation, broadening the application potential of elastic topological metamaterials. In this study, we design the local resonant phononic crystal, employing a spiral support structure to ensure low-frequency characteristics and adjustable mass for flexible configuration. By utilizing the designed lattices with distinct topological phases, the topological valley edge states are constructed. The frequency and group velocity variation of the topological edge states under different stiffness and mass parameters are analyzed. Furthermore, we further constructed the mass and stiffness gradient metamaterial to analyze the transmission law of elastic waves in topological metamaterials. Additionally, the fluctuation features of the wave transmittance under disordered and impurity defects were discussed, confirming the robustness of waveguides within low-frequency topological metamaterials. Finally, we explored the potential applications of the designed metamaterials in energy localization and low-frequency reconfigurable waveguides. Numerical analysis showed that the topological gradient metamaterials can enhance the vibration energy at a specific interface, and low-frequency bend waveguide paths can be adjusted flexibly by configurable mass. In summary, this paper focuses on the low-frequency and gradient features of elastic topological metamaterials, aiming to unlock their application potential in vibrational energy harvesting, vibration suppression, and information transmission, which accelerate the practical implementation of topological metamaterials.

Smart whole-body vibration attenuation, cushion for heavy equipment seating: Model and simulation

Off-road mobile machine operators are exposed to whole-body vibration (WBV) which can result in adverse health effects. Seat suspensions are used to reduce WBV exposure, but typical passive seats cannot attenuate frequencies below 1.13 Hz. The proposed device is designed to minimize transmissibility from 0 to 20 Hz because this bandwidth contains the dominant frequency for most off-road vehicles. The semi-active smart device uses bang-bang control and is designed to be installed in place of the seat-pan cushion in OEM passive seats. Modelled as a two degree of freedom system, simulations were performed using a lumped mass model (ωn = 3 Hz; sinusoidal base excitation 0-20 Hz). Using a hexapod robot, a prototype reduced transmissibility compared to a passive OEM seat. The device was up to 5 times more effective than a passive seat in reducing vibration transmissibility. Simulations revealed that operator mass and seat stiffness variations have little effect on device WBV attenuation performance.

The Effects of Adding TiO2 and CuO Nanoparticles to Fuel on Engine and Hand–Arm Driver Vibrations

Occupant comfort is a key consideration in automobile dynamics, with vibrations potentially causing long-term physical discomfort, especially for drivers. This study investigates the impact of adding TiO2 and CuO nanoparticles to fuel on engine-induced vibrations. Experiments were conducted at various nanoparticle concentrations (0, 50, 100, and 150 ppm) and engine speeds (1000, 2000, and 3000 rpm). Key performance metrics, including kinematic viscosity, density, heating value, thermal conductivity, and brake power (BP), were analyzed. The results indicated that increasing nanoparticle concentration led to a rise in BP. The highest reduction in root mean square (RMS) vibration accelerations occurred at 3000 rpm and 150 ppm, with vibration reductions of 30.33% for CuO and 28.61% for TiO2. Additionally, 8–10% of engine vibrations were transmitted to the steering wheel. The use of 150 ppm CuO nanoparticles resulted in reduced vibration transmission to the steering wheel at all tested speeds. These findings suggest that nanoparticle-enhanced fuels can significantly reduce engine vibrations, potentially improving driver comfort and reducing wear on vehicle components.

Experimental study of the transmission of vibrations and noise of an hydrofoil excited by cavitation in a hydrodynamic tunnel

Ship propellers are responsible for radiated noise in the near and far environment. One of the main sources of noise from propellers is due to the cavitation phenomenon that occurs on each blade. This phenomenon produces strong pressure fluctuations, which in turn generate noise that propagates in the ocean but also inside the boat. The strong wall pressure fluctuations excite the hull structure, which then transmits the noise inside the ship. The transmission is problematic for passenger ships and cruise liners, for whom silence is synonymous with quality. Efforts are being made to improve sound absorption and insulation, but the phenomenon of noise transmission from propellers to the hull via strong pressure fluctuations is still poorly understood. The aim of the paper is to simplify the problem studying a hydrofoil excited by a controlled flow and subjected to different states of cavitation. Vibration and acoustic measurements will be carried out to study the transmission of noise and vibration through the tunnel wall in order to be correlated to the different states of cavitation.

Flanking transmission from structure-borne sound sources in heavyweight buildings over multiple junctions

In many buildings, rooms that contain vibrationally-active machinery are not always adjacent to habitable rooms; hence it is useful to be able to predict vibration transmission over multiple junctions to non-adjacent rooms. In the first version of the European Standard EN 12354 Part 5 (2009) the equivalent vibration reduction index was introduced to account for transmission across multiple junctions. This was removed in the 2023 version but there remains a need for these estimates at the design stage of a building. This paper compares predictions of vibration transmission from a wall to different receiving rooms in a large heavyweight building. The SEA matrix solution is compared with SEA path analysis using different numbers of paths to assess whether path analysis is feasible, and if so, what errors can be expected when using a limited number of paths. An alternative approach to path analysis is to use transmission functions for heavyweight buildings, and an initial assessment is made to see whether these are expected to vary significantly depending on the position in the building.

Using wave based SEA methods to model noise and vibration in underwater structures across a broad frequency range

Modelling noise and vibration transmission in underwater structures is often challenging due to the large size of the structures and the need for analysis across a broad frequency range. Finite Element and Boundary Element methods are useful at lower frequencies but are typically not computationally tractable for system level models at mid and high frequencies. Statistical Energy Analysis (SEA) methods are widely used for modeling structures in air at mid and high frequencies. However, traditional SEA methods often do not contain enough detail to describe wave propagation in heavy fluid loaded structures in underwater applications. This paper discusses the use of a more general 'wave based' SEA method that uses periodic structure theory to accurately calculate the wavetypes of typical underwater structures. The paper illustrates the method by initially considering simple structural sections and showing the effects of: curvature, heavy fluid-loading, panel stiffeners/ribs. The method is then applied to a simplified full scale submarine model and comparisons are made with a nodal finite element model. The domain of validity and the hypotheses of the method are then discussed.

Analysis, design & installation of vibration isolation for lightweight helipads: a case study

The heliport isolation aims to mitigate the transmission of helicopter-induced vibrations to the building structure during approach, landing, and take-off by introducing vibration isolators at the supports of the heliport structure. As a case study, this paper presents the design and manufacturing steps for the installation of a vibration isolation solution for two lightweight helidecks installed on the rooftop of an existing medical center building. Design of a very high-performance isolation system for a lightweight helideck, requires a series of stability checks under various load conditions. In practice, the primary challenge is to control the substantial differential deflection of the helideck, which is supported by relatively soft isolators, during approach and landing conditions. The solution delivered was a prefabricated spring box comprising essential components such as failsafe and uplift restraints to deal with the challenging aspects of the isolation of lightweight helidecks. Certainly, a collaborative effort between the isolation solution provider and the helideck supplier facilitated a progressive design process aimed at meeting stringent acoustic performance requirements and addressing the complex functionality of a lightweight helideck. The paper also discusses the challenges and best practices encountered during the production and installation of the system.

Inverse design of acoustic metamaterial-based vibration control for offshore wind turbines

This paper presents an inverse design approach for mechanical metamaterial turbines utilising a deep learning algorithm. We first establish a theoretical model for metamaterial turbines using the spectral element method to analyse their vibration characteristics. Subsequently, we predict the vibration transmission properties of these turbines and achieve on-demand inverse design of metastructures through a fully connected deep-learning neural network model. The efficacy of the forward prediction and reverse design network models is validated using an inverse neural network. Our results demonstrate a strong agreement between the predicted and target values, affirming the feasibility of employing deep learning for on-demand meta-turbine design. This intelligent design approach holds promise for expediting and enhancing the design of metamaterials tailored for low-frequency vibration isolation in engineering structures.