Vibration Isolation Properties Research Articles

3D printed metamaterials for damping enhancement and vibration isolation: Schwarzites

Schwarzites are 3D solids with negative Gaussian curvatures that have unusual and interesting mechanical properties. Energy dissipation is one such property Schwarzites offer due to their high ductility and strength. The energy dissipating mechanism can be exploited to remove energy from dynamic systems that have continuous energy input and reduce the system response. Here, the energy dissipation is characterized for 3D printed specimen with solid and Schwarzite geometry. Further, the usefulness of the property is shown by analyzing the reduction in response quantities by performing dynamical simulations. It is found that having Schwarzites geometry increases the damping ratio by nearly 80% with the same amount of material as a solid support. Further, vibration isolation properties of Schwarzites are also illustrated.

An innovative wide and low-frequency bandgap metastructure for vibration isolation

Engineering the architecture of materials is a new and very promising approach to obtain vibration isolation properties. The biggest challenge for lattice structures exhibiting vibration isolation properties is the trade-off between compactness and wide and low-frequency bandgaps, i.e., frequency ranges where the propagation of elastic or acoustic waves is prohibited. Here, we, both numerically and experimentally, propose and demonstrate a new design concept for compact metamaterials exhibiting extraordinary properties in terms of wide and low frequency bandgap and structural characteristics. With its 4 cm side length unit cell, its bandgap opening frequency of 1478 Hz, its band-stop filter behavior in the range 1.48–15.24 kHz, and its structural characteristics, the proposed 1×1×3 metastructure represents great progress in the field of vibration isolation and a very promising solution for hand-held vibration probes applications that were unattainable so far through conventional materials.

On the Forced Vibration of Bending-Torsional-Warping Coupled Thin-Walled Beams Carrying Arbitrary Number of 3-DoF Spring-Damper-Mass Subsystems

This paper presents an analytical transfer matrix modeling framework for the forced vibration of a bending-torsional-warping coupling Euler-Bernoulli thin-walled beam carrying an arbitrary number of three degree-of-freedom (DOF) spring-damper-mass (SDM) subsystems. The thin-walled beam is divided into a series of distinct sub-beams whose ends are connected to the SDM subsystems. The transfer matrix for each sub-beam is developed based on the exact shape functions of the bending-torsional-warping coupling Euler-Bernoulli theory. Each SDM system is modelled by a set of effective springs based on the dynamic condensation method. The governing matrix equation is formulated based on the compatibility conditions of the placement and the force at the common interfaces of two adjacent sub-beams. Then, a closed-form expression for the frequency response function of the thin-walled beam system is proposed. The results computed by the proposed method achieve good agreement with those obtained by the conventional finite-element method, which shows the accuracy and reliability of the proposed method. The effects of the system parameters on the vibration transmission and vibration isolation properties of the thin-walled beam system are studied. The presented method can simultaneously consider arbitrary number of SDM subsystems and boundary conditions. Furthermore, none of the associated matrices are larger than 12 × 12, which provides a significant computational advantage.

Dynamic mechanical analysis of rubber based products in under ballast mat rail applications

Rubber has long been a material used for vibration isolation in railroad applications due to the attractive material performance and environmental stability. In addition to the inherent sustainability benefits relative to alternatives, rubber in particular offers the opportunity for further material engineering by controlling particle size distribution, density, binder properties etc. at the manufacturing stage and has found widespread use globally in under ballast mat applications from tramway to heavy-haul/mainline track types. In this paper we explore in detail the basic vibration isolation properties of a variety of rubber based ballast mats via dynamic mechanical analysis and connect fundamental properties such as dynamic modulus, natural frequency, degree of damping to the relevant design criteria defined in widely accepted industry standards DIN 45673-5 and the more recent EN 17282.

Vibration isolation properties of the nonlinear X-combined structure with a high-static and low-dynamic stiffness: Theory and experiment

A nonlinear X-combined structure is proposed and designed using an X-shaped structure (positive/negative stiffness mechanism) and two inclined springs (positive stiffness mechanism) to avoid existing negative stiffness and unstable factors and to improve vibration isolation characteristics. The mechanism possesses high-static and low-dynamic stiffness in a larger displacement range. In order to identify the coupling mechanism of the combination of two nonlinear mechanisms, its static and dynamic properties are investigated. The displacement transmissibility with multi-valued solutions is used to evaluate the vibration isolation of the combined structure. A new mathematical method is used to obtain a multi-valued analytical solution to the nonlinear equation of motion, which is then validated using the ADAMS software and the least square method (LSM). The novelty of this study is (a) the system has a very useful nonlinear stiffness with positive/quasi-zero/zero stiffness over the entire working range, and the quasi-zero stiffness (QZS) range is greater than that of an X-shaped structure; (b) compared to the existing nonlinear vibration isolator, such as three-spring systems and X-shaped structures, the proposed structure has the lower equivalent stiffness in the vibration isolation range, and the vibration isolation performance is better when each system has the same loading capacity; (c) the completed and accurate nonlinear solutions can more scientifically reflect the vibration isolation characteristics of the system; (d) the introduction of oblique springs into the X-shaped structure can make it easier to adjust the stiffness of the structure and use the tensile spring as the oblique spring, and the X-combined structure is easier to be designed and installed. This study shows that the proposed structure can provide excellent vibration isolation by combining two nonlinear mechanisms. These advantages are also confirmed by experiments and comparison with existing QZS isolators. This vibration isolation system will provide a new analytic method and innovative approach to the QZS isolator.

Origami-inspired lattice for the broadband vibration attenuation by Symplectic method

This work investigates the elastic wave propagation in origami-inspired lattice which is a space network established by the beams at the mountain lines and valley lines in Miura-origami. The eigenvalue equation describing the dispersion relation is established by the finite element method and Bloch theorem, and the band structure is obtained by using the Symplectic method to simplify the calculation of the eigenvalue problem. The participation factor is applied to evaluate the Bloch wave modes. The origami-inspired lattice has a wide band gap that suppresses the planar wave propagation. The participation factor explains the phenomenon that the origami-inspired lattice can only suppress plane waves. The vibrational response of the finite lattice further verifies the vibration isolation properties. We find that the origami-inspired lattice provides a new way to design the vibration-isolating structures.

Effect of Relative Humidity on Main Resonance Frequency for Paper Honeycomb Packaging System

Paper honeycomb sandwich plate is often used as transport packaging for the good cushioning and vibration isolation properties. However, the change of relative humidity has a great influence on the vibration performance of paper honeycomb sandwich plate because of its strong water vapor absorbing characteristics. In order to avoid the system resonance and reduce the product vibration damage, the main resonance frequencies for the paper honeycomb packaging system were evaluated by the sinusoidal vibration tests, further the effects of relative humidity, static compression stress, and the geometric parameters of honeycomb core on the main resonance frequencies were investigated. The results show that the main resonance frequency decreases with the increase of relative humidity, static compression stress, honeycomb cell length, and plate thickness.

Phononic band gap optimization in truss-like cellular structures using smooth P-norm approximations

The emergence of additive manufacturing and the advances in structural optimization have boosted the development of tailored cellular materials. These modern materials with complex architectures show higher structural efficiency when compared to traditional materials. In particular, truss-like cellular structures show great potential to be applied in lightweight applications due to their large strength/stiffness to mass ratio. Besides lightweight, these materials may exhibit incredible vibration isolation properties known as phononic band gaps. The present investigation addresses the topology optimization of two-dimensional (2D) truss-like cellular structures. The formulation aims to find the optimal geometrical and mechanical properties of each truss element to create a material exhibiting outstanding vibration (elastic wave) isolation at a certain frequency range (band gap). A new method to handle the non-differentiation of repeated eigenvalues, as well as mode switching, is proposed, where P-norms are used to create continuous approximation for extreme frequency values for all wave vectors of the band diagram. Results show that the proposed formulation is effective and avoids convergence problems associated to mode switching and to repeated eigenvalues.

Dynamic Fractals in Biomechanics: The Vibration Receptors of Pacinian Corpuscles

In this article, the concept of dynamically fractal structures (dynamic fractals) is introduced. The concept supposes that the dynamic, i.e., elastic–inertial, parameters of the constituent cells change on an equal scale. It is shown that a lengthwise descending dynamic fractal has the property of amplifying the input signal along the structure. On the contrary, a lengthwise increasing dynamic fractal, the attenuation rate of which is higher than that of the periodic structure, has good vibration isolation properties. The dynamic properties of the Pacinian corpuscle, a vibration receptor that detects vibrations, have been studied. A mechanical model of the corpuscle has been constructed. It is shown that a vibration receptor is a fractal with lengthwise decreasing parameters that, therefore, amplifies the input signal, which allows detecting even weak vibration impacts on a human being.

LITERATURE STUDY ON SEISMIC RESISTANCE OF STRUCTURES USING 3-D PRINTED MODELS

Seismic waves dampening is a mechanism of reducing the intensity of vibrating waves coming on the structures and thus reducing energy dissipating demand on structures. Beam column joint, when it undergoes severe vibrations, will have a large impact on the structure and results in the formation of cracks and leads to failure of the structure. Hence beam column joint is considered as the critical zone under seismic vibrations. In the beam column, damages occur in the joints when compared to the other areas. Traverse shear reinforcement, applied in the joints will surge the shear strength, until threshold limit. When it goes beyond the threshold limit, it will decrease the shear strength. This requests for more research and analysis in controlling joint failures. In recent days, three-dimension printing (3DP), also termed as Additive manufacturing, is highly developing and provides new idea for engineers and researchers in the construction industry. 3DP provides high building efficiency, less construction waste, low labor cost compared to traditional construction technology. In the modern era, researchers are involved in the analysis and design of experimental verified lattice structure, developed using 3DP, to improve the vibration isolation properties. The focus of this project is to develop 3-D printed beam column joint – shear dissipating models- and test the specimens for wide range of frequencies. The strength of the 3-D models is tested using ANSYS Software. Based on the results obtained from ANSYS Software, experiments will be conducted by placing the 3-D models in the beam-column joint and the comparison study will be performed.

Vibration isolation by novel meta-design of pyramid-core lattice sandwich structures

Pyramid-core lattice sandwich structures (PCLSSs) have been widely used in various engineering fields due to their high stiffness-to-density ratio. Although the advantages of such structures are obvious, the rather poor vibration isolation property restricts their applications. In the present work, we develop the chessboard-designed and gradient PCLSSs in order to improve their out-of-plane vibration isolation performance. The numerical results are obtained by the finite element method (FEM). Our results show that the chessboard-designed PCLSS has a lower and wider band-gap for the out-of-plane vibration than the classical PCLSS. The effects of the geometry and material parameters on the band-gap are analyzed. A gradient PCLSS with the core radius varying linearly is proposed. Compared to the classical PCLSS, the gradient PCLSS can expand the frequency range of the band-gaps significantly while maintains the high stiffness-to-density ratio. Moreover, the spatial gradient of the pyramid-core is utilized to realize the rainbow trapping and the nonreciprocal transmission of the elastic flexural waves. The novel meta-designed PCLSSs show potential applications where both a good vibration isolation and a high stiffness-to-density ratio are needed.0

Shock response of a two-stage vibration isolation system

Abstract. Two-degree of freedom system, or two-stage mount are used to improve the high frequency vibration isolation performance with the disadvantage of increasing the mass of the system and adding a second resonance. The vibration isolation property is a well-understood topic for harmonic vibration considering linear and nonlinear elements, but not its shock response. The absolute and relative response of a two-stage mount under shock excitation is investigated in this paper. Analysing the effect of the mass ratio between the two-stage, and its respective viscous damping. The potential advantages and issues behind this system are discussed and compared with the single mount. Experimental validation was performed using two commercial isolator and different masses. Findings suggested that a large secondary mass could reduce the shock response in terms of absolute motion. This effect is only significant for the case of short pulses and when the added mass is at least five times greater than the main mass. Being useful to have light damping only on the secondary stage.

Calculated and experimental tests of dynamic vibration isolators for use in the suspension system of the traction vehicle cabin

The article gives a brief description of operational vibration effects on the tractor cab, protective qualities of standard rubber monoblock vibration isolators used in the systems of cabin suspension of domestic tracked tractors. The principle of operation and advantages of dynamic vibration dampers are described. The description of methods and results of calculation and experimental studies of vibration insulating properties of standard and dynamic vibration isolators is given.

Calculated evaluation of the efficiency of dynamic vibration isolators of the tractor cab suspension system

The article gives a brief analysis of vibration-protective properties of standard rubber monoblock vibration isolators used in the systems of cabin suspension of domestic tracked tractors. The advantages of dynamic vibration dampers are described. The dynamic model of the tractor with standard and dynamic vibration isolators is described. The article presents the review of the methods of performed design researches and the analysis of their results.

Influence characteristics of electrical parameters and vibration isolation properties of the stretcher system based on parallel mechanism and self-powered magneto-rheological damper

For reducing multidimensional vibrations endured by supine patients on ambulances, a new ambulance stretcher composed of parallel mechanism and self-powered magneto-rheological damper is introduced. The main thrust of this work is to investigate the vibration isolation capability and energy conversion efficiency of the proposed stretcher with changes in electrical parameters. First, the kinematic and dynamic equations are deduced by geometry and Lagrange approach, respectively. Subsequently, the circuit model of self-powered magneto-rheological damper is created. The frequency response function is derived by Kirchhoff’s law, which indicates the electrical power utilization rate. Then, the vibration isolation capability of the self-powered stretcher system is analyzed with changes in electrical parameters. Compared with passive control, the vibration isolation capability of the self-powered stretcher is improved significantly in horizontal, longitudinal, vertical, and pitch directions. The first two resonance peaks of displacement response are insensitive to changes in electrical parameters in all directions. Last, the energy conversion efficiency of the self-powered stretcher is discussed. Decreasing resistance and inductance could improve energy conversion efficiency significantly.

Identification of multi-dimensional elastic and dissipative properties of elastomeric vibration isolators

Abstract Experimental methods must be adopted to characterize the dynamic properties of elastomeric isolators, especially their multi-dimension elastic and dissipative properties. To facilitate a tractable problem statement a rigid body isolation system (under a weight-type preload) is proposed and reduced to a planar problem with 3 degrees of freedom that can be replicated in any vertical plane. First, this article employs modal methods in tandem with analytical, lumped-parameter models to experimentally characterize the dynamic stiffness matrix, including off-diagonal terms. Fundamental stiffness properties are identified about the elastic center, facilitating a clear relationship between component- and system-level dynamics. Dissipative properties are analyzed in terms of global, structural type and mode-dependent viscous type damping formulations. Modal decomposition is employed to demonstrate the effectiveness of the dissipative models for both coupled and uncoupled motions. The proposed characterization method is validated by comparing predicted dynamic properties of a multi-isolator system with measured responses in multiple directions. Finally, physical insight into the underlying behavior of elastomeric interfacial elements is sought by highlighting the role of the elastic center, comparing structural loss factor and viscous damping matrix models, identifying the correlation between surface hardness and Young’s Modulus, and briefly comparing non-resonant and resonant methods. Several annular or cylindrical elastomeric devices with varying size and material demonstrate the proposed method’s breadth of application; subsequently, two production mounts are utilized for validation purposes. Various identification issues such as uniqueness of the identified stiffness, damping and elastic center properties are discussed throughout the article.

Mechanical and vibration isolation behaviour of acrylonitrile-butadiene rubber/multi-walled carbon nanotube composite machine mounts

ABSTRACTAn effective analytical-experimental test method is used in the current work to characterize the vibration isolation performance of nitrile-butadiene rubber (NBR) reinforced with multi-walled carbon nanotubes (MWCNTs). A series of specimens were manufactured with 10 different NBR/MWCNTs concentrations (0 to 20wt% MWCNTs). In order to determine the static compression stiffness and hysteresis of the mounts, compression and cyclic tests were conducted. The vibration isolation properties were determined through the analysis of the transmissibility of a suitably designed test system. NBR’s mechanical properties and vibration isolation properties were improved with the addition MWCNTs, suggesting that the enhancement of NBR with MWCNTs was rather effective. Considering the obtained results, the dynamic stiffness of NBR and its capacity to isolate vibration can be adjusted by controlling the proportion of MWCNTs.

Design and analysis of strut-based lattice structures for vibration isolation

This paper presents the design, analysis and experimental verification of strut-based lattice structures to enhance the mechanical vibration isolation properties of a machine frame, whilst also conserving its structural integrity. In addition, design parameters that correlate lattices, with fixed volume and similar material, to natural frequency and structural integrity are also presented. To achieve high efficiency of vibration isolation and to conserve the structural integrity, a trade-off needs to be made between the frame’s natural frequency and its compressive strength. The total area moment of inertia and the mass (at fixed volume and with similar material) are proposed design parameters to compare and select the lattice structures; these parameters are computationally efficient and straight-forward to compute, as opposed to the use of finite element modelling to estimate both natural frequency and compressive strength. However, to validate the design parameters, finite element modelling has been used to determine the theoretical static and dynamic mechanical properties of the lattice structures. The lattices have been fabricated by laser powder bed fusion and experimentally tested to compare their static and dynamic properties to the theoretical model. Correlations between the proposed design parameters, and the natural frequency and strength of the lattices are presented.

Dynamic Mechanical Characterization of Polyurethane/Multiwalled Carbon Nanotube Composite Thermoplastic Elastomers

ABSTRACTAn effective analytical–experimental test method is used in the current work to characterize the vibration isolation behavior of thermoplastic polyurethane multiwalled carbon nanotube nanocomposites with five different concentrations. To determine the static compression stiffness and hysteresis of the specimens, compression and cyclic tests were conducted. The vibration isolation properties were determined through the analysis of transmissibility of a suitably designed test system. Thermoplastic polyurethane’s mechanical properties and vibration isolation properties were improved with the addition of multiwalled carbon nanotubes. Considering the obtained results, the dynamic stiffness of thermoplastic polyurethane and its capacity to isolate vibration can be adjusted by controlling the proportion of multiwalled carbon nanotubes.

Estimation of the transient response of a tuned, fractionally damped elastomeric isolator

This article addresses the frequency dependent properties of elastomeric vibration isolators in the context of lumped parameter models with fractional damping elements. A mass is placed between two fractional calculus Kelvin-Voigt elements to develop a minimal order system for the example case of a conventional elastomeric bushing typical of automotive suspension systems. Model parameters are acquired from measured dynamic stiffness spectra and a finite element model. The minimal order system model accurately predicts dynamic stiffness in both broadband resonant behavior as well as the lower-frequency regime that is controlled by damping. For transient response analysis, an inverse Laplace transform of the dynamic stiffness spectrum is taken via the Residue Theorem. Since the fractional calculus based solution is given in terms of problematic integrals, a new time-frequency domain estimation technique is proposed which approximates time-domain responses for a class of transient excitation functions. The approximation error is quantified and found to be reasonably small, and tractable closed-form transient response functions are provided along with a discussion of numerical issues.