arXiv subjects

Andrea Bergamini

Publications and source records attributed to Andrea Bergamini.

9 recordsLinked to original sources

arXiv2026

Effect of introducing viscoelastic polyurethane on the dispersion and vibration isolation efficiency of chiral phononic crystals

Phononic crystals, a sequence of masses and (damped) springs, are being used more and more in practical applications, exploiting Bragg bandgaps to attenuate vibration transmission in a wide frequency range. In particular, chiral phononic crystals have demonstrated their ability to achieve low frequency bandgaps while maintaining a high static stiffness, and thus load bearing capacities. However, tuning of the bandgap frequencies is non-trivial because of their complex geometry. In this paper, viscoelastic inserts between the masses of the chain are introduced to improve the tunability of the crystal and take advantage of viscous damping. Modeling true viscoelasticity requires the implementation of frequency-dependent material properties, which is introduced in this work both for dispersion curve calculation and for harmonic force transmission simulations. As a real-world example, the intricate frequency-dependency of polyurethane is studied by examining the influence of four fractional derivative model parameters, which define the storage modulus and loss factor. The calculated dynamic force transmissibility of the phononic crystal is compared to classical, single-layer, isolation solutions. The results show that high viscous damping does not negatively affect the bandgap efficiency, which is a major advantage over resilient layer isolators where damping deteriorates the isolation properties. To validate the models, three crystals with different viscoelastic material properties in terms of stiffness and damping are manufactured and the measured force transmissibility is successfully compared to the numerical models.

physics.app-ph↗

arXiv2026

Pressure sensing by electro-mechanical coupling in compliant dielectric membranes polarized by a bias voltage

Among smart materials, piezoelectric materials occupy a very prominent position for sensing and actuation functions. Combined with simple or more advanced shunts, they are also proposed in various vibration mitigation schemes. However, the selection of available piezoelectric materials is mainly limited to ceramics (with an elastic modulus in the order of 10 Gpa (e.g. PZT ceramics) and a few polymer materials, with elastic modulus in the range of 1 Gpa (e.g. PVDF). In both cases, the high mechanical impedance and, consequently, the small dynamic strains limit the application of these materials to stiff structures. In this contribution, we discuss using a bias voltage to polarize dielectric materials and thereby compensate for the lack of spontaneous polarization observed in piezoelectrics. This enables access to materials with a wider range of elastic properties, such as soft elastomers, e.g. poly(dimethylsiloxane). As an example, we present a practical implementation of a silicone rubber membrane used as a highly compliant dynamic pressure sensor. For such nearly-incompressible materials, the capacitance change during dynamic deformation of the membranes is sufficiently large to generate a measurable dynamic voltage change over the membrane.

physics.app-ph↗

arXiv2025

Practical implementation of a chiral phononic crystal demonstrator with ultra-low frequency bandgap

The use of phononic crystals for vibration attenuation and isolation has been widely studied, showing that the attenuation frequency range depends on their mass and stiffness. The concepts of chirality and tacticity have been introduced into classical phononic crystals to enrich the dynamics of the mass elements and thereby achieve lower frequency ranges with high vibration attenuation. Although these concepts have demonstrated their effectiveness on lab-scale crystals, their implementation in industrial applications is still rare. Chiral phononic crystals require a complex geometry that complicates their manufacturing. Existing examples require to be fabricated by 3D printing, making them expensive to build on a large scale for demonstration purposes or in-situ applications. In this study, we redefine a chiral phononic crystal design for translational-rotational coupling in order to enable its manufacturability using exclusively conventional processes. We then investigate the design space of these newly designed phononic crystals, using a simplified unit cell FEM model that minimizes computation time. A parametric study is conducted to investigate the crystal's tunability by modifying the dimensions of the chiral links between the masses. A large crystal with ultra-low frequency range attenuation -- starting at 60~Hz -- is then designed, with the aim to demonstrate the influence of the crystal's tacticity on the vibration isolation by hand sensing. A crystal composed of 2 unit cells is manufactured and its measured transfer function is compared with numerical predictions, thus highlighting the disparities between the behavior of the structure under real-life and ideal excitation conditions.

physics.app-ph↗

arXiv2024

Implementation of tunable frequency-dependent stiffness elements via integrated shunted piezoelectric stacks

Piezoelectric transducers applied on or integrated in structures, combined with appropriate circuits have been extensively investigated as a smart approach to the mitigation of resonant vibrations with high relative amplitudes. \cmt{A resonant shunt circuit consisting of the capacitive piezoelectric transducer and an inductance can be configured to target specific eigenmodes of a structure, if appropriately placed and tuned. Their effect is expressed in terms of mechanical impedance of the host structure, allowing for the exchange of energy between the mechanical and electrical domain, to dramatically affect the dynamic response of the structure. By re-framing the function of resonant shunted piezoelectric transducers as frequency dependent variable stiffness elements, this paper investigates their capability to realize a frequency dependent structural mechanical connectivity, where the load path within a lattice structure can be interrupted at will for specific frequencies by tunable null-stiffness components. Here, we offer the numerical and experimental verification of this idea, by demonstrating the ability to significantly affect the dynamic response of a unit cell of an adaptive lattice metamaterial, even away from a structural resonance. In the latter case, the null-stiffness shunt leads to an additional resonance peak in the truss' dynamic response.} Its realization as additively manufactured component points to the feasibility of such structures in real life.

physics.app-ph↗

arXiv2024

A Nonlinear Damped Metamaterial: Wideband Attenuation with Nonlinear Bandgap and Modal Dissipation

In this paper, we incorporate the effect of nonlinear damping with the concept of locally resonant metamaterials to enable vibration attenuation beyond the conventional bandgap range. The proposed design combines a linear host cantilever beam and periodically distributed inertia amplifiers as nonlinear local resonators. The geometric nonlinearity induced by the inertia amplifiers causes an amplitude-dependent nonlinear damping effect. Through the implementation of both modal superposition and numerical harmonic methods the finite nonlinear metamaterial is accurately modelled. The resulting nonlinear frequency response reveals the bandgap is both amplitude-dependent and broadened. Furthermore, the modal frequencies are also attenuated due to the nonlinear damping effect. The theoretical results are validated experimentally. By embedding the nonlinear damping effect into locally resonant metamaterials, wideband attenuation of the proposed metamaterial is achieved, which opens new possibilities for versatile metamaterials beyond the limit of their linear counterparts.

physics.app-ph↗

arXiv2022

A Graded Metamaterial for Broadband and High-capability Piezoelectric Energy Harvesting

This work studies a broadband graded metamaterial, which integrates the piezoelectric energy harvesting function targeting low-frequency structural vibrations, lying below 100 Hz. The device combines a graded metamaterial with beam-like resonators, piezoelectric patches and a self-powered piezoelectric interface circuit for energy harvesting. Based on the mechanical and electrical lumped parameters, an integrated model is proposed to investigate the power performance of the proposed design. Thorough numerical simulations were conducted to analyse the spatial frequency separation capacity and the slow-wave phenomenon of the graded metamaterial for broadband and high-capability piezoelectric energy harvesting. Experiments with realistic vibration sources show that the harvested power of the proposed design yields a five-fold increase with respect to conventional harvesting solutions based on single cantilever harvesters. Our results reveal the significant potential on exploitation of graded metamaterials for energy-efficient vibration-powered devices.

physics.app-ph↗

arXiv2022

Long-range order Bragg scattering and its effect on the dynamic response of a Penrose-like phononic crystal plate

In this article, we present scattering and localization phenomena in a thin elastic plate comprising an aperiodic arrangement of scatterers. By analysing the form factor of the scattering cluster, we sample the reciprocal space which shows strong scattering points associated with non trivial dispersion. Wide frequency regimes with very different dynamic responses are identified: isotropic wave dispersion at low frequency, and an attenuating regime with strong localization effects at higher frequencies. Illustrative comparisons are drawn with a periodic counterpart having the same density of scatterers. The novel findings are corroborated by analytical estimates, numerical finite-element simulations and vibrometric experiments. The results are relevant for the research community interested in extending phononic crystal phenomena to lower frequencies.

physics.class-ph↗

arXiv2021

Inherent Non-Linear Damping in Resonators with Inertia Amplification

Inertia amplification is a mechanism coupling degrees of freedom within a vibrating structure. Its goal is to achieve an apparent high dynamic mass and, accordingly, a low resonance frequency. Such structures have been described for use in locally resonant metamaterials and phononic crystals to lower the starting frequency of a band gap without adding mass to the system. This study shows that any non-linear kinematic coupling between translational or rotational vibrations leads to the appearance of amplitude-dependent damping. The analytical derivation of the equation of motion of a resonator with inertia amplification creates insight in the damping process, and shows that the vibration damping increases with its amplitude. The theoretical study is validated by experimental evidence from two types of inertia-amplification resonators. Finally, the importance of amplitude-dependent damping is illustrated when the structure is used as a tuned mass damper for a cantilever beam.

physics.app-ph↗

arXiv2019

Shapely Atoms

The study of vibrational properties in engineered periodic structures relies on the early intuitions of Haüy and Boscovich, who regarded crystals as ensembles of periodically arranged mass points interacting via attractive and repulsive forces. Contrary to electromagnetism, where mechanical properties do not couple to the wave propagation mechanism, in elasticity this paradigm inevitably led to low stiffness and high-density materials. Here, we transcend the Haüy-Boscovich perception, proposing the concept of shaped atoms, which relaxes the link between the mass and inertia of atoms, to achieve unusual dynamic behavior at lower frequencies, leaving the stiffness unaltered. Exploiting tacticity, we successfully demonstrate its feasibility in continuous elastic chiral systems, opening the way to the conception of new mechanisms for wave control, selective wave filtering and vibration isolation.

cond-mat.mes-hall↗