Andrea Sorrentino

University of Modena and Reggio Emilia

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Davide Castagnetti

University of Modena and Reggio Emilia

Andrea Spaggiari

University of Modena and Reggio Emilia

Matteo Della Corte

Lorenzo Nicolini

University of Modena and Reggio Emilia

Deputazione Napoletana di Storia Patria Sezione di Salerno

Società Salernitana di Storia Patria

Michele De Angelis

Ospedale San Donato

G Bianchi

University of Parma

Enrico Radi

University of Modena and Reggio Emilia

Paolo Emilio Bilotti

Cooperative Institutions

University of Modena and Reggio Emilia

University of Naples Federico II

Azienda Sanitaria Unità Locale di Reggio Emilia

University of Padua

University of Bologna

Ingegneria dei Trasporti (Italy)

Istituto Nazionale di Fisica Nucleare, Sezione di Napoli

Medica (Italy)

Sapienza University of Rome

Politecnico di Milano

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A comparison between rotating squares and anti-tetrachiral systems: Influence of ligaments on the multi-axial mechanical response

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science (2021)

Luke Mizzi Andrea Sorrentino Andrea Spaggiari Davide Castagnetti

Rotating unit systems are one of the most important and well-known classes of auxetic mechanical metamaterials. As their name implies, when loaded, these systems deform primarily via rotation of blocks of material, which may be connected together either directly through joints (or ‘joint-like’ connections made by overlapping vertices of the rotating units) as in the case of rotating rigid polygonal-unit systems or by ligaments/ribs as in the case of chiral honeycombs. In this work, we used Finite Element Analysis to investigate the effect which the presence/absence of ligaments has on the on-axis and off-axis mechanical properties of these systems by analysing two of the most well-known structures which characterise these two cases: the rotating square system and the anti-tetrachiral honeycomb. It was found that while the presence of ligaments has a negligible effect on the on-axis Poisson’s ratio of these systems, it has a profound influence on nearly all other mechanical properties as well as on the off-axis loading behaviour. Systems with ligaments were found to exhibit a high level of anisotropy and also a severely reduced level of stiffness in comparison to their non-ligamented counterparts. On the other hand, the rotating square system suffers from high localized stress-intensities and has a very low strain-tolerance threshold. In addition, an optimized ‘hybrid’ geometry which is specifically designed to capture the best features of both the anti-tetrachiral and rotating square system, was also analysed. This work shows the main differences between ligament-based and non-ligament-based auxetic structures and also highlights the importance of considering the off-axis mechanical response in addition to the on-axis properties when investigating such systems.

Auxetics

Square (algebra)

Poisson's ratio

Aspect ratio (aeronautics)

10.1177/09544062211043145

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Citations (17)

Instabilità di pull-in per pinze in nano-tubi di carbonio: formulazione analitica e convalida sperimentale di macro modelli

G. Bianchi Andrea Sorrentino

Macro

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Experimental characterization of pull-in parameters for an electrostatically actuated cantilever

Applications in Engineering Science (2020)

Andrea Sorrentino G Bianchi Davide Castagnetti Enrico Radi

MEMS-NEMS applications extensively use micro-nano cantilever structures as actuation system, thanks to their intrinsically simple end efficient configuration. Under the action of an electrostatic actuation voltage the cantilever deflects, until it reaches the maximum value of the electrostatic actuation voltage, namely the pull-in voltage. This limits its operating point and is a critical issue for the switching of the actuator. The present work aims to experimentally measure the variation of the pull-in voltage and the tip deflection for different geometrical parameters of an electrostatically actuated cantilever. First, by relying on a nonlinear differential model from the literature, we designed and built a macro-scale cantilever switch, which can be simply adapted to different configurations. Second, we experimentally investigated the effect of the free length of the suspended electrode, and of the gap from the ground, on the pull-in response. The experimental results always showed a close agreement with the analytical predictions, with a maximum relative error lower that 10% for the pull-in voltage, and a relative difference lower than 18% for the pull-in deflection.

Nanoelectromechanical systems

Bimorph

10.1016/j.apples.2020.100014

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Citations (2)

Rotating squares auxetic metamaterials with improved strain tolerance

Smart Materials and Structures (2021)

Andrea Sorrentino Davide Castagnetti Luke Mizzi Andrea Spaggiari

Abstract Rotating squares auxetic metamaterials have the peculiar feature of a negative Poisson’s ratio. This work proposes and examines how an innovative variable arcs fillet solution, at the interconnection regions between the rotating units, improves the structural response of a titanium alloy-based rotating squares metamaterial. Through a 2D finite element (FE) model of the auxetic structure, we investigated and optimized two fillet configurations: first, a double circular arcs profile; second, a combined elliptical and circular arc fillet. According to the FE results, the optimal configuration of the combined elliptical and circular arc fillet allows an overall 3% elastic strain of the metamaterial, with a Poisson’s ratio (PR) equal to ca. −1. In order to assess the deformation behavior of the proposed metamaterial, we performed a tensile test on a prototype of the optimal solution, 3D printed in Onyx material. The experimental displacement field of the specimen, measured through digital image correlation, exhibited excellent agreement with the FE predictions, with a PR equal to ca . − 1 up to a 3% overall strain.

Auxetics

Fillet (mechanics)

Poisson's ratio

Digital image correlation

10.1088/1361-665x/abde50

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Citations (29)

Struttura reticolare in metamateriale auxetico per protesi ossee vertebrali in stampa 3d

Andrea Sorrentino Davide Castagnetti

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ATLAS - E’ Così AuTonomus cLeAning System

Davide Castagnetti Michele Mistrulli Andrea Spaggiari Andrea Sorrentino Eugenio Dragoni

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Rassegna storica salernitana. A.2, n.1/2(1938)

UniSa. Sistema Bibliotecario di Ateneo (1938)

Antonio Marzullo Andrea Sorrentino Luigi Giliberti Luisa Becherucci Armando Schiavo

La Societa Salernitana di Storia Patria aderisce al progetto EleA e autorizza la pubblicazione dei fascicoli.

10.14273/unisa-74

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Struttura reticolare progettata razionalmente per protesi ossee vertebrali trabecolari

Andrea Sorrentino

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Periodic tetrahedral auxetic metamaterial

Extreme Mechanics Letters (2024)

Andrea Sorrentino Davide Castagnetti

Auxetics

Tetrahedron

10.1016/j.eml.2024.102214

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A tunable multi-arm electromagnetic pendulum for ultra-low frequency vibration energy harvesting

Smart Materials and Structures (2022)

Lorenzo Nicolini Davide Castagnetti Andrea Sorrentino

Abstract Autonomous electronic devices and sensors are essential to reduce expensive maintenance, increasing job security and reliability, avoiding battery replacements and wired systems. Industrial systems and civil structures vibrate dissipating an important amount of energy that can be harvested to power small devices. This work continues and extends a previous work from the authors (Castagnetti 2019 Meccanica 54 749–60). Here we improved that initial configuration by proposing a tunable multi-arm electromagnetic pendulum for ultra-low frequency vibrations energy harvesting. This configuration features five electromagnetic converters and a magnetic spring, each supported by a pendulum arm with different length: when excited by external vibrations, this six arms frame is free to oscillate around a central pivot. The paper starts from conceptual design, includes a detailed multiphysics dynamic simulation implemented with Matlab Simscape software, presents the prototype development through three-dimensional printing and experimental validation. Systematic experimental tests investigated different pendulum configurations for three stiffness levels of the magnetic spring and confirmed both the ultra-low frequency response (from 2 to 10 Hz), as predicted by the dynamic simulation, and the good voltage and power outputs. Specifically, for the higher stiffness of the magnetic spring, corresponding to an oscillation frequency of about 9.5 Hz, the power output was up to 8.4 mW and the output voltage of about 2 Volt.

Multiphysics

Pendulum

Proof mass

Mechanical energy

10.1088/1361-665x/ac9658

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Citations (9)