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Antonio ZIPPO

Professore Associato
Dipartimento di Ingegneria "Enzo Ferrari"


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Pubblicazioni

2023 - Fluid–Structure Interaction of a thin cylindrical shell filled with a non-Newtonian fluid [Articolo su rivista]
Zippo, A.; Iarriccio, G.; Bergamini, L.; Colombini, E.; Veronesi, P.; Pellicano, F.
abstract

This paper presents the results of an extensive experimental campaign on the dynamic interactions between an elastic structure and a non-Newtonian fluid. The structure consists of a thin circular cylindrical shell, with the bottom end clamped to a shaking table, and the top end carrying a heavy mass. The fluid is a mixture of water and cornstarch, also known as oobleck. The system dynamics has been analyzed in the presence of different fluid levels (i.e., empty, partially, and full-filled). The experimental modal analysis has been carried out to identify the modal properties of the system. High energy tests have been performed by means of a seismic excitation consisting in a stepped sine sweep, spanning the forcing frequency within the neighborhoods where strong resonance phenomena take place. Different excitation amplitudes have been considered in order to induce phase transitions in the fluid, and the onset of complex dynamics has been detected using Fourier spectra and bifurcation diagrams of the Poincaré maps: when the fluid–solid​ transition occurs, the entangled non-Newtonian fluid rheology results in a complex dynamic scenario where period-doubling cascades, quasiperiodic and chaotic responses can be observed.


2023 - Spiral Bevel Gears: nonlinear dynamic model based on accurate static stiffness evaluation [Articolo su rivista]
Molaie, Moslem; Samani, Farhad S.; Zippo, Antonio; Pellicano, Francesco
abstract

In the present paper non-linear dynamics of a spiral bevel gear pair with backlash are investigated in order to clarify the internal excitations of major importance from the vibration point of view: manufacturing errors in the teeth profile, teeth spacing errors, and elastic deformation of the teeth. In some conditions, like in the case of backside contact, the destructive effect of internal excitations can be intensified leading to complex dynamics; for such reasons here backside contacts and reverse rotation are investigated in detail using a nonlinear time-varying model. The effect of damping is investigated as well. A one-DOF model is developed in order to study the dynamic behavior; the resulting a nonlinear differential equation with time-varying mesh stiffness is solved via numerical integration based on an adaptive step-size implicit Runge-Kutta scheme. The dynamic response of the system is analyzed through time histories, phase portraits, bifurcation diagrams, and Poincaré maps. Results show that for small backlash values, the possibility of backside contact increases. Meanwhile, by increasing the backlash value, the amplitude vibration of the gear rotation rises as well. By comparing the dynamic response of the system with different damping ratios, the results show that higher damping effectively reduces gear vibration resonance, although the probability of unsteady response still exists.


2022 - Asymmetric vibrations and chaos in spherical caps under uniform time-varying pressure fields [Articolo su rivista]
Iarriccio, G.; Zippo, A.; Pellicano, F.
abstract

This paper presents a study on nonlinear asymmetric vibrations in shallow spherical caps under pressure loading. The Novozhilov’s nonlinear shell theory is used for modeling the structural strains. A reduced-order model is developed through the Rayleigh–Ritz method and Lagrange equations. The equations of motion are numerically integrated using an implicit solver. The bifurcation scenario is addressed by varying the external excitation frequency. The occurrence of asymmetric vibrations related to quasiperiodic and chaotic motion is shown through the analysis of time histories, spectra, Poincaré maps, and phase planes.


2022 - Correction to: Asymmetric vibrations and chaos in spherical caps under uniform time-varying pressure fields (Nonlinear Dynamics, (2022), 107, 1, (313-329), 10.1007/s11071-021-07033-7) [Articolo su rivista]
Iarriccio, G.; Zippo, A.; Pellicano, F.
abstract

The original article was published with erroneous author information. The correct authorship is as it stands in this correction. The original article has been corrected.


2022 - Digital Twins: Neural-Networks for the implementation of digital twins of gearboxes [Relazione in Atti di Convegno]
Zippo, A.; Bergamini, L.; D'Elia, G.; Pellicano, F.; Dalpiaz, G.; Iarriccio, G.; Molaie, M.
abstract


2022 - Effects of laser surface texturing on the dynamic performance of spur gears [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Molaie, M.; Bergamini, L.; Pellicano, F.
abstract

Laser Surface Texturing (LST) has been successfully applied to improve the tribological performance of reciprocating surfaces. In this context, although the relative motion between the meshing teeth is a combination of sliding and rolling, gears provided with LST could further reduce losses and vibrations in power transmissions. In this study, experimental results on the efficiency and the vibrations of gears are reported. The tests were carried out through a test bench that allows for evaluating the power losses of the transmission and the dynamic transmission error thanks to a set of torquemeters and accelerometers. Different load and speed conditions were investigated, and a comparison of the results between textured gears and standard carburized gears is provided.


2022 - Experiments on a Quasi-zero Stiffness Suspension for Passive Vibration Control [Relazione in Atti di Convegno]
Iarriccio, G.; Molaie, M.; Zippo, A.; Pellicano, F.
abstract

Experimental measurements on a quasi-zero stiffness (QZS) isolator under base excitations are reported. The setup is described and the QZS isolator is compared to a standard mass-spring system. The role of the geometric nonlinearities on the dynamic behavior is clear: the QZS isolator transmissibility shows a natural frequency reduction, and the system effectively suppresses the ground vibration about the fundamental frequency of the standard system. The QZS isolator performance has been tested also under real earthquake signals, showing satisfactory acceleration mitigation.


2022 - Loaded and unloaded tooth contact analysis of spiral bevel gears in consideration of misalignments [Articolo su rivista]
Moslem, M.; Zippo, A.; Iarriccio, G.; Bergamini, L.; Pellicano, F.
abstract

Bevel gear pairs are employed extensively in transmission systems, such as vehicle transmissions (rear axle drive), aircraft engines/turbines and helicopter gears, to transfer power between non-parallel shafts at high speed or high torque. The most complex form of bevel gear is the spiral bevel gear (SBG). SBG pairs are commonly used in applications that require high load capacity at higher operating speeds than are typically possible with other types of bevel gear. When manufactured in a metal-cutting process, spiral bevel gears can either be produced using single indexing (a face-milling method, which is considered in this study) or continuous indexing (a face-hobbing method). Due to manufacturing imperfections and the flexibility of components, the system might experience misalignments that intensify or exert a destructive effect on the gear vibration, which causes disruption in the stress distribution, thereby decreasing the lifetime of the gearbox. The main purpose of this study is to carry out loaded tooth contact analysis (LTCA) and unloaded tooth contact analysis (UTCA) for an SBG pair in the presence of two types of misalignment, axial and radial misalignment, and represent their effects on the mesh stiffness (MS). To calculate the MS, it is essential to determine the geometrical mismatch between two mating tooth profiles by means of UTCA. To conduct LTCA, three main approaches can be utilised: the finite element method (FEM) and experimental and analytical approaches. Due to the development of software packages during the last decade, Transmission3D-Calyx, an FEM-based software, is used in this study to carry out LTCA and UTCA. Finally, the MS for different misalignment cases is compared to represent the effect of misalignment on the SBG pair.


2022 - Modal localization in vibrations of circular cylindrical shells with geometric imperfections [Articolo su rivista]
Hemmatnezhad, M.; Iarriccio, G.; Zippo, A.; Pellicano, F.
abstract

The present study aims to investigate the effect of geometric imperfections in circular cylindrical shells on the vibration characteristics. Perfect circular shells are characterized by the presence of double shell-like modes, i.e., modes having the same frequency with modal shape shifted of a quarter of wave-length in the circumferential direction. However, in the presence of geometric imperfections, the double natural frequencies split into a pair of distinct frequencies, the splitting is proportional to the level of imperfection. In some cases, the imperfections cause an interesting phenomenon on the modal shapes, which present a strong localization in the circumferential direction. The present study has been carried out by means of a semi-analytical approach. Theoretical formulation were derived based on Sanders–Koiter thin shell theory. The analytical results have been compared with those of standard finite element analyses. The results corresponding to the analysis of modal localization are novel and can be used as a benchmark for further studies.


2022 - Planet Load-Sharing and Phasing [Articolo su rivista]
Molaie, M.; Deylaghian, S.; Iarriccio, G.; Samani, F. S.; Zippo, A.; Pellicano, F.
abstract


2021 - Efficiency and Durability of Spur Gears with Surface Coatings and Surface Texturing [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Barbieri, M.; Pellicano, F.
abstract

Experimental results on mechanical efficiency and durability of spur gears are presented. Reducing the power losses and increasing the reliability of gears are fundamnetal aspects of the design of transmissions. In order to analyze the tribological performance of innovative coatings and laser texturing, three different types of spur gears were tested: standard carburized gears, WC/C-coated carburized gears, and carburized gears with laser texture pattern. Tests have been carried out through a power recirculating test rig equipped with a single-stage transmission; power losses were evaluated by analyzing the torque-meters signals; several pictures of the teeth were taken at scheduled times to monitor the wear progression. In conclusion, results are presented and discussed.


2021 - Gear diagnostic: Experimental data comparison of radial accelerometers, tangential accelerometers and torquemeter [Abstract in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Bergamini, L.; D'Elia, G.; Dal Piaz, G.
abstract

Industry 4.0 is the next step of the evolution of future companies in order to improve efficiency sustainability and performances. With a view to industry 4.0 and to improve the efficiency of gear transmission a measurement campaign has been performed comparing four gear pair with different surface treatment, damages and coating The experimental results on the measurement of radial accelerometers, tangential accelerometers and torque-meter measurement of spur gears rig with surface coatings, advanced pitting with a crack and damaged gears are presented and analysed with Time Synchronous Averaged (TSA) method and results are explained, comparing the effectiveness of the different sensors used to monitor the system under investigation.


2021 - Gear prognostics: A predictive algorithm for lifetime estimation of operating gearboxes [Abstract in Atti di Convegno]
Bergamini, L.; Zippo, A.; Pellicano, F.; Iarriccio, G.; Molaie, M.
abstract

For the realization of optimized, effective gearboxes, both the set of design rules and the study of operation conditions, interconnected to each other, have to be taken into account. Condition monitoring is an essential tool when study of gearbox operation is tackled, and many techniques have been developed to detect the onset and the development of wear. However, these techniques fall short when prediction of gearbox conditions is concerned, as in the case of tracking the useful lifetime during operation. Within this framework, a prognostic software is developed and presented. This software is able to estimate the useful lifetime of a gearbox on the base of design features (safety factors and parameters), standards and codes (ISO) and realistic/measured load spectra, representative of the operation condition of the gearbox. This tool opens up the possibility of combining condition monitoring and prediction for a wider, comprehensive study of gearbox operation. Moreover, it potentially allows to detect machinery misuse and plan accurate usage-dependent maintenance in industrial environment.


2021 - Seismic vibration of shells with non-Newtonian fluid interaction: Experiments [Abstract in Atti di Convegno]
Pellicano, F.; Zippo, A.; Iarriccio, G.
abstract

In the presented study the nonlinear vibrations of a fluid-filled circular cylindrical shell under seismic excitation is investigated. A PET thin shell with an aluminum top mass is harmonically excited from the base through an electrodynamic shaker in the neighborhood of the natural frequency of the first axisymmetric mode. The dilatant fluid is composed of a cornstarch-water mixture with 60% cornstarch and 40% water of total weight. The preliminary results show a strong non-linear response due to the coupling between the fluid and structure and the shaker-structure interaction that leads to a very interesting dynamic response of the system. The specimen is a polymeric circular cylindrical shell: an aluminum cylindrical mass is glued on the shell top edge; conversely, the bottom edge of the shell is clamped to a shaking table. The following sensors have been adopted: three triaxial accelerometers placed on the top mass at 120°, a monoaxial accelerometer at the base of the shell, a laser vibrometer to measure the lateral velocity on the mid-height of the shell. The test article has been excited in the axial direction through a harmonic load, with a step-sweep controlled output, the voltage signal sent to the shaker amplifier is closed-loop controlled; to avoid interaction between the control system and the specimen under study, no controls have been used for controlling the shaker base motion. The harmonic forcing load consists of a stepped-sine sweep of frequency band 100-500 Hz with a step of 2.5 Hz. All the tests have been performed with the shell full filled with quiescent fluid. The dynamic scenario is carefully analyzed by means of time histories, spectra, phase portraits and Poincaré maps. The experiments show the onset of complex dynamics: subharmonic and quasiperiodic responses, Chaos.


2021 - Synchronicity Phenomena in Circular Cylindrical Shells Under Random Excitation [Capitolo/Saggio]
Zippo, A.; Iarriccio, G.; Pellicano, F.
abstract

In many engineering areas, the structures are subjected to external forcing with a prevalent harmonic component in conjunction with significant likely non-deterministic contribution; moreover, the coupling between loading conditions and extreme environmental temperatures can lead to complex dynamic phenomena. In this paper, an experimental study on the nonlinear dynamics of a thin polymeric circular cylindrical shell, carrying a top mass, subjected to thermal gradients and random excitation is presented. Tests have been performed in controlled temperature conditions and the shell has been excited through an electrodynamic shaker. The experimental results pointed out that a broadband random excitation at the base of the shell can give rise to the synchronicity of the response to the resonance corresponding to the first axisymmetric mode of the shell; the vibration energy is conveyed to specific harmonics, some of which are outside and far from the excitation band.


2021 - Time series analysis of arm and forearm measurement for functional electrical stimulation control [Abstract in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.
abstract

Identify the dynamics of the muscular group of arm and forearm related to accelerometric and surface electromyographic signals is not an easy task especially in persons affected by pathological tremor, in which irregular tremor is not voluntary. The vibrational phenomena studied in this work regards the arm and forearm vibration that are monitored by means of SEMG (surface electro-myographic) sensor and accelerometer sensor with the purpose to detect and recognize the dynamic properties and correlations of onset of pathological tremor in patients affected by Parkinson disease and essential tremor. These pathologies that affect skeletal muscles present a typical characteristic vibration frequency between 1Hz and 12Hz, this property is monitored in out-patient tests. A condition monitoring system has been developed to monitor the tremor and produce an electrical stimulation to reduce the tremor: the system allows data monitoring with a portable microcontroller board powered with low voltage batteries and is based on a cDAQ9191 data acquisition system with a chassis controller module designed for data input, controlling and output generation. The algorithm generates functional electrical stimulation signals for control purpose. Experimental measurement data on parkinsonian patient are presented. Data are analyzed, and the results are presented.


2020 - Dynamic characterization of polymeric vibration dampers [Relazione in Atti di Convegno]
Barbieri, Marco; DE FELICE, Alessandro; Pellicano, Francesco; Sorrentino, Silvio; Zippo, Antonio
abstract

Polymeric dampers are used in many fields for vibration isolation. These devices are based upon a low stiffness and high damping connection between a vibrating support and the item to be fastened. Whenever the connection is assured by a polymeric element, it is mandatory to be aware that stiffness and damping change with the excitation frequency. The characterization of stiffness and damping of the polymeric element in terms of storage modulus and loss modulus is commonly carried out at low frequency by means of a Dynamic Mechanical Analysis (DMA), nonetheless this approach cannot be applied at higher frequency. In the present study, a novel experimental approach for estimating the frequency dependent storage modulus and loss modulus in a polymeric vibration damper is presented. The proposed method is based on a direct measurement of the energy loss in hysteretic cycles and it is suitable for simple implementation using common instruments for vibration measurement.


2020 - Efficiency and Durability of DLC-Coated Gears [Relazione in Atti di Convegno]
Barbieri, M.; Iarriccio, G.; Pellicano, F.; Strozzi, M.; Zippo, A.
abstract

This paper presents an experimental study on spur gears. Gears with and without tungsten-carbide coatings (WC/C) are compared in terms of efficiency, durability and vibration performance. In order to carry out the experiments, a test rig including two electric motors/brakes is described. Gears are designed for this specific experimental campaign, so that the number of teeth, the selected materials and thermochemical treatments are optimal to investigate gear efficiency and durability. The experimental procedure allows for a simultaneous evaluation of efficiency and dynamic transmission error by varying the rotational velocity of the gear pair. An additional investigation has been performed for varying load, so that a complete characterization of the effect of WC/C coating on gear performance is presented.


2020 - Experimental Study on Nonlinear Random Excitation [Relazione in Atti di Convegno]
Pellicano, F.; Zippo, A.; Iarriccio, G.; Barbieri, M.
abstract

Experimental design methods are instruments for directing useful, time-effective and efficient experiments and an accurate strategy in experimental activities lead to successful results. In the present paper is explained an experimental campaign focused on the random vibrations of circular cylindrical shells under thermal gradients across the shell thickness and broadband random loading to identify a particular phenomenon called synchronicity: the investigation is fully experimental. Nuclear, aerospace and automotive are some of the engineering fields involved in this subject, and in these real environments non-deterministic excitations can be coupled with a thermal load; extreme thermal conditions can cause differences of the temperature inside and outside the shell, e.g. thermal ex-changers. Due to the importance of the subject, the literature on shell vibration is extremely wide, it is not analyzed here for the sake of brevity; however, it is to note that the number of papers containing experimental results is not large. Under a random forcing, a system generally expects a random response, the statistical properties of the random response are correlated with the forcing through the transfer function in the case of linear systems, or more complicated relationships in the case of nonlinear systems. However, in some particular conditions (e.g. internal resonances, parametric resonances, ...) the presence of nonlinearity in the systems can give rise to a surprising phenomenon, said synchronicity or entrainment. In this work a shell subjected to a random base excitation is analyzed experimentally, the excitation is random (flat or limited frequency band), and takes advantage of previous setup and experimental techniques [3–5] developed by the present research team. The phenomenon of synchronicity is clearly observed for some particular thermal conditions: a strong transfer of energy from a broadband excitation signal to an almost harmonic response is experimentally observed, confirming the general findings of refs. [1, 2].


2020 - Experimental study on large amplitude vibrations of a circular cylindrical shell subjected to thermal gradients [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Barbieri, M.; Pellicano, F.
abstract

In this paper, an experimental study on large amplitude vibrations of a thin-walled shell, subjected to thermal gradient across the thickness, is presented. The temperature gradient effects on the shell dynamic behavior are investigated. The vibration tests are performed on a polymeric cylindrical shell that carries a top mass. The structure is harmonically excited in the longitudinal direction by means of an electrodynamic shaker. The results of the experimental study are here reported and discussed.


2020 - Nonlinear vibrations of circular cylindrical shells with thermal effects: an experimental study [Articolo su rivista]
Zippo, Antonio; Barbieri, Marco; Iarriccio, Giovanni; Pellicano, Francesco
abstract

The nonlinear dynamics of a polymeric cylindrical shell carrying a top mass under axial harmonic excitation are experimentally investigated; the tests have been carried out in a controlled environment under several conditions of homogeneous temperature and excitation amplitude. The thermal effects on shells dynamics have been studied. The purpose of this paper is to fill an important gap in the literature regarding the effect of the temperature on the complex dynamics of shells. The cylindrical shell is excited in the axial direction by means of a seismic excitation provided by an electrodynamic shaker. The analysis is focused on the range of frequencies of excitation close to the first axisymmetric mode resonance; the base motion induces a parametric excitation. A saturation phenomenon of the top mass vibration is observed; the vibrating energy directly transferred from the shaker to the first axisymmetric mode is transferred to radial motion of the shell. The experimental data are examined and discussed in detail; a complete dynamic scenario is analyzed by means of: amplitude–frequency curves, bifurcation diagrams, spectrograms, Poincaré maps, phase portraits, Fourier spectra and time histories. Results show that: (i) the temperature strongly affects the instability regions and the magnitude of the measured kinematic quantity, (ii) high environmental temperature leads to a more complex shell dynamics.


2020 - Resonances and nonlinear vibrations of circular cylindrical shells, effects of thermal gradients [Articolo su rivista]
Iarriccio, G.; Zippo, A.; Pellicano, F.; Barbieri, M.
abstract

In this paper, the results of an experimental campaign focused on the vibrations of shells are presented. More specifically, the goal is to investigate the effect of thermal gradients across the shell thickness on the nonlinear dynamics. The shell is made of polymeric material and an aluminum mass is clamped on one end of the shell; the other shell end is clamped to an electrodynamic shaker, which provides a base harmonic excitation. Tests are performed in a controlled environment where a thermal gradient on the shell thickness is generated by means of a climatic chamber and an internal cartridge heater. Different temperature gradients and base excitation levels have been considered. The nonlinear dynamic scenario is analyzed through amplitude–frequency diagrams, bifurcation diagrams, waterfall diagrams, time histories, Fourier spectra, phase portraits, and Poincaré maps. Results show a strong effect of the temperature on the dynamic response of the shell: subharmonic, quasi-periodic, and chaotic vibrations take place as well as large amplitude vibrations, high sound levels are detected.


2020 - Vibrations of circular cylindrical shells under random excitation and thermal gradients [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Barbieri, M.
abstract

The present paper is focused on the random vibrations of circular cylindrical shells subjected to thermal gradients across the shell thickness; the investigation is fully experimental. The topic is of practical interest in many engineering fields such as: Aerospace, Automotive, Civil, Nuclear. Indeed, in real environments the excitations are likely non deterministic, moreover, extreme thermal conditions can cause differences of temperature inside and outside the shell, e.g. thermal exchangers. Due to the importance of the subject the literature on shell vibration is extremely wide, it is not analyzed here for the sake of brevity; however, it is to note that the number of papers containing experimental results is not large. When a system is excited with random forcing one generally expects a random response of the system, the statistical properties of the random response are correlated with the forcing through the transfer function in the case of linear systems, or more complicated relationships in the case of nonlinear systems. However, in some particular conditions (e.g. internal resonances, parametric resonances,…) the presence of a nonlinearity in the systems can give rise to a surprising phenomenon, said synchronicity or entrainment (see [1, 2]), which consists in a response made of a combination of random and harmonic signals. In this work a shell subjected to a random base excitation is analyzed experimentally, the excitation is random (flat or limited frequency band). The work take advantage from previous setup and experimental techniques [3–5] developed by the present research team. The phenomenon of synchronicity is clearly observed for some particular thermal conditions: a strong transfer of energy from a broad band excitation signal to an almost harmonic response is experimentally observed, confirming the general findings of refs. [1, 2].


2020 - Vibrations of plates with complex shape: Experimental modal analysis, finite element method, and R-functions method [Articolo su rivista]
Zippo, A.; Iarriccio, G.; Pellicano, F.; Shmatko, T.
abstract

In this paper, the dynamic behavior of 3D-printed plates with different shapes and boundary conditions is investigated. The natural frequencies and mode shapes were determined using three different methods: the experimental analysis, the finite element method, using Nastran, and the R-functions method. The experimental and theoretical results are compared. Thespecimens tested included four cases. The test procedure is deeply described, and the material properties of the plates are given. The fixed-fixed configuration shows a better agreement both in the rectangular plate and in the plate with rectangular cuts, and the R-functions method gives better convergence with respect to the experimental and finite element analysis. The simply supported arrangement indicates some uncertainty in the boundary realization of the specimen.


2019 - Condition monitoring of parkinson pathological tremor for functional electrical stimulation control [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Valzania, F.; Cavallieri, F.
abstract

The aim of this work is to identify the correlation of accelerometric and electromyographic signals and the difference between healthy patients (control group) and patients affected by Parkinson disease (PD) and essential tremor (ET). The vibrational phenomena studied in this work regards the forearm and hand vibration that are monitored by means of SEMG (surface electro-myographic) sensor and accelerometer sensor with the purpose to detect and recognize the dynamic properties of onset of pathological tremor in patients affected by (PD) and (ET). PD and ET present a typical characteristic vibration frequency between 3Hz and 12Hz, this property is monitored in out-patient tests. Two condition monitoring systems have been developed and deep described to monitor the tremor: the former system allows data monitoring with a portable lightweight microcontroller board powered with low voltage batteries (5Volt); and the latter is based on a CompactRio data acquisition system with a chassis controller module designed for data input, controlling and output generation, powered by 12 Volt battery. The CRio System provide an algorithm to generate functional electrical stimulation signals for control purpose. Experimental measurement data on healthy control subjects are presented. Data are analyzed, and results are presented.


2019 - Experimental durability test for condition monitoring of carburized spur gears [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Barbieri, M.; Pellicano, F.
abstract

An experimental study on the durability of spur gears has been carried out. Tests have been performed through a power re-circulating test rig at a fixed speed and torque load. For condition monitoring purpose, vibrations have been measured through a triaxial accelerometer mounted on the shaft frame. Acquired data have been post-processed and preliminary results are shown. The aim of the present work is to analyze the changes in the vibrations signal in order to depict a clear view on the onset and progression of the wear and damages in gear transmissions.


2019 - Experimental investigation on spur gears with novel coatings and surface micro texturing [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Barbieri, M.
abstract

Gears fault diagnostic and prognostic techniques have been the significant subjects of the condition-based monitoring systems in recent time due to the potential advantages that could be gained from. The present work is part of a more extensive study regarding efficiency and durability of novel tungsten carbide coatings and surfaces laser micro-texturing applied on carburized and nitride gears for several industrial application. In this paper, the effect of the different gear coatings and texturing on the vibration level is investigated experimentally. The durability and the pitting arising have been examined. The test rig consists of two electric motors with an electric power recirculating layout and is equipped with a temperature monitoring of the oil-jet type lubrication system. Vibrations phenomena are measured through triaxial accelerometer mounted on the shaft frame, close to the bearings, in order to detect spectral characteristics of vibration signals due to gear fault. Tests have been conducted far from the resonances of the system at a fixed speed and torque load; Vibration measurements have been performed at planned intervals. Results are presented and discussed


2019 - Experimental study on the nonlinear vibrations of a circular cylindrical shells: Effects of thermal gradients [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Barbieri, M.; Pellicano, F.
abstract

In this paper, an experimental study on the large amplitude vibrations of a thin polymeric cylindrical shell subjected to a thermal gradient across the thickness is presented. The effects of the temperature gradient on the shell dynamic behavior are investigated. The present study has the aim of providing a deeper contribution to the experimental literature on the shell structures. Test have been carried out in controlled environment condition thanks to a climatic chamber and a heater cartridge placed inside the shell. The shell carries a top mass and an electro-dynamic shaker has been used in order to excite, with a harmonic load, the test specimen in the longitudinal direction. The harmonic forcing load consists of a stepped-sine sweep with frequency band limits containing the resonance frequency of the first axisymmetric vibration mode. Four different excitation amplitude levels and two different thermal gradients have been considered. The experimental results are presented and discussed in detail by means of frequency response analysis and bifurcation analysis


2019 - Identification of dynamic behaviour of forearm for active control of pathological tremor [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Franco, V.; Francesco, C.
abstract

Pathological tremor is defined as an oscillatory and rhythmic movement of a segment of the body caused by the alternating activation of muscle groups in antagonism between them; a typical pathological condition known as essential tremor, which is the most common form of tremor also having a family character (2-5% of the population) have a characteristic frequency between 5 Hz and 7 Hz, such as Parkinsonian tremor that arises at frequencies higher than 8 Hz. The purpose of this study is to investigate the dynamic behavior of the forearm induced by the hand movements, measured due to the electromyographic sensors and accelerometers. The relationships of accelerometric and electromyographic signals are compared between a control group of healthy subjects and patients affected by Parkinson disease (PD) and essential tremor (ET). The vibrational phenomena analyzed in this experimental investigation are observed by means of SEMG (surface electro-myographic) sensors placed on flexor and extensor muscle compartment of forearm and accelerometer sensors for the hand vibration with the aim to detect and recognize the dynamic properties of onset of pathological tremor in patients affected by (PD) and (ET). A real-time monitoring and data logger system have been developed and deep described to monitor the tremor: the system allows data monitoring with a portable lightweight microcontroller board based on a CompactRio data acquisition system with a chassis controller module designed for data input, controlling and output generation, powered by 12 Volt battery. The CRio System provides an algorithm to generate functional electrical stimulation signals with different waveforms for control purpose. Experimental measurement data on healthy control subjects are presented. Data are analyzed, and the results are discussed


2019 - Temperature gradient effect on dynamic properties of a polymeric circular cylindrical shell [Articolo su rivista]
Zippo, Antonio; Barbieri, Marco; Pellicano, Francesco
abstract

In this paper, an experimental study on the dynamic of cylindrical shells made of Polyethylene terephthalate (PET) is presented; a thermic gradient has been applied on a specimen of the present work to obtain a functionally gradient material (FGM) equivalent properties: the PET shell had been exposed at a thermal temperature gradient in the range of its glass transition temperature of 79 °C. A complex setup has been specifically designed and built to characterise, with dynamic tests, the structural properties of the specimen on temperature change from −10 °C up to about 90 °C and under thermic gradient with different forcing load. Predicting the mechanical properties of shells, panels and plates is one of the main concerns of structural engineers; since shell elements present complicated stability behaviours, rich linear vibration spectra (high modal density), high sensitivity to perturbations and strong interactions with surrounding elements. The linear and dynamic behaviour have been investigated. The shell behaviour is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.


2018 - Experimental identification of static and dynamic stiffness of polymeric vibration dampers [Relazione in Atti di Convegno]
Barbieri, Marco; DE FELICE, Alessandro; Pellicano, Francesco; Sorrentino, Silvio; Zippo, Antonio
abstract

Polymeric dampers are frequently used in the automotive field in order to filter engine produced vibrations and thus protecting electronic devices. An accurate knowledge of damper stiffness is therefore important for a proper design of such mechanical filters. Since viscoelastic materials exhibit a significant stiffness–frequency dependency, characterization of dynamic stiffness is required for automotive vibration dampers. In the present paper, a method for broadband identification of the dynamic complex stiffness is described; since the proposed method is reliable at medium and high frequency only (500–1500 Hz), an additional static measurement has been performed. Therefore, the resulting method is a combination of static and dynamic measurements and it does not require specific DMA equipment: all experiments have been carried out using typical vibration testing equipment.


2018 - Thermal effects on dynamics of circular cylindrical shell [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.
abstract

In this paper, an experimental study on the dynamic of cylindrical shells made of Polyethylene terephthalate (PET) is presented; a thermic gradient has been applied on a specimen of the present work to obtain a functionally gradient material (FGM) equivalent properties: the PET shell had been exposed at a thermal temperature gradient in the range of its glass transition temperature of 79°C. A complex setup has been specifically designed and built to characterise, with dynamic tests, the structural properties of the specimen on temperature change from -10°C up to about 90°C and under thermic gradient with different forcing load. Predicting the mechanical properties of shells, panels and plates is one of the main concern of structural engineers; since shell elements present complicated stability behaviours, rich linear vibration spectra (high modal density), high sensitivity to perturbations and strong interactions with surrounding elements. The linear and dynamic behaviour have been investigated. The shell behaviour is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.


2017 - A novel method for dynamic characterization of polymeric vibration dampers [Relazione in Atti di Convegno]
Barbieri, Marco; DE FELICE, Alessandro; Pellicano, Francesco; Sorrentino, Silvio; Zippo, Antonio
abstract

Polymeric vibration dampers are very important devices used in many fields for vibration isolation and damping. These devices are based upon a low stiffness and high damping connection between a vibrating support and the item to be fastened. Whenever the connection is assured by a polymeric element, it is mandatory to be aware that stiffness and damping change with the excitation frequency as well as with temperature. Characterization of stiffness and damping of the polymeric element in terms of storage modulus and loss modulus is commonly carried out at low frequency by means of a Dynamic Mechanical Analysis (DMA), nonetheless this approach cannot be applied at higher frequency. In the present paper, a novel experimental approach for estimating the frequency dependent storage modulus and loss modulus in a polymeric vibration damper is presented. The proposed method is based on a direct measurement of the energy loss in hysteretic cycles, and it is suitable for simple implementation using common instruments for vibration measurement.


2017 - Dynamic imbalance of high-speed planetary gears [Articolo su rivista]
Masoumi, Asma; Barbieri, M; Pellicano, F; Zippo, A; Strozzi, M
abstract

A non-linear 2D lumped mass model of a single-stage spur planetary gear system with time-varying mesh stiffness, bearing compliance and non-smooth non-linearity due to backlash is taken into account. The time-varying meshing stiffness is evaluated by means of a non-linear finite element model, through an accurate evaluation of global and local tooth deformation. The non-linear dynamic behaviour of the system is analysed over a reasonable range of rotation speed and torque. The possibility of occurrences of different dynamic phenomena and instability of the system with respect to the bearing compliance and operating parameters are also evaluated. The possibility of dynamic imbalance of equally-spaced planetary gears in the presence of chaotic regimes is discussed. Such imbalance may lead to unexpected high-level stresses on bearings and gears.The effect of tooth profile modification at the sun-planet and ring-planet meshes on the vibration behaviour of the planetary gear system is also investigated in this paper. In order to avoid modification on the ring gear, both tip and root reliefs are considered for sun and planet gears.


2017 - Experimental analysis of pre-compressed circular cylindrical shell under axial harmonic load [Articolo su rivista]
Zippo, Antonio; Barbieri, Marco; Pellicano, Francesco
abstract

In this paper the nonlinear dynamics of circular cylindrical shells under axial static (compressive) and periodic resonant loads have been experimentally investigated, the goal is to study the dynamic scenario and to analyze nonlinear regimes. A special test rig has been developed for the experiment in order to apply a static axial load combined with a dynamic axial load. The setup allows for investigating the linear behavior under static preload by means of the usual modal testing techniques; moreover, it allows for analyzing the nonlinear response which occurs when the dynamic axial load is periodic and gives rise to complex resonances. The complex dynamics, arising when a periodic axial load excites the asymmetric (shell like) modes, are analyzed by means of amplitude frequency diagrams, waterfall spectrum diagrams, bifurcation diagrams of Poincaré maps; a deep analysis of time histories, spectra, phase portraits and Poincaré maps completes the study of the complex dynamic scenario.


2017 - Experimental identification of FGM shell properties (aimeta 2017) [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Barbieri, M.; Strozzi, M.; Masoumi, A.
abstract

Functionally gradient materials (FGMs) have attracted a growing interest as advanced structural materials because of their heat-resistance properties. In this paper, an experimental study on the vibration of cylindrical shells made of a functionally gradient material (FGM) composed of Polyethylene terephthalate (PET) is presented: to obtain functional gradient proprieties the PET shell had been exposed at a thermal temperature gradient in the range of its glass transition temperature of 79°C. The setting up of the experiment is explained and deeply described along with the thermal characterisation of the specimen. The linear and the nonlinear dynamic behaviour have been investigated. The shell behaviour is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.


2017 - Modal localization in vibrating circular cylindrical shells [Relazione in Atti di Convegno]
Pellicano, F.; Zippo, A.; Barbieri, M.; Strozzi, M.
abstract

The goal of the present paper is the analysis of the effect of geometric imperfections in circular cylindrical shells. Perfect circular shells are characterized by the presence of double shell-like modes, i.e., modes having the same frequency with modal shape shifted of a quarter of wavelength in the circumferential direction. In presence of geometric imperfections, the double natural frequencies split into a pair of distinct frequencies, the splitting is proportional to the level of imperfection. In some cases, the imperfections cause an interesting phenomenon on the modal shapes, which present a strong localization in the circumferential direction. This study is carried out by means of a semi-analytical approach compared with standard finite element analyses.


2017 - Numerical simulation and experimental validation of normal strain distribution and pitting phenomenon in industrial gears [Relazione in Atti di Convegno]
Strozzi, M.; Barbieri, M.; Zippo, A.; Pellicano, F.
abstract

In this paper, the normal strain distribution and pitting phenomenon on gears are investigated by means of numerical finite element analyses and experimental activities. In the first part of the paper, results of experimental tests for the investigation of the pitting phenomenon on gears are reported. These durability tests are made at a specific nominal load and far from the resonance. The experimental data are collected periodically from two tri-axial accelerometers placed on the gear shafts. After a short time, a visible pitting phenomenon arises on the gear teeth, where the contact pattern is perfectly centered (due to the high lead crown imposed on the teeth) and the wear pattern is consistent with FE simulations. In the second part of the paper, numerical finite element studies on the normal strain distribution at the base of the gear teeth during the contact are reported. These analyses are made at the same nominal load of the previous pitting analyses and at very low rotational speed (static analyses). A peak of normal strain at the base of the contact tooth is found around the contact time, preceded and followed by a low constant value of normal strain. The numerical results are validated by comparisons with experimental tests carried out in the same operating conditions and placing strain gauges at the tooth base of the gears.


2017 - Numerical study on nonlinear vibrations, energy exchange and resonant interactions in single walled carbon nanotubes [Relazione in Atti di Convegno]
Strozzi, M.; Barbieri, M.; Zippo, A.; Pellicano, F.
abstract

In this paper, the nonlinear vibrations, energy exchange and resonant interactions of singlewalled carbon nanotubes (SWNTs) are investigated. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The SWNT deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported boundary conditions are considered. The circumferential flexural modes (CFMs), radial breathing modes (RBMs) and beam-like modes (BLMs) are studied. A numerical model of the SWNT dynamics is proposed. The three displacement fields are expanded in the nonlinear field by using approximate linear eigenfunctions. An energy method based on the Lagrange equations is used to reduce the nonlinear partial differential equations of motion to a set of nonlinear ordinary differential equations, which is solved using the implicit Runge-Kutta numerical method. The nonlinear energy exchange along the SWNT axis is analysed for different initial excitation amplitudes. The resonant interactions between CFMs, RBMs and BLMs are investigated. The transition from energy beating to energy localization in the nonlinear field is studied.


2017 - Vibration Localization of Imperfect Circular Cylindrical Shells [Relazione in Atti di Convegno]
Pellicano, Francesco; Zippo, Antonio; Barbieri, Marco; Strozzi, Matteo
abstract


2017 - Vibration of functionally graded cylindrical shells [Relazione in Atti di Convegno]
Zippo, A.; Pellicano, F.; Barbieri, M.; Strozzi, M.
abstract

Functionally gradient materials (FGMs) have attracted a growing interest as advanced structural materials because of their heat-resistance properties. In this paper, an experimental study on the vibration of cylindrical shells made of a functionally gradient material (FGM) composed of Polyethylene terephthalate (PET) is presented: to obtain functional gradient proprieties the PET shell had been exposed at a thermal temperature gradient in the range of its glass transition temperature of 79°C. The setting up of the experiment is explained and deeply described along with the thermal characterisation of the specimen. The linear and the nonlinear dynamic behaviour have been investigated. The shell behaviour is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.


2016 - Active vibration control of a composite plate [Relazione in Atti di Convegno]
Zippo, A.; Barbieri, M.; Pellicano, F.; Strozzi, M.
abstract

A new active vibration control methodology is proposed and experimentally tested. The technique is applied to a honeycomb panel having a carbon-fiber reinforced polymer (CFRP) outer skins and a polymer-paper core, subjected to an orthogonal disturbance, due to an electrodynamics exciter. The control is carried out by means of Macro Fibre Composite (MFC) actuators and sensors. MFC parches consist of rectangular piezoceramic rods sandwiched between layers of adhesive, electrodes and polyamide film. The MFC actuators and sensors are controlled by a programmable digital dSPACER controller board. The control algorithm proposed in this paper is based on the Positive Position Feedback (PPF) technique, Single Input - Single Output, MultiSISO and Multi Input Multi Output controls are applied in order to control the first four normal modes. The control appears to be robust and efficient in reducing vibration in linear (small am- plitude) and nonlinear (large amplitude) vibrations regimes, although the structure under investigation exhibits a relativity high modal density, i.e. four resonances in a range of about 100Hz. The control strategy allows to effectively control each resonance both individually or simultaneously.


2016 - Dynamic imbalance of high speed planetary gears [Relazione in Atti di Convegno]
Masoumi, A.; Barbieri, M.; Pellicano, F.; Zippo, A.; Strozzi, M.
abstract

A nonlinear 2D lumped mass model of planetary gear system with time varying mesh stiffness, bearing compliance and nonsmooth nonlinearity due to the backlash is taken into account. The time varying meshing stiffness is evaluated by means of a nonlinear finite element model, through an accurate evaluation of global and local tooth deformation. Nonlinear dynamic behaviour of the system is analyzed over a reasonable range of rotation speed and torque. Possibility of occurrences of different dynamic phenomena and instability of the system with respect to bearing compliance and operating parameters is evaluated as well. Bifurcation diagrams are extracted as well and for specific regimes, the nonlinear scenario of system is discussed using the spectra, phase portraits and Poincare maps. Periodic, quasiperiodic and chaotic regimes are found and discussed with respect to system parameters. The possibility of dynamic imbalance of equally spaced planetary gears in presence of chaotic regimes is discussed. Such imbalance may lead to unexpected high level stresses on bearings and gears.


2016 - Experimental investigation of dynamic behaviour of pre-compressed circular cylindrical shell [Relazione in Atti di Convegno]
Zippo, Antonio; Pellicano, Francesco; Barbieri, Marco; Strozzi, Matteo
abstract

Circular cylindrical shells are very efficient structures that have many applications and plays as key elements in several engineering fields. Shells usually exhibit a complicated dynamic behaviours because the curvature will effectively couple the flexural and in-plane deformations together as the three displacement fields simultaneously appear in each of the governing partial differential equations and boundary conditions. Therefore, it is understandable that the axial constraints can have direct effects on a predominantly radial modes. For instance, it has been shown that the natural frequencies for the circumferential modes of a simply supported shell can be noticeably modified by the constraints applied in the axial direction. In this paper the results of experimental tests on pre-compressed circular cylindrical shell will be presented: different combinations of preload and harmonic external axial load have been tested but for brevity only few results are shown.


2016 - Experiments on shells under base excitation [Articolo su rivista]
Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio; Strozzi, Matteo
abstract

The aim of the present paper is a deep experimental investigation of the nonlinear dynamics of circular cylindrical shells. The specific problem regards the response of circular cylindrical shells subjected to base excitation. The shells are mounted on a shaking table that furnishes a vertical vibration parallel to the cylinder axis; a heavy rigid disk is mounted on the top of the shells. The base vibration induces a rigid body motion, which mainly causes huge inertia forces exerted by the top disk to the shell. In-plane stresses due to the aforementioned inertias give rise to impressively large vibration on the shell. An extremely violent dynamic phenomenon suddenly appears as the excitation frequency varies up and down close to the linear resonant frequency of the first axisymmetric mode. The dynamics are deeply investigated by varying excitation level and frequency. Moreover, in order to generalise the investigation, two different geometries are analysed. The paper furnishes a complete dynamic scenario by means of: (i) amplitude frequency diagrams, (ii) bifurcation diagrams, (iii) time histories and spectra, (iv) phase portraits and Poincaré maps. It is to be stressed that all the results presented here are experimental.


2016 - Linear vibrations of multi-walled carbon nanotubes [Relazione in Atti di Convegno]
Strozzi, Matteo; Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio
abstract

In this paper, the linear vibrations of Multi-Walled Carbon Nanotubes (MWNTs) are analysed. A multiple elastic shell model is considered. The shell dynamics is studied in the framework of the Sanders-Koiter shell theory. The van der Waals (vdW) interaction between two layers of the MWNT is modelled by a radius-dependent function. The shell deformation is described in terms of longitudinal, circumferential and radial displacements. Simply supported, clamped and free boundary conditions are considered. The three displacement fields are expanded by means of a double mixed series based on Chebyshev orthogonal polynomials for the longitudinal variable and harmonic functions for the circumferential variable. The Rayleigh-Ritz method is applied to obtain approximate natural frequencies and mode shapes. The present model is validated in linear field by means of data derived from the literature. This study is focused on determining the effect of the geometry and boundary conditions on the natural frequencies of the MWNTs.


2016 - Modelling and Testing Techniques for Gear- boxes Analysis and Optimization [Relazione in Atti di Convegno]
Andrisano, A. O.; Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio; Strozzi, Matteo
abstract


2016 - Nonlinear Dynamics of Pre-Compressed Circular Cylindrical Shell Under Axial Harmonic Load: Experiments [Relazione in Atti di Convegno]
Pellicano, Francesco; Zippo, Antonio; Barbieri, Marco; Strozzi, Matteo
abstract


2016 - Novel spectral kurtosis technology for adaptive vibration condition monitoring of multi-stage gearboxes [Articolo su rivista]
Gelman, L; Harish Chandra, N.; Kurosz, R.; Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio
abstract

In this paper, the novel wavelet spectral kurtosis (WSK) technique is applied for the early diagnosis of gear tooth faults. Two variants of the wavelet spectral kurtosis technique, called variable resolution WSK and constant resolution WSK, are considered for the diagnosis of pitting gear faults. The gear residual signal, obtained by filtering the gear mesh frequencies, is used as the input to the SK algorithm. The advantages of using the wavelet-based SK techniques when compared to classical Fourier transform (FT)-based SK is confirmed by estimating the toothwise Fisher's criterion of diagnostic features. The final diagnosis decision is made by a three-stage decision-making technique based on the weighted majority rule. The probability of the correct diagnosis is estimated for each SK technique for comparison. An experimental study is presented in detail to test the performance of the wavelet spectral kurtosis techniques and the decision-making technique.


2016 - Pitting and stress analysis of gears: A numerical and experimental study [Relazione in Atti di Convegno]
Strozzi, M.; Barbieri, M.; Pellicano, F.; Zippo, A.
abstract

In this paper, the pitting phenomenon and stress distribution of gears are investigated by means of experimental activities and numerical finite element analyses. In the first part, results of experimental accelerated endurance tests for the investigation of the pitting phenomenon of gears are reported. These durability tests are made at a specific nominal load and far from the resonance. After a short time, a visible pitting phenomenon arises. In the second part, finite element numerical analyses for the evaluation of gear stresses are listed. The numerical analyses start from stress-vibration correlations and dynamic factors obtained by a 2-dof dynamic model; these results are used in the dynamic FEM simulations in order to calculate the maximum normal stress and the contact pressure on the contact tooth of the pinion vs. vibration amplitude for different dynamic factors.


2015 - Active vibration control of a composite sandwich plate [Articolo su rivista]
Zippo, Antonio; Ferrari, Giovanni; Amabili, Marco; Barbieri, Marco; Pellicano, Francesco
abstract

Active vibration control of a free-edge rectangular sandwich plate is proposed and tested. The experimental setup consists of a honeycomb panel having a carbon-fiber reinforced polymer (CFRP) outer skins and a polymer-paper core, subjected to an orthogonal disturbance, due to an electrodynamics exciter and controlled by Macro Fibre Composite (MFC) actuators and sensors. MFC parches consist of rectangular piezoceramic rods sandwiched between layers of adhesive, electrodes and polyamide film. The MFC actuators and sensors are controlled by a programmable digital dSPACE (R) controller board. The control algorithm proposed in this paper is based on the Positive Position Feedback (PPF) technique and is successfully applied with different combinations of inputs/outputs (Single Input Single Output, MultiSISO, Multi Input Multi Output) in order to control the first four normal modes. The control appears to be robust and efficient in reducing vibration in linear (small amplitude) and nonlinear (large amplitude) vibrations regimes, although the structure under investigation exhibits a relativity high modal density, i.e., four resonances in a range of about 100 Hz. The control strategy allows to effectively control each resonance both individually or simultaneously.


2015 - Beating phenomenon and energy localization in Single-Walled Carbon Nanotubes [Abstract in Atti di Convegno]
Strozzi, Matteo; Manevitch, Leonid I.; Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio
abstract

In this paper, the low-frequency nonlinear oscillations and energy localization of Single-Walled Carbon Nanotubes (SWNTs) are analysed. The SWNTs dynamics is studied in the framework of the Sanders-Koiter nonlinear shell theory. The circumferential flexure vibration modes (CFMs) are considered. Simply supported, clamped and free boundary conditions are analysed. Two different approaches are compared, based on numerical and analytical models. The numerical model uses a double mixed series expansion for the displacement fields based on the Chebyshev polynomials and harmonic functions. The Lagrange equations are considered to obtain a set of nonlinear ordinary differential equations of motion which are solved using the implicit Runge-Kutta numerical method. The analytical model considers a reduced form of the shell theory assuming small circumferential and tangential shear deformations. The Galerkin procedure is used to get the nonlinear ordinary differential equations of motion, which are then solved using the multiple scales analytical method. The natural frequencies of SWNTs obtained by considering the analytical and numerical approaches are compared for different boundary conditions. A convergence analysis in the nonlinear field is carried out for the numerical method in order to select the correct number of the axisymmetric and asymmetric modes providing the actual localization threshold. The effect of the aspect ratio on the analytical and numerical values of the localization threshold for SWNTs with different boundary conditions is investigated in the nonlinear field.


2015 - Dynamic modelling of gear pairs [Relazione in Atti di Convegno]
Barbieri, Marco; Zippo, Antonio; Strozzi, Matteo; Serafini, Lorenzo; Pellicano, Francesco; Bonori, Giorgio
abstract

A clear understanding of the dynamics of gear pairs is important for many reasons. First of all, gear vibration is a main source of noise in gearboxes and vehicle trasmissions, secondly the torsional elasticity of the gear trasmission can produce relevant amplification of the contact force, and thus of the gear stress. Furthermore, gear vibrations are a useful parameter for gear monitoring and prognostics. In the present work, an overview of the models used to describe the dynamic behaviour of gear pairs will be presented, along with a comparison between a dynamic finite element model and different lumped parameter approaches. A correlation between the vibration transmitted to the gearbox, and thus easily measurable in a real application, and the local stresses in the gear pair will be drawn. The proposed approach is suitable to describe the effect of localized defects on the gear pair, such as tooth root cracks and pitted profiles, on the signal measured on a gearbox.


2015 - Dynamics and Stability of Carbon Nanotubes [Abstract in Atti di Convegno]
Strozzi, Matteo; Barbieri, Marco; Zippo, Antonio; Pellicano, Francesco
abstract

The low-frequency oscillations and energy localization of Single-Walled Carbon Nanotubes (SWNTs) are studied in the framework of the Sanders-Koiter shell theory. The circumferential flexure modes (CFMs) are analysed. Simply supported, clamped and free boundary conditions are considered. Two different approaches are proposed, based on numerical and analytical models. The numerical model uses in the linear analysis a double mixed series expansion for the displacement fields based on Chebyshev polynomials and harmonic functions. The Rayleigh-Ritz method is applied to obtain approximate natural frequencies and mode shapes. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions. An energy approach based on Lagrange equations is considered in order to obtain a set of nonlinear ordinary differential equations, which is solved by the Runge-Kutta numerical method. The analytical model considers a reduced version of the Sanders-Koiter shell theory obtained by assuming small circumferential and tangential shear deformations. These two assumptions allow to condense the longitudinal and circumferential displacement fields into the radial one. A nonlinear fourth-order partial differential equation for the radial displacement field is derived, which allows to calculate the natural frequencies and to estimate the nonlinearity effect. An analytical solution of this equation is obtained by the multiple scales method. The previous models are validated in linear field by means of comparisons with experiments, molecular dynamics simulations and finite element analyses retrieved from the literature. The concept of energy localization in SWNTs is introduced, which is a strongly nonlinear phenomenon. The low-frequency nonlinear oscillations of the SWNTs become localized ones if the intensity of the initial excitation exceeds some threshold which depends on the SWNTs length. This localization results from the resonant interaction of the zone-boundary and nearest nonlinear normal modes leading to the confinement of the vibration energy in one part of the system. The value of the initial excitation corresponding to this energy confinement is referred to as energy localization threshold. The effect of the aspect ratio on the analytical and numerical values of the energy localization threshold is investigated; different boundary conditions are considered.


2015 - Experimental and numerical study of MIMO active vibration control [Relazione in Atti di Convegno]
Zippo, Antonio; Pellicano, Francesco; Barbieri, Marco; Amabili, Marco
abstract

In this paper the finite element method is used for choosing the best position of nearby collocated pairs of actuator-sensor couples, an experimental investigation of active vibration control validates the theory; the application regards a rectangular sandwich laminated plate (carbon-epoxy outer skins and Nomex paper honeycomb core) with free boundary conditions. The piezoelectric unidirectional patches are used as strain sensors and strain actuators, respectively. The collocation of the patches is led by the results of a finite element modal analysis and allows the design of a modal control strategy, the efficiency of which is targeted to single vibration modes. The control configurations presented in this paper is a MIMO configuration in linear field. The identification activity and the extraction of stabilised transfer functions are performed by means of a dedicated Matlab algorithm. The stability and the robustness of the algorithm are briefly studied. A substantial reduction of the vibration amplitude is obtained both at specific frequencies and in a broadband random excitation-disturbance. It is also possible to control disturbances that would otherwise trigger geometrically nonlinear vibrations. The modal character of the resulting control is guaranteed by means of the MAC. An experimental setup has been developed, two to four Macro Fiber Composite (MFC) actuators and two MFC sensors are used in conjunction with a DSPACE controller system. The control appears robust and efficient in reducing vibration levels in linear and nonlinear field, even though the structure under investigation exhibits a high modal density, four resonances in a range of about 100Hz, and allows controlling each resonance separately or together.


2015 - Nonlinear oscillations of carbon nanotubes [Relazione in Atti di Convegno]
Strozzi, Matteo; Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio; Manevitch, Leonid I.
abstract

In this paper, the low-frequency nonlinear oscillations and energy localizations of Single-Walled Carbon Nanotubes (SWNTs) are analysed. The SWNTs dynamics is studied within the framework of the Sanders-Koiter thin shell theory. The circumferential flexure vibration modes (CFMs) are considered. Simply supported boundary conditions are investigated. Two different approaches are compared, based on numerical and analytical models. The numerical model uses a double series expansion for the displacement fields based on the Chebyshev polynomials and harmonic functions. The Lagrange equations are considered to obtain a set of nonlinear ordinary differential equations of motion which are solved using the implicit Runge-Kutta numerical method. The analytical model considers a reduced form of the shell theory assuming small circumferential and tangential shear deformations. The Galerkin procedure is used to get the nonlinear ordinary differential equations of motion which are solved using the multiple scales analytical method. The natural frequencies obtained by considering the two approaches are compared in linear field. The effect of the aspect ratio on the analytical and numerical values of the localization threshold is investigated in nonlinear field.


2014 - Adaptive grid-size finite element modeling of helical gear pairs [Articolo su rivista]
Barbieri, Marco; Zippo, Antonio; Pellicano, Francesco
abstract

A method for solving the contact problem for generic helical gear pairs (either external or inter- nal) is described. Gear profiles are obtained by means of numerical simulation of the cutting pro- cess and an accurate description is provided in terms of NURBS curves or surfaces. A new method for finding the enveloping profiles for a generic tool (e.g. from a measured topography) is pro- posed. The minimum number of parameters needed to describe the profile in the presence of tip and root reliefs, helix modification and crowning is discussed. A reference structured grid is de- fined on the tooth, then refinement criteria are applied in order to obtain accurate solutions in terms of tooth deflection, contact pressure and fillet stress. The method allows to automatically perform a Loaded Tooth Contact Analysis (LTCA) starting from the design data of a gear pair. Re- sults from the LTCA include contact pressure and contact pattern maps, as well as maximum fillet stress and fatigue strength. Combining several analyses within a mesh cycle, information about the Static Transmission Error (STE) and mesh stiffness is provided. The whole procedure has been implemented in a software called helical pair. A comparison with other approaches is given.


2014 - Nonlinear dynamics of axially loaded shells: experimental study [Relazione in Atti di Convegno]
Pellicano, Francesco; Zippo, Antonio; Barbieri, Marco
abstract

In this paper recent experiments on nonlinear dynamics of shells are described, such experiments were focused to circular cylindrical shells subjected to axial loads. Different types of axial loads were considered: inertial loads due to rigid bodies connected to the shell; static and dynamic loads induced by direct shell excitation. The latter type of loading allows to study the effect of pre-compression, which typically induces natural frequency variation and changing of the dynamic scenario. The experiments show an extremely complex dynamic scenario, which needs a deep analysis to be interpreted and explained. The goal of the present work is twice: describe experimental evidence of complex dynamics and furnish explanation when possible.


2013 - Circular Cylindrical Shells under combined axial loads: an experimental study [Relazione in Atti di Convegno]
Zippo, Antonio; Barbieri, Marco; Pellicano, Francesco
abstract

Thin shells structures have an important role in engineering; several important examples can be found in Structural Engineering, Mechanical Engineering and Aerospace: water tanks, containment shells of nuclear power plants, concrete arch domes, piping systems, pressure vessels, aircrafts, missiles, rockets, ships. Even though many researchers have extensively studied nonlinear vibrations of cylindrical shells, experimental studies are rather limited in number; in particular, rare experimental reports have been published about shells loaded with in-plane . In this paper the response of a circular cylindrical shells subjected to axial compressive and periodic loads has been experimentally investigated. The experimental setup is explained and deeply described along with the analysis of preliminary results. The linear shell behavior is investigated by means of a finite element model in order to enhance the comprehension of experimental results in the linear field. The main goal is to investigate the nonlinear phenomena associated with a combined effect of compressive static and a periodic axial loads, the investigation have been carried out for different combinations of loads. Several interesting nonlinear phenomena have been observed such as softening-type non-linearity and non stationary response when the periodic axial load is resonant with one of the shell modes.


2013 - Nonlinear vibrations and energy conservation of Single-Walled Carbon Nanotubes [Relazione in Atti di Convegno]
Zippo, Antonio; Strozzi, Matteo; Manevitch, Leonid I.; Pellicano, Francesco; Barbieri, Marco
abstract

The nonlinear vibrations of Single-Walled Carbon Nanotubes are analysed. The Sanders-Koiter elastic shell theory is applied in order to obtain the elastic strain energy and kinetic energy. The carbon nanotube deformation is described in terms of longitudinal, circumferential and radial displacement fields. The theory considers geometric nonlinearities due to large amplitude of vibration. The displacement fields are expanded by means of a double series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. The Rayleigh-Ritz method is applied in order to obtain approximate natural frequencies and mode shapes. Free boundary conditions are analysed. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions; an energy approach based on the Lagrange equations is considered in order to reduce the nonlinear partial differential equations to a set of nonlinear ordinary differential equations. Nondimensional parameters are considered. The total energy conservation of the system is verified by considering the combinations of different vibration modes. The effect of the companion mode participation on the nonlinear vibrations of the carbon nanotube is analysed.


2012 - Experimental Study on Prestressed Circular Cylindrical Shell [Relazione in Atti di Convegno]
Zippo, Antonio; Barbieri, Marco; Strozzi, Matteo; Errede, Vito; Pellicano, Francesco
abstract

In this paper an experimental study on circular cylindrical shells subjected to axial compressive and periodic loads is presented. Even though many researchers have extensively studied nonlinear vibrations of cylindrical shells, experimental studies are rather limited in number. The experimental setup is explained and deeply described along with the analysis of preliminary results. The linear and the nonlinear dynamic behavior associated with a combined effect of compressive static and a periodic axial load have been investigated for different combinations of loads; moreover, a non stationary response of the structure has been observed close to one of the resonances. The linear shell behavior is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.


2012 - Linear and nonlinear dynamics of a circular cylindrical shell under static and periodic axial load [Relazione in Atti di Convegno]
Zippo, Antonio; Barbieri, Marco; Strozzi, Matteo; Errede, Vito; Pellicano, Francesco
abstract

In this paper an experimental study on circular cylindrical shells subjected to axial compres- sive and periodic loads is presented. The setting of the experiment is explained and deeply described along with a complete analysis of the results. The linear and the nonlinear dynamic behaviour associated with a combined effect of compressive static and a periodic axial load has been considered and a chaotic response of the structure has been observed close to the resonance. The linear shell behaviour is also investigated by means of a theoretical and finite element model, in order to enhance the comprehension of experimental results, i.e. the natural frequencies of the system and their ratios.


2012 - Nonlinear vibrations of functionally graded cylindrical shells: Effect of the geometry [Relazione in Atti di Convegno]
Strozzi, Matteo; Pellicano, Francesco; Zippo, Antonio
abstract

In this paper, the effect of the geometry on the nonlinear vibrations of functionally graded (FGM) cylindrical shells is analyzed. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The shell deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported boundary conditions are considered. The displacement fields are expanded by means of a double mixed series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. In the linear analysis, after spatial discretization, mass and stiff matrices are computed, natural frequencies and mode shapes of the shell are obtained. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions obtained by the linear analysis; specific modes are selected. The Lagrange equations reduce nonlinear partial differential equations to a set of ordinary differential equations. Numerical analyses are carried out in order to characterize the nonlinear response of the shell. A convergence analysis is carried out to determine the correct number of the modes to be used. The analysis is focused on determining the nonlinear character of the response as the geometry of the shell varies.


2011 - 3D Nonlinear Finite Element Modeling of Helical Gears [Relazione in Atti di Convegno]
Zippo, Antonio; Barbieri, Marco; Pellicano, Francesco
abstract

A method for carrying out the Loaded Tooth Contact Analysis (LTCA) of helical gear pairs is described in this paper. Gear profiles are obtained by means of numerical simulation of the cutting process and an accurate description is provided in terms of NURBS curves or surfaces.The minimum number of parameters needed to describe accurately the profile in presence of tip and root reliefs, helix modification and crowning is discussed. Some cases are presented and discussed.


2011 - Adaptive Grid-Size Modelling of Helical Gear Pairs [Relazione in Atti di Convegno]
Barbieri, Marco; Zippo, Antonio; Pellicano, Francesco
abstract

Amethod for solving the contact problem in a generic helical gear pair (either external or internal) is described. Gear profiles are obtained by means of numerical simulation of the cutting process and an accurate description is provided in terms of NURBS curves or surfaces. The minimum number of parameters needed to describe accurately the profile in presence of tip and root reliefs, helix modification and crowning is discussed. A reference structured grid is defined on the tooth, then refinement criteria are discussed in order to obtain accurate solutions in terms of tooth deflection, contact pressure and fillet stress. A comparison with other approaches is given.


2011 - Effect of the geometry on the nonlinear vibrations of functionally graded cylindrical shells [Relazione in Atti di Convegno]
Pellicano, Francesco; Strozzi, Matteo; Zippo, Antonio
abstract

In this paper, the effect of the geometry on the nonlinear vibrations of functionally graded (FGM) cylindrical shells is analyzed. The Sanders-Koiter theory is applied to model nonlinear dynamics of the system in the case of finite amplitude of vibration. Shell deformation is described in terms of longitudinal, circumferential and radial displacement fields; the theory considers geometric nonlinearities due to the large amplitude of vibration. Simply supported boundary conditions are considered. The displacement fields are expanded by means of a double mixed series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. Both driven and companion modes are considered, allowing for the travelling-wave response of the shell. The functionally graded material is made of a uniform distribution of stainless steel and nickel, the material properties are graded in the thickness direction, according to a volume fraction power-law distribution.The first step of the procedure is the linear analysis, i.e. after spatial discretization mass and stiff matrices are computed and natural frequencies and mode shapes of the shell are obtained, the latter are represented by analytical continuous functions defined over all the shell domain. In the nonlinear model, the shell is subjected to an external harmonic radial excitation, close to the resonance of a shell mode, it induces nonlinear behaviors due to large amplitude of vibration. The three displacement fields are re-expanded by using approximate eigenfunctions, which were obtained by the linear analysis; specific modes are selected. An energy approach based on the Lagrange equations is considered, in order to reduce the nonlinear partial differential equations to a set of ordinary differential equations.Numerical analyses are carried out in order characterize the nonlinear response, considering different geometries and material distribution. A convergence analysis is carried out in order to determine the correct number of the modes to be used; the role of the axisymmetric and asymmetric modes carefully analyzed. The analysis is focused on determining the nonlinear character of the response as the geometry (thickness, radius, length) and material properties (power-law exponent and configurations of the constituent materials) vary; in particular, the effect of the constituent volume fractions and the configurations of the constituent materials on the natural frequencies and nonlinear response are studied.Results are validated using data available in literature, i.e. linear natural frequencies.


2011 - Nonlinear vibrations of functionally graded circular cylindrical shells [Relazione in Atti di Convegno]
Strozzi, Matteo; Pellicano, Francesco; Zippo, Antonio
abstract

In this paper, the effect of the geometry on the nonlinear vibrations of functionally graded cy- lindrical shells is analyzed. The Sanders-Koiter theory is applied to model nonlinear dynamics of the system in the case of finite amplitude of vibration. Shell deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported boundary conditions are considered. Numerical analyses are carried out in order to characterize the nonlinear response when the shell is subjected to an harmonic external load; different geometries and material distribu- tions are considered. A convergence analysis is carried out in order to determine the correct number of the modes to be used; the role of the axisymmetric and asymmetric modes is carefully analyzed. The analysis is focused on determining the nonlinear character of the response as the geometry (thickness, radius, length) and material properties (power-law exponent N and configurations of the constituent materials) vary. The effect of the constituent volume fractions and the configurations of the constituent materials on the natural frequencies and nonlinear response are studied.