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Giulia CATELLANI

Personale tecnico amministrativo
ILO-Industrial Laison Office

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Pubblicazioni

2004 - Nonlinear dynamics and stability of circular cylindrical shells [Relazione in Atti di Convegno]
Pellicano, F.; Catellani, G.; Amabili, M.
abstract

The nonlinear dynamic response of an imperfect circular cylindrical shell under combined static and dynamic axial load is analyzed. A suitable expansion of the radial displacement, able to describe both buckling and dynamic behaviors is developed; the effect of geometric imperfections is accounted for. The response of the shell subjected to a sinusoidal axial excitation at its ends, giving rise to a parametric excitation, is considered. The effect of the imperfections on the critical value of the dynamic load, that causes the loss of stability of the system, is analyzed. Interesting nonlinear dynamic phenomena are observed: direct resonance with softening behavior and parametric instability with period doubling response. Copyright © 2004 by ASME.

2004 - Parametric instability of a circular cylindrical shell with geometric imperfections [Articolo su rivista]
Catellani, Giulia; Pellicano, Francesco; D., Dall'Asta; M., Amabili
abstract

The static and dynamic behavior of a compressed circular cylindrical shell having geometric imperfections is analyzed. The analysis is mainly performed by means of the Donnell´s nonlinear shallow-shell theory. However, the refined Sanders shell theory is also used for comparison. A suitable expansion of the radial displacement, able to describe both buckling and dynamic behaviors is developed; the effect of geometric imperfections is accounted for by means of a modal representation. The response of the shell subjected to a sinusoidal axial excitation at its ends, giving rise to a parametric excitation, is considered. The effect of imperfections on the critical value of the dynamic load, that causes the loss of stability of the system, is analyzed. Interesting nonlinear dynamic phenomena are observed: direct resonance with softening behavior and parametric instability with period doubling response.

2004 - Parametric instability of belts: theory and experiments [Articolo su rivista]
Pellicano, Francesco; Catellani, Giulia; Fregolent, A.
abstract

In this paper, the dynamic stability of a power transmission belt excited by an eccentric pulley is investigated. A theoretical model is developed to predict the belt response: simply supported boundary conditions are considered, neglecting the pulley curvature, and including the effect of the lower belt span. The transverse displacement field is expanded into sine series and the Galerkin method is applied to reduce the partial differential equation (PDE) into a set of ordinary differential equations. In order to forecast the belt response, the elastic characteristics only of the belt must be provided to the theoretical model. An experimental investigation is performed on a belt-pulley system with a pulley eccentricity; a laser displacement transducer is used to measure the transverse displacement. The combination of a direct and a parametric excitation is analyzed in detail. Interesting post-critical nonlinear dynamic behaviors are found: sub-harmonic responses and quasi-periodic motions seem to coexist, depending on the initial conditions. Experiments confirm the numerical results, thus validating the present theoretical model.

2004 - Vibration and stability of compressed shells with imperfections and fluid-structure interaction [Relazione in Atti di Convegno]
Pellicano, F.; Catellani, G.; Amabili, M.
abstract

In this work the nonlinear dynamic response of an imperfect circular cylindrical shell under combined static and dynamic axial load is analyzed. In order to define completely the shell behavior and to introduce a suitable expansion of the radial displacement, a buckling analysis, including the effect of geometric imperfections, is developed. The effect of the imperfections on the postbuckling path is studied. The response of the shell subjected to a sinusoidal axial excitation at its ends, giving rise to a parametric excitation, is considered. The effect of the imperfections on the critical value of the dynamic load, that causes the loss of stability of the system, is analyzed. Interesting nonlinear dynamic phenomena are observed: direct resonance with softening behavior and parametric instability with period doubling response. The effect of a contained heavy fluid on the shell vibration and stability is investigated.

2002 - Dynamic Stability of a Pipe Subjected to a Pulsating Flow [Relazione in Atti di Convegno]
Catellani, Giulia; Milani, Massimo; Pellicano, Francesco
abstract

Power transmission pipes are widely present in industrial applications. Moreover, the physical and mathematical model describing the dynamics of a pipe is similar to that of many mechanical systems such as heat exchangers high-speed magnetic tapes, band saw blades, aerial cable threadlines, and sheet production processes. All previous systems are axially moving systems. The dynamic behaviour of an axially moving system is greatly influenced from the presence of the internal flowing fluid, which affects the pipes dynamics and stability. When a critical value of the axial speed is reached, the first linear natural frequency vanishes; the straight equilibrium position loses stability and bifurcates into new equilibrium states. In the sub-critical speed range, all natural frequencies decrease as the axial speed increases and the vibration modes are complex. In actual operating conditions, pipe lines are subjected to many external disturbances, such as external excitations or dynamic disturbances exerted by the flow fluctuations induced by a volumetric pump. Some example of pump-pipes interactions can be found in literature, that highlight the great influence of pump irregularity on lines stability and system noising. When an oscillating external excitation causes a resonance, very dangerous conditions can be met and the axially moving continuum can undergo to catastrophic failures. The presence of an internal flow can cause divergence and flutter type instabilities. The fluid structures interaction analysis requires a deep investigation of the internal velocity field

2002 - On a FRF based experimental sub-structuring technique for linear vibrating systems [Relazione in Atti di Convegno]
Andrisano, Angelo Oreste; Catellani, Giulia; Pellicano, Francesco
abstract

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2002 - Parametric instability of belts: Theory and experiments [Relazione in Atti di Convegno]
Pellicano, F.; Catellani, G.; Fregolent, A.
abstract

In this paper, the dynamic stability of a power transmission belt excited by an eccentric pulley is investigated. A theoretical model has been developed in order to predict the belt response: simply supported boundary conditions are introduced, neglecting the pulley curvature, and considering the presence of the lower span of the belt. The transversal displacement field is expanded in sine series of the still belt modes; the Galerkin method is applied to reduce the partial differential equation of motion into a set of ordinary differential equations. In order performing an accurate response prediction, the following information must be supplied to the model: elastic characteristic; geometry; initial tension; damping. An experimental investigation is performed on a belt mounted on two pulleys and a tensioner, where one of the pulleys presents a variable eccentricity; measurement are performed using a Laser Displacement transducer. The combination of direct and parametric excitation is analyzed in detail. Interesting postcritical nonlinear dynamics are found: sub-harmonic responses and quasi-periodic motion seem to coexist, depending on the initial conditions. Experiments confirm the numerical findings validating the present theoretical model.

2001 - Nonlinear resonance and parametric instability of a power transmission belt: Numerical analysis with experiments [Relazione in Atti di Convegno]
Vestroni, F.; Pellicano, F.; Catellani, G.; Fregolent, A.
abstract

In this paper a numerical approach is developed to forecast the dynamic behavior of a power transmission belt running on eccentric pulleys. Basic partial differential equations are developed, considering the elastic effect of the lower branch of the belt. Nonlinear resonances and dynamic instabilities are analyzed in detail using a high dimensional discrete model, obtained through the Galerkin procedure. The numerical analysis is performed by means of direct simulations and a continuation software. Numerical results are compared with available experimental data. It is shown that the numerical method is able to predict correctly the amplitudes of oscillation in several operating conditions: direct and parametric resonances. Frequency response curves are obtained when the belt is harmonically excited close to the first and second linear natural frequency. The damping ratio and the linear frequencies are identified at zero axial speed.