101,928 research outputs found
Un modello per la stima degli errori introdotti nel campo delle basse frequenze in misure FRF di sistemi liberi
No full text
Prefazione
No full textLe trasformazioni avvenute impngono un ripensamento dell'uso del suolo e la definizione di strumenti capaci di governare il consumo di suolo
La ricerca accademica e le sue responsabilità
No full textPostfazione ad un libro che presenta per alcuni aspetti il carattere di un manifesto; alcune questioni vengono messe in evidenza negli scritti di apertura per rivendicare un ruolo che la ricerca accademica ha sempre avuto ma che nel tempo ha in parte perso, e cioè di potente mezzo non solo di riflessione ma di costruzione di un pensiero collettivo.
Il libro quindi pone l'accento sul fatto di essere stato costruito come esempio di ricerca collettiva finalizzata alla costruzione di un “rinnovato progetto di convivenza e di solidarietà urbana: un progetto in cui puntare a un innalzamento della qualità della vita fondato su un rinnovato welfare urbano”
Parametric instability of belts: Theory and experiments
No full textIn 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
Experimental dynamic substructuring: Significance and perspectives
No full textDynamic substructuring allows to describe an assembled structural system in terms of component subsystems. In experimental dynamic substructuring, the model of at least one (sub)system derives from experimental tests: this allows to consider systems that may be too difficult to model. The degrees of freedom (DoFs) of the assembled system can be partitioned into internal DoFs (not belonging to the couplings) and coupling DoFs. A possible application of experimental dynamic substructuring is substructure decoupling, i.e. the identification of the dynamic model of a structural subsystem embedded in a structural system known from experiments (assembled system) and connected to the rest of the system (residual subsystem) through a set of coupling DoFs. Coupling DoFs are often difficult to observe, either because they cannot be easily accessed or because they include rotational DoFs. However, whilst coupling DoFs and in particular rotational DoFs are needed when coupling together different subsystems, they are not essential in substructure decoupling, because the actions exchanged through the coupling DoFs are already included in the dynamic response of the assembled system. The most promising fields in substructure coupling are: coupling with configuration dependent interface and nonlinear coupling with localized nonlinearities. With reference to substructure decoupling, the most remarkable topics are: interface optimization, configuration dependent coupling conditions, and joint identification
Experimental dynamic substructuring. significance and perspectives
No full textDynamic substructuring allows to describe an assembled structural system in terms of component subsystems. In experimental dynamic substructuring, the model of at least one (sub)system derives from experimental tests: this allows to consider systems that may be too difficult to model. The degrees of freedom (DoFs) of the assembled system can be partitioned into internal DoFs (not belonging to the couplings)
and coupling DoFs. A possible application of experimental dynamic substructuring is substructure decoupling, i.e. the identification of the dynamic model of a structural subsystem embedded in a structural
system known from experiments (assembled system) and connected to the rest of the system (residual subsystem) through a set of coupling DoFs. Coupling DoFs are often difficult to observe, either because they cannot be easily accessed or because they include rotational DoFs. However, whilst coupling DoFs and in particular rotational DoFs are needed when coupling together different subsystems, they are not essential in substructure decoupling, because the actions exchanged through the coupling DoFs are already included in the dynamic response of the assembled system. The most promising fields in substructure coupling are: coupling with configuration dependent interface and nonlinear coupling with localized nonlinearities. With reference to substructure decoupling, the most remarkable topics are: interface optimization, configuration dependent coupling conditions, and joint identification
Parametric instability of belts: Theory and experiments
No full textIn 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
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