Search results for "Scienza"
showing 10 items of 1408 documents
Identità, differenza, diversità
2022
Il volume su “Identità,differenza,diversità”è incentrato sul tema del convegno organizzato a Palermo nei giorni 11 e 12 novembre del 2021. Si richiama ai temi dei volumi pubblicati nel 2020 su “Interculturalità e pluralismo” e nel 2019 su “Filosofia e scienza a confronto”.In tal modo,la filosofia viene posta a confronto con le altre discipline dell’area umanistica,senza con ciò rinunciare alla propria specificità. Gli autori che hanno partecipato al convegno provengono dalle diverse aree geografiche e culturali del Paese,confrontandosi con i colleghi che hanno, a loro volta, dato contributi non marginali dal Giappone, dal Libano, dalla Romania, dalla Francia, dall’Austria, dalla Polonia. Pe…
A Cohesive-Frictional Interface Model with Frictional Properties Degradation
2009
The paper is devoted to an interface constitutive modeling which couples a cohesive behavior, based on the damage mechanics theory, with a frictional one, defined in a non-associative plasticity framework. By means of a specific interpretation of the damage variable, the formulation follows the transition of the initial sound interface material layer, up to the fully cracked condition. The macrocrack surfaces have initial frictional properties and is subjected to degradation phenomena. Namely, the smoothing and breaking of surface asperities cause a progressive reduction of dilatancy effects and also of the frictional angle. These phenomena are modeled as uncoupled: dilatancy saturation is …
A nonlinear finite element approach with cohesive-frictional interfaces for mode II Transverse Crak Tension test insight
2016
In many circumstances structural failure modes are driven by the formation and propagation of fractures. For instance in composite laminate structures one of the most worrying condition is delamination, which is an interlaminar progressive fracture. Fracture toughness is the material mechanical parameters which ensure fracture safe condition and it is also an essential parameter for performing nonlinear structural analysis, no matter if based on Fracture Mechanics or by means of Interface Cohesive theories. It is then of paramount relevance to evaluate the critical fracture energy by means of simple and reliable laboratory tests. Several tests are available for the direct determination of m…
Cohesive-frictional interface model with oligocyclic degradation of surfaces roughness
2008
The present work is devoted to the constitutive modelling, through the classical interface kinematical formulation, of the mechanical behaviour of the internal adhesive layers, connecting different bodies. The proposed interface constitutive model couples a cohesive behaviour with a frictional one and it is able to follow the transition from the sound condition to the fully cracked one by means of a specific interpretation of the damage variable. In the fully cracked condition, the dilatancy exhaustion and the frictional strength degradation are also modelled.
An Interface Mechanical Model with a Cohesive to Frictional Transition
2009
A thermodynamically consistent mechanical interface model is presented. The model is based on the interface damage mechanic theory applied in a special fashion such that the interface damage variable is also used as a parameter which drives the continuous and smooth transition from the sound initial cohesive state to the final fully fractured frictional state. Interface damage activation and fictional sliding are promoted by a damage activation function and a Coulomb frictional yielding function. The main features of the model are discussed in details and some numerical results for the material response are shown in monotonic and cyclic loading regimes.
Analisi del comportamento flessionale del legno attraverso la interferometria Speckle
2009
Nel lavoro vengono presentati i risultati di uno studio sperimentale effettuato sul comportamento flessionale di due differenti essenze di legno: l’abete rosso ed il ciliegio. L’analisi viene effettuata sottoponendo il provino al test di flessione a quattro punti ed utilizzando la interferometria speckle, una tecnica di misura non a contatto ed a campo intero, che consente di ottenere i campi di spostamento e di deformazione sulla superficie del provino. Al fine di mettere in evidenza le peculiarità del comportamento flessionale del legno i risultati ottenuti vengono confrontati con quelli di un provino di Plexiglas nelle stesse condizioni. Tale confronto conferma la complessità del comport…
Moving multi-loads problem in layered cracked beams with interlayer slip
2017
This contribution concerns the vibration response of layered cracked uniform beams with interlayer slip under moving multiple loads. Considering a linear constitutive relation between the horizontal slip and the interlaminar shear force, the Euler-Bernoulli hypothesis is assumed to hold for each layer separately. Modeling cracks as internal elastic rotational joints, related discontinuities of the response variables are treated by the theory of generalized functions. In this manner, exact eigenfunctions are derived from a characteristic equation built as determinant of 6x6 matrix, for any number of cracks. Building pertinent orthogonality conditions for the deflection eigenfunctions, the re…
Material Internal Frictional Dissipation Modelling
2009
This presentation is concerned with a first introductory study devoted to internal frictional dissipation modelling of cracked materials. The problem is set as periodic Representative Volume Element (RVE) with oriented cracks diffused in the bulk material. As first stage, useful for moderate loading levels, cracks are considered fixed and stable at certain position and are modelled as perfect frictional mechanical interface with unilateral contact features. Analyses on cyclic material response are discussed for 2D problems. A second type of analyses is performed considering a further cohesion strength and a crack propagation criteria, which are typical of interface damage mechanical approac…
A constitutive framework based on elastic and internal energy degradation
2001
A general constitutive framework is presented capable of representing different irreversible deformation modes, like plasticity, elastic damage, complex evolution of the hardening properties and the induced coupling effects. The formulation can be framed in the generalized standard material models with internal variables and multiple dissipative activation functions. The formulation is thermodynamically consistent and the state laws, the structure of the dissipation and of the activation functions are all derived complying with the principles of thermodynamics. The generalized flow rules are derived under the hypothesis of generalized associativity. The main aspect of the proposed model is …
The new transatlantic agenda: transatlantic security relations between post-hegemonic cooperation and interdependence
2003
The New Transatlantic Agenda: Transatlantic Security Relations Between Post-Hegemonic Cooperation and Interdependence