Forced response of shrouded blades with a coupled static/dynamic approach

A coupled static-dynamic method is proposed and applied to bladed disks with shrouds, in order to calculate the nonlinear forced response in presence of friction damping in the frequency domain. The novel approach allows to improve the already existing methods, which require a preliminary static analysi

Sistemi abitativi di permanenza temporanea

Scopo di questa ricerca è quello di offrire agli allievi ed ai tecnici del settore, un quadro generale dello stato dell’arte in ambito di progettazione transitoria. L’analisi storica viene sviluppata attraverso lo studio di proposte elaborate da numerosi progettisti che, nel tempo, si sono interessati a queste problematiche. Sono esaminate le tipologie ed i differenti campi di applicazione di unità abitative temporanee, con il contributo di esperti del settore che hanno affrontato tematiche relative alla sostenibilità delle scelte tecnologiche e costruttive, all’analisi dei criteri di progettazione per nuove forme di insediamenti temporanei e al benessere ambientale delle forme di architettura transitoria

reduced order modeling of large contact interfaces to calculate the non linear response of frictionally damped structures

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Innovative technologies for temporary architecture

Problem risen from temporariness and flexibility concepts of built concern, always constituted, all over technological advanced countries and throughout the whole history of scientific research, some of the most interesting aspects of technologies, industry and industrialization processes. Several project proposals about really light structures easily gatherable, transportable, that can be dismantled and reconverted, are proves of that such as their use in order to obtain flexible and functional living solutions. They are systems adaptable to different needs and fit to offer a concrete solution for the necessities related to the new ways of living. In fact temporary buildings that were thought during the past to face living emergencies, caused by natural calamities or men themselves, find today a wide range of applications such as living places for nomads, refugees, exiles, migrants, homelesses. These buildings can moreover be used as courtesy-houses during renovation, restoration, changeover and recovery interventions both of single handiworks and of urban scale or can be used as accommodation structures for wandering tourism, support systems to mass manifestations and so on. Today research is even more oriented to the discovery of innovative building technologies that concern the adoption of usages, materials and building elements with high performance characteristics that respond to eco-compatibilities priority needs. Under this point of view, temporary architectures can be transformed into structures able to guarantee the top level of comfort and eco-sustainability because they offer wide opportunities to the experimentation of new building materials and allow a more direct check of building processes such as a more immediate management of comfort control. The theme of temporary architectures has been, during this years, the object of the didactic experience inside the course of Environmental Design belonging to the Architecture Faculty in Palermo. The problem of environmental compatibility of the anthropic intervention has been afforded by students through a design approach of bioclimatic kind, preferring solutions economically fit both under the realization costs point of view, and management such as maintenance and re-employment, using materials and techniques fit in order to: - guarantee the living quality of the built area; - rationalize the consumes of natural resources especially the not renewable ones; - allow the adaptability of the handiwork to the changeable needs (in continue evolution) that characterize the contemporary society. This contribute wants to present a synthesis of the design proposals elaborated till today, in order to witness the experiences carried on such theme

Stress recovery algorithm for reduced order models of mechanical systems in nonlinear dynamic operative conditions

Nonlinear forced response analyses of mechanical systems in the presence of contact interfaces are usually performed in built-in numerical codes on reduced order models (ROM). Most of the cases these derive from complex finite element (FE) models, resulting from the high accuracy the designers require in modeling and meshing the components in commercial FE software. In the technical literature several numerical methods are proposed for the identification of the nonlinear forced response in terms of a kinematic quantity (i.e. displacement, velocity and acceleration) associated either to the master degrees-of-freedom retained in the ROM, or to the slave ones after having expanded the reduced response through the reduction matrix. In fact, the displacement is the quantity usually adopted to monitor the nonlinear response, and to evaluate the effectiveness of a partially loose friction interface in damping vibrations, with respect to a linear case where no friction interfaces exist and no energy dissipation can take place. However, when a ROM is used the engineering quantities directly involved in the mechanical design, i.e. the strains and stresses, cannot be retrieved without a further data processing. Moreover, in the case of a strong nonlinear behavior of the mechanical joints, the distributions of the nonlinear strains and stresses over the structure is likely different than the one obtained as a superposition of linear mode shapes whose definition require a-priori assumptions on the boundary conditions at the contact interface. This means that the mentioned approximation cannot be used to predict the safety margins of a structure working in real (nonlinear) operative conditions. This paper addresses this topic and presents a novel stress recovery algorithm for the identification of the strains and stresses resulting from a nonlinear forced response analysis on a ROM. The algorithm is applied to a bladed disk with friction contacts at the shroud joint, which make the behavior of the blades nonlinear and non-predictable by means of standard linear analyses in commercial FE software

Il Bambù

Il volume fa parte di una collana dal titolo Tecnologia dei Materiali per un'Architettura Sostenibile, che raccoglie i risultati di ricerche, sperimentazioni ed esperienze didattiche condotte dall'autrice negli ultimi anni, presso l'Università degli Studi di Palermo. Ogni volume della collana è dedicato allo studio di uno specifico materiale da costruzione e dei suoi derivati, delle loro peculiarità e possibili applicazioni nel costruito al fine di offrire agli studenti, ai professionisti e ai tecnici del settore, un quadro generale dello stato dell'arte ed un motivo in più per una scelta consapevole di materiali conformi alle esigenze di sostenibilità ambientale e tecnologica, oggi inderogabili per salvaguardare l'ambiente ed il futuro delle generazioni che ci seguiranno

Smorzatori sotto-pala per turbomacchine: un nuovo metodo basato sul calcolo simultaneo delle forze statiche e dinamiche di contatto

Underplatform dampers are widely used to reduce vibration amplitude of turbine bladed disks by friction. They are metal devices placed under the blade platforms and held in contact with them by the centrifugal force acting during rotation. The common procedure used to calculate the static loads acting on underplatform dampers consists in decoupling the static and the dynamic balance of the damper. A preliminary static analysis of the contact is performed in order to compute the static pressure distribution over the damper/blade interfaces, assuming that it does not change when vibration occurs. In this paper a coupled approach is proposed to solve the static and the dynamic balance equations of the system. Numerical case studies are presented in order to show the capabilities of the method and the improvements with respect to the state of the ar