Dipartimento di Ingegneria Meccanica, Energetica e Gestionale - Tesi di Dottorato

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Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Ingegneria Meccanica, Energetica e Gestionale dell'Università della Calabria.

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Start date: 2010End date: 2019

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Now showing 1 - 10 of 89
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    Metodi e tool per l'ottimizzazione della calibrazione e della validazione dei sistemi di controllo motore
    (2012-09-29) Guzzo, Alessandra; Rizzuti, Sergio; Bova, Sergio; Riegel, Alessandro
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    Shape Memory Alloy connectors for Ultra High Vacuum applications: a breakthrough for accelerator technologies
    (2017-06-29) Niccoli, Fabrizio; Furgiuele, Franco; Cedric, Garion
    The design of tight connections for ultrahigh-vacuum (UHV) systems is a key subject for vacuum technology. Design requirements become even more stringent when dealing with UHV beam-pipe coupling in high-energy particle accelerators, where reliability and safety are core issues. For this specific application, additional needs often arise: strict geometrical and/or space limitations, connection of dissimilar materials and installation in restricted access areas. The latter constraint is of major concern, especially in the new generation of high-energy particle accelerators such as the HL-LHC (High Luminosity Large Hadron Collider), which will be operational at CERN (European Organization for Nuclear Research) in 2026. Owing to the increased proton-beam intensity and luminosity of the HL-LHC, radioactivity will be higher at some points than in the present LHC. The radiation exposure time of the technical personnel in some critical areas will be strictly controlled and minimized. The use of standard ConFlat® flanges (CF) or quick connect ConFlat® flanges (QCF) could result in significant design and operational/maintenance limitations. In particular, the mounting and dismounting of CFs are time-consuming due to the high number of bolts and lead to significant radiation doses incurred by operators. Conversely, QCFs can be installed more quickly, but they suffer from the requirement of more space and are unwieldy components comprising heavy stainless-steel chain clamps. Within this framework, Shape Memory Alloys (SMAs) offer a unique possibility to generate tight connections and fast clamping/unclamping by remotely changing the temperature of the SMA junction unit; at the microscopic scale this occurs trough a reversible solid-state transformation between the parent austenitic phase and the product martensitic one. In this PhD work, SMAs were used to develop a new generation of vacuum tightening systems for accelerator beam-pipe coupling by exploiting their shape recovery capabilities and actuation principles. The proposed coupling system consists of a SMA ring and a sealing element to be placed at the SMA-vacuum chambers interface, i.e. a copper coating or a thin cylindrical aluminum/copper gasket. Commercial NiTiNb rings and NiTi sleeves ad-hoc developed by Intrinsic Devices Inc. (USA) based on CERN technical constraints were properly investigated. The rings show two-way shape memory effect 􀍞remembering􀍟 a contracted austenitic shape and an enlarged martensitic one. The thermomechanical properties of the selected SMAs were measured experimentally. The tightening performance of SMA rings, was studied for different values of the initial clearance between the SMA ring and the vacuum pipe. The contact pressure was estimated by both strain gauge (SG) measurements and by Digital Image Correlation (DIC), using an ad-hoc developed numeric procedure. A novel design method was proposed that involves numerical results, obtained from Finite Element (FE) simulations and a literature vacuum sealing model. Leak tightness tests were carried out to assess the sealing performance of the of SMA-based prototype UHV chambers even after ageing at room temperature and repeated thermal cycles. Irradiation tests on SMA-based prototype vacuum chambers (SMA absorbed dose > 100 kGy) was performed at CHARM (Cern High energy AcceleRator Mixed field) facility at CERN and the functional and leak tightness performance of the couplings was successfully verified afterwards. The main results revealed that the contact pressure is not significantly affected by the initial SMA ring-pipe assembly clearance due to the plateau in the stress-strain response of the material. Thermal dismounting and subsequent re-clamping is obtained by exploiting the two-way shape memory recovery capabilities of the alloys. Leak rate measurements showed that the constraints for UHV applications could be easily satisfied (leak rate < 10-10 mbar l s-1) even after multiple thermal cycles; this opens the possibility of remotely clamping/unclamping the tight couplers by well-defined temperature variations. The proposed SMA-based beam-pipe couplers can be installed without using any connection flange. They are smaller and lighter than CF and QCF devices currently used in UHV systems at CERN. These bolt-free SMA-based connectors could provide significant benefits in terms of installation-dismounting time, space occupancy, bi-material joining and, above all, possible remote thermal activation, obtainable, for example, with removable heating/cooling collars. Based on these results, possible applications in CERN accelerators have already been identified. A first use has been proposed for the ISOLDE (Isotope Separator On Line DEvice). A second application is the vacuum system of the Large Hadron Collider (LHC) between the two high-luminosity experiments (ATLAS and CMS) and the beam focusing-defocusing quadrupole magnets (frequently called inner triplets). Moreover, particle collimators are also critical devices of accelerator equipment. In all these applications, high-energy particles induce a large radioactivity and, consequently, personnel access is restricted. The use of SMA rings with remote clampingunclamping features could be beneficial to avoid contamination and irradiation of technical personnel. Finally, SMA coupling installations are already planned in the CLEAR test facility at CERN, which provides the electron beam for the Compact Linear Collider (CLIC) study.
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    Occupants behavior influence on buildings energy performance. Investigations in residential and office buildings
    (2017-10-27) Mora Guerra, Dafni Yeniveth; Furgiuele, Franco; De Simone, Marilena
    The general objective of the research was to evaluate the main factors affecting the energy performance of buildings by considering both physical and occupancy variables. The research had two different approaches, one of them was regarding occupant behavior related to energy consumption in residential buildings and the other focused on the office buildings. The investigations were conducted by means of data collection and statistical analyses in existing residential buildings. Furthermore, different procedures for obtaining occupancy profiles were applied. Finally, a case of design and modeling of Nearly Zero Energy Buildings was developed in order to study the influence of occupancy in high efficient energy buildings. The results showed that different approaches of modeling occupancy can lead to considerable variations in building energy performance. In office buildings, the detection of occupancy was obtained by an experimental approach. First of all, the state of the art regarding the sensors and devices used for measuring and monitoring indoor parameters was defined. Successively, an experimental setup was created in an office of the University of Calabria in order to collect data on occupancy and energy consumption by means of sensors and manual observations. The criterion of sensor fusion was adopted. Data were processed by using different statistical techniques: clustering analysis, descriptive and stochastic elaborations. The results were models that can be used either to describe or predict occupancy profiles. Structure of this work The thesis is divided into six chapters. The first chapter is a general introduction titled Occupant behavior in buildings, regarding occupant behavior and its relationship to the energy consumption in residential buildings, office buildings, and low energy buildings. At the end of this chapter a brief description of occupant behavior and energy simulation in buildings is presented. In the second chapter, Building occupancy is presented with a description concerning the occupancy sensing techniques used and general classification following different approaches. Residential buildings is the title of the third chapter in which we attempt to describe the objectives and main findings of three investigations regarding residential buildings and occupancy profiles definition by means of the development of cases of study. The title of the fourth chapter is Office buildings: the experimental study. It consists of the description of the experimental study realized at the University of Calabria in an office building. A description of the sensors and the monitored data were presented. The Office buildings: data analysis is the fifth chapter of the thesis, with the different approaches used to analyze experimental data. It begins with the statistical analysis and ends with the results of the modeling based on indoor environment measurements. The General conclusions is the last chapter of the thesis, with a review and discussion of the key contributions of this research work
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    Modelli organizzativi e servizi ICT a supporto dello sviluppo sostenibile di sistemi agroalimentari e turistici locali
    (2018-05-04) Della Gala, Marco; Furgiuele, Franco; Volpentesta, Antonio Palmiro
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    Reduced Basis method for closed-form affine dependent second order systems
    (2018-08-30) Lappano, Ettore; Furgiuele, Franco; Mundo, Domenico
    This thesis proposes the use of Reduced Basis (RB) methods to improve the computational efficiency of simulations in the field of elastodynamics and acoustics including poroelastic materials. RB methods are Model Order Reduction techniques used to generate parametric Reduced Order Models (ROM). The are many reasons for current researchers to focus on MOR for computational improvements. The technological development of computers and hardware has led to using brute force for calculations of large matrices projected onto simple shape-functions rather than, as it was normally done in the 60s and 70s, trying shrink the size of the matrices using special shapefunctions (i.e., specific for the different systems) [1]. The purpose of MOR techniques is to use these enormously detailed but slow (to compute and even to read) data to generate those smart shape functions. Hence, the resulting ROM contain the level of detail of those huge models, referred to as high fidelity models or full order models (FOM), offering high computational performances. These characteristics of ROM can strongly enlarge the horizons of optimization techniques enabling repeated simulation at high rate or, in some cases, allow real-time simulations paving the way for e.g. virtual sensing, haptic technology, computer graphics. A common strategy to do MOR is to use projection-based techniques that apply to semi-discretised models (e.g. finite element models). A projection transforms the basis that describes the multidimensional space of the model to be much smaller. Thus, a projection of the model into a subspace that contains all and only the dimensions necessary to describe the model will minimize the computation effort. The field of MOR includes dozens of methodologies and this thesis does not pretend to cover all of them. The focus of the work is to develop methods based on projection that are able to generate ROM with explicit parametric dependency typically indicated under the category Parametric Model Order Reduction (PMOR). Changes of the parameters configuration affect the shape of the multidimensional space. Therefore, to obtain a reduced parametric solution, a manifold of all the basis corresponding to the different parameter configurations is needed. Among the possible approaches available to do PMOR, the RB methods achieve efficient results separating the parametric dependent and parametric independent quantities in the FOM. This enable an efficient reduction and originates ROM whose operations are independent from the size of the former FOM. The research brought to a parametric approach in the frequency domain that can take into account the nonlinear frequency dependent characteristics of poroelastic materials (PEM). Also this methodology is verified using few numerical examples. In addition, a parametric approach to study elastodynamic problems of linear structures made of beams is presented and applied. The results of the study are discussed and validated with direct comparison to direct FE simulations. In addition to the original contribution, the research reported in this thesis raises some new questions that could set the start of new research projects in the field of PMOR and are discussed in the conclusion to this work.
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    Thermo‐Fluid Dynamics Study of Oxy‐MILD combustion of pulverized coal in furnaces and in a novel concept of boiler
    (2017-06-16) Perrone, Diego; Furgiuele, Franco; Amelio, Mario
    The thermal power plant for the generation of electricity, which uses coal as a primary energy source, presents multiple issues linked to the emission of pollutants and greenhouse gas (CO2) into the atmosphere. Furthermore, the conventional boilers greatly contribute to the increase of these harmful substances. The aim of this work is to propose and analyze the possibility of combining two new combustion technologies: the so-called oxy and MILD combustion. The rst one, allows to capture the carbon dioxide, while the second one provides several advantages, not only because it reduces the emission of nitrogen oxides, but also because it is characterized by uniform ows in the combustion chamber. Therefore, the challenge is to combine the two technologies with applications in furnaces and a new concept of boiler. For the latter, the planned applications include the ultra-super critical plants. For this reason, numerical simulations have been carried out by means of technical CFD (Computational Fluid Dynamics) because it is hard to provide large-scale tests. The initial phase of the work involves the application of the two technologies in furnaces. The rst one focuses on the MILD combustion by analyzing di erent positions of the pulverized coal jet, while the second one focuses on the application of the combination of the two technologies in order to analyze their e ects in terms of temperature and species concentration distributions. The next phase of the work, instead, has a focus on an innovative boiler. The testing of di erent geometrical solutions and models of char combustion has also allowed to study their e ects in terms of temperature, combustion products concentrations, burnout and, above all, wall heat ux. These latter results have been compared with the ones of traditional boilers and the results reported in the literature. The nal aim of this work is to analyze the advantages deriving from the combination of two technologies into a new concept of boiler, in order to reduce pollutant emissions, greenhouse gases and obtain a better performance than the one at the current state of the art.
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    Development and characterization of advanced ceramic materials
    (2017-06-29) Lamuta, Caterina; Furgiuele, Franco; Pagnotta, Leonardo
    Il presente lavoro di tesi è incentrato sullo sviluppo e la caratterizzazione di materiali ceramici avanzati. In particolare, tre diversi materiali sono stati prodotti e analizzati, e i risultati ottenuti sono stati presentati in tre differenti capitoli. Il primo capitolo si focalizza sullo studio di rivestimenti ceramici nanostrutturati di zirconia parzialmente stabilizzata con yttria (YSZ), realizzati mediante un processo di Air Plasma Spray (APS). Tali rivestimenti sono stati prodotti presso il centro ricerche ENEA di Brindisi e sono stati caratterizzatti nei laboratori del Dipartimento di Ingegneria Meccanica dell’Università della Calabria. L’obiettivo dell’attività di ricerca svolta è stato quello di analizzare l’influenza di alcuni parametri di processo sulle proprietà microstrutturali, meccaniche e tribologiche dei suddetti rivestimenti. E’ stato dimostrato che, modificando in maniera opportuna tali parametri, è possibile controllare la percentuale di aree nanostrutturate contenute all’interno del materiale e quindi conferire al rivestimento proprietà differenti. In tal modo si possono quindi ingegnerizzare tali rivestimenti in funzione dei diversi campi di applicazione, che spaziano dalle produzione di barriere termiche a quella di rivestimenti abradibili, utilizzati per ridurre i flussi di bypass tra le pale e lo statore dei motori a turbina degli aerei. La microstruttura dei rivestimenti prodotti è stata analizzata mediante acquisizioni SEM (Scanning Electron Microscopy), mentre per la caratterizzazione meccanica e ad usura sono stati realizzati test di indentazione e test tribologici, rispettivamente. Mentre la zirconia può essere considerata un materiale ceramico avanzato ben noto, il materiale analizzato all’interno del secondo capitolo, una malta geopolimerica a base di metacaolino, è presentato come materiale ceramico avanzato per la prima volta nel presente lavoro di tesi. Tale materiale è stato interamente prodotto e caratterizzato presso i laboratori di Ingegneria Meccanica e Chimica dell’Università della Calabria. I geopolimeri sono materiali ceramici consolidati a freddo, ottenuti dall’attivazione alcalina di precursori alluminosilicati. Tali materiali, sviluppati nel 1970 come alternativa al cemento Portland, pur essendo più ecosostenibili rispetto a quest’ultimo presentano proprietà meccaniche e applicazioni simili a quelle del comune cemento. Non trovando impiego nell’ambito di applicazioni high-tech, i geopolimeri sono sempre stati annoverati tra i materiali ceramici tradizionali. La scoperta di un effetto piezoelettrico diretto all’interno di tali materiali, proposta per la prima volta nella presente trattazione, ha però il potere di trasformare i geopolimeri in materiali ceramici avanzati. Nuove ed interessanti applicazioni derivano infatti da questa scoperta, sia nell’ambito della sensoristica che in quello dell’ energy harvesting. In particolare, è stato proposto un nuovo modello chimico-fisico per la descrizione dell’effetto piezoelettrico osservato all’interno dei geopolimeri. Per la prima volta l’attività piezoelettrica è stata ricondotta ad un fenomeno di mobilità ionica anziché alla deformazione di una struttura cristallina non centro-simmetrica. Il coefficiente di carica misurato per le malte geopolimeriche prodotte varia da 4 pC/N a 40 pC/N, in base alla quantità di acqua contenuta all’interno del materiale. Oltre alla caratterizzazione piezoelettrica, sono state proposte anche una caratterizzazione piezoresistiva e meccanica. Quest’ultima in particolare, è stata condotta a diverse scale. Per la caratterizzazione alla nano e alla micro scala, sono state realizzate prove di indentazione, mentre per la caratterizzazione alla macroscale, è stata sviluppata ed ottimizzata una nuova metodologia, caratterizzata dalla combinazione della correlazione digitale delle immagini (DIC) e del Brazilian Disk Test. Il coefficiente piezoelettrico misurato per le malte geopolimeriche prodotte risulta essere sufficientemente elevato per applicazioni sensoristiche; tuttavia, alcune applicazioni, soprattutto nell’ambito dell’ energy harvesting, richiedono spesso coefficienti più elevati. Con lo scopo di incrementare le prestazioni elettro-meccaniche dei geopolimeri analizzati, si è deciso di utilizzare nanoplatelets di grafene (GNPs) come fillers all’interno delle malte prodotte. I risultati relativi alla produzione e alla caratterizzazione chimica, meccanica, ed elettromeccanica di tali nanocompositi sono stati presentati all’interno del terzo ed ultimo capitolo. Mentre l’aggiunta di GNPs sembra non aver modificato in maniera incisiva le proprietà meccaniche dei geopolimeri, sono stati misurati promettenti incrementi del gauge factor e del coefficiente piezoelettrico (pari al 20% e al 198%, rispettivamente) in seguito all’aggiunta dell’1% in peso di grafene. Ulteriori analisi sono tuttavia necessarie per la formulazione di un modello fisico in grado di chiarire il ruolo del grafene nell’ambito dell’attività elettro-meccanica dei geopolimeri. Nella seconda parte del terzo capitolo, alcuni isolanti topologici (Bi2Te3, Bi2Se3 e SnSe) sono stati proposti come nanofillers alternativi per l’incremento delle performances elettro-meccaniche dei geopolimeri. Gli isolanti topologici, noti anche come “graphene like materials”, pur essendo semiconduttori nel bulk, sono caratterizzati da un’eccellente conducibilità elettrica in superficie, paragonabile a quella del grafene. Rispetto a quest’ultimo inoltre, presentano una conducibilità priva di dissipazioni in presenza di difetti superficiali e possono essere prodotti tramite processi relativamente economici. La conoscenza delle proprietà meccaniche di tali materiali è tuttavia estremamente limitata e i pochi lavori presenti in letteratura sono quasi interamente di carattere teorico e computazionale. A tal proposito, il Bi2Te3, il Bi2Se3 e lo SnSe sono stati caratterizzati mediante prove di indentazione strumentata e simulazioni DFT (Density Functional Theory), tenendo in considerazione l’anisotropia meccanica che tali materiali presentano. I risultati ottenuti sono di fondamentale importanza per tutti gli studi futuri incentrati sulla produzione e la caratterizzazione di nanocompositi geopolimerici rinforzati con nanofillers di Bi2Te3, Bi2Se3 e SnSe. “Ingegnerizzare”, “concepire” e “migliorare” un materiale ceramico avanzato sono quindi i tre differenti approcci proposti all’interno dei tre differenti capitoli del presente lavoro di tesi.
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    Modelli per la gestione ed il controllo dei sistemi di accumulo distribuito in ambiente Power Cloud
    (2018-06-01) Vizza, Pasquale; Critelli, Salvatore; Menniti, Daniele; Sorrentino, Nicola; Pinnarelli, Anna
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    Control system for a nanogrid for home application: dynamic analysis and and implementation aspects using a behaviour tree
    (2018-06-01) Motta, Michele; Critelli, Salvatore; Menniti, Daniele; Pinnarelli, Anna; Sorrentino, Nicola