Stabilità cromatica di resine per protesi fissa provvisoria sottoposte a immersione in soluzioni pigmentanti.

Resistenza alla frattura di quattro materiali per protesi fissa provvisoria: valutazione comparativa in vitro.

Scopo del presente lavoro è stato quello di analizzare la resistenza alla frattura di quattro resine del commercio (Jet Kit, Duralay, Protemp 3 e Systempt C&B), usate per la fabbricazione di protesi parziali provvisorie fisse. Sono stati realizzati venti provini sperimentali di dimensioni standardizzate seguendo le istruzioni dei fabbricanti, suddivisi in quattro gruppi, uno per ciascuno dei quattro materiali testati. Cinque provini di ogni materiale sono stati inseriti in una macchina tipo T.E.M.A, bloccati tra due bracci, uno superiore ed uno inferiore, attraverso un sistema simile a quello di una morsa. La resistenza determinata dai provini sulla trazione esplicata dalla velocità di allo…

Improving the Downwind Sail Design Process by Means of a Novel FSI Approach

The process of designing a sail can be a challenging task because of the difficulties in predicting the real aerodynamic performance. This is especially true in the case of downwind sails, where the evaluation of the real shapes and aerodynamic forces can be very complex because of turbulent and detached flows and the high-deformable behavior of structures. Of course, numerical methods are very useful and reliable tools to investigate sail performances, and their use, also as a result of the exponential growth of computational resources at a very low cost, is spreading more and more, even in not highly competitive fields. This paper presents a new methodology to support sail designers in ev…

ANALISI SPERIMENTALE DELLA DISTRIBUZIONE DELLE PRESSIONI AL CONTATTO RUOTA-SUOLO PER UN PNEUMATICO DA FUORI STRADA

Studio comparativo in vitro della resistenza alla trazione applicata a corone protesiche metal-free cementate con due diversi cementi adesivi definitivi

Study of the performances of a fluidynamic actuator

Aim of this paper is presented a new methodology to study how different geometric parameters affect the performance of a hydraulic actuator. Preliminarily, the real working conditions of a hydraulic machine have been simulated by means of a CFD module. After, to test the reliability of the simulations, the obtained numerical results have been compared with the experimental data of a real prototype. This comparison demonstrates a good level of agreement between numerical and experimental results. Different simulations have been setup by modifying the actuator geometry and evaluating the efficiency of every analysed configuration. The results of this study give useful guidelines for the choic…

Valutazione sperimentale della resistenza alla frattura di riabilitazione proteiche fisse, per settori posteriori, con struttura in ossido di zirconio realizzata con tecnologia Cad-Cam: simulazione di dieci casi clinici

La riabilitazione protesica metal-free dei settori posteriori: analisi sperimentale della resistenza al carico statico di un materiale composito.

MIsura del campo di spostamenti di un foro espanso a freddo mediante tecniche DSPI e DIC

Determination of the Stress Intensity Factor by Means of the Espi Technique

The experimental determination of stress intensity factors by means of non-destructive techniques is a research topic of actual interest, In fact there are many applications, where a reliable and accurate experimental procedure is needed to evaluate numerical or theoretical models about the behaviour of cracked or notched structures.

AA6082-T6 Friction Stir Welded Joints Fatigue Resistance: Influence of Process Parameters

In the paper the results of a wide range of experiments on friction stir welding (FSW) of aluminium alloys are reported. In particular, the AA6082-T6 butt joints fatigue resistance was investigated by varying the most relevant process parameters. In addition, a revolutionary pitch was utilized in order to investigate the effects of the tool rotating speed and the tool feed rate. Observations of the fracture insurgence were developed for different levels of applied load.

Infiltrazione marginale di tre diversi sistemi di cementazione per inlay in composito: Analisi comparativa in vitro.

Effects of matrix cracks on the mechanical behavior of polimeric matrix composites

Determination of the Stress Intensity factor by means of the Electronic Speckle Pattern Interferometry technique

FEM model achievement for dental implant characterization

Ottimizzazione di Forma della Deriva di una Barca a Vela: applicazione al caso della classe 5o5

Con questo lavoro gli autori propongono un metodo di indagine automatizzato per la ricerca della forma ottimale di una deriva di uno scafo a vela che garantisca la portanza necessaria, nelle ordinarie condizioni di navigazione controvento, offrendo al contempo la minore resistenza. L’ampio spettro di forme adottate denuncia forse il problema dei progettisti, i quali si rifanno alla teoria classica dell’aerodinamica, nell’interpretare il complesso problema idrodinamico. Da questo punto di vista un valido aiuto viene offerto dai codici di fluidodinamica computazionale (CFD) i quali permettono, con buona approssimazione, di individuare la distribuzione delle forze e delle velocità di un flusso…

A Numerical Approach to the Keel Design of a Sailing Yacht

This paper describes an approach to the keel design of a sailing yacht. The related software, which is fully automatic, permits to obtain an optimal shape by modifying the surface used to define the keel planform. B-spline curves and surfaces have been used because of their ability in following complex shapes. The algorithm integrates ad hoc implemented original software with Computational Fluid Dynamics (CFD) commercial ones. The optimisation procedure makes use of Genetic Algorithms (GAs) and a gradient – based optimiser for the refinement of the solution. A careful CAD and CFD modelling leads to a stable and efficient generalised method, which has been applied to the design of the centre…

OTTIMIZZAZIONE DI FORMA ATTRAVERSO ANALISI CFD DI UN CATAMARANO CON SCAFI ASIMMETRICI PER USO AD ALTA VELOCITÀ

PROGETTAZIONE E VERIFICA SPERIMENTALE DI UNA MICROTURBINA IDRAULICA PER L’INDUSTRIA ALIMENTARE

In questo articolo sono descritte le attività di ricerca e sviluppo di una micro-turbina idraulica inserita all’interno di un macchinario che opera un nuovo processo di abbattimento della carica batterica applicabile nell’industria dell’imbottigliamento delle bevande. Peculiarità della turbina progettata è la geometria della palettatura della girante, dritta ed a sviluppo puramente assiale, che ne rende estremamente economica la realizzazione. Lo scambio di energia avviene grazie al moto vorticoso impresso al fluido (swirl) mediante opportuno posizionamento dei condotti di adduzione. Lo studio della turbina è stato condotto mediante classico approccio unidimensionale, mentre il dimensioname…

CFD parametric analysis and experimental results on a hydraulic actuator

Valutazione sperimentale della resistenza alla frattura di riabilitazioni protesiche fisse, per settori posteriori, con struttura in ossido di zirconio realizzata con tecnologia CAD/CAM: simulazione di 10 casi clinici.

Experimental analysis of the contact pressure distribution in an off-road tyre

In this paper the results of experimental tests are shown, lead by extended method of measurement, on a tire for an off-road vehicle 175/82 R16, inserting Prescale paper at the contact with the ground. The experimental analysis of the pressures is lead, in cross-sectional direction, in 5 zones correspondents to the middle of the single dowels constituting the tread. The results are analyzed by means of software predisposed to the scope so as to go back easily to the value of the pressure. The obtained results are critically analyzed and the result are compared with those obtained by the formulas of Rowland and MacLaurin, and by the nominal pressure at ground, concluding that the expression …

Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II

The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between t…

Valutazione delle caratteristiche di assorbimento delle resine proteiche mediante un metodo RGB

EFFECT OF SURFACE FINISH ON THE TENSILE BEHAVIOR OF DACRON© 360 WOVEN

Nel presente lavoro vengono presentate alcune indagini sperimentali mirate alla caratterizzazione dell’effetto del trattamento superficiale sul comportamento costitutivo di un tessuto in Dacron© 360. Tale tessuto, largamente utilizzato nella realizzazione di vele, è ottenuto dalla tessitura di fili di polietilene tereftalato (PET) e presenta alcune peculiarità dovute al processo manifatturiero. Le prove di trazione realizzate evidenziano le caratteristiche di ortotropia del materiale e l’effetto del trattamento superficiale che si manifesta principalmente in un comportamento più rigido nella direzione dell’ordito ed in quella inclinata e in un aumento della resistenza ultima in tutte le dir…

Studio dei fattori di intensificazione delle tensioni per cricca che avanza in un pannello forato mediante analisi fotoelastica

Numerical simulations and experimental measurements of the stress intensity factor in perforated plates

A numerical procedure, which combines two hybrid finite element formulations, was developed to analyse the stress intensity factors in cracked perforated plates with a periodic distribution of holes and square representative volume elements. The accuracy of the method in predicting the stress intensity factor was verified by a comparison with experimental measurements, carried out by a photoelasticity method, and by commercial finite element software. Several simulations were executed by varying both the crack length and the hole diameters, and the effects of the holes on the stress intensity factor are illustrated. The method shows high accuracy and efficiency, as small differences were ob…

Progettazione e Confronto di Barche a Vela Mediante Analisi CFD

Le simulazioni fluidodinamiche computazionali (CFD) forniscono uno strumento particolarmente utile alla valutazione delle caratteristiche di barche a vela. La possibilità di studiare differenti carene e piani velici, ha permesso di mettere a punto geometrie che senza l’ausilio di queste tecniche innovative sarebbero apparse difficilmente raggiungibili. Nel presente lavoro sono state messe a confronto due barche a vela progettate e costruite per partecipare alle regate di Mille e una Vela per l’Università – manifestazione didattico/sportiva organizzata dall’Università Roma Tre.

Fluid–structure interaction of downwind sails: a new computational method

The spreading of high computational resources at very low costs led, over the years, to develop new numerical approaches to simulate the fluid surrounding a sail and to investigate the fluid–structure interaction. Most methods have concentrated on upwind sails, due to the difficulty of implementing downwind sailing configurations that present, usually, the problem of massive flow separation and large displacements of the sail under wind load. For these reasons, the problem of simulating the fluid–structure interaction (FSI) on downwind sails is still subject of intensive investigation. In this paper, a new weak coupled procedure between a RANS solver and a FEM one has been implemented t…

Analysis of mechanical behaviour of wood species by speckle interferometry

The understanding of the mechanical behaviour of wood is a very important task in modern structural engineering. This is due to the increasing role played by wood structures in modern architecture as well as to its use in the restoration of ancient buildings. However, solid mechanics of wood is very difficult since it is a complex, polymer-based, cellular, inhomogeneous material. Moreover, at the cellular scale wood is not a continuum due to the presence of vascular vacuums and it can be regarded as an anisotropic material. Conversely, at a macroscopic scale when the analysis is carried out on a structural member which is large in comparison to the size of cell, wood is usually considered a…

Effect of surface finish on the mechanical behaviour of Dacron© 360 woven

Abstract In the present paper some experimental analyses of Dacron© 360 woven with and without surface treatment are presented to evaluate the effect of this treatment on the constitutive behaviour. This woven, widely adopted in sail manufacturing, is obtained by weaving polyethylene terephthalate (PET) yarn and it shows some peculiar features due to the manufacturing process. The experimental tensile tests, clearly show the orthotropy behaviour of the material. The effect of the treatment results in a stiffer behaviour especially along the warp and bias direction and in an increment of ultimate strength in all directions.

Propagazione di difetti all’interfaccia adesivo aderendo in giunti incollati

ON THE EFFECTS OF A CRACK PROPAGATING TOWARD THE INTERFACE OF A BIMATERIAL SYSTEM

This paper deals with the influence of matrix cracks on the failure mode of bimaterial systems and composite materials. In order to investigate such an influence, the stress field near a crack embedded into the more yielding material and propagating perpendicularly to the interface, has been analyzed by using systematic numerical simulations. Such analysis has shown that the crack propagation give rises to transversal stresses that can damage the reinforcing materials when this has low modulus, as glass fibers, or low transversal strength, such as carbon fibers. Moreover, the longitudinal stress concentration can damage the reinforcing material only if this has high stiffness, as in the cas…

Experimental and numerical analysis of flexural behaviour of GFRP pultruded material

Displacement measurement through DIC and DSPI techniques in cold-expanded holes

In this paper, the displacement field induced by the split-sleeve cold expansion of holes was measured using both digital image correlation (DIC) and digital speckle pattern interferometry (DSPI) techniques. Thus, the experimental results, which were evaluated on the inlet surface of a 6082-T6 aluminium plate, were compared with those from theoretical prediction. DIC provided accurate measurements up to the elastic-plastic boundary, whereas the DSPI technique highlighted the changes of displacement in the elastic domain. Prediction of the displacement based on the existing analytical model agreed with the experimental results achieved with both techniques. Possible explanations for the diff…

Displacement Measurement Through Digital Image Correlation and Digital Speckle Pattern Interferometry Techniques in Cold-Expanded Holes

:  In this paper, the displacement field induced by the split-sleeve cold expansion of holes was measured using both digital image correlation (DIC) and digital speckle pattern interferometry (DSPI) techniques. Thus, the experimental results, which were evaluated on the inlet surface of a 6082-T6 aluminium plate, were compared with those from theoretical prediction. DIC provided accurate measurements up to the elastic–plastic boundary, whereas the DSPI technique highlighted the changes of displacement in the elastic domain. Prediction of the displacement based on the existing analytical model agreed with the experimental results achieved with both techniques. Possible explanations for the d…

CFD Study of an Innovative Catamaran with Asymmetrical Hulls

The purpose of this paper is the study of the shape of catamaran with asymmetrical hulls by both experimental and numerical viewpoint. The experimental study is based on the towing tank tests on a catamaran hulls shape obtained from previous works, showing that the wave resistance is very low produces a lower energy loss and a greater effectiveness. The hulls shape is optimized by the CFD application by force of commercial software, which shows that the reduction of wasted energy is very sensitive to make some changes; in particular three different width of the catamaran are tested and their performances are compared.

Electronic speckle pattern interferometry for the analysis of wood bending behaviour

Resistenza a fatica di tre diversi sistemi di cementazione per inlay in composito.