Search results for " costruzione"

MULTIBODY NUMERICAL SIMULATION OF AN INTERNAL COMBUSTION ENGINE WITH APPRAISAL OF THE WEAR DAMAGE

2009

An internal combustion engine at four times (Otto cycle) and three cylinders is simulated by multibody software MSC Visual Nastran. The bearings are simulated by means of the library of constraint of the software, putting a particular attention to bench bearings and to the lubrication conditions. The loads on the bench bearings and in both the feet and head of the connecting rods, are evaluated by dynamical simulation, so that the inertia loads can be take in account, considering the condition of the maximum couple furnished by the engine. By making the necessary hypothesis, the evaluation of the wear damage is executed by Bayer theory on zero wear, obtaining that a good expectation of life…

DYNAMIC BEHAVIOUR COMPARISON OF ROTATING SHAFT SUSPENDED BY TWO RADIAL ACTIVE MAGNETIC BEARINGS.

2012

Ruolo della variazione di larghezza e di spessore nelle spatole delle lucertole e degli insetti

2012

Molti dispositivi biologici di adesione degli insetti, dei ragni e dei gechi consistono di matrici di peli (setae) che terminano con elementi di contatto di diverse forme. Tuttavia, la forma più osservata è una spatola appiattita. Nonostante nei diversi animali le spatole esistano in una notevole varietà di dimensioni, la maggior parte di esse non sono uniformi ma posseggono un gradiente sia in spessore che in larghezza. In questo lavoro investighiamo perché le spatole dei gechi diventano gradualmente più sottili e più larghe avvicinandosi alla loro estremità. Il motivo di questa particolare geometria è studiato utilizzando un approccio numerico basato sul metodo degli elementi finiti. La m…

ANALISI CFD DELLE PRESTAZIONI DI UN CATAMARANO CON SCAFI ASIMMETRICI DOTATO DI SOSTENTAMENTO IDRODINAMICO

2010

Nel presente lavoro è proposto uno studio di ottimizzazione su di un catamarano a scafi asimmetrici con murate piane esterne, grazie al progetto di due alettoni posizionati trasversalmente alla direzione del moto al di sotto del piano di galleggiamento ai quali è affidato il sostentamento idrodinamico dell’intero catamarano. L’obiettivo finale dello studio è quello di ridurre la resistenza totale all’avanzamento del catamarano dopo aver progettato in maniera opportuna le due appendici alari. Le analisi CFD, sia del catamarano senza alettoni che del catamarano con agli alettoni, hanno dato la possibilità di operare un confronto tra i due catamarani evidenziando un beneficio del 38% in termin…

Dissection Properties of Ascending Thoracic Aortic Aneurysms Associated with Bicuspid and Tricuspid Aortic Valves

2012

An optimised tapered shape of the terminal contact elements in biological attachment devices

2009

Many biological attachment devices of insects, spiders and geckoes consist of arrays of hairs (setae), which are terminated by contact elements of different shapes. However, the most frequently observed shape is a thin plate-like spatula. In spite of a rather wide range of sizes and thicknesses, most spatulae of different animals are not uniform but possess a gradient in thickness. The thickness of spatulae in the longitudinal section becomes gradually thinner close to the tip. This geometrical effect is numerically explained in the present paper, by using a numerical approach for modeling the van der Waals-like adhesion and friction between the contact element and the substrate. The approa…

Does the 5-strand-graft have superior biomechanical behaviour than 4-strand-graft during acl reconstruction?

2019

Purpose. This study aimed to compare the biomechanical proprieties of 4 and 5-strand- grafts. Methods. For the present study, fresh-frozen bovine common digital extensor tendons were used. Tendon grafts were prepared and sized to have a length of almost 27 cm and a cylinder 4 strand diameter of 8 mm. In half of all samples (Group A, n=12,), the graft was formed by 2 bundles duplicated around a metallic rod creating a 4-strand-tendon construct. In the other half of samples (Group B, n= 12,) 5-strand-tendon construct was created duplicating a single tendon around the rod, and tripling the other one. The grafts were preconditioned at 50 N for 10 min, followed by 1,000 cyclic loading between 50…

Carbon Nanotube Based Composites: Processing, Properties, Modelling and Application

2012

The object of this book is to bring together all available information on the carbon nanotube based composites. Details of the more important processing techniques for manufacturing carbon nanotubes-polymer composites are discussed in Chapter 1, including preprocessing treatments as purifi-cation, graphitization and functionalization. Chapters 2 explores the state of the art concern-ing mechanical, thermal, electrical and optical properties of CNTs composites made of the most frequently used polymer matrixes. Two tables gives quick access to a vast amount of the available data on the mechanical and electrical properties of CNTs composites. In Chapter 3 a reviews of the numerical models, whi…

Reinforcing effect of carbon nanotubes (CNT) on polymer nanocomposites – A numerical-analytical study

2012

A mixed model, numerical-analytical, is presented that allows one to predict the elastic properties of carbon nanotube (CNT)/polymer composites containing a random distribution of CNTs, while taking account of the curvature that they show when immersed in the polymer. This hybrid approach is a significant advance over micromechanical modeling and can be applied to all nanostructured composites.

Numerical model for the electromechanical characterization of carbon nanotubes

2010

Carbon nanotubes (CNTs) can be metallic or semiconductors depending simply on geometric characteristics [e.g., 1]. This peculiar electronic behavior, combined with high mechanical strength, make them potential building blocks of a new nano-electronic technology. Most discussions of the electronic structure of CNTs assume perfect cylindrical symmetry, but this is somewhat of an oversimplification. High resolution images of CNTs often disclose structural deformations such as bent, twisted, or collapsed tubes. These deformations may develop during growth, deposition, and processing, or upon interaction with other CNTs, and with surfaces and surface features such as electrodes. Deformations bre…