1,721,048 research outputs found
Study of a vibrating propulsion system for marine vessels: Evaluation of the efficiency for a boat 13 m long
No full textThis paper illustrates recent advancements relative to a non-conventional propulsion system for boats and is based on two previous papers of
the author presented at a conference (see Muscia, 2015a,b). The system does not consider propellers and utilizes the vibration generated by two
or more pairs of counter rotating masses. The resultant of the centrifugal forces applies an alternate thrust to the hull that oscillates forward and
backward along the longitudinal axis of the boat. The different hydrodynamic drag forces that oppose to the oscillation produce a prevalently
forward motion of the vessel. The vibration that causes the motion can be suitably defined to maximize the forward displacement and the
efficiency propulsion of the system. This result is obtained by using elliptical gears to rotate the counter rotating masses. The computation of the
propulsion efficiency is based on a suitable physical mathematical model. Correlations between numerical experiments on models and possible
full scale application are discussed. Some remarks in relation to practical applications and critical issues of the propulsive solution are illustrated.
The results have been obtained with reference to a CAD model of a real boat already manufactured whose length is approximately equal to 13 m.
Copyright © 2016 Society of Naval Architects of Korea. Production and hosting by Elsevier B.V. This is an open access article under the
CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Mechanical Design of Innovative Electromagnetic Linear Actuators for Marine Applications
No full textWe describe an engineering solution to manufacture electromagnetic linear actuators for moving rudders and fin stabilizers of military shipsItalian Ministry of Defence, General Direction of Naval Equipments (NAVARM), Projects ISO (2012-2014) and EDDA (2015-2017).. The solution defines the transition from the conceptual design of the device initially studied from an electromagnetic point of view to mechanical configurations that really work. The structural problems that have been resolved with the proposed configuration are described. In order to validate the design choices discussed we illustrate some results of the numerical simulations performed by the structural finite elements method. These results quantitatively justify the suggested mechanical solution by evaluating stresses and deformations in a virtual prototype of the structure during its functioning. The parts of the device that have been studied are the most critical because in cases of excessive deformation/stress, they can irreparably compromise the actuator operation. These parts are the pole piece-base set and the retention cages of the permanent magnets. The FEM analysis has allowed us to identify the most stressed areas of the previous elements whose shape has been appropriately designed so as to reduce the maximum stresses and deformations. Moreover, the FEM analysis helped to find the most convenient solution to join the pole pieces to the respective bases. The good results obtained by the suggested engineering solution have been experimentally confirmed by tests on a small prototype actuator purposely manufactured. Finally, a qualitative analysis of the engineering problems that have to be considered to design electromagnetic linear actuators bigger than the one already manufactured is illustrated
Identification of Mass and Stifness Matrices Based on Incomplete Modal Analysis of Structures
No full textValutazione della Matrice di Massa Basata sull'Analisi Modale Incompleta di Strutture Dotate di un Piano di Simmetria
No full text
Cinematica Applicata allo Studio dei Meccanismi Piani con l'Uso dell'Elaboratore e Metodi Matriciali
No full textMemoria interna - Dipartimento di Energetic
Computation of the Magnetic Field Generated by Helicoidal Toroidal Permanent Magnets
No full textThis article presents an analytical numerical procedure to compute the
magnetostatic field generated from permanent magnets shaped by a helicoidal geometry of a toroidal kind. The transversal section of these magnets is pseudorectangular, and the magnetization model that has been used is based on the equivalent magnetic charge. The modulus of the magnetization vector M has a constant value in all points of the magnet case study. M has the same direction as the binormal in each
point of the barycentric curve relative to the helicoidal magnet of a toroidal kind. The procedure proposed to evaluate the magnetic field is shown by computing the distribution of the magnetic flux B on a surface parallel to one of the four surfaces that surround the magnet. This evaluation has been performed with reference to a discrete set of points belonging to the same surface. Successively, a bidimensional interpolant function is used to virtually evaluate B in each point of the previous surface that contains the points where B has been actually computed. The results are presented using a three-dimensional representation of vector B obtained by the computation
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