Search results for " meccanica"
showing 10 items of 819 documents
The Rotary Aero-Engine from 1908 to 1918
2012
The rotary aero engine is a special type of air-cooled radial engine, where the cylinders are arranged like the spokes of a wheel and turn around the crankshaft. The propeller is connected to the cylinders, while the crankshaft is fixed to the frame. The rotary aero engine, developed in 1908, set new standards of power and light weight within the aircraft industry. It was adopted by many pioneer aviators and widely used to set records of endurance, speed and height. Many aero engine manufacturers produced different models and variants of this type of engine, which was extensively used until the end of the First World War. The latest evolution of the rotary engine was the counter-rotary arra…
Hysteretic whirl stabilization in rotor-shaft-bearing systems on dry friction suspension
2009
SUMMARY. The undesired whirl of rotating machines can be reduced by elastic journal box suspension systems equipped with dry friction dampers. The critical speeds can be cut off by the adhesion of the friction surfaces and the whirl amplitude can be restrained throughout the remaining sliding range by a proper choice of the suspension-to-shaft stiffness ratio and of the support-to-rotor mass ratio. The dry friction forces counteract also efficiently the well known destabilising effect of the shaft hysteresis in the supercritical range. This lecture deals firstly with the natural precession speeds, investigates the steady response to unbalance and defines the ranges of adhesive or sliding co…
On the isochronism of Galilei's horologium
2013
Measuring the passage of time has always fascinated the humankind throughout the centuries. It is amazing how the general architecture of clocks has remained almost unchanged in practice to date from the Middle Ages. However, the foremost mechanical developments in clock-making date from the seventeenth century, when the discovery of the isochronism laws of pendular motion by Galilei and Huygens permitted a higher degree of accuracy in the time measure.
A Two-Dimensional Approach to Rubber V-Belt Mechanics
2010
A new two-dimensional approach to the mechanics of rubber V-belt CVT's takes into account the change, along the belt sides, of the sliding velocity on the pulley walls, together with the cross section rotation due to the shear forces. The results show significant differences with the one-dimensional thin belt model and point out the gradual increase or decrease of the belt curvature in the entrance and exit regions of the contact arc, which implies the negligibility of the belt arching in the free spans. Some experimental tests on the global variables of a rubber belt CVT indicate a very fine acceptability of the theoretical model.
ON THE WEIGHT DISPLACEMENT IN CURVE AND THE ROADABILITY OF A 4WS VEHICLE
2013
A simplified theory on the vehicle stability in curve is explained in this paper; it allows the calculation of the force on the wheels during the motion in curve, supposing unchanging the position of the rolling centre; moreover it does not take in account the turn of the wheels and the behaviour of the tires, so that the theory can be applied to 2WS and 4WS vehicles for vertical loads calculation. The virtual simulations of 2WS and 4WS vehicles are executed, extracting all the data interesting the vehicle stability; it needs the distinction between manoeuvrability and handling. The simulations of two different tests are executed: the elk test like manoeuvrability test and a similar one at …
STUDIO DI UNA FRIZIONE MAGNETOREOLOGICA PER AUTOVEICOLI
2013
Dopo un’accurata ricerca bibliografica sui fluidi magnetoreologici, il loro comportamento ed impiego, si è passati alla progettazione di una frizione magnetoreologica per autoveicoli. Considerando le caratteristiche di coppia trasmessa e potenza, il dispositivo è stato dimensionato tenendo presente i vincoli di ingombro del veicolo preso in esame. Sottoponendo il dispositivo ad analisi magnetostatica agli elementi finiti, si è determinato l’andamento delle linee di flusso del campo magnetico nel meato di fluido e nelle zone di maggior interesse, calcolando la coppia teoricamente trasmessa dall’innesto.È stato anche eseguito il confronto delle prestazionifra una frizione MR ed una frizione t…
Influenza della Morfologia Funzionale della Valvola Aortica sull'Emodinamica di Pazienti con Aneurisma Toracico dell'Aorta Ascendente
2013
Il presente lavoro si propone di studiare le differenze emodinamiche e i carichi di parete che si sviluppano in pazienti con aneurisma toracico dell'aorta ascendente (ATAA) con differente morfologia della valvola aortica. Sono stati identificati 5 pazienti con ATAA sottoposti a scansione TC per il controllo del diametro dell'aneurisma presso l'Istituto Mediterraneo per i Trapianti e Terapie ad Alta Specializzazione. In particolare, tre pazienti presentano valvola aortica di tipo tricuspide(TAV) mentre due valvola aortica di tipo bicuspide (BAV) generalmente associata alla formazione di ATAA. Sono state ricostruite le geometrie dei ATAA includendo anche la ricostruzione delle valvole aortich…
STUDY OF NEW AUTOMOTIVE REAR SUSPENSION MECHANISM
2011
The paper presents firstly an introduction discussing: the problem’s statement emphasizing the actual problem of research of passenger car suspension to improve driving comfort and dynamic of the vehicle movement; aspects regarding the studies of car suspension mechanisms; the paper’s aims and objectives showing that a new configuration of suspension mechanism having in structure mobile frame and an actuator offering some important operational advantages is proposed. After this, the innovative concept is presented. The motions of mechanism elements and actuator and kinematic displacements are largely presented. The simulation using modern software (MSC Patran 2007, MD R2 Nastran and MSC ADA…
Adding Autonomy to Robotic Enabled Sensing
2022
The capabilities of most non-destructive testing methods have been combined with some degree of automation in recent years, to enhance data acquisition speed, part coverage and inspection reliability. A plethora of automated or semi-automated inspection systems have been engineered to enable the robotic manipulation of specific types of sensors. Robotic inspection systems are usually operated through off-line programmed tool-paths. This approach works well when an accurate model of the part is available and the robotic inspection takes place in a well-structured environment, where the part position is precisely registered with respect to the robot reference system. However, it makes the ins…
Autonomous Robotic Sensing for Simultaneous Geometric and Volumetric Inspection of Free-Form Parts
2022
Robotic sensing is used in many sectors to improve the inspection of large and/or complex parts, enhancing data acquisition speed, part coverage and inspection reliability. Several automated or semi-automated solutions have been proposed to enable the automated deployment of specific types of sensors. The trajectory to be followed by a robotic manipulator is typically obtained through the offline programmed tool paths for the inspection of a part. This method is acceptable for a part with known geometry in a well-structured and controlled environment. The part undergoing assessment needs to be precisely registered with respect to the robot reference system. It implies the need for a setup p…