1,895 research outputs found
Peck drilling of CFRP/titanium stacks: effect of tool wear on hole dimensional and geometrical accuracy
No full textThe effect of tool wear on dimensional and geometrical accuracy of holes machined by peck drilling in carbon fibre reinforced plastic (CRFP) and titanium (Ti) stacks is studied. Coated and uncoated tungsten carbide drills of both fine and ultra-fine microstructures are employed to assess the importance of grain size and coating on hole accuracy. Hole profiles show two maxima: one at the hole entry and the other at the CFRP/Ti interface. Hole cylindricity as function of tool wear shows a minimum. It firstly decreases due to flank wear and subsequent reduction of the drill diameter. Then the rise of tool instability prevails with the result that an increase of the cylindricity with tool wear is brought about. Less wear-resistant drills attain this minimum in a shorter time of cutting
Impero mondiale e ordine globale: forme e (nuovi') linguaggi del potere?
No full textIl titolo del mio intervento pone in relazione impero globale e ordine mondiale non per darne come sottintesa, attraverso quella e, la loro connessione, ma nemmeno per intendere quella congiunzione con la funzione di polarizzare i due termini. Mi interessa, piuttosto, interrogare la natura semantica e la valenza simbolica di queste due espressioni e i presupposti di una loro eventuale connessione o disgiunzione. E da qui tentare di comprendere se siano linguaggi o manifestazione di nuove dinamiche di potere, e di quale potere parliamo. O se non sia il caso di considerare l’idea di un potere globale di cui tali nozioni rappresentano i linguaggi di dominio e di controllo. Ma, su chi, o su cosa? E a quale fine
Set-up of an experimental procedure for the surface smoothing of FDM parts through acetone vapor
No full textFused deposition modeling (FDM) is an additive manufacturing technology where three-dimensional physical models are manufactured by layer-by-layer deposition. However, the layered surface built with FDM suffers from poor surface quality and dimensional accuracy even for basic part geometries. This proves to be unacceptable and not satisfactory for most general purposes with the consequence of a decreased value of the final product. Several methods for post-processing were proposed to achieve fine surface of manufactured components. In particular, for components manufactured with polylactic acid (PLA) the chemical post-processing with dimethyl ketone (acetone), named vapor smoothing process, seems to be very promising to significantly improve the surface roughness. Moreover, acetone has the main advantage to have a low cost, low toxicity and high diffusion rate. However, this polishing procedure may dissolve the outer surface of the parts affecting the structural reliability of the part. In this work, a novel device, consisting of a cylindrical chamber in Pyrex, is set-up for the vapor smoothing process with acetone. The system is designed to permit the injection of a gas containing acetone at different concentrations and at different operating conditions (temperature, contact time). The samples used for the test are truncheon design manufactured using different printer settings; each truncheon is built at inclination angles varying from 0o to 45o in step of 5o. The variation of the surface roughness was investigated using a confocal microscope Leica DCM3D, equipped with the software LeicaScan and LeicaMap
Messico; ovvero, Repubblica ed impero,
No full text"2. ed. splendidamente illustrata."Added t.-p., illustrated, has title: Messico; ovvero, Repubblica ed impero, romanzo politico-sociale ... Prima traduzione italiana del professor F. Meriss sulla quinta edizione originale tedesca.Mode of access: Internet
Storia della decadenza e fine dell´Impero Romano
No full textSignaturizadoAntepA f. de map. preg. en vol. I, representa zona do Imperio RomanoContén : T. I : Dai tempi di Trajano e degli Antonini fino a Constantino ossia Storia degli impertatori. T. II : Dei tempi di Constantino fino ad Augustolo ossia Storia del Basso Impero. T. III : Dai tempi di Zenone fino a Carlomagno ossia Storia dell´Impero d´Oriente
Sulla proprietà della terra nella Calabria romana tra Repubblica e Impero
No full textManacorda Daniele. Produzione agricola, produzione ceramica e proprietà della terra nella Calabrìa romana tra Repubblica e Impero. In: Epigrafia della produzione e della distribuzione. Actes de la VIIe Rencontre franco-italienne sur l'épigraphie du monde romain (Rome, 5-6 juin 1992) Rome : École Française de Rome, 1994. pp. 3-59. (Publications de l'École française de Rome, 193
Surface and mechanical characterization of stationary shoulder friction stir welded lap joints: experimental and numerical approach
No full textFriction Stir Welding (FSW) is one of the most used solid-state welding processes in the aeronautical, aerospace, ground transportation and naval fields. Stationary Shoulder Friction Stir Welding (SSFSW) is a recently introduced variant of the process allowing lower heat input into the joints, with beneficial effects in terms of joint mechanical properties, microstructure and top surface finish. In the paper, lap joints produced by SSFSW and made out of AA6082-T6 aluminum alloy sheets have been analyzed with the aim to investigate the effect of the stationary shoulder on the lap joints surface, metallurgical, and mechanical properties. The lap joints produced by SSFSW have been compared to the ones produced by “conventional” FSW in order to highlight the differences between the two processes. The top surface of the joints obtained with the two processes has been quantitatively evaluated. Finally, a dedicated numerical model has been utilized to highlight the causes of the observed differences through the distributions of the main field variables, namely temperature, strain and strain rate. It was found that SSFSW results in narrower weld nugget and smaller areas involved by micro hardness reduction caused by smaller peak temperature and high temperature zone. Additionally, better surface quality was found for the joint welded by SSFSW with lower heights and flash, allowing to avoid subsequent finishing operations needed for most industrial applications
On the performances and wear of WC-diamond like carbon coated tools in drilling of CFRP/Titanium stacks
No full textThe use of hybrid structures made of CFRP and titanium alloys is growing more and more in the last years in the aerospace industry due to the high strength to weight ratio. Because of their very different characteristics, the mechanical fastening represent the most effective joining technique for these materials. As a consequence, drilling process plays a key role in the assembly. The one shot drilling, i.e. the contemporary drilling of the stack of the two materials, seems to be the best option both in terms of time saving and assembly accuracy. Nevertheless, due to the considerable different machinability of fiber reinforced plastics and metallic materials, the one shot drilling is a critical process both for the holes quality and for the tools wear. This research was carried out to study the effectiveness of new generation tools in the drilling of CFRP/Titanium stacks. The tools are made of sintered grains of tungsten carbide (WC) in a binder of cobalt and coated with Diamond like carbon (DLC), and are characterized by a patented geometry; they mainly differ in parent WC grain size and binder percentage. Both the cutting forces and the wear phenomena were accurately investigated and the results were analyzed as a function of number of holes and their quality. The results show a clear increase of the cutting forces with the number of holes for all the used drilling tools. Moreover, abrasive wear phenomena that affect initially the tools coating layer were observed. © 2016 Author(s)
Imperium, Impero, Imperi: usi politici e significati linguistici nel Settecento e nell'Ottocento italiano
No full textThis article analises the semantic history of the words "Imperium" / "Impero" in Italian language of 18th century
Considerazioni introduttive.
Get PDFIl contributo mette in luce le problematiche connesse alla trasformazione della condizione femminile in Roma antica tra età repubblicana e primo impero, definendo le tematiche su cui porteranno l'attenzione i contributi compresi nel volume
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