1,720,970 research outputs found
REDESIGN OF ENERGY ABSORBING CAR COMPONENT BY CRASH TEST SIMULATION
No full textThis paper deals with the redesign of a car energy absorbing systems (EAS) for low impact forces in an integrated virtual environment
FATTORI DI FORMA DA INTAGLIO LATERALE FORMULE CLASSICHE E VERIFICA FEM
No full textAlcuni degli esiti traibili dalle tante formule, quelle tradizionali, di più comune impiego, nel tempo proposte per la valutazione del fattore di forma relativo a lastre intagliate lateralmente e sotto carico monodirezionale, sono stati posti a confronto con le risultanze individuate tramite ricorso al FEM.Dando fede alla deduzioni attinte mediante il suddetto metodo, gli autori hanno elaborato anche una formula che meglio delle altre prese in esame, ed in campo più esteso delle variabili del problema, approssima le citate deduzioni
Micromechanical study and simulation of the interlaminar failure of a woven composite laminate
No full textThe laminate load bearing capability is often compromised by the interlaminar failure even though the integrity of the individual lamina remains intact. The out-of-plane components of the stress tensor, defined at the interfaces between plies, are typically responsible for the delamination of multi-layered materials. Failure models for delamination usually make use of both shear and normal interlaminar stresses but their reliable calculation by finite element analysis requires cautions and special techniques. This is particularly true for woven composites in which the fabric architecture may generate unexpected local normal stresses and consequently influence the fracture occurrence. In this paper a numerical analysis was performed using layered solid elements to predict the global response of the laminate. Then sub-modeling techniques are used with several solid elements through the layer thickness in order to obtain accurate interlaminar stresses in the critical regions. As case study, the short-beam configuration under three-point bending condition was selected. Experimental tests show a reduction of the maximum interlaminar shear stress at failure as effect of the span-depth ratio increase for a given laminate thickness. That evidence, assuming a homogenized material behavior, is unpredicted because the span-depth ratio increase has no significant influence on the interlaminar stresses. The work aims to clarify this not well explained phenomenon with a micromechanics approach
On the geometric transferability of the delamination shear limit for CFRP laminate in bending
No full textThe laminate load bearing capability is often compromised when delamination occurs even though the
laminae remain intact. The out-of-plane components of the stress tensor, defined at the interfaces
between plies, are typically responsible for the delamination of multi-layered materials. Commonly used
failure criteria for delamination make use of both shear and normal interlaminar stresses. In this work the
out-of-plane stresses inside a woven laminate were numerically evaluated using a micromechanical
model. Under three point bending the existence of local normal interlaminar stress related to the fabric
architecture was demonstrated. The influence of the due to texture normal interlaminar stress on the
fracture occurrence was discussed. The reduction of the apparent interlaminar shear strength as effect
of the span-to-depth ratio increase was successfully reproduced introducing a dependence of the delamination
shear limit from the stress triaxiality gradient
Banco Tensore d'Inerzia
No full textNella presente relazione si descrive il Banco Tensore d'Inerzia realizzato presso il Dipartimento al fine di soddisfare la richiesta, avanzata in particolar modo dalle aziende del settore automotive, di disporre della misura dei parametri d'inerzia di interi veicoli o di suoi componenti.
Dopo aver descritto il principio di funzionamento, si illustreranno le procedure di prova e le tecniche adottate per la calibrazione
Sull'effetto del welding repair sulle proprietà di resistenza a fatica di getti in lega d'alluminio
No full textProgettazione di un prototipo di espansore a motore rotativo
No full textNella presente memoria si riportano i risultati dell’attività di ottimizzazione strutturale dei principali componenti di un espansore per la produzione di scatole metalliche per uso alimentare del tipo open top cans. Le condizioni operative analizzate sono quelle definite dal processo di sagomatura della lamiera di partenza, fino al raggiungimento della forma finale del manufatto, e dal relativo assemblaggio con saldatura. Innanzitutto è stato necessario effettuare la caratterizzazione meccanica del materiale delle lamiere. A valle della progettazione, è stato realizzato un prototipo dell'espansore con il quale sono state prodotte delle scatole per verificarne la qualità, in termini di tolleranza geometrica del prodotto finito e di presenza di eventuali cedimenti locali nella zona termicamente alterata del cordone di saldatura. La fase conclusiva dell'attività ha riguardato prove di compressione assiale sulle stesse scatole, al fine di studiare le condizioni che potrebbero farle collassare per buckling durante il loro impilaggio
About the Impact Behaviour of Railway Fastening Systems
No full textOn the basis of what established by the Product Technical Specifications - Specifiche Tecniche di Prodotto RFI (STP) - regarding the performance requirements that fastening systems between sleepers and rails should meet to be homologated, a test plant was designed and a procedure to determine the capabilities of the above-mentioned systems to lessen the effects of impact loads was defined. Moreover, specific guidelines concerning the ways in which impacts are generated are not supplied by the same STP. Issues arise in designing the test plant due to the need of guarantee a certain adjustment margin on the drop height as well as on the determination of the weight of the drop mass. Before building the plant, to check that it could perform impact tests in compliance with the Norms specifications, a massive numerical simulation campaign have been carried out. Numerical results allowed to solve optimally the design problem of the test apparatus here proposed
Wear Characterization of a Coated Sintered Steel for Moulds
No full textIt refers to the use of a graphical technique in combination with the experimentation standardized by ASTM G99 to identify a parameter that characterizes and quantifies the wear behavior of a steel thermally and/or chemically variously treated, such as those used to build tools for working hard materials or moulds for the powder metallurgy. In particular, the experimental procedure adopted, the data acquisition modes of the tests, the processing mode and interpretation of these latter are described. Finally, the precision with which the wear parameter is evaluated by the graphical technique and the possibility to distinguish - with only one test - the wear behavior of the treated surface layer from that of the base metal are pointed out. The material used for the creation of the various specimens' samples is the sintered Vanadis 4 Extra. Each sample was subjected preliminarily to one or two of the following treatments: quenching, cryogenization, nitrogenization and coating with the PVD coating technique
PROGETTAZIONE, SVILUPPO, E CERTIFICAZIONE DI STRUTTURE IN MATERIALE COMPOSITO DEL VELIVOLO DI AVIAZIONE GENERALE "SKYCAR"
No full textLo scopo del lavoro è quello di descrivere, dalla fase di "concept" fino alla realizzazione finale, l'intero processo di design, sviluppo e testing per strutture primarie in materiale composito con particolare riferimento al bordo d'attacco (leading edge) del velivolo subsonico di aviazione generale "SKYCAR" (classe CS/FAR 23) sviluppato dalla OMA SUD Sky Tecnologies di Capua(CE
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