Gruppo Italiano Frattura (IGF)
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A magnetorheological clutch for efficient automotive auxiliary device actuation
No full textIn this paper the results of a project funded by Regione Toscana aimed at reducing the powerabsorption of auxiliary devices in vehicles are presented. In particular the design, testing and application of amagnetorheological clutch (MR) is proposed, aimed at disengaging the vacuum pump, which draws in air fromthe power-brake booster chamber, in order to reduce the device power absorption.Several clutch preliminary studies done to choose the clutch geometry and the magnetic field supply areillustrated. The final choice consisted in an MR clutch with permanent magnet, which satisfied size, torque andfail-safe specifications. The clutch characteristics, in terms of torque versus slip, were obtained experimentallyfor three different clutch prototypes on an ad-hoc developed test bench.As result of a preliminary simulation, a comparison between the power absorption of a current productionvacuum pump, an innovative vacuum pump and both vacuum pumps coupled with the MR clutch is presented.The New European Driving Cycle is considered for simulating the vacuum pump operation both in urban andhighway driving. Results show that the use of the innovative vacuum pump reduces the device consumption ofabout 35%, whereas the use of MR clutch coupled with the innovative vacuum pump reduces it up to about44% in urban driving and 50% in highway driving
Design and realization of a multisamples rotating high cycle fatigue machine
No full textIn this work the design and the technical characteristic of a Moore rotating bending machine are presented. The machine has been realized at the University of Cassino in order to run tests on multiple specimens at different temperature. The user can choose independently the load and the temperature for each specimen. The machine has been designed to produce in short time a several numbers of data of materials fatigue strength at low costs. The machine is in assembling step at the Laboratory of Industrial Design of the University of Cassino
Current state of existing project risk modeling and analysis methods with focus on fuzzy risk assessment – Literature Review
No full textRisk modeling and analysis is one of the most important stages in project success. There are manyapproaches for risk assessment and an investigation of existing methods helps in developing new models . Thispaper is an extensive literature survey in risk modeling and analysis methods with main focus on fuzzy riskassessment
On the preparation and characterization of thin NiTi shape memory alloy wires for MEMS
No full textShape memory alloy (SMA) wires are employed as actuators in small devices for consumerelectronics, valves and automotive applications. Because of the continued miniaturization of all the industrialproducts, nowadays the tendency is to produce MEMS (micro electromechanical systems). Among the mostpromising functional MEMS materials, the thin SMA wires that are offering a rapid actuating response withhigh power/weigh ratio of the material, are attracting a world wide interest. This paper is aimed at showing theproduction process and the characterizations of thin NiTi shape memory wires. The activity was focused ondrawing procedure and on functional and TEM characterizations of the final products. In particular, it wasevaluated the performance of the SMA wires for actuators in terms of functional fatigue and thermo-mechanicalproperties by means of an experimental apparatus design ad hoc for these specific test
Fractography as a tool to assess the occurrence of fatigue fractures in complex microstructure structural components
No full textFractographic assessment of fatigue fractures may be difficult if they occur in metallic components characterized by low ductility complex microstructures. In these cases reconciliation of known fatigue rupture mechanisms with fractographic appearance of fatigue fractured surfaces is challenging. Special techniques coupled with theory development may be necessary. Pearlitic steels or steels with predominant pearliticmicrostructures are among the ones that are visited and their fatigue fractures interpreted. Analogously, fatigued Al foundry alloys, with hypoeutectic Al-Si compositions, are also illustrated
Fracture toughness of TiAl-Cr-Nb-Mo alloys produced via centrifugal casting
No full textFracture toughness of a TiAl base intermetallic alloy has been investigated at room temperature.The Ti-48Al-2.5Cr-0.5Nb-2Mo (at. %) alloy produced via centrifugal casting exhibits fine nearly lamellar microstructures, consisting mainly of fine lamellar grains, together with a very small quantity of residual ? phases along lamellar colony boundaries. In order to determine the alloy fracture toughness compact tension specimens were tested and the results were compared with those available in literature
A numerical study of squeeze-film damping in MEMS-based structures including rarefaction effects
No full textIn a variety of MEMS applications, the thin film of fluid responsible of squeeze-film dampingresults to be rarefied and, thus, not suitable to be modeled though the classical Navier-Stokes equation. Thesimplest way to consider fluid rarefaction is the introduction of a slight modification into its ordinaryformulation, by substituting the standard fluid viscosity with an effective viscosity term. In the present paper,some squeeze-film damping problems of both parallel and torsion plates at decreasing pressure are studied bynumerical solving a full 3D Navier-Stokes equation, where the effective viscosity is computed according toproper expressions already included in the literature. Furthermore, the same expressions for the effectiveviscosity are implemented within known analytical models, still derived from the Navier-Stokes equation. In allthe considered cases, the numerical results are shown to be very promising, providing comparable or evenbetter agreement with the experimental data than the corresponding analytical results, even at low air pressure.Thus, unlike what is usually agreed in the literature, the effective viscosity approach can be efficiently applied atlow pressure regimes, especially when this is combined with a finite element analysis (FE
Natural minerals mixture for enhancing concrete compressive strength
No full textThe construction material quality is required to be improved in order to enhancing structure stability, optimizing construction cost and quality. The kaolin and bentonite have been mixed in equal quantity and treated by heat for 1 hour under 600 oC, 800 oC and 1000 oC to create new minerals under high temperature condition to introduce an acceptable concrete additive for achieving concrete compressive strength in early age.To study micro properties of additive-cement mixture, X-ray and FESEM experiments have been used. The results indicate that acceptable proportion of unheated kaolin-bentonite is improving the concrete compressive response. But if kaolin-bentonite mixture treated by heat under 800 oC and in quantity of 12 % has been used in concrete mixed design, then the concrete compressive strength of 7 days shows the best result. The result is due to the development of new minerals under high temperature condition in mineral mixture and also kaolin-bentonite additive change cement past crystal and lead to enhancement of nano structural cement bonding
A three-parameter model for fatigue crack growth data analysis
No full textA three-parameters model for the interpolation of fatigue crack propagation data is proposed. It has been validated by a Literature data set obtained by testing 180 M(T) specimens under three different loading levels. In details, it is highlighted that the results of the analysis carried out by means of the proposed model are more smooth and clear than those obtainable using other methods or models. Also, the parameters of the model have been computed and some peculiarities have been picked out
Evaluation of stress intensity factor of multiple inclined cracks under biaxial loading
No full textA finite rectangular plate of unit thickness with two inclined cracks (parallel and non parallel) under biaxial mixed mode condition are modelled using finite element method. The finite element method is used for determination of stress intensity factors by ANYSIS software. Effects of crack inclination angle on stress intensity factors for two parallel and non parallel cracks are investigated. The significant effects of different crack inclination parameters on stress intensity factors are seen for lower and upper crack in two inclined crack.The present method is validated by comparing the results from available experimental data obtained by photo elastic method in same condition