Time filter

Source Type

Grande E.,University Guglielmo Marconi | Milani G.,Polytechnic of Milan
Composite Structures | Year: 2016

The present paper aims at developing a simple but effective numerical model for the study of the bond behavior of Fiber Reinforced Strengthening systems (FRP) externally applied on curved masonry substrates. The main peculiarities of the proposed model are its simplicity and the possibility to straightforwardly introduce at the interface level coupled cohesive laws for accounting a mixed mode debonding mechanism. Indeed, the model relies on a discretization based on in-series and in-parallel springs for modeling the substrate, the reinforcement and the reinforcement/substrate interface layer. In particular, while both the substrate and the reinforcement springs are assumed linear-elastic, nonlinear constitutive laws are accounted for the interface springs where, in addition, a coupled behavior between normal and shear springs is assumed considering the Mohr-Coulomb failure domain. The proposed numerical model is used in the paper as a tool for the assessment of formulas specifically devoted to the evaluation of the bond resistance of curved masonry samples strengthened with FRPs. In particular, both formulas derived from the closed form solution of equilibrium equations and a formula derived by approximating the closed form solution through an exponential law are here presented. With the main purpose to validate the proposed model, numerical analyses are preliminary presented in the paper with reference to experimental bond tests on masonry samples with concave and convex substrate configurations strengthened by glass FRP strips. Then, further numerical analyses developed by considering different values of the geometry curvature and mechanical properties of the interface, are subsequently developed with the main goal to check the reliability of the proposed formulas. © 2016 Elsevier Ltd

Cavallini C.,University Guglielmo Marconi | Giorgetti A.,University Guglielmo Marconi | Citti P.,University Guglielmo Marconi | Nicolaie F.,Ferrari
Materials and Design | Year: 2013

In engineering design, the selection of material alternatives usually depends of different criteria based on the specific problem. Due to the different units of this criteria, a normalization process is needed in the selection model. A lot of normalization approach can be found in literature and at the same time many algorithms have been developed to ensure the optimal material selection for a certain industrial application. Two elements of reflection can be drawn from the analysis of these. The first is the absence of an aided support to the selection of the correct engineering criteria by whom operate the selection process. The second is the need to define a weighting method that at the same time can be user-friendly to use and representative of the project's needs. A new selection model based on the integration between House of Quality and the Comprehensive Vikor Algorithm is presented in this paper. This approach, called Integral Aided Material Selection (IAMS), can overcome the main lack of traditional material selection model and provide a real support tool to the project team. That way the project team can optimally choose the selection criteria and assign to these the correct priority coherently with the project needs. A case study is presented to illustrate and justify the proposed method. The topic of the case study concerns the identification of the best coating for the protection of an aluminum alloy substrate (Al-7075) from the effects of abrasive wear against an alternating counterpart made by a high-strength cast iron. © 2012 Elsevier Ltd.

Castellani F.,University of Perugia | Garinei A.,University Guglielmo Marconi
Applied Energy | Year: 2013

The utilization of high-altitude wind energy potential is a very attractive challenge. This is mainly due to the perspective of producing a large amount of electricity from a renewable source without using land, and having a very low visibility impact. The wind flow on the upper levels of the surface boundary layer is characterized by good power with low variability of wind conditions.Many innovative wind energy conversion flying devices are currently under development for this purpose. The technological solutions can be grouped in:. •land installed generators (such as kite systems);•airship flying generators that can produce electricity far from the ground and are tethered by control wires, also used for the power transmission.Flying generators could prove more problematic in maintaining flying conditions due to their heavier weight, but they have the advantage that they can be moved to different locations with less intervention on the ground.Another important characteristic that the airship wind generator has, is the possibility of changing its height of operation very quickly and simply by using control cables.In this study, the operational scenario of the possible application of an innovative airship wind generator is studied and discussed. The possibility of adjusting the height of operation was analysed, and a methodology for choosing the optimal operating level was developed and applied to real test cases. Numerical and experimental techniques used to assess the characteristics of high-altitude winds, were also considered.Remotely sensed wind data obtained from a monostatic phased-array Doppler Sonic Detection and Ranging (SODAR) system were used to validate and tune the CFD model in one of the real-test cases investigated. © 2013 Elsevier Ltd.

Garinei A.,University Guglielmo Marconi | Marsili R.,University of Perugia
Measurement: Journal of the International Measurement Confederation | Year: 2012

Ball screw actuators are electro-mechanical actuators that translate rotational motion to linear motion with little friction; they are used in precise engineering and particularly in aerospace applications where they replace hydraulic linear actuators. Until now, few diagnostic approaches have been developed with regard to fault detection and characterization of ball screw actuators. Here, a new diagnostic non-contact measurement technique is proposed to detect faults on ball screw actuators. A Hall effect sensor is applied to the ball return channel and the output signal is analyzed in-depth and validated through video monitoring and then post-processed with a new approach based on time domain analysis; maxima and minima distributions are used to distinguish between damaged and undamaged ball screw actuators. A considerable series of tests was performed in many configurations to define an optimal setup, and high repeatability was obtained. The proposed method can be easily applied to ball screw actuators because of the reduced dimensions of the components and thus, can be used to support the development of optimized repair and preventive maintenance policies that play a major role in the case of aerospace applications. © 2012 Elsevier Ltd. All rights reserved.

Garinei A.,University Guglielmo Marconi | Marsili R.,University of Perugia
Measurement: Journal of the International Measurement Confederation | Year: 2014

In the frame of intercomparison testing among different optical full-field measurement techniques, the crucial aspect concerning contact problems between bodies has been extensively analyzed through thermoelasticity. This technique has allowed us to obtain stress patterns in terms of the first stress invariant by measuring temperature fluctuation on the surface of a cyclically loaded mechanical component. For the present study, a special-purpose test bench was assembled to be used within a round robin test, so as to properly load the sample. The test case taken into account is the very well-known contact problem between a cylinder and a flat plate. The results obtained from thermoelasticity through the use of a zoom lens, were compared to classical Hertz theory prediction and FEA models. © 2014 Elsevier Ltd. All rights reserved.

Garinei A.,University Guglielmo Marconi | Marsili R.,University of Perugia
International Journal of Industrial Ergonomics | Year: 2014

Pressure distribution measurements are becoming increasingly important in the automotive field for ergonomic optimization of components like seats or steering wheel. Nowadays, traditional sensors shows several drawbacks such as response variation in time, low sensitivity and high level of intrusiveness. Moreover the great difficulty of carrying out dynamical analysis in the area of interest highly limits their use. A new type of matrix, now available, promises to overcome such problems, and it has been widely tested in the automotive field. The matrix is based on a series of condensers which vary the capacity depending on the pressure applied on their surface. The high sensitivity and the chance of monitoring pressure distribution with frequency contents up to 200Hz make this tool particularly suitable for evaluating steering wheel's goodness effectiveness in an on-road test. Relevance to industry: The knowledge of the behavior of capacitive sensor matrix for pressure distribution at the operator's hand-car steering wheel interface may benefit automobile designers and manufacturers to evaluate steering wheel goodness and seat effectiveness perform through on-road tests and to evaluate the efficiency of the power steering mechanism. © 2013 .

Risitano A.,University of Catania | Risitano G.,University Guglielmo Marconi
International Journal of Fatigue | Year: 2013

This work reports fatigue stress test results for AISI 304 steel (R = -1) that has been subjected to a high cycle number. It shows that the energetic effect (employing different temperature increments for equal loading of uniaxial stress) can be used to evaluate the cumulative damage caused by any prior loading. Various load histories were applied to AISI 304 specimens, and the resulting damage was evaluated in reference to the energy factor, Φ, which is dependent on the maximum temperature at the sample surface when irreversible plastic deformation begins. The time curves (Wöhler curves) and the damage ratio based on the consumed energy were compared to those obtained according to Palmgren-Miner rules; this comparison served to show how under-evaluations can occur with high damage ratios. © 2012 Elsevier Ltd. All rights reserved.

Di Carlo A.,University of Rome La Sapienza | Borello D.,University of Rome La Sapienza | Bocci E.,University Guglielmo Marconi
International Journal of Hydrogen Energy | Year: 2013

The aim of this work is to experimentally and numerically analyze the performance of a integrated power plant composed by a steam oxygen fluidized bed biomass gasifier fed by woods, a Solid Oxide Fuel Cell (SOFC) and a micro Gas Turbine (mGT). The numerical analysis is carried out by using ChemCAD software. In particular, SOFC and gasifier were modeled using proper developed Fortran subroutines interfaced to the basic software. The adopted SOFC model was already validated by the authors in previous works, while the gasifier model was here developed and validated by means of experimental activities carried out by using a bench scale gasifier. Different compounds (Benzene, Toluene, Naphthalene, Phenols) were chosen to analyze the tar evolution in the gaseous stream during the gasification process. Hot gas cleaning (based on catalytic ceramic filter candles inserted in the freeboard of the gasifier-UNIQUE concept) was adopted to remove tar and particulates from the fuel hot gas stream. Different moisture contents in the range between 10 and 30% (i.e. in a deviation of 10% around the usual wood moisture content of 20%) were numerically simulated as well as the degree of purity of the oxygen utilized in the power plant (between 25% and 95%, the rest being N2). The power requirement for pure oxygen production leads to a reduction of the electrical efficiency of the whole power plant. For this reason, a sensitivity analysis was conducted to find the optimal operation conditions in order to maximise the syngas (H2, CO) content in the produced gas, while maintaining a high overall electrical efficiency. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Di Carlo A.,University of L'Aquila | Dell'Era A.,University Guglielmo Marconi | Del Prete Z.,University of Rome La Sapienza
International Journal of Hydrogen Energy | Year: 2011

Ammonia decomposition in an integrated Catalytic Membrane Reactor for hydrogen production was studied by numerical simulation. The process is based on anhydrous NH3 thermal dissociation inside a small size reactor (30 cm3), filled by a Ni/Al2O3 catalyst. The reaction is promoted by the presence of seven Pd coated tubular membranes about 203 mm long, with an outer diameter of 1.98 mm, which shift the NH3 decomposition towards the products by removing hydrogen from the reaction area. The system fluid-dynamics was implemented into a 2D and 3D geometrical model. Ammonia cracking reaction over the Ni/Al2O3 catalyst was simulated using the Temkin-Pyzhev equation. Introductory 2D simulations were first carried out for a hypothetic system without membranes. Because of reactor axial symmetry, different operative pressures, temperatures and input flows were evaluated. These introductory results showed an excellent ammonia conversion at 550 °C and 0.2 MPa for an input flow of 1.1 mg/s, with a residual NH 3 of only a few ppm. 3D simulations were then carried out for the system with membranes. Hydrogen adsorption throughout the membranes has been modeled using the Sievert's law for the dissociative hydrogen flux. Several runs have been carried out at 1 MPa changing the temperature between 500 °C and 600 °C to point out the conditions for which the permeated hydrogen flux is the highest. With temperatures higher than 550 °C we obtained an almost complete ammonia conversion already before the membrane area. The working temperature of 550 °C resulted to be the most suitable for the reactor geometry. A good matching between membrane permeation and ammonia decomposition was obtained for an NH3 input flow rate of 2.8 mg/s. Ammonia reaction shift due to the presence of H2 permeable membranes in the reactor significantly fostered the dissociation: for the 550 °C case we obtained a conversion rate improvement of almost 18%. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Garinei A.,University Guglielmo Marconi | Risitano G.,Messina University | Scappaticci L.,University Guglielmo Marconi
Transportation Research Part D: Transport and Environment | Year: 2014

In this work, the efficiency of absorbing barriers for the mitigation of ground vibrations induced by railway traffic has been evaluated by means of two different experimental campaigns conducted in situ, along the newly-built, high-speed railway line that connects the Italian cities of Milan and Bologna. In the first stage of testing, a series of ideal barriers created from unsupported empty trenches were tested to assess the effects of barrier depth on their efficiency in reducing vertical ground accelerations. The second stage of testing was performed to investigate the efficiency of a full-scale prototype barrier, made of a 2-meter-deep trench supported by two precast reinforced concrete plates connected by steel bars, during transit of an ETR 500 train at a speed of 120. km/h. © 2014 Elsevier Ltd.

Loading University Guglielmo Marconi collaborators
Loading University Guglielmo Marconi collaborators