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132 results on '"Ugues, D"'

11. Softening the ultra-stiff: controlled variation of Young's modulus in single crystal diamond

Author

Battiato, A., Lorusso, M., Bernardi, E., Picollo, F., Bosia, F., Ugues, D., Zelferino, A., Damin, A., Baima, J., Pugno, N. M., Ambrosio, E. P., and Olivero, P.

Subjects
Condensed Matter - Materials Science
Abstract

A combined experimental and numerical study on the variation of the elastic properties of defective single-crystal diamond is presented for the first time, by comparing nano-indentation measurements on MeV-ion-implanted samples with multi-scale modeling consisting of both ab initio atomistic calculations and meso-scale Finite Element Method (FEM) simulations. It is found that by locally introducing defects in the 2x10^18 - 5x10^21 cm-3 density range, a significant reduction of, as well as of density, can be induced in the diamond crystal structure without incurring in the graphitization of the material. Ab initio atomistic simulations confirm the experimental findings with a good degree of confidence. FEM simulations are further employed to verify the consistency of measured deformations with a stiffness reduction, and to derive strain and stress levels in the implanted region. Combining these experimental and numerical results, we also provide insight into the mechanism responsible for the depth dependence of the graphitization threshold in diamond. This work prospects the possibility of achieving accurate tunability of the mechanical properties of single-crystal diamond through defect engineering, with significant technological applications, i.e. the fabrication and control of the resonant frequency of diamond-based micromechanical resonators., Comment: 32 pages, 7 figures

Published
2016
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32. Anisotropic mechanical and fatigue behaviour of Inconel718 produced by SLM in LCF and high‐temperature conditions.

Author

Sausto, F., Marchese, G., Bassini, E., Calandri, M., Biamino, S., Ugues, D., Foletti, S., and Beretta, S.

Subjects
HIGH temperatures, INTERNAL combustion engines, FATIGUE life, FRACTURE mechanics, FRACTURE strength, EXTREME value theory
Abstract

Additive manufacturing (AM) is one of the processes with the most potential for producing components used in internal combustion engines and features high efficiency due to the possibility of building very complex shapes. Several drawbacks of parts produced using AM are still unresolved, like poor surface quality, the presence of internal defects and anisotropic mechanical behaviour, which all contribute to decreasing the fatigue strength compared with the material produced using conventional processes. The effect of building direction on both the macroscopic mechanical behaviour and the crack propagation mechanism of Ni‐base superalloy Inconel718 produced using AM was investigated under the combined effect of low cycle fatigue (LCF) and high temperature. The different crack growth mechanisms investigated using compact tension (CT) specimens, tested at high temperature, showed a significant difference between the two building directions. The LCF fatigue experiments also showed a significant difference in the ε‐N curves from the two directions together with a high level of scatter due to the dispersion of the defect size at the fracture origin. The dimensions of the defects (as measured using the area parameter) were analysed by means of extreme value statistics and showed a significant difference between the two orientations investigated. The aim of this work is to propose a simplified approach (based on ΔJeff concepts) to estimate the fatigue life of a component produced using AM that takes into account the material variability due to the combined effect of mechanical anisotropic behaviour and the presence of defects at high‐temperature conditions. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Toughness and microstructure stability in hot-working tool steels subjected to washout in molten aluminium

Author

Perrone, R., Ugues, D., Torres, E., Regina, U., and Rosso, M.

Subjects
Microstructure -- Analysis, Microscope and microscopy -- Analysis, High technology industry
Abstract

Byline: R. Perrone, D. Ugues, E. Torres, U. Regina, M. Rosso A basic and a modified AISI H11 steels were selected for the research. Impact toughness and microstructure in the quenched and tempered state were analysed. Cyclic immersions in molten aluminium with the aim of simulating the washout, typical of aluminium die casting tools, were applied. Optical and electronic microscopy analysis were used to evaluate damages provided by washout on the specimen surface. XRD measurements were applied to identify the corrosion and soldering products deposited on the steel surface. Microhardness profiles were recorded before and after the test to assess any softening effect. Impact tests were performed on specimens subjected to increasing immersion cycles. A detailed study of the evolution of damages provided by cyclic contact with molten aluminium is presented for two hot working tool steels. An analysis of the modulation of the impact toughness as a function of the number of immersions in molten aluminium is reported.

Published
2008

34. Austempering effect on structure properties and performances of hot-work tool steel

Author

Mattavelli, D., Cislaghi, L., Rosso, M., and Ugues, D.

Subjects
Microstructure -- Analysis, High technology industry
Abstract

Byline: D. Mattavelli, L. Cislaghi, M. Rosso, D. Ugues In this article an investigation has been carried out on different austempering cycles conducted on samples of the most diffused hot-work tool steel: AISI H 11. The laboratory tests have been addressed to the examination of the structure and to the evaluation of its mechanical properties: the hardness, the impact strength and the thermal fatigue. The aim of the analysis is to verify what are the effects of structure transformation, of different austempering temperature and of the microstructure morphology on the mechanical properties in terms of impact-absorbed energy and thermal fatigue resistance. The ultimate application aimed at for such heat treatment study is the high-pressure die casting and the enhancement of the performance of the relative tools.

Published
2008

35. Study of the resistance to washout of PVD coated hot working tool steels

Author

Ugues, D., Miranda, E. Torres, Perucca, M., Albertinazzi, M., and Rosso, M.

Subjects
Cadmium coatings -- Research, Tool-steel -- Mechanical properties, Dies (Metalworking) -- Mechanical properties, High technology industry
Abstract

Byline: D. Ugues, E. Torres Miranda, M. Perucca, M. Albertinazzi, M. Rosso Wear and failure of die casting dies involve a complex interaction between various mechanisms. A CrAlSiN coating system was deposited on the base material, modulating the chemical composition of the chromium or the aluminium-silicon content. A set of the coated specimens was directly analysed through optical and electronic microscopy, so as to assess the overall quality. Other was subjected to a cyclic immersion program in molten aluminium bath. Coating efficiency was determined through electron microscopy analysis. Thermal fatigue was investigated, quantified. The transverse section of the specimens was polished to evaluate the microhardness changes occurred due to the thermal cycling.

Published
2007

39. Experimental determination of Young's modulus reduction in ion implanted diamond

Author

Bernardi, Ettore, Ambrosio, E. P., Battiato, Alfio, Bosia, Federico, La Torre, L., Lorusso, M., Olivero, Paolo, Rigato, V., Ugues, D., Vittone, Ettore, and Picollo, Federico

Subjects
Ion implantation, Mechanical properties, Single-crystal diamond, Ion implantation, Mechanical properties, Single-crystal diamond
Published
2014

40. The influence of plasma nitriding and post oxidising treatment on the resistance ofaisi h11 to cycling immersion in molten aluminium alloy

Author

Ugues, D., Rosso, M., Albertinazzi, M., Raimondi, F., and Silipigni, A.

Abstract

This paper is based on an experimental tests plan, which aims at strengthening the knowledge on the influence on die life of plasma nitriding and post oxidising surface modification treatment.An AISI H11 steel obtained through modern vacuum melting and remelting processes was used as base material.Un-notched impact test specimens were fabricated from a core vacuum heat treated block.Some specimens were plasma nitrided and oxidised. Impact toughness was evaluated both on some of the heat treated and surface modified specimens.The other specimens were subjected to a program of cyclic immersion in molten aluminium alloy and cooling in water.The heat checking and soldering phenomena were analysed through periodic inspections and, after the test through, the evaluation of cracks and cavities length and density.At the end of thermal fatigue test the impact test was also performed to assess the toughness modification in comparison with the initial condition.Finally, a metallographic investigation was performed through optical and electron microscopy on all the specimens considered.Both soldering and heat checking were found to be active damaging mechanisms on both simply heat treated and nitrided and oxidised specimens.However, all the revealed damages resulted to be limited to the surface and sub-surface layers.The clearer effect which was detected was the softening, clearly visible through impact toughness increases and microhardness decreases along with the number of immersion cycles.The amount of softening was found to be limited by the surface modification treatment.The plasma nitriding and post oxidising treatment had also prevented the metallic surface from corrosion attack (acting as a barrier to the aluminium aggression) at least for the first 8,500 immersion cycles.The developed test rig for cyclic immersion in molten aluminium alloy provided results similar to other experiences currently present in the open literature.

Published
2013

41. Caratterizzazione ad usura di rivestimenti PVD con e senza laser texturing

Author

Lecis, NORA FRANCESCA MARIA, Ugues, D., Previtali, Barbara, and Demir, ALI GOKHAN

Abstract

Il processo di laser texturing (LST) è una delle tecniche più promettenti nel campo delle microlavorazioni superficialiin quanto consente di ottenere un eccellente controllo della forma e delle dimensioni delle microcavitàprodotte ed è estremamente veloce e senza ricadute dannose per l’ambiente. Recentemente si è assistito allosviluppo di diversi lavori nei quali il laser è stato impiegato per migliorare il comportamento tribologico di componentimeccanici in materiale metallico. Le microcavità, realizzate per ablazione dal fascio laser sulla superficiedi interesse, infatti hanno diversi aspetti positivi da questo punto di vista perché generano un sistema diffusodi microspinte idrodinamiche sulla superficie e agiscono come riserve di lubrificante da una parte e come trappoleper i detriti di usura dall’altra, ritardando così, l’innesco di meccanismi di usura da terzo corpo. Nel presentelavoro si presentano i risultati di una sperimentazione volta a valutare l’effetto dell’introduzione di unalavorazione superficiale di texturing laser sulla superficie di riporti PVD in TiN. Per il texturing è stata utilizzatauna sorgente laser in fibra innovativa ad alta efficienza che ha consentito, una volta ottimizzati i parametridi processo, di ottenere dimensioni controllate delle microcavità, una buona geometria delle stesse e di evitarela presenza di residui di lavorazione anche sui coating ceramici oggetto dello studio. I test di usura in condizionidi strisciamento lubrificato con alto carico applicato e bassa velocità relativa , sono stati condotti sul rivestimentoTiN microlavorato e per confronto sul tal quale e su un rivestimento autolubrificante commerciale,il WC/C. I risultati ottenuti mostrano un marcato incremento delle prestazioni a usura per il rivestimento lasercon texturing (fino al 50% di riduzione del volume di usura) e l’assenza di significativi danneggiamenti del rivestimentoin presenza delle microcavità e delle sollecitazioni di usura applicate. Nel breve futuro si eseguiràpertanto un approfondimento ulteriore per valutare anche l’economia di scala del ciclo di lavorazione.

Published
2013

47. Prediction of the critical load of a metal-rolling system by considering the damage of the coated surface

Author

Feng, J, Qin, Y, Lorusso, M, Ugues, D, Feng, J, Qin, Y, Lorusso, M, and Ugues, D

Abstract

Under various working conditions, rolling elements may suffer from different types of damage behaviour, including fractures in the coatings and bonding interfaces, and plastic deformation in the substrate materials. The present paper reports research into the prediction of the critical load of a metal-rolling system (metal-rolling system) by considering the damage of the coated surface based on a novel FE simulation-procedure developed by the present authors. The modelling procedure features several modelling approaches including: parameterised FE modelling, Cohesive-Zone modelling and a sub-modelling technique. The typical case examined in this study is linecontact between two cylindrical bodies. The studied surface-modified systems are CrN, TiN and TiN/CrN multilayer PVD coatings applied on 42CrMo4 steel in both the nitrided and quenched-and-tempered states. It was observed through the numerical simulation that for almost all of the configurations, cracking occurs at the edge of the contact when one cylinder is pressing against the other cylinder, due to a bending effect. The critical load of the system was determined by referring to the initiation of the first crack of the coated surface of the ring. Comparison between the numerical-simulation results and the experimental results showed excellent agreement.

Published
2012

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