1,721,016 research outputs found
Deep cryogenic treatment of AISI 302 stainless steel: Part I - Hardness and tensile properties
No full textcryogenic treatment, stainless steel, tensile strength, hardnes
Fatigue scatter reduction through deep cryogenic treatment on the 18NiCrMo5 carburized steel
No full textProposal of a coast-down model including speed dependent coefficients for the retarding forces
Full text linkCoast-down techniques are widely used on bicycles and motorized vehicles in order to estimate retarding forces and respective coefficients. The mathematical model behind coast-down data analysis is usually based on the assumption that both drag and rolling resistance coefficients do not depend on the vehicle speed. This assumption restricts the model validity to the specifically tested range of speeds and provide averaged values for the force coefficients. In the attempt to overcome this limit, the proposal of a complete polynomial equation of motion is developed, evaluated and discussed on a human powered vehicle case study. The analysis points out that the extended model is adequate for experimental data fitting and could potentially provide a more reliable power-speed prediction outside the testing range. However, the expressions included in the model in order to account for speed dependent coefficients is a first approximation with limited capability to represent these complex phenomena. As a consequence, further experimental testing is needed in order to achieve a validation. Advantages and side effects of both the classical and the complete polynomial models are discussed, concluding that the two approaches could be complementary and could answer different needs that specifically depend on the purpose of the coast-down analysis
Andrea Baldissera; Paolo Pintacuda; Paolo Tanganelli (a cura di), “Con llama que consume y no da pena”, El hispanismo integral de Giuseppe Mazzocchi
No full textAndrea Baldissera; Paolo Pintacuda; Paolo Tanganelli (a cura di), “Con llama queconsume y no da pena”. El hispanismo integral deGiuseppe Mazzocchi, Como-Pavia, Ibis, 2022, 1037 pp. ISBN 978887164656
Effects of deep cryogenic treatment on static mechanical properties of 18NiCrMo5 carburized steel
No full textIn consideration of the raising interest about the application of the deep cryogenic treatment (DCT) on materials, its effects on the static mechanical properties of a commercial gear carburized steel (18NiCrMo5) are investigated through hardness and tensile tests followed by optical fractographic observations. The present study focuses on the comparison between the results given by different sequences of DCT and tempering performed after the conventional case hardening. In addition, the soaking time parameter influence is analyzed for the case of the pre-tempering DCT. A special attention is paid to the statistical analysis of the experimental data in order to avoid misinterpretations. The results point out substantial hardness increases (from +0.6 HRC to +2.4 HRC) for all the cryotreated groups and a remarkable enhancement of the tensile strength (+11%) in one case, indicating that different sequences and DCT parameters must be considered depending on the application requirements. The experimental results are then discussed in consideration of the literature about the DCT on similar steels with the aim of correlating the obtained improvements to the microstructural mechanisms that are commonly ascribed to this treatmen
Pedalando verso i 145 km/h
No full textIN UNA SFIDA AL LIMITE TRA SPORT E TECNOLOGIA, DOVE SI RAGGIUNGONO VELOCITÀ AUTOSTRADALI CON L A SOL A FORZA MUSCOL ARE, IL POLITECNICO DI TORINO RAPPRESENTA L’ITALIA TRA I TOP COMPETITOR MONDIALI GRAZIE AGLI STUDENTI DEL TEAM POLICUMBENT
Finite Element Thermo-Structural Methodology for Investigating Diesel Engine Pistons with Thermal Barrier Coating
Full text linkTraditionally, in combustion engine applications, metallic materials have been widely employed due to their properties: castability and machinability with accurate dimensional tolerances, good mechanical strength even at high temperatures, wear resistance, and affordable price. However, the high thermal conductivity of metallic materials is responsible for consistent losses of thermal energy and has a strong influence on pollutant emission.
A possible approach for reducing the thermal exchange requires the use of thermal barrier coating (TBC) made by materials with low thermal conductivity and good thermo-mechanical strength.
In this work, the effects of a ceramic coating for thermal insulation of the piston crown of a car diesel engine are investigated through a numerical methodology based on finite element analysis. The study is developed by considering firstly a thermal analysis and then a thermo-structural analysis of the component. The loads acting on the piston are considered both separately and combined to achieve a better understanding of their mutual interaction and of the coating effect on the stress state.
The thermal analysis pointed out a decrease of temperature up to 40°C in the upper part of the piston for the coated model. Despite the lower deformations induced by the reduced thermal load, the stiffening effect provided by the TBC results in higher peak stress. However, the lower temperature field inside the piston compensates by allowing higher yielding stresses for the component and reducing the impact on the safety factor.
The methodology is validated by comparison of the model results with numerical data available from the literature; limitations and potential future improvements are also discussed
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