Browsing by Author "Peñalba, F."
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Item Austenitic grain size evolution and continuous cooling transformation diagrams in vanadium and titanium microalloyed steels(1996) Peñalba, F.; Garcia De Andres, C.; Carsi, M.; Zapirain, F.; Centros PRE-FUSION TECNALIA - (FORMER)The evolution of the austenitic grain size in medium carbon steels microalloyed with vanadium and titanium was studied as a function of reheating temperature, heating rate, and titanium content. High resolution dilatometric techniques were used to determine the continuous cooling transformation (CCT) diagrams for two different austenitization temperatures. The microstructure and hardness were determined for different cooling rates. The results revealed a significant effect of titanium concentration on the austenitic grain growth control. The smallest grain size was found in the steel with a Ti concentration = 0.019 wt %. Low heating rates produced smaller grain sizes than high heating rates although an abnormal grain growth took place. In these steels, at temperatures above 1050°C the influence of the reheating temperature on their hardness for cooling rates around 2°C·s-1 was negligible. The higher reheating temperatures caused a slight increase in their hardenability. Finally, it was found that the greater the titanium content, the greater the hardness of these steels, but only when the titanium percentages were higher than 0.020 wt %.Item Estudio de la intercara de una preforma híbrida infiltrada sin presión(2010) Merchán, M.; García De Cortázar, M.; Egizabal, P.; Peñalba, F.; López, A. J.; Torres, B.; Rodrigo, P.; Rams, J.; CIRMETAL; Tecnalia Research & InnovationThis work presents an interfacial characterization of the matrix/reinforcement interface of an aluminium matrix composite reinforced with Saffil fibres and alumina particles was manufactured using the Primex ™ pressureless infiltration process. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to carry out the microstructural and chemical characterization of the composite material. In addition, a mechanical characterization was conducted by the nanoindentation technique. This research concludes that the composite presents a good bonding between the matrix and the reinforcements.Item A hybrid approach to the development of a multilayer neural network for wear and fatigue prediction in metal forming(2007-10) Belfiore, N. P.; Ianniello, F.; Stocchi, D.; Casadei, F.; Bazzoni, D.; Finzi, A.; Carrara, S.; González, J. R.; Llanos, J. M.; Heikkila, I.; Peñalba, F.; Gómez, X.; EXTREMATIn this paper an approach to surface damage prediction is proposed for the case of metal forming. The method is mainly based on three fundamental stages: (a) the detection of a feasible physical model which is able to give some important understanding of the phenomenon, although with limited generality; (b) the extensive development of an organized experimental campaign, which is necessary to tune up the developed model; and (c) the organization of an efficient and intelligent way of data collecting. The three aspects of the research work have been integrated by means of a neural network which is trained by using data coming from the real plant, from the standard tribometers, and from the reference numerical model. In this sense, the neural network is indented as hybridized. Predictions are shown to be very close to the experimental data obtained in the production plant. The method is useful for minimizing the number of experiments in the process of materials and treatment selection, and in maintenance.Item Influence of thermomechanical processing on superplastic forming of Mg-Al alloys(2007-04) Pérez-Prado, M. T.; Del Valle, J. A.; Salort, F.; Peñalba, F.; Gómez, X.; Ruano, O. A.; EXTREMATThe aim of this paper is to study the influence of the initial microstructure of several Mg-Al alloys on their superplastic formability and on their post-forming microstructure and mechanical properties. Various thermomechanical processing routes, such as annealing, conventional rolling, severe rolling and cross rolling, were used in order to fabricate AZ31 and AZ61 alloys with different grain sizes. These materials were then blow formed into a hat shaped die. It was found that the processing route has only a small effect in the formability of Mg-Al alloys or on the postforming microstructures and properties due to rapid dynamic grain growth taking place at the forming temperatures. Nevertheless, good formability is achieved as a result of the simultaneous operation of grain boundary sliding and crystallography slip during forming.Item Mechanical properties and forming behavior of a type 9%Cr steel containing 2%W(Trans Tech Publications Ltd, 2010) Peñalba, F.; Gómez, X.; Allende, R.; Carsí, M.; Ruano, O. A.; Chandra, Tara; Chandra, Tara; Chandra, Tara; Wanderka, N.; Wanderka, N.; Wanderka, N.; Reimers, Walter; Reimers, Walter; Reimers, Walter; Ionescu, M.; Ionescu, M.; Ionescu, M.; EXTREMATThe possibilities to improve the properties of steels for tubes exposed at high temperatures are explored. The mechanical properties and forming behavior of an experimental casting of type 9Cr-ferritic steels, P92, containing 2%W, are studied. The hardenability was determined by means of continuous cooling diagrams associated with hardness measurements and microstructure observations. Tensile tests from room temperature to 650°C were carried out to determine the variation of the strength and ductility in this temperature range. In addition, Charpy impact tests were conducted to characterize the toughness of the steel and the ductile-brittle transition temperature. Finally, hot torsion tests at various temperatures and strain rates were carried out and the generalized stresses and strains to rupture for each test are determined. With these data forming stability maps were generated to characterize the best forming conditions.Item Stress corrosion cracking in tinplate destined for legume and pet food packaging(2006-12) Gelati, S.; Peñalba, F.; Gomez, X.; Ferretti, C.; Montanari, A.; EXTREMATProblems associated with stress corrosion of tinplate cans for foodstuffs are occurring at an increasing rate. The appearance of stress corrosion usually entails heavy financial penalties and high risk to the food. Unfortunately, at present, no practical measures exist to counteract this phenomenon. Stress corrosion is a type of localised corrosion which develops by way of the simultaneous action of particular media, which, in the absence of stress, may be only mildly aggressive or even non-aggressive, and a stress which is lower than that required for purely mechanical cracking. The aim of the present work was to study the susceptibility of tinplate to stress corrosion in different test media simulating foodstuffs. To this end, two approaches were used: an electrochemical technique, fast and slow polarisation, and a dynamic-mechanical technique, the slow strain rate test. The results of both tests enabled identification of the environment-material combination most susceptible to this type of corrosion. In particular, it emerged that the most critical environment for the development of stress corrosion is a solution simulating meat products at pH 6, whereas the most sensitive material was found to be tinplate produced from single reduction continuous annealing steel.