Papers by Author: M.A. Sebastián

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Authors: J.M. Sánchez, M.A. Sebastián, E. Rubio, Manuel Sánchez-Carrilero, L. Sevilla, Mariano Marcos Bárcena
Abstract: Light alloys are increasingly applied in different industrial sectors, mainly aerospace. Because of this, it is needed to analyze their behavior in the different processing procedures and, specially, machining. On the other hand, up to a few years, cutting fluids were successfully employed in these processes since their coolant and lubricant properties. Notwithstanding, environmental necessities have promoted researches focused on the development of cleaner processes avoiding cutting fluids, in particular, dry machining. However, this process can change tool geometry and affect to the material giving rise to changes in the design specifications. In this work, geometrical deviations, particularly straightness deviations, in the dry turning of UNS A92024 (Al-Cu) alloy are studied as a function of feed and cutting speed through a parametric model.
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Authors: F.J. Olivares, A.M. Camacho, M.A. Sebastián
Abstract: The scope of this work is to study a forging process at room temperature and at macroscopic level. The mechanism of deformation is influenced by the friction and the reduction ratio, but the influence of the geometry of the billet (aspect ratio) needs also to be taken into account. The objective will be to compare the results obtained during a simulation with the code based on Finite Element Method (DEFORM 2D/3D), with those obtained by analytical methods in order to validate the numerical model. Taking into account that deformation is not uniform and the free surface suffers a phenomenon known as barrel-shaped, that is not covered by analytical methods, the data obtained will compared with those obtained with the FEM code ABAQUS. The aim of this comparison between analytical and numerical methods using two commercial codes instead one, is a proposed way to validate a Finite Element simulation when experimental data are not available or do not exist yet.
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Authors: A.M. Camacho, M.M. Marín, E.M. Rubio, M.A. Sebastián
Abstract: The analysis of LIF operations is often difficult, especially when several strokes are necessary to obtain the final shape of the part. The use of FE models is highly recommended and it is known that implicit FE models give more robust results than explicit FE models; however, with the former methodology there are several problems that must be faced. With the main goal to extend the analysis capability of LIF operations, some explicit FE models are developed in this paper and results are compared to those obtained by implicit methodology. It can be concluded that taking into account these guidelines, the developed models could be further used in the analysis of multi-strokes LIF operations, where more complicated trajectories are going to be used.
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Authors: J.M. Piquero Calleja, E.M. Rubio Alvir, M.A. Sebastián
Abstract: This paper presents SimUned-CN, software to learn the programming for Computer Numerical Control Machine Tools. This software is able to interpret any code of numerical control and simulates both lathes as milling machines. In addition, it has developed a help system for users less experts. Finally, the application takes up a small size, requires few resources and is able to run on most computers.
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Authors: Rosario Domingo, José M. Arenas Reina, Mariano Marcos Bárcena, M.A. Sebastián
Abstract: This paper presents a study of the thrust forces in the aluminium alloy, UNS A97050-T7. The measurement of these forces during the dry drilling in plates is evaluated under cutting different conditions and in through and blind holes. The experiments have been performed in a CNC milling and HSS Co drills have been utilised with unlike diameters (6.3 mm and 4 mm). The thrust forces have been measured by means of a piezoelectric dynamometer. In addition, the results have been compared with theoretical forces, obtained by the Kronenberg equation. The ANOVA study has allowed confirming the similitude between the forces obtained, independently of number of holes drilled, with the exception of through holes of 4 mm, in whose case the Kruskal-Wallis test has corroborated the dissimilitude. Moreover, the comparison with Kronenberg forces is coherent for diameters 6.3 mm, but it is very different for diameter 4 mm. Thus, the results respect to through and blind holes are dependent of diameter of drill, and also the differences found in the theoretical forces. The high variability of the forces for minor drills, in through and blind holes, points to an inadvisable use in this material.
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Authors: B.T. Rieger, M.A. Sebastián
Abstract: Productivity is an important factor in any industrial production. Based on several concepts and philosophies such as Kaizen and others, it is possible to realize an increase of productivity. Since it is of great interest to know and to evaluate the improvement, a suitable method that allows not only analyzing the improvement of cost but also of time is of interest. Based on the value stream map (VSM) and the profile of cost and time (PCT) the author has developed the PECOTA method, a graphical method of analysis. The concept of investment in time and cost by PECOTA allows first-time analysis and evaluation of a change in a manufacturing process in an easy and fast way. The method includes also the possibility to define the limit of lean manufacturing with the current processes.
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Authors: L. Sevilla, B. Peinado, M.A. Sebastián
Abstract: Currently, when the most suitable material manufacturing process is chosen, not only technical or economical aspects have to be considered, otherwise, it has to emphasize its sustainability. In this document, an easy method to compare mass reduction processes and mass conservation processes, with an application to compare drawing process and machining process, is shown. The comparative comparison makes possible to justify that plastic deformation processes usually have more advantages.
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Authors: Alfredo Sanz, E.M. Rubio Alvir, Carmen Martínez Murillo, M.A. Sebastián
Abstract: Present work shows many of Virtual Reality (RV) developments carried out in manufacturing processes field by the collaboration between Aerospace Materials and Production Department at the UPM University and Manufacturing and Construction Engineering at the UNED university. Most of them have been directed towards Numerical Control Machine Tools field and towards equipment that configure automated manufacturing systems like Flexible Manufacturing Systems (FMS).
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Authors: Rosario Domingo, A.M. Camacho, E.M. Rubio Alvir, M.A. Sebastián
Abstract: This paper present a study focused on hot forward extrusion by upper bound method. In particular, hot forward extrusion of plates through square face dies under plane strain conditions. Slater defines the models used for large fractional reduction. Different models have been taken in account; they are dissimilar in relation to the dead metal zone (if covers or not the entire die face, partially or totally). Triangular rigid patterns of velocity discontinuities have been validated by analytical methods and a range of use for the selected configurations has been established. This methodology has been applied to other process with good results. Thus, the mechanical parameters analysed are fractional reduction, dead metal zone, length die and friction. Finally the calculation of the energy has been achieved by upper bound method. The results allow researching an optimisation of use of upper bound method in hot forward extrusion.
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Authors: J.M. Sánchez, M.A. Sebastián, J.M. González, M.S. Carrilero, Mariano Marcos Bárcena
Abstract: Tool adhesion wear can be produced by two different ways. On the one hand, direct adhesion wear is caused by the incorporation of tool particles to the chips. On the other hand, indirect adhesion wear is caused by the incorporation of fragment of the workpiece material to the tool. When these fragments are removed, they can drag out tool particles causing tool wear. Indirect adhesion can be localised in the tool edge, giving rise to Built-Up Edge (BUE), or in the tool rake face, giving rise to Built-Up Layer (BUL). In this work microstructural differences between both effects in different machining processes of Al-Cu alloys have been analysed. From these microstructural differences, a model has been proposed for the mechanism of formation of both effects.
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