Persona: Agustina Tejerizo, Beatriz De
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Agustina Tejerizo
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Beatriz De
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Publicación Study of Drilling Process by Cooling Compressed Air in Reinforced Polyether-Ether-Ketone(MDPI, 2020-04-22) Domingo Navas, María Rosario; Agustina Tejerizo, Beatriz De; Marín Martín, Marta MaríaThis study is focused on the application of a cooling compressed air system in drilling processes; this environmentally friendly technique allows removing material at very low temperatures, approximately up to −22 °C in the cutting area. The main goals are to find the most improve cutting conditions with less energy consumption, for the drilling of reinforced polyether-ether-ketone with glass fiber at 30% (PEEK-GF30) with cooling compressed air by a Ranque-Hilsch vortex tube, and to find a balance between environmental conditions and adequate process performance. Drilling tests were carried out on plates of PEEK-GF30 to analyze the influence of cutting parameters and environmental temperature (–22, 0 and 22 °C) on variables such as thrust forces, energy and material removed rate by the use of statistical methods; analysis of variance, analysis of means, response surface, and desirability function were employed to identify the optimum region that provides the most improved values of the aforementioned variables. Drill bit diameter was also analyzed to determine the quality of drilled holes. During the drilling processes, force signals were detected by a piezoelectric dynamometer connected to multichannel amplifier and a pyrometer was used to control the temperature. The diameters of the drilled holes were measured by a coordinate measuring machine. Cooling compressed air can be considered an adequate technique to improve the results from an environmental and efficient perspective; in particular, the maximum desirability function was found at a spindle speed of 7000 rpm, a feedrate of 1 mm/rev and a temperature close to −22 °C.Publicación Geometric Optimization of Drills Used to Repair Holes in Magnesium Aeronautical Components(MPDI, 2020-11-18) Berzosa Lara, Fernando; Davim, J. Paulo; Rubio Alvir, Eva María; Agustina Tejerizo, Beatriz DeMagnesium alloys are used in the aeronautical sector due to their excellent strength/weight ratios, motivated by the reduction of weight that their use entails. In this sector, drilling is one of the most common operations, if not the most, due to the large number of holes that are used in joining processes, mainly by riveting. The appearance of cracks is a risk to the structural safety of the components, such that it is necessary to regularly check them for maintenance and/or repair tasks. The present study tries to determine the optimization of the characteristics of the twist drills, which are re-sharpened successively to restore the cutting edge after use, as well as the operating parameters in machining. For this purpose, a full factorial experimental design was established, analyzing through the analysis of the variance (ANOVA) the response variables. Surface integrity was considered to carry out a global vision of the quality obtained, covering as response variables the surface roughness, the size of the burrs and the modification of the hardness produced, in addition to a topological characterization by optical means of machined surfaces. The main conclusion is that it is possible that the geometric optimization of the tools and the operating parameters considered in this study in drilling processes allow them to be performed, while maintaining quality and environmental requirements, and at the same time, maximize the productivity of operations.Publicación Experimental study of magnesium drilling based on the surface quality(Elsevier, 2019) Berzosa Lara, Fernando; Agustina Tejerizo, Beatriz De; Rubio Alvir, Eva María; Marín Martín, Marta MaríaNowadays, the use of magnesium and its alloys for transport applications is based on the combination of high mechanical properties and low density. In general, the machinability of these materials is considered to be good. Nevertheless, it has been reported that the machining of these alloys involves some critical problems regarding their tendency to be flammable at high temperatures and consequently, there is a risk of chip ignition in the working area during the process. This fact is especially critical when the size of chips is reduced. In this study, the influence of cutting conditions on surface roughness, in terms of Ra, obtained by drilling of magnesium alloy (AZ91D-F) was carried out. A factorial design 2 4 was employed for the planning of the drilling tests. The factors considered were the feed rate (0.05 and 0.2 mm/r), cutting speed, 40 and 60 m/min, the type of tool, in particular, the point angle of 118º and 135º, and the cooling system, Dry conditions and MQL (Minimum Quantity Lubrication) system. As main conclusions it can be affirmed that improved surface roughness is obtained with the cutting conditions selected in this study. Furthermore, at 0.05 mm/r and 40 m/min the use of tools with a point angle of 135º provides lower values of Ra than the tool of 118º point angle. Slightly lower values of Ra are obtained with tools of 118º point angle at 0.2 mm/r and 60 m/min.Publicación Feasibility Study of Hole Repair and Maintenance Operations by Dry Drilling of Magnesium Alloy UNS M11917 for Aeronautical Components(MDPI, 2019-06-30) Berzosa Lara, Fernando; Davim, J. Paulo; Agustina Tejerizo, Beatriz De; Rubio Alvir, Eva MaríaMagnesium alloys are increasingly used due to the reduction of weight and pollutants that can be obtained, especially in the aeronautical, aerospace, and automotive sectors. In maintenance and repair tasks, it is common to carry out re-drilling processes, which must comply with the established quality requirements and be performed following the required safety and environmental standards. Currently, there is still a lack of knowledge of the machining of these alloys, especially with regards to drilling operations. The present article studies the influence of different cutting parameters on the surface quality obtained by drilling during repair and/or maintaining operations. For this propose, an experimental design was established that allows for the optimization of resources, using the average roughness (Ra) as the response variable, and it was analyzed through the analysis of variance (ANOVA). The results were within the margins of variation of the factors considered: the combination of factor levels that keep the Ra within the established margin, those that allow for the minimization of roughness, and those that allow for the reduction of machining time. In this sense, these operations were carried out in the most efficient way.Publicación Estudio de la fuerza de avance y la circularidad de los agujeros en el taladrado criogénico de materiales compuestos con aramida(['Universidad Nacional de Educación a Distancia (España)', 'Universidad Politécnica de Madrid. Departamento de Ingeniería Mecánica'], 2022) Rodríguez Martín, Manuel; Domingo Navas, María Rosario; Ayllón Pérez, Jorge; Agustina Tejerizo, Beatriz DeEl uso de refrigerantes criogénicos en los procesos de mecanizado en los últimos años están teniendo una especial atención, así como su incidencia cuando se usan materiales compuestos, como aquellos reforzados por fibras de aramida o kevlar. Este trabajo analiza los resultados experimentales del taladrado criogénico con nitrógeno líquido en pletinas de aramida, en las fuerzas de avance, los diámetros de los agujeros taladrados y la rugosidad de las paredes, para posteriormente realizar un análisis mediante la metodología de superficie de respuesta (RSM). Este trabajo encuentra que, en el rango de las condiciones de corte empleadas, el diámetro del agujero no depende de la velocidad de rotación de la broca, mientras que la fuerza de avance y la rugosidad son dependientes de la velocidad de rotación y de avance; además aporta resultados que muestran la viabilidad de este proceso a temperaturas inferiores a -150ºC.