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Agustina Tejerizo, Beatriz De

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0000-0003-0149-6928
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Agustina Tejerizo
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Beatriz De
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2017 - 201952020 - 20223
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Mostrando 1 - 8 de 8
  • Miniatura
    Publicación
    Analysis of Force Signals for the Estimation of Surface Roughness during Robot-Assisted Polishing
    (MDPI, 2018-08-15) Teti, Roberto; Agustina Tejerizo, Beatriz De; Marín Martín, Marta María; Rubio Alvir, Eva María
    In this study feature extraction of force signals detected during robot-assisted polishing processes was carried out to estimate the surface roughness during the process. The purpose was to collect significant features from the signal that allow the determination of the end point of the polishing process based on surface roughness. For this objective, dry polishing turning tests were performed on a Robot-Assisted Polishing (RAP) machine (STRECON NanoRAP 200) during three polishing sessions, using the same polishing conditions. Along the tests, force signals were acquired and offline surface roughness measurements were taken at the end of each polishing session. As a main conclusion, it can be affirmed, regarding the force signal, that features extracted from both time and frequency domains are valuable data for the estimation of surface roughness.
  • Miniatura
    Publicación
    A Multi-Response Optimization of Thrust Forces, Torques, and the Power of Tapping Operations by Cooling Air in Reinforced and Unreinforced Polyamide PA66
    (MDPI, 2018-03-20) Domingo Navas, María Rosario; Agustina Tejerizo, Beatriz De; Marín Martín, Marta María
    The use of cooling air during machining is an environmentally conscious procedure, and its applicability to different processes is a research priority. We studied tapping operations, an important operation in the assembly process, using cooling air with unreinforced polyamide (PA66) and polyamide reinforced with glass fiber (PA66-GF30). These materials are widely used in industry, but their behavior with respect to tapping has not been studied. We analyze the outcomes regarding the thrust force, torque, and power at cutting speeds between 15 and 60 m/min. The experimental tests were executed using cooling air at 22 °C, 2 °C, and −18 °C in dry conditions. The M12 × 1.75 mm taps were high-speed steel, with cobalt as the base material and coatings of TiN and AlCrN. To identify the more influential factors, an analysis of variance was performed, along with multi-response optimization to identify the desirability values. This optimization shows that the optimum for PA66can be found in environments close to 3 °C, while the optimum for PA66-GF30 is found at the minimal temperature studied (−18 °C). Thus, cooling air can be considered an adequate procedure for tapping operations, to increase the sustainability of the manufacturing processes.
  • Miniatura
    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 María
    This 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.
  • Miniatura
    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 María
    Nowadays, 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.
  • Miniatura
    Publicación
    Tool Selection in Drilling of Magnesium UNSM11917 Pieces under Dry and MQL Conditions based on Surface Roughness
    (Elsevier, 2017) Berzosa Lara, Fernando; Agustina Tejerizo, Beatriz De; Rubio Alvir, Eva María
    Nowadays, the use of lighter materials for transportation purposes is still a challenge; especially in the aeronautical and aerospace sectors. The use of certain materials, such as magnesium alloys which have exceptional mechanical properties relative to density as structural materials, allows a remarkable reduction of weight. These alloys have significant challenges in machining. On the one hand, their use with water-based lubricants can produce flammable hydrogen atmospheres and, on the other hand, the operational parameters can produce tiny chips which, at high temperature, could burn. Regarding the tools, drills are the most used ones in drilling operations; manufacturers do not always take in consideration magnesium alloys. This is why, sometimes, the data from other types of similar alloys need to be extrapolated. This work shows an experimental study about the drilling of magnesium pieces based on surface roughness. The main goal is to determine the tools that best suit the requirement of surface roughness for this type of operations, which, for the aeronautical sector, is from 0.8 to 1.6 μm. The tests have been conducted under different cutting conditions, using several types of tools and two sustainable lubrication systems. In particular, dry machining and minimum quantity of lubrication (MQL) system have been used. A design of experiments (DOE) has been used to optimize the resources. The average roughness, Ra, has been selected as a response variable. The roughness values obtained are lower than 0.9 μm (namely, from 0.13 μm to 0.87 μm); so, it is possible to increase some of the parameter values, in order to improve the productivity, without they go outside the established limits. The results have been analyzed using the analysis of variance (ANOVA) method. A model for estimating the expected surface roughness in terms of the Rae, has been developed.
  • Miniatura
    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 De
    Magnesium 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.
  • Miniatura
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    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 María
    Magnesium 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.
  • Miniatura
    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 De
    El 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.