Persona: Agustina Tejerizo, Beatriz De
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Agustina Tejerizo
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Beatriz De
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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 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 MaríaNowadays, 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.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.