Examinando por Autor "Davim, J. P."

Mostrando 1 - 6 de 6
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    Publicación
    Desenvolvimento de Tratamentos Térmicos para Peças Estruturais Injetadas em Ligas de Alumínio
    (Universidad Nacional de Educación a Distancia (España), Universidad de Concepción - Chile. Departamento de Ingeniería Mecánica, 2024-10-22) Soares, Gonçalo; Silva, Rui Pedro; Gomes, Rui; Madureira, Rui; Neto, Rui; Reis, Ana; Babo, Tiago; Figueiredo, Daniel; Guimarães, Bruno; Davim, J. P.
    Com o intuito de minimizar o peso dos veículos, cada vez mais são utlizadas peças em ligas de alumínio produzidas por fundição injetada. Contudo, devido às elevadas velocidades de injeção durante o processo de HPDC, ar fica aprisionado no metal líquido, originando porosidades nos componentes. Estas porosidades gasosas impossibilitam a realização de tratamentos térmicos devido ao fenómeno de “blistering”. Assim, o trabalho realizado centra-se no desenvolvimento de tratamentos térmicos (T5 e T6 relâmpago) em peças obtidas pelo processo de HPDC assistido por vácuo, recorrendo às ligas AlSi10MnMg e AlSi10Mg(Fe). As peças foram caracterizadas tendo em consideração a ocorrência de “blistering”, microestrutura e propriedades mecânicas alcançadas. Adicionalmente, foi avaliada a maquinabilidade da liga primária AlSi10MnMg, recorrendo a uma ferramenta com PCD produzida por fabrico aditivo, sendo esta comparada com a da liga convencional AlSi9Cu3(Fe). Para todas as combinações de parâmetros usadas no tratamento térmico de solubilização verificaram-se “blisters” nos componentes. Com o tratamento térmico T5 não houve formação de “blisters” e a resistência mecânica aumentou. Em termos de maquinabilidade da liga primária AlSi10MnMg, esta apresenta uma rugosidade superficial ligeiramente superior e forças de corte inferiores, comparativamente à liga de injeção convencional AlSi9Cu3(Fe).
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    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, Fernando; Agustina Tejerizo, Beatriz De; Rubio Alvir, Eva María; Davim, J. P.; MDPI
    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 di erent 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 e cient way.
  • Miniatura
    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, Fernando; Davim, J. P.; 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
    Geometric Optimization of Drills Used to Repair Holes in Magnesium Aeronautical Components
    (MDPI, 2020-11-18) Berzosa, Fernando; Rubio Alvir, Eva María; Agustina Tejerizo, Beatriz De; Davim, J. P.; MDPI
    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
    Publicación
    Geometric Optimization of Drills Used to Repair Holes in Magnesium Aeronautical Components
    (MPDI, 2020-11-18) Berzosa, Fernando; Davim, J. P.; 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
    Publicación
    Repairing Hybrid Mg–Al–Mg Components Using Sustainable Cooling Systems
    (MDPI, 2020-01-15) Blanco, David; Rubio Alvir, Eva María; Marín Martín, Marta María; Davim, J. P.; MDPI; https://orcid.org/0000-0002-3776-5010
    This paper focused on the maintenance or repair of holes made using hybrid Mg–Al–Mg components by drilling, using two sustainable cooling techniques (dry machining and cold compressed air) and taking surface roughness on the inside of the holes as the response variable. The novelty of the work is in proving that the repair operations of the multi-material components (magnesium–aluminum–magnesium) and the parts made of aluminum and magnesium (separately) but assembled to form a higher component can be done simultaneously, thus reducing the time and cost of the assembly and disassembly of this type of component. The study is based on a design of experiments (DOE) defined as a product of a full factorial 23 and a block of two factors (3 2). Based on our findings, we propose that the analyzed operations are feasible under sustainable conditions and, in particular, under dry machining. Also, the results depend on the machining order