Repositorio DSpace :: Examinando por Autor "MDPI"

Examinando por Autor "MDPI"

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Analysis of Force Signals for the Estimation of Surface Roughness during Robot-Assisted Polishing
(MDPI, 2018-08-15) Agustina Tejerizo, Beatriz De; Marín Martín, Marta María; Teti, Roberto; Rubio Alvir, Eva María; MDPI
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.
Cutting Parameter Selection for Efficient and Sustainable Repair of Holes Made in Hybrid Mg–Ti–Mg Component Stacks by Dry Drilling Operations
(MDPI, 2018-08-07) Rubio Alvir, Eva María; Villeta, María; Valencia, José Luis; Sáenz de Pipaón, José Manuel; MDPI
Drilling is one of the most common machining operations in the aeronautic and aerospace industries. For assembling parts, a large number of holes are usually drilled into the parts so that they can be joined later by rivets. As these holes are subjected to fatigue cycles, they have to be checked regularly for maintenance or repair, since small cracks or damage in its contour can quickly cause breakage of the part, which can have dangerous consequences. This paper focuses on finding the best combinations of cutting parameters to perform repair and maintenance operations of holes in stacked hybrid magnesium–titanium–magnesium components in an efficient, timely, and sustainable (without lubricants or coolants) manner, under dry drilling conditions. For the machining trials, experiments were designed and completed. A product of a full factorial 23 and a block of two factors (3 2) was used with surface roughness as the response variable measured as the mean roughness average. Analysis of variance (ANOVA) was used to examine the results. A set of optimized tool and cutting conditions is presented for performing dry drilling repair operations.
Efficiency and Sustainability Analysis of the Repair and Maintenance Operations of UNS M11917 Magnesium Alloy Parts of the Aeronautical Industry Made by Intermittent Facing
(MDPI, 2021-06-28) Fernández, Jacobo; Rubio Alvir, Eva María; Carou, Diego; Lorente Pedreille, Raquel María; MDPI
This paper analyzes the efficiency and sustainability of facing operations that are required within maintenance operations in the aeronautical industry. Due to the elevated cost and environmental impact of such processes, reducing the operating time while repairing parts is required. In this work, an experimental study of intermittent facing carried out on a magnesium alloy rod was developed. The experiment resembles real repair and maintenance machining operations, where an intermittent facing represents a more realistic scenario and where the results obtained in continuous turning studies are not always applicable. The work was performed with different cooling and lubrication systems and various cutting conditions, also considering the size of the interruption to analyze their impact in the surface roughness. To this end, surface finished in different measuring zones was studied. The aims of the study are to get a better understanding of the intermittent facing process in magnesium alloys typically employed in aeronautical applications and find the most efficient cutting parameters to obtain an improved surface under the safest and most environmentally respectful conditions.
Evolution and Latest Trends in Cooling and Lubrication Techniques for Sustainable Machining: A Systematic Review
(MDPI, 2025-02-05) Polo, Samuel; Rubio Alvir, Eva María; Marín Martín, Marta María; Sáenz de Pipaón, José Manuel; MDPI
This document presents a review on cooling and lubrication methods in machining. A systematic search of information related to these methods was carried out based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. The importance of the sustainability of machining processes is highlighted, as they represent between 10 and 17% of the total manufacturing cost of the final part and have negative environmental and health impacts. Although dry machining completely eliminates the use of cutting fluids, in many cases it produces unsatisfactory results due to the increase in temperature inside the tool, which requires prior analysis to ensure its viability compared to conventional techniques. On the other hand, semi-dry machining, which significantly reduces the volume of cutting fluids, is a more competitive alternative, with results similar to those of conventional machining. Other sustainable cooling and lubrication methods are also being investigated, such as cryogenic and high-pressure cooling, which offer better machining results than conventional processes. However, they have a high initial cost and further research is needed to integrate them into industry. While the combination of these cooling and lubrication methods could lead to improved results, there is a notable lack of comprehensive studies on the subject.
Experimental Study for Improving the Repair of Magnesium–Aluminium Hybrid Parts by Turning Processes
(MDPI, 2018-01-16) Rubio Alvir, Eva María; Villeta, María; Valencia, José Luis; Sáenz de Pipaón, José Manuel; MDPI
One of the lightest metallic materials used in the aeronautics, aerospace, and automotive industries, among others, is magnesium, due to its excellent weight/strength ratio. Most parts used in these industries need to be made of materials that are rigid, strong, and lightweight, but sometimes the materials do not simultaneously satisfy all of the properties required. An alternative is to combine two or more materials, giving rise to a hybrid component that can satisfy a wider range of properties. The pieces machined in these industrial fields must satisfy stringent surface roughness requirements that conform to the design specifications. This work shows an experimental study to analyse the surface roughness reached in hybrid components made up of a base of magnesium alloy (UNS M11917) and two inserts of aluminium alloy (UNS A92024) obtained by turning. Its purpose is to determine the influence of the factors and their possible interactions on the response variable, the surface roughness Ra. The study is carried out using a design of experiments (DOE). A product of a full factorial 23 and a block of two factors 3 2 was selected. The factors identified as possible sources of variation of the surface roughness are: depth of cut, feed rate, spindle speed, type of tool, location with respect to the specimen (LRS), and location with respect to the insert (LRI). Data were analysed by means of the analysis of variance (ANOVA) method. The main conclusion is the possibility to carry out the repair and maintenance of parts of magnesium–aluminum hybrid components by dry turning; that is, without cutting fluids and, therefore, in the most sustainable way that the process can be carried out. In addition, different combinations of cutting parameters have been identified that allow these operations to be carried out in an efficient manner, reducing mechanization times and, therefore, also the direct and indirect costs associated with them.
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. Paulo; 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.
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. Paulo; 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.
Guidelines for Selecting Plugs Used in Thin-Walled Tube Drawing Processes of Metallic Alloys
(MDPI, 2017-12-18) Rubio Alvir, Eva María; Camacho López, Ana María; Pérez, Rául; Marín Martín, Marta María; MDPI
In this paper, some practical guidelines to select the plug or set of plugs more adequate to carry out drawing processes of thin-walled tubes carried out with fixed conical inner plug are presented. For this purpose, the most relevant input parameters have been considered in this study: the tube material, the most important geometrical parameters of the process (die semiangle, a, and cross-sectional area reduction, r) and the friction conditions (Coulomb friction coefficients, m1, between the die and the tube outer surface, and m2, between the plug and the tube inner surface). Three work-hardening materials are analyzed: the annealed copper UNS C11000, the aluminum UNS A91100, and the stainless steel UNS S34000. The analysis is realized by means of the upper bound method (UBM), modelling the plastic deformation zone by triangular rigid zones (TRZ), under the validated assumption that the process occurs under plane strain conditions. The obtained results allow establishing, for each material, a group of geometrical parameters, friction conditions, a set of plugs that make possible to carry out the process under good conditions, and the optimum plug to carry out the process using the minimum amount of energy. The proposed model is validated by means of an own finite element analysis (FEA) carried out under different conditions and, in addition, by other finite element method (FEM) simulations and real experiments taken from other researchers found in the literature (called literature simulations and literature experimental results, respectively). As a main conclusion, it is possible to affirm that the plug that allows carrying out the process with minimum quantity of energy is cylindrical in most cases.
Impact of Global Warming on Kryal Fauna: Thermal Tolerance Response of Diamesa steinboecki (Goetghebuer, 1933; Chironomidae)
(MDPI, 2023-05-26) Muñiz González, Ana Belén; Martínez Guitarte, José Luis; Lencioni, Valeria; MDPI; https://orcid.org/0000-0002-4341-9923
The ice fly Diamesa steinboecki Goetghebuer, 1933 (Diptera: Chironomidae: Diamesinae) is exclusive to glacier-fed streams in the East Palaearctic region and is threatened by extinction due to global warming and glacier retreat. To date, no data are available on its thermal tolerance or ability to develop a heat shock response (HSR) or involve other biomarkers when exposed to higherthan-natural temperatures (i.e., >4–6 ◦C). Our study aimed to investigate the warmth resistance of IV-instar larvae of D. steinboecki in terms of (1) ability to survive heat shock and (2) gene expression of four genes known to be involved in the detoxification/stress response (cytochrome p450 (Cyp450), heat shock protein 70 (hsp70), hsp70 with intron and heat shock protein cognate 70 (hsc70)). Larvae were exposed to short-term shocks for 1 h at increasing temperatures (26, 28, 30, 32, 34, 36, 38, and 40 ◦C) to estimate the lethal temperature, obtaining high values (LT10 = 38.1 ◦C, LT50 = 39.2 ◦C, LT99 = 40.3 ◦C), suggesting a strong heat resistance up to 38 ◦C and a very rapid decline in survival thereafter. Moreover, gene expression analysis by real-time PCR was performed on larvae from the control (at 2 ◦C) and larvae found alive after the previous treatment at 26, 28, 30, 32, 34, 36, and 38 ◦C. Modulation of the expression was observed only for hsc70 and hsp70 genes. Specifically, hsc70 resulted in constitutive overexpression, even at 26 ◦C when all larvae were found alive without evidence of suffering. By contrast, hsp70 showed up and downregulation according to the specific temperature, suggesting the activation of an HSR at 28 ◦C, when some larvae were found alive but suffering (almost paralyzed). The results suggest that, based on LTs, D. steinboecki is more thermally tolerant than other Diamesa species (e.g., D. tonsa) from cold freshwaters, but, as in these, hsp70 and hsc70 are involved in surviving short-term heat shock. This makes the ice fly from the Alps different from Belgica antarctica and other cold-adapted organisms living in extremely cold habitats that, constantly exposed to cold, have lost the ability to develop an HSR. Further research is needed to investigate the response to prolonged exposure to temperatures higher that the natural one, giving new insights into the biological response to climate change of alpine species threatened by extinction.
Influence of the Main Blown Film Extrusion Process Parameters on the Mechanical Properties of a High-Density Polyethylene Hexene Copolymer and Linear Low-Density Polyethylene Butene Copolymer Blend Used for Plastic Bags
(MDPI, 2023-11-09) Cuesta, Francisco; Camacho López, Ana María; Rubio Alvir, Eva María; MDPI
Polyethylene plastic bags manufactured via blown film extrusion have different quality specifications depending on their intended use. It is known that the mechanical properties of a film depend on the process parameters established, but little is known concerning how they affect one another, even more so due to the variety of polyethylene materials and processing techniques. This study focuses on establishing a proper correspondence of important mechanical properties like the dart impact, tensile strength at break, and elongation at break with commonly used process parameters like the blow-up ratio, take-up ratio, thickness reduction, and neck height, for a highdensity polyethylene hexene copolymer and a linear low-density polyethylene butene copolymer blend film. Because this polyethylene mixture is an anisotropic material, interesting R2 values equal to or higher than 0.90 were found: a BUR with elongation at break and tensile strength at break in the MD and TD, a TUR with elongation at break in the MD and tensile strength at break in the MD and TD, and a TR with elongation at break and tensile strength at break in the MD. Also, a relationship between the dart impact and both the neck height and thickness were found.
Parametric Analysis of the Mandrel Geometrical Data in a Cold Expansion Process of Small Holes Drilled in Thick Plates
(MDPI, 2019-12-08) Calaf-Chica, José; Marín Martín, Marta María; Rubio Alvir, Eva María; Teti, Roberto; Secreto, Tiziana; MDPI
Cold expansion technology is a cold-forming process widely used in aeronautics to extend the fatigue life of riveted and bolted holes. During this process, an oversized mandrel is pushed through the hole in order to yield it and generate compressive residual stresses contributing to the fatigue life extension of the hole. In this paper, a parametric analysis of the mandrel geometrical data (inlet angle straight zone length and diametric interference) and their influence on the residual stresses was carried out using a finite element method (FEM). The obtained results were compared with the conclusions presented in a previous parametric FEM analysis on the influence of the swage geometry in a swaging cold-forming process of gun barrels. This process could be considered, in a simplified way, as a scale-up of the cold expansion process of small holes, and this investigation demonstrated the influence of the diameter ratio (K) on the relation between the mandrel or swage geometry and the residual stresses obtained after the cold-forming process.
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, João Paulo; MDPI
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
Surface Roughness Evaluation Based on Acoustic Emission Signals in Robot Assisted Polishing
(MDPI, 2014-11-14) Agustina Tejerizo, Beatriz De; Marín Martín, Marta María; Teti, Roberto; Rubio Alvir, Eva María; MDPI
The polishing process is the most common technology used in applications where a high level of surface quality is demanded. The automation of polishing processes is especially difficult due to the high level of skill and dexterity that is required. Much of this difficulty arises because of the lack of reliable data on the effect of the polishing parameters on the resulting surface roughness. An experimental study was developed to evaluate the surface roughness obtained during Robot Assisted Polishing processes by the analysis of acoustic emission signals in the frequency domain. The aim is to find out a trend of a feature or features calculated from the acoustic emission signals detected along the process. Such an evaluation was made with the objective of collecting valuable information for the establishment of the end point detection of polishing process. As a main conclusion, it can be affirmed that acoustic emission (AE) signals can be considered useful to monitor the polishing process state.
Surface Roughness Model Based on Force Sensors for the Prediction of the Tool Wear
(MDPI, 2014-04-04) Agustina Tejerizo, Beatriz De; Rubio Alvir, Eva María; Sebastián Pérez, Miguel Ángel; MDPI
In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along the process is correlated to several parameters of the cutting forces (thrust forces, feed forces and cutting forces), so the effect that the tool wear causes on the surface roughness is evaluated. In a first step, the best cutting conditions (cutting parameters and radius of tool) for a certain quality surface requirement were found for pieces of UNS A97075. Next, with this selection a model of surface roughness based on the cutting forces was developed for different states of wear that simulate the behaviour of the tool throughout its life. The validation of this model reveals that it was effective for approximately 70% of the surface roughness values obtained.
Thicknesses/Roughness Relationship in Mg-Al-Mg and Mg-Ti-Mg Hybrid Component Plates for Drilled Aeronautical Lightweight Parts
(MDPI, 2020-11-19) Blanco, David; Rubio Alvir, Eva María; Sáenz de Pipaón, José Manuel; Marín Martín, Marta María; MDPI
Multimaterial hybrid compounds formed from lightweight structural materials have been acquiring great importance in recent years in the aeronautical and automotive sectors, where they are replacing traditional materials to reduce the mass of vehicles; this will enable either an increase in the action ratio or a reduction in the fuel consumption of vehicles and, in short, will lead to savings in transport costs and a reduction in polluting emissions. Besides, the implementation of production and consumption models based on the circular economy is becoming more and more important, where the repair and, for this purpose, the use of recyclable materials, is crucial. In this context, the analysis of a repair process is carried out by re-drilling Mg-Al-Mg multimaterial components using experimental design (DoE) based on Taguchi methodology, an analysis of variance (ANOVA) and descriptive statistics. The study concludes which are the significant factors and interactions of the process, comparing the results with previous similar studies, and establishing bases to determine the optimum thicknesses of hybrid magnesium-based component plates of drilled parts in the aeronautical industry, guaranteeing surface roughness requirements in repair and maintenance operations throughout their lifetime.
A WoT Platform for Supporting Full-Cycle IoT Solutions from Edge to Cloud Infrastructures: A Practical Case
(MDPI, 2020-07-05) Pastor Vargas, Rafael; Tobarra Abad, María de los Llanos; Robles Gómez, Antonio; Martín Gutiérrez, Sergio; Hernández Berlinches, Roberto; Cano Carrillo, Jesús; MDPI; https://orcid.org/0000-0001-6926-1311
Internet of Things (IoT) learning involves the acquisition of transversal skills ranging from the development based on IoT devices and sensors (edge computing) to the connection of the devices themselves to management environments that allow the storage and processing (cloud computing) of data generated by sensors. The usual development cycle for IoT applications consists of the following three stages: stage 1 corresponds to the description of the devices and basic interaction with sensors. In stage 2, data acquired by the devices/sensors are employed by communication models from the origin edge to the management middleware in the cloud. Finally, stage 3 focuses on processing and presentation models. These models present the most relevant indicators for IoT devices and sensors. Students must acquire all the necessary skills and abilities to understand and develop these types of applications, so lecturers need an infrastructure to enable the learning of development of full IoT applications. AWeb of Things (WoT) platform named Labs of Things at UNED (LoT@UNED) has been used for this goal. This paper shows the fundamentals and features of this infrastructure, and how the different phases of the full development cycle of solutions in IoT environments are implemented using LoT@UNED. The proposed system has been tested in several computer science subjects. Students can perform remote experimentation with a collaborativeWoT learning environment in the cloud, including the possibility to analyze the generated data by IoT sensors.

Examinando por Autor "MDPI"

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