Persona: Marín Martín, Marta María
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mmarin@ind.uned.es
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0000-0003-2686-909X
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Marín Martín
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Marta María
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Publicación Experimental study of magnesium drilling based on the surface quality(Elsevier, 2019) Berzosa, 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 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; MDPIThe 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.Publicación 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; https://orcid.org/0000-0002-3776-5010Multimaterial 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.Publicación 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; MDPIThis 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.Publicación 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; MDPIIn 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.Publicación Injection Mold for Plastics Manufactured by Metal-FFF with Conformal Cooling Channels: A Proof-of-Concept Case(MDPI, 2025-09-01) Solis, José Enrique; Claver Gil, Juan; Marín Martín, Marta María; Rubio Alvir, Eva María; García Domínguez, AmabelInjection molding is widely used for mass-producing plastic components, demanding precise thermal control to optimize cycle times and part quality. Traditional CNC-machined molds limit design flexibility and restrict advanced cooling features like conformal cooling channels (CCCs). Integrating CCCs improves cooling performance, reduces cycle times, and offers more efficient, cost-effective designs. Additive manufacturing (AM), especially Metal-Fused Filament Fabrication (Metal-FFF), offers geometries unattainable by machining. While most mold research focuses on Laser Powder Bed Fusion (LPBF), the feasibility of Metal-FFF molds remains underexplored. This study presents the design, fabrication, and experimental evaluation of an injection mold produced via Metal-FFF with integrated CCCs. The process included computational design, resistance simulations, fabrication, debinding, sintering, and post-processing, followed by testing under injection molding conditions. Results show that Metal-FFF molds with CCCs boost cooling efficiency, cutting cycle times by about 30% compared to conventional molds, while offering greater design freedom and economic benefits. Nonetheless, issues such as porosity and shrinkage need further refinement to fully leverage this technology for industrial use.Publicación 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; MDPICold 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.Publicación Assisted-Driven Design of Customized Maintenance Plans for Industrial Plants(MDPI, 2022-07-15) Rodríguez Padial, Néstor; Marín Martín, Marta María; Domingo Navas, María RosarioCurrent production systems that respond to market demands with high rates of production change and customization use complex systems. These systems are machines with a high capacity for communication, sensing and self-diagnosis, although they are susceptible to failures, breakdowns and a loss of reliability. The amount of data they provide as a productive system and, individually, as a machine can be treated to improve customized maintenance plans. The objective of this work, with an operational scope, is to collect and exploit the knowledge acquired in the industrial plant on failures and breakdowns based on its historical data. The acquisition of the aforementioned data is channeled through the human intellectual capital of the work groups formed for this purpose. Once this knowledge is acquired and available in a worksheet format according to the Reliability-Centered Maintenance (RCM) methodology, it is implemented using Case-Based Reasoning algorithms in a Java application developed for this purpose to carry out the process of RCM, accessing a base of similar cases that can be adapted. This operational definition allows for the control of the maintenance function of an industrial plant in the short term, with a weekly horizon, to design a maintenance plan adjusted to the reality of the plant in its current operating context, which may differ greatly from the originally projected plan or from any other plan caused by new production requirements. This new plan designed as such will apply changes to the equipment, which make up the production system, as a consequence of the adaptation to the changing market demand. As a result, a computer application has been designed, implemented and validated that allows, through the incorporation of RCM cases already successfully carried out on the productive system of the plant, for the development of a customized maintenance plan through an assistant, which, in a conductive way, guides the plant maintenance engineer through their design process, minimizing human error and design time and leveraging existing intellectual capital.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/0000-0002-3776-5010This 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 orderPublicación 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.