Análisis, Desarrollo y Validación del Método del Límite Superior en Procesos de Conformado por Indentación

La presente Tesis Doctoral, cuyo desarrollo ha sido financiado por el Ministerio de Educación, Cultura y Deportes de España a través de la concesión de las becas de Formación de Profesorado Universitario (FPU) 2010, se enmarca dentro del programa de doctorado “Ingeniería de Fabricación”, regulado por el Real Decreto 1393/2007, asociado al grupo de investigación PAI de la Junta de Andalucía TEP 933 Ingeniería de Fabricación, dentro de la línea de investigación “Métodos de análisis de procesos de Deformación Plástica”. En ella se aborda el estudio relativo al desarrollo del Teorema del Límite Superior, mediante su configuración modular de Bloques Rígidos Triangulares, para su implementación en el análisis de procesos de indentación. Para ello, se realiza un estudio previo sobre la investigación llevada a cabo por F. Martín, “Desarrollo, integración y optimización en el estudio del proceso de forja mediante el Teorema del Límite Superior a través del modelo de Bloques Rígidos Triangulares”, conducente a la adaptación del modelo modular a los procesos de indentación. Posteriormente, se configuran diversos modelos de análisis y se realiza un análisis comparativo entre los resultados obtenidos, con el fin de concretar el modelo óptimo para el proceso de indentación estudiado. Se aborda la necesidad de presentar una división en las piezas analizadas entre finitas e infinitas, para adaptar el modelo desarrollado al patrón de deformación presente en cada caso. Asimismo, una vez obtenido el modelo modular óptimo, se estudia su aplicación tanto para punzones planos, como para punzones inclinados y su respuesta ante la introducción de diferentes factores presentes en los procesos de deformación, tales como el efecto del rozamiento y la consideración del endurecimiento del material. Igualmente, se llevan a cabo simulaciones por elementos finitos del proceso analizado, comparando los resultados con los obtenidos mediante el modelo desarrollado en la aplicación analítica del Teorema del Límite Superior. Los resultados de la aplicación de ambos métodos muestran una gran similitud y, por tanto, una gran precisión en los resultados obtenidos. Además, se configura una serie de ensayos experimentales del proceso, realizando otra comparación con los resultados obtenidos tanto de la aplicación del Teorema del Límite Superior, como del análisis mediante elementos finitos, demostrando, una vez más, la validez de los resultados arrojados por el modelo analítico desarrollado. Con la presente Tesis Doctoral se realiza un estudio amplio y profundo de la aplicación del Teorema del Límite Superior a los procesos de deformación plástica de indentación, ampliando el conocimiento sobre este tipo de análisis y demostrando la viabilidad, en cuanto a aplicación práctica y precisión, de la obtención de los esfuerzos requeridos para la deformación plástica mediante el modelo modular planteado

Application of the Upper Bound Theorem to indentation processes with tilted punch by means of Modular Model

Nowadays, the indentation processes are resuming it importance due to the new deformation processes that are being developed, as the Incremental Forming Process (IFP) or the Localized-Incremental Forming Process (LIFP) [1]. In this paper, a tilt punch is considered in order to cover the largest possible number of cases in the study of the indentation,. Thus, using combinations of flat and tilt punches, it will be possible to analyze complex geometries in future studies. Present study shows the analysis of the indentation process by the Upper Bound Theorem (UBT), when it is performed with a tilt punch. A modular model is developed, compound by two modules of Triangular Rigid Zones (TRZ) each [2], which adapts to the configuration of the punch.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Use of additive manufacturing on models for sand casting process

Casting is a forming process based on material pouring in liquid state. Heat is applied to melt the material from its solid state and pour it in a mold previously constructed to obtain the desired shape after letting it cool. Molds can be permanent or expendable. In sand casting processes, the mold is manufactured from a model that usually is extracted before pouring the melted material (Figure 1). To obtain the part, the sand model needs to be destroyed. Notwithstanding, the sand can be reused several times for new molds. Several elements are needed to obtain a part by a sand casting process: permanent patterns, flasks (cope and drag), gating system (pouring cup, sprue, risers and feeding channels) and cores (only if it is needed). The aim of this work is the manufacturing of some of these elements by additive manufacturing process. The equipment will be used for the practical activities (Figure 1) that currently take place on the subjects where this topic is taught, in the different Degrees in Industrial Engineering at the University of Malaga.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Fatigue test bench manufacturing by reusing a parallel lathe

Fatigue life of machined parts strongly depends on their surface condition. The rotating bar bending fatigue testing method is widely used to obtain the fatigue behavior of metallic materials due to its simplicity. In this work, the methodology for the design, manufacturing and setup of a fatigue test bench is exposed. The main novelty lies on the reuse of several elements from an old parallel lathe, currently out of order, and their use to manufacture some parts for the test bench. In this way, a double objective is achieved: high quality elements are recycled and the machine manufacturing cost is reduced.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Material flow analysis in indentation process by 3D Digital Image Correlation

Focusing in the application of the 3D Digital Image Correlation technique, this work proposes a material flow analysis in an indentation process. The study establishes the methodology for the calibration and implementation of the 3D image sensing technology for deformation measurements. The purpose is to continue with the validation of the DIC application to the indentation processes, where a deep penetration is achieved and extensive material flow is produced. With the 3D DIC technique is possible to perform accurate deformation measurements in not planar specimens and study the material emerging towards the exterior of the tested specimen, which is not possible with the 2D DIC technique. Although previous 2D studies were efficient detecting the flow field and von Mises strains on the specimens tested, the bulge emerging under the punch on the front surface (dead zone) could not be studied due to its predominantly 3D character. Therefore, present work implements a 3D methodology that carries out a complete study of the deformation, including the material flow that occurs on the Z axis, towards the exterior of the tested specimen, optimizing previous analyses.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Manufacture of an abrasive jet machining (AJM) equipment adapted for the treatment of rotary flexion fatigue specimens

The influence of micro-geometric irregularities on fatigue strength and, in particular, surface topography is widely accepted. The different machining processes generate surface roughness on machined parts that may significantly modify their fatigue behaviour and compromise their use in components where structural stability is required. Therefore, the study of these materials behavior under cyclic loading stresses becomes highly relevant. The aim of this work is to design and manufacture an abrasive jet machining machine, in order to improve the surface roughness in the dry turning of aluminium alloys, using similar parameters to any equivalent industrial equipment. For this purpose, several components from obsolete machines belonging to the Manufacturing Engineering Department of the University of Malaga have been reused, to reduce the final cost. Several test have been carried out with the aim of testing the manufactured equipment. The experimental data have shown results in line with those offered by others in industrial use for similar abrasives and processing material. The equipment has been built in accordance with the ISO 12100:2010 Safety of machinery - General principles for design - Risk assessment and risk reduction.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influence of printing parameters and short carbon fibre reinforcement on fatigue behaviour, dimensional accuracy and macrogeometrical deviations of polylactic acid in material extrusion

This paper evaluates the potential of short carbon fibres as a reinforcement material in order to improve the fatigue resistance of PLA. The fatigue behaviour has been analysed through rotational bending fatigue tests. The influence of printing parameters, such as layer thickness, printing temperature and printing speed, on the mechanical behaviour, dimensional accuracy and macrogeometrical deviations of printed parts have also been analysed as they can too interfere with the mechanical behaviour of the parts. The results show that there is no improvement on the mechanical behaviour of the printed parts with the incorporation of short carbon fibres. On the contrary, the fatigue behaviour worsens due to the poor adhesion between the short carbon fibres and the PLA matrix. Fatigue life is reduced by 6% compared to PLA. Focusing only on the printing parameters, it is shown that at the highest temperature allowed, the fatigue behaviour improves a 12%. The Printing speed is the least influential variable, with the layer thickness having the greatest influence, increasing fatigue life by 15% comparing 0.1 mm and 0.3 mm. Therefore, the best combination would be to print with the highest temperature and the highest layer thickness, for this case study. Finally, a parametric relationship is presented in order to relate the layer thickness with the fatigue behaviour.FundiFunding for open access charge: Universidad de Málaga / CBU

Estudio y metodología para la puesta en valor del conjunto patrimonial textil de Antequera, Málaga

Actualmente, Antequera recoge un programa especial de recuperación del patrimonio inmueble textil, mediante el cual se han generado museos de conservación, exposiciones y rutas de las fábricas textiles. Aprovechando la corriente conservadora, se propone realizar un estudio del entorno y núcleos fabriles y el planteamiento de una metodología para la puesta en valor de aquellos inmuebles que se encuentran en un posible estado de recuperación viable, mediante la utilización de drones. Una de las principales ventajas del empleo de aeronaves no tripuladas (Unmanned Aerial Vehicle, UAV) es su capacidad de acceso a lugares que puedan resultar de difícil o peligroso acceso a pie y la posibilidad de incorporar tecnología de análisis basada en la fotografía del terreno y del bien inmueble. Cabe destacar la captación de fotografía térmica, multiespectral y la aplicación de técnicas de fotogrametría a las imágenes aéreas captadas por el dron. A través de las técnicas de fotogrametría, mediante ingeniería inversa, se pueden analizar los datos obtenidos mediante la utilización de software especializado, generando una nube de puntos que puedan pasar a reconstruir digitalmente el bien inmueble, dando paso a diversos usos de este archivo 3D, desde recreaciones tridimensionales simples, realidad aumentada o simulación virtual.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Geometrical analysis in material extrusion process with polylactic acid (PLA)1carbon fiber.

Purpose: The purpose of this study is to cover the influence of selected printing parameters at a macro and micro-geometrical level, focusing on the dimensions, geometry and surface of printed parts with short carbon fibers reinforced PLA. For this case study, a hollow cylindrical shape is considered, aiming to cover the gap detected in previous works analyzed. Design/methodology/approach: Nowadays, additive manufacturing plays a very important role in the manufacturing industry, as can be seen through its numerous research and applications that can be found. Within the engineering industry, geometrical tolerances are essential for the functionality of the parts and their assembly, but the variability in three-dimensional (3D) printing makes dimensional control a difficult task. Constant development in 3D printing allows, more and more, printed parts with controlled and narrowed geometrical deviations and tolerances. So, it is essential to continue narrowing the studies to achieve the optimal printed parts, optimizing the manufacturing process as well. Findings: Results present the relation between the selected printing parameters and the resulting printed part, showing the main deviations and the eligible values to achieve a better tolerance control. Also, from these results obtained, we present a parametric model that relates the geometrical deviations considered in this study with the printing parameters. It can provide an overview of the piece before printing it and so, adjusting the printing parameters and reducing time and number of printings to achieve a good part. Originality/value: The main contribution is the study of the geometry selected under a 3D printing process, which is important because it considers parts that are created to fit together and need to comply with the required tolerances. Also, we consider that the parametric model can be a suitable approach to selecting the optimal printing parameters before printing.Funding for open access charge: Universidad de Málaga/CBUA – Andalucia Tech Campus of International Excellence

Dimensional Analysis in Additive Manufacturing Processes with PLA+Carbon Fiber

The rise of Additive Manufacturing (AM) processes is due to the need to reduce material and energy costs. It has the capacity to achieve specialized tools fast while offering the possibility of customize products for the end user. Unlike the majority of the traditional manufacturing processes, AM generally generates the part by depositing material in layers that fuse and create a specific geometry, like Fuse Deposition Modeling (FDM). This comparatively recent technology is still being developed and adapted to the industry and materials requirements. Thus, im-provements are needed in areas like dimensional accuracy, geometric repeatability and material defects, among others, to be able to compare and have the same relia-bility that the products obtained by conventional manufacturing processes. Present work aims to carry out a dimensional control of workpieces designed to fit (axis-hole), so that the influence of certain printing parameters and the final dimensional precision of the specimens can be stablished. The printing parameter relation is studied for a composite material with a PLA matrix, reinforced with Carbon Fibers (PLA+CF), studying the influence of the printing temperature, the layer thickness and the printing direction. This material has been selected because PLA, together with ABS, is one of the most applied materials in AM. Notwithstanding, PLA is easy to process but lacks on resistance, which can be improved introducing carbon fiber as reinforcement. The best result is obtained decreasing the thickness. Also, In comparison with the vertical printing direction,Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech