Examinando por Autor "López-Alba, Elías"

Mostrando 1 - 12 de 12

Applied computer vision for composite material manufacturing by optimizing the impregnation velocity: An experimental approach
(Elsevier, 2021-11-30) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Díaz-Garrido, Francisco Alberto
The application of the cutting edge industrial solutions in composite manufacturing are optimizing the processes, quality control and resources usage. Computer vision is currently used in many quality control stages, although its potential advantages have not been applied in the process control. In this paper, computer vision is used to control the impregnation velocity in VARI (Vacuum Assisted Resin Infusion) process. As it is known, there is a relationship between the impregnation velocity and the final mechanical properties in LCM (Liquid Composite Manufacturing) processes. Constant and optimum flow front velocity mean optimum mechanical properties, although the nature of the process makes it difficult to keep these conditions. Then, a methodology has been proposed to identify and use the optimum velocity during the manufacturing process. Firstly, the flow front recognition algorithm was calibrated to be used in different reinforcement and fluid systems. Then, tensile and impact specimens have been manufactured and tested at different controlled and uncontrolled velocities. As a result, the tensile modulus has been increased up to 12.6%, as the tensile strength has increased up to 8.7%. Similarly, the maximum reaction force during the impact test has been increased up to 6.5%, as the damaged area has been reduced by 8.8%. For stitched laminates, force results increase up to 3.2%, as the damaged area has been reduced up to 31% when the optimum velocity is used. The experimental results have demonstrated the advantage of using mechanisms to control the impregnation process to achieve improved mechanical properties of composite materials.
Enhanced Low-Velocity Impact Properties for Resin Film Infusion-Manufactured Composites by Flow-Control Approach
(Multidisciplinary Digital Publishing Institute, 2021-10-06) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Schmeer, Sebastian; Díaz-Garrido, Francisco Alberto
The optimization of the mechanical properties of composite materials has been a challenge since these materials were first used, especially in aeronautics. Reduced energy consumption, safety and reliability are mandatory to achieve a sustainable use of composite materials. The mechanical properties of composites are closely related to the amount of defects in the materials. Voids are known as one of the most important defect sources in resin film infusion (RFI)-manufactured composites. Minimizing the defect content leads to maximized mechanical properties and lightweight design. In this paper, a novel methodology based on computer vision is applied to control the impregnation velocity, reduce the void content and enhance the impact properties. Optimized drop-impact properties were found once the impregnation velocity was analyzed and optimized. Its application in bot conventional and stitching-reinforced composites concludes with an improvement in the damage threshold load, peak force and damaged area. Although stitching tends to generate additional voids and reduces in-plane properties, the reduction in the damaged area means a positive balance in the mechanical properties. At the same time, the novel methodology provides the RFI process with a noticeable level of automation and control. Consequently, the industrial interest and the range of applications of this process are enhanced.
Evaluation of modal identification under base motion excitation using vision techniques
(ELSEVIER, 2022-11) Molina-Viedma, Ángel; Felipe-Sesé, Luis; Pastor-Cintas, Manuel; López-Alba, Elías; Díaz, Francisco
In certain situations, employing a movable base acting as the excitation of a mechanical system is the best or even the only way to determine the response model for modal analysis. However, the obtained transmissibility functions must be modified prior to modal identification with a conventional procedure based on frequency response functions. Moreover, when employing vision techniques, the response curves are noisier and even poorly defined as the sensitivity is significantly lower than traditional sensors. Using the right model for curve-fitting is particularly relevant in this case. The current study performs an analysis of the adaptation of transmissibility functions, obtained by a vision technique, to improve the accuracy of the modal data estimation with conventional procedures. Two sets of transmissibility functions were evaluated: the originally obtained in the experiment, and the adapted one. After modal identification, significant differences were found concerning mode shapes and curve synthesis. The adaptation improved the accuracy of the identification in all the measurement points, proved by statistical indicators of the curve-fitting procedure like the correlation coefficient and the error between the synthesised and the experimental curves.
Exploiting phase-based motion magnification for the measurement of subtle 3D deformation maps with FP+ 2D-DIC
(Elsevier, 2022-05-31) Felipe-Sesé, Luis; Molina-Viedma, Ángel J.; Pastor-Cintas, Manuel; López-Alba, Elías; Díaz, Francisco
Phase-Based Motion Magnification (PBMM) is an effective methodology to visualise imperceptible phenomena based on magnifying periodic subtle movements on image sequences. Moreover, the integration of the optical techniques Fringe Projection and 2D Digital Image Correlation (FP + 2D-DIC) make it possible to obtain 3D displacement maps employing a single camera. In this study, the integration of PBMM with FP + 2D-DIC is exploited for the determination of subtle 3D displacements. An initial solid-rigid test validates of the combination of those techniques. A later test, employing a cantilever beam, demonstrates its correct performing in the determining of Operational Deflection Shapes. In both cases, the results are compared with those obtained with 3D-DIC and Scanning Laser Doppler Vibrometer (SLDV) to evaluate the relation between the magnification factor and the result obtained. Finally, the potential of the proposed integration for the determination of complex mode shapes is demonstrated by obtaining the ODSs of an industrial component.
FP+DIC for low-cost 3D full-field experimental modal analysis in industrial components
(ELSEVIER, 2019-04-07) Felipe-Sesé, Luis; Molina-Viedma, Ángel J.; López-Alba, Elías; Díaz, Francisco A.
High Speed 3D Digital Image Correlation has reached notorious popularity in dynamic characterisations because of the full-field non-invasive performance. It is being especially relevant for experimental modal analysis due to the importance of the modal parameters to define the dynamic behaviour. However, the economic cost of a stereoscopic system of two high speed cameras is a main concern regarding traditional instrumentations. In the search for low-cost alternatives, different methodologies have arisen that employ a single camera for 3D measurements. One approach consists in obtaining a stereo-vision in a single image using, for instance, a mirror system. These approaches involve important field of-view restrictions. An interesting approach employs the full resolution by combining Fringe Projection and 2D-DIC for out-of-plane and in-plane displacements, respectively. In this study, this technique is explored to perform experimental modal analysis in a large non-flat aeronautical panel. The validation of the results has been performed using accelerometer measurements during an impact hammer test. The results of the study stand this technique as an attractive low-cost technique for 3D full-field modal characterisations of complex components
Full-field 3D displacement and strain analysis during low energy impact tests employing a single-camera system
(Elsevier, 2020) Felipe-Sesé, Luis; López-Alba, Elías; Díaz, Francisco
Characterising materials behaviour during dynamics events such as impact require several features related to monitoring and instrumentation which find in full-field techniques one of the main responses due to high spatial and, nowadays, also temporal resolution. 3D-Digital Image Correlation has provided an interesting tool to evaluate the material response during impact testing. It contributes with displacement and strain fields at high frame rates, which represents enormous potential for subsequent analysis. However, 3D-DIC also presents some issues which may condition the experimentation. The first of them is the requirement of a stereoscopic optical system, which lead to important economic issues if high speed cameras are required. Secondly, certain impact arrangements have limited space which make complicated to dispose of a proper stereoscopic system observing an area of interest with a suitable angle that makes it possible r a successful processing. In this work, a recent procedure combining Fringe projection and 2D-DIC is presented as an alternative for impact testing analysis. As main characteristic, the optical arrangement is simplified to only one high speed camera and an additional simple LCD projector which makes it easier the experimentation, reducing significantly the setup cost. To demonstrate that capabilities of FP+2D-DIC as a simpler approach with results comparable to those obtained with 3D-DIC, in this work it was analysed 2, 3, 4, and 5 mm thickness aluminium plates under low speed impacts with different energy levels. Impacts were performed employing an impact tower with a hemispherical impactor, connected to a load cell. During the impact, displacement and strain maps were measured at the non-impacted face of the specimen, using a single camera system implementing the combination of FP and 2D-DIC techniques. Permanent displacement and strain maps were validated with those obtained with a 3D-DIC system, supporting the potential of this FP+2D-DIC approach for impact testing.
Human femur fracture by mechanical compression: Towards the repeatability of bone fracture acquisition
(ELSEVIER, 2023-09) Pérez-Cano, Francisco Daniel; Jiménez-Pérez, Juan Roberto; Molina-Viedma, Ángel Jesús; López-Alba, Elías; Luque-Luque, Adrián; Delgado-Martínez, Alberto Damián; Díaz-Garrido, Francisco Alberto; Jiménez-Delgado, Juan José
The increase in life expectancy combined with greater bone fragility over the years is causing a rise in the bone fracture cases. Femur fractures are the most important due to their high mortality rate. This multidisciplinary work is carried out in this context and focuses on the experimental reproduction of human femur fractures by compression. We describe a sequence of steps supervised by orthopaedic surgeons for the correct arrangement of specimens on the system set up to perform the experiment. The device applies force by compression until the human bone is fractured. All tests performed have been monitored and evaluated from different knowledge perspectives. The results obtained have demonstrated the repeatability of the fracture type in a controlled environment as well as identifying the main features involved in this process. In addition, the fractured bones have been digitized to analyze the fracture zone to recreate and evaluate future simulations.
Improving composite tensile properties during resin infusion based on a computer vision flow-control approach
(Multidisciplinary Digital Publishing Institute, 2018-12-05) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Díaz-Garrido, Francisco Alberto
Liquid composite manufacturing techniques, mainly applied in the transport industry, have been studied and optimized for decades while defect analysis and its minimization have been a goal to increase reliability and mechanical performance. Researchers have found that many process parameters have a strong influence on the mechanical behavior of composite structures where the flow front velocity, closely related to voids, plays a considerable role. In this work, the optimal flow front velocity was evaluated and controlled using a computer vision system for different laminates improving the mechanical tensile properties and void content. Enhanced mechanical tensile properties were found using a feedback flow-controller vision system which was able to keep the optimal flow front velocity constant to reduce the air traps among tows and fibers. Tensile strength was enhanced up to 18% for fiber orientation at 0◦ and 3.3% at 90◦, whereas tensile modulus was increased up to 18.4% for fibers at 0◦ and 8.7% at 90◦. A novel methodology is presented through this work, aiming to improve the robustness of resin film infusion (RFI) processes while ensuring the quality of the composite material.
Indentation Measurement in Thin Plates under Bending Using 3D Digital Image Correlation
(Multidisciplinary Digital Publishing Institute, 2021-03-17) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Rubio, Luis; Díaz-Garrido, Francisco Alberto
In the current paper, a novel experimental methodology to characterize the contact behavior on thin plates under bending is presented. The method is based on the experimental measurement of the indentation observed during contact experiments. Tests were conducted using aluminum thin plates and a steel sphere to evaluate the effect of thickness and bending during contact. For this purpose, a non-contact optical technique, 3D Digital Image Correlation (3D-DIC), has been employed to measure the out-of-plane displacements experienced at the rear face of the specimens (opposite where the contact is occurring). An indirect measurement of the experimental contact law is obtained for different plate thicknesses (2 mm, 3 mm, 4 mm, 5 mm and 6 mm) as the contact load increases. An energy balance performed during contact experiments made it possible to evaluate and quantify the applied energy to generate bending and contact deformation. When the specimen thickness increases from 2 mm to 6 mm, contact deformation reaches higher values from the total applied energy. In addition, it is also possible to evaluate the portion of the elastically recovered energy for contact and bending deformation during the unloading. It has been observed that thicker specimens show a lower elastic energy recovery due to bending and a higher elastic energy recovery due to contact. Results clearly show how the ratio between absorbed and applied energy changes as the specimen thickness increases, highlighting the relevance of the proposed method for the characterization of contact behavior in thin plates.
Optimización del proceso de infusión de resina mediante el control de la velocidad del frente de flujos en materiales compuestos reforzados con fibra
(Jaén : Universidad de Jaén, 2020-12-18) Almazán-Lázaro, Juan Antonio; Díaz-Garrido, Francisco Alberto; López-Alba, Elías; Universidad de Jaén. Departamento de INGENIERÍA MECÁNICA Y MINERA
Se presenta una metodología basada en el control y análisis de la velocidad de impregnación aplicada a procesos de fabricación de materiales compuestos por infusión de resina. Se fundamenta en la relación entre la velocidad de impregnación y la generación de atrapamientos de aire. Mediante un sistema de control específicamente desarrollado, se realiza el proceso a velocidad óptima, tanto en laminados convencionales como reforzados tridimensionalmente por stitching. Mediante su aplicación, las propiedades a tracción e impacto han mostrado aumentos significativos. Por su parte, el stitching ha aportado ventajas relevantes al proceso de infusión al aumentar la capacidad de éste. Así, supone un avance significativo en el proceso de fabricación mediante el que se obtendrán materiales con mayores prestaciones, fiabilidad, optimización de peso y uso más eficiente de los recursos utilizados. Asimismo, el sistema aporta cierto grado de automatización al proceso caracterizado por su elevada labor manual.
Parametrización mecánica de materiales para impresión 3D
(2018-09) Felipe Sesé, Luis; Suárez Guerra, Fernando; López-Alba, Elías; Díaz, Francisco A.
La impresión en 3D es en la actualidad una técnica de fabricación de piezas cada vez más popular y cuyo uso se está extendiendo progresivamente a un mayor número de campos de aplicación. Una de las tecnologías de impresión en 3D más popular es la Fabricación por Fusión de Filamento (FFF) , que es la que se emplea en el presente estudio. Cuando se precisa que las piezas fabricadas posean unas ciertas capacidades resistentes, resulta fundamental conocer sus características mecánicas y, por el propio método de fabricación, las probetas producidas mediante FFF presentan direcciones con propiedades mecánicas claramente diferenciadas. En este estudio se realiza una caracterización mecánica sobre probetas fabricadas con dos de los materiales más habituales cuando se emplea esta tecnología, PLA y ABS. Se estudian sus propiedades mecánicas mediante el ensayo de tracción para dos direcciones de impresión diferentes (paralela y perpendicular a la dirección de la carga) y se comparan los resultados con simulaciones numéricas realizadas en ABAQUS empleando modelos de material habituales en el campo de los materiales compuestos. Se observa que la previsible anisotropía del material no resulta notable en régimen elástico, aunque el comportamiento en rotura sí muestra claras diferencias entre probetas con distinta orientación de impresión.
The mechanical effect of monitoring and controlling the impregnation in the resin infusion process
(Wiley, 2022-01-25) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Díaz-Garrido, Francisco Alberto
Nowadays, most of industries are optimizing their processes to make their products more competitive. In the composites manufacturing industry, there is a big gap between the almost fully automated processes and those which require an intensive labor-work. Although it has many advantages, the resin infusion process is characterized for its lack of automation. As a consequence, the results are strongly dependent on the process boundaries, the operator skills and expertise, and the result is usually far away from the optimum. In this work, the application of a novel methodology and its capability to maximize the mechanical properties of infusion-manufactured composite materials is presented. After manufacturing stitched and unstitched materials at different impregnation velocities, an optimum value was assessed. The application of this value during the manufacture has increased the tensile and impact properties.

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Examinando por Autor "López-Alba, Elías"