14 research outputs found
A Material Model Optimization Approach for the Sheet Metal Forming Process Using the Hole Expansion Test
No full textPublisher Copyright: © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.Sheet metal forming is an important manufacturing process widely used to produce complex stamped parts from flat sheet stock in industries such as automotive and packaging. Due to the global economic climate, these industries need to be highly competitive by reducing production costs and increasing process efficiency. Numerical simulation combined with sheet metal forming expertise is one of the technological innovations adopted to meet these requirements by reducing the traditional time-consuming and costly testing steps. With the progress of finite element simulation, questions about the accuracy or limitations of the type of material description adopted have become particularly important. The influence of the plasticity model is examined in this work by a numerical study using the hole expansion test. This work first presents the yield locus criterion adopted and developed by Tata Steel, which is hereafter referred to as the Tata Steel material model. Hole expansion tests are performed at different hole diameters and the results are compared with FE simulation. The simulations are performed with the finite element software Autoform R11 in which the yield criterion proposed by Abspoel & Scholting [1] has been implemented. The discussion therefore focuses on the influence of the material model on the numerical predictions and its accuracy based on the optimization of the different material parameters measured.The authors would like to acknowledge experimental work carried out at Tata Steel R&D by Frank Schouten and Tushar Khandeparkar.Peer reviewe
Thermographic monitoring and numerical analyses of GFRP delaminated specimen
No full textLAUREA MAGISTRALEMeccanica del comportamento di campioni GFRP non danneggiati e delaminati per valutare l'effetto dei difetti in modo quantitativo. A tal fine, verranno effettuati test sperimentali su campioni contenenti una regione pre-delaminata ottenuta dallo strato di Teflon durante la produzione, per evitare l'adesione completa della resina. In questo modo, viene creata una delaminazione controllata artificialmente, simile in tutti i campioni.
Il parametro meccanico che è stato determinato è lo stress dell'iniziazione del danno. Questo stress si ottiene per affaticamento graduale. Lo stress da danno di un composito vetroso / epossidico, così come l'identificazione dell'inizio e dell'evoluzione della cricca, sono valutati attraverso diverse tecniche termografiche, cioè analizzando la temperatura superficiale del campione. Queste tecniche si basano sull'analisi dell'ampiezza e della fase della temperatura.
Per studiare ulteriormente l'evoluzione del danno nel materiale, le simulazioni dei campioni delaminati vengono eseguite con il software degli elementi finiti Abaqus. L'implementazione degli elementi coerenti, che sono particolari elementi finiti con la possibilità di una variazione locale di rigidità. I modelli saranno calibrati sulla base dei risultati dei test sperimentali. Questi modelli possono essere utilizzati per estrapolare le caratteristiche meccaniche del composito e possono essere utilizzati per la progettazione strutturale di strutture composite.Aim of this thesis is to study the mechanical behavior of undamaged and delaminated GFRP specimens to evaluate the effect of defects in a quantitative way. With this aim, experimental tests will be carried out on specimens containing a pre-delaminated region obtained by placing a Teflon layer during manufacturing, to avoid complete resin adhesion. In this way, an artificial controlled delamination is created, similar in all the specimens.
The mechanical parameter that has been determined is the stress of damage initiation. This stress is obtained by means of stepwise fatigue load tests monitored by thermal camera. The damage stress of a glass/epoxy composite, as well as the identification of crack initiation and evolution, are evaluated through different thermographic techniques, i.e. by analyzing the surface temperature of the specimen. These techniques are based on the analysis of the temperature amplitude and phase.
In order to further investigate the damage evolution into the material, in parallel to experimental tests, simulations of the delaminated specimens are run with the finite element software Abaqus. The implementation of a delamination requires the application of the cohesive elements, that are particular finite elements with the possibility of offering a local variation in stiffness. The models will be calibrated based on the results of the experimental tests. These models can be used to extrapolate the mechanical characteristics of the composite, as well as they can be used for the structural design of composite structures
Experimental characterization of material by means of shear testing at intermediate strain rate and elevated temperatures
No full textLos capítulos 2 y 3 están sujetos a confidencialidad por el autor.
133 p.El doctorado forma parte del proyecto ENABLE (European Network for Alloys Behaviour Law Enhancement) que ha recibido financiación del programa de investigación e innovación Horizon 2020 de la Unión Europea bajo el acuerdo de subvención Marie Sklodowska-Curie N°764979. El trabajo también se ha desarrollado en el marco del laboratorio transfronterizo conjunto LTC ÆNIGME, entre la Universidad del País Vasco (UPV/EHU), la Universidad de Bordeaux (UBx) y Arts et Métiers Science et Technologie (ENSAM). El objetivo del doctorado es caracterizar experimentalmente el comportamiento a cizalla de una aleación de aluminio (AA7075-T6), en el rango de velocidad de deformación intermedia (101-103s-1) y temperatura elevada (hasta 0,7 veces la temperatura de fusión).La fabricación de componentes metálicos implica a menudo la deformación del material a velocidades de deformación de medias a altas y a temperaturas elevadas, especialmente en los procesos de conformación, mecanizado, soldadura por fricción (FSW), etc. Además, en muchos procesos de fabricación, la deformación dentro del material se genera por esfuerzos de cizallamiento y no por esfuerzos de tracción o compresión. Sin embargo, los dispositivos de ensayo mecánico existentes no son capaces de proporcionar un historial completo del comportamiento del material durante el proceso de fabricación en el rango de la velocidad de deformación y la temperatura.Los principales pasos tecnológicos y científicos para superar la preocupación:- Diseño y desarrollo de un nuevo banco de pruebas experimental para realizar el ensayo de cizallamiento a una velocidad de deformación intermedia.- La definición de ensayos termomecánicos capaces de reproducir las mismas solicitaciones que durante el mecanizado (velocidad de deformación media y deformación de rango medio), FSW (velocidad de deformación media, alta deformación), etc.- Proporcionar un comportamiento experimental detallado del material y realizar investigaciones microestructurales.Se desarrolla un nuevo dispositivo experimental de prueba de torsión basado en el principio de la rueda volante de inercia para reproducir localmente los niveles de tensión y las tasas de deformación que se encuentran en procesos como el mecanizado o el FSW. EnAbstractuna primera etapa, este dispositivo permite, mediante esfuerzos de torsión, alcanzar deformaciones a velocidades de deformación medias (en el rango de 102-103s-1). A continuación, se realizará una evolución para realizar ensayos de temperatura (hasta 0,7 veces la temperatura de fusión para las tres aleaciones estudiadas). La novedad de este equipo radica en los ensayos dinámicos en torsión que pueden realizarse bajo velocidades de deformación intermedias controlando la velocidad de carga. La deformación de la muestra se mide mediante una cámara de grabación de alta velocidad y la carga se mide mediante la técnica de la barra de Hopkinson. El nuevo banco de pruebas se implementa en la plataforma dinámica presente en el I2M, Burdeos, Francia.Tras la fabricación del dispositivo de prueba, se lleva a cabo la calibración de los diferentes componentes de medición para obtener resultados precisos de par y deformación. Por último, se realizan las pruebas preliminares. Una vez validado el banco de pruebas, se realizan ensayos a temperatura ambiente y a alta temperatura. Para ello, se adopta el diseño del experimento (DOE), con el fin de optimizar y organizar la campaña de ensayos. Los ensayos se realizan a diferentes velocidades de carga y temperaturas. También se realizan varias investigaciones microestructurales con el fin de identificar claramente los mecanismos que rigen la evolución de la respuesta plástica cubriendo un amplio rango de temperaturas, deformaciones y velocidades de deformación. Se estudia a fondo la caracterización mecánica y microestructural del material.Por último, se comparan las curvas de tensión de flujo obtenidas en el nuevo banco de ensayos de torsión a diferentes velocidades de deformación y a diferentes temperaturas con los modelos clásicos de material existentes que se utilizan habitualmente para la modelización del comportamiento constitutivo del AA7075-T6. Los parámetros de los modelos de material se determinan experimentalmente. La comparación con los resultados experimentales permite evaluar la adecuación de los modelos existentes y proponer una línea de base para la mejora del modelo existente o el desarrollo de un nuevo modelo de material
Effect of the Metal Transfer Mode on the Symmetry of Bead Geometry in WAAM Aluminum
No full textPublisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.The symmetrical nature in the case of wall fabrication by wire arc additive manufacturing (WAAM) has been observed in the literature, but it has not been studied as a source of knowledge. This paper focuses on the comparative study of three drop transfer methods employing Gas Metal Arc Welding (GMAW) technology, one of the most reported for the manufacture of aluminum alloys. The transfer modes studied are the well-known pulsed GMAW, cold arc, and the newer pulsed AC. The novelty of the last transfer mode is the reversal of the polarity during the preparation phase of the substance for droplet deposition. This study compares the symmetry of zero beads to determine the best parameters and transfer modes for wire arc additive manufacturing of 5 series aluminum. The pulsed transfer modes show values of 0.6 for symmetry ratio, which makes them more interesting strategies than cold arc with a symmetry ratio of 0.5. Furthermore, the methodology proposed in this study can be extrapolated to other materials manufactured with this technology.Peer reviewe
Study of the Mechanical Behavior of Topologically Optimized Arc Wire Direct Energy Deposition Aerospace Fixtures
No full textPublisher Copyright: © 2022, ASM International.The reliability and performance qualification of additively manufactured metal parts is essential for their successful and safe use in engineering applications. Additive Manufacturing (AM) allows parts to be produced more easily than traditional manufacturing. Arc Wire Direct Energy Deposition (AW-DED) is one of the lesser-known metal additive manufacturing technologies. It has enormous potential for large-scale 3D printing applications in the aerospace industry. However, in the aerospace industry, one of the main challenges today is to reduce the weight of components without compromising their structural functionality. Topology optimization offers design engineers the opportunity to create lightweight and complex structural parts. In arc wire direct energy deposition (AW-DED) processes, processing parameters affect material microstructure features, overall part quality, and integrity, as well as bulk mechanical behavior. To address such challenges, the investigation presented in this paper describes a novel digital design approach combining topology optimization, process simulations, and size optimization of the tool components used in the aerospace industry to address effects caused during manufacturing by using Finite Element Modeling (FEM) simulations. This can lead to reduced costs, development time, material consumption, and product weight. Due to the flexibility mentioned above, parts designed for AM have the same structural load as conventional parts but with reduced mass and better part design. The results of this application are discussed in depth in this paper. This is a new research work with useful results and conclusions in the methodology for the evaluation of mechanical behavior of topologically optimized metal additive manufactured components. For this purpose, aerospace fixtures have been topologically designed by means of AW-DED-process-oriented techniques. Aerospace fixtures are normally used in the aerospace industry to support and hold various components. These new design paradigms make it possible to save on material costs oriented toward more sustainable and flexible manufacturing.Peer reviewe
Effect of delamination on the fatigue life of GFRP: A thermographic and numerical study
No full textPublisher Copyright: © 2019Delamination is the major failure mechanism in composite laminates and eventually leads to material failure. An early-detection and a better understanding of this phenomenon, through non-destructive assessment, can provide a proper in situ repair and allow a better evaluation of its effects on residual strength of lightweight structural components. Here we adopt a joint numerical-experimental approach to study the effect of delamination on the fatigue life of glass/epoxy composites. To identify and monitor the evolution of the delamination during loading, we carried out stepwise cyclic tests coupled with IR-thermography on both undamaged and artificially-damaged samples. The outcome of the tests shows that IR-thermography is able to identify a threshold stress, named damage stress σ D , which is correlated to the damage initiation and the fatigue performance of the composite. Additionally, we performed FE-simulations, implementing the delamination by cohesive elements. Such models, calibrated on the basis of the experimental fatigue results, can provide a tool to assess the effect of parameters, such as the delamination size and location and composite stacking sequence, on the residual strength and fatigue life of the composite material.Peer reviewe
Influence of Heat Input on the Formation of Laves Phases and Hot Cracking in Plasma Arc Welding (PAW) Additive Manufacturing of Inconel 718
No full textNickel-based alloys have had extensive immersion in the manufacturing world in recent decades, especially in high added value sectors such as the aeronautical sector. Inconel 718 is the most widespread in terms of implantation. Therefore, the interest in adapting the manufacture of this material to additive manufacturing technologies is a significant objective within the scientific community. Among these technologies for the manufacture of parts by material deposition, plasma arc welding (PAW) has advantages derived from its simplicity for automation and integration on the work floor with high deposition ratios. These characteristics make it very economically appetizing. However, given the tendency of this material to form precipitates in its microstructure, its manufacturing by additive methods is very challenging. In this article, three deposition conditions are analyzed in which the energy and deposition ratio used are varied, and two cooling strategies are studied. The interpass cooling strategy (ICS) in which a fixed time is expected between passes and controlled overlay strategy (COS) in which the temperature at which the next welding pass starts is controlled. This COS strategy turns out to be advantageous from the point of view of the manufacturing time, but the deposition conditions must be correctly defined to avoid the formation of Laves phases and hot cracking in the final workpiece.The authors acknowledge the Basque Government ELKARTEK 2019 program (KK-2019/00004) and HARIPLUS project, HAZITEK 2019 program (ZL-2019/00352) and to the European commission through EiT Manufacturing programme in DEDALUS project (reference ID 20094)
Review of Intermediate Strain Rate Testing Devices
No full textMaterials undergo various loading conditions during different manufacturing processes, including varying strain rates and temperatures. Research has shown that the deformation of metals and alloys during manufacturing processes such as metal forming, machining, and friction stir welding (FSW), can reach a strain rate ranging from 10−1 to 106 s−1. Hence, studying the flow behavior of materials at different strain rates is important to understanding the material response during manufacturing processes. Experimental data for a low strain rate of <101 s−1 and a high strain rate of >103 s−1 are readily available by using traditional testing devices such as a servo-hydraulic testing machine and the split Hopkinson pressure bar method, respectively. However, for the intermediate strain rate (101 to 103 s−1), very few testing devices are available. Testing the intermediate strain rate requires a demanding test regime, in which researchers have expanded the use of special instruments. This review paper describes the development and evolution of the existing intermediate strain rate testing devices. They are divided based on the loading mechanism; it includes the high-speed servo-hydraulic testing machines, hybrid testing apparatus, the drop tower, and the flywheel machine. A general description of the testing device is systematically reviewed; which includes the working principles, some critical theories, technological innovation in load measurement techniques, components of the device, basic technical assumption, and measuring techniques. In addition, some research direction on future implementation and development of an intermediate strain rate apparatus is also discussed in detail
High-Temperature Mechanical Properties of IN718 Alloy: Comparison of Additive Manufactured and Wrought Samples: Comparison of additive manufactured and wrought samples
No full textPublisher Copyright: © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Wire Arc Additive Manufacturing (WAAM) is one of the most appropriate additive manufacturing techniques for producing large-scale metal components with a high deposition rate and low cost. Recently, the manufacture of nickel-based alloy (IN718) using WAAM technology has received increased attention due to its wide application in industry. However, insufficient information is available on the mechanical properties of WAAM IN718 alloy, for example in high-temperature testing. In this paper, the mechanical properties of IN718 specimens manufactured by the WAAM technique have been investigated by tensile tests and hardness measurements. The specific comparison is also made with the wrought IN718 alloy, while the microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. Fractographic studies were carried out on the specimens to understand the fracture behavior. It was shown that the yield strength and hardness of WAAM IN718 alloy is higher than that of the wrought alloy IN 718, while the ultimate tensile strength of the WAAM alloys is difficult to assess at lower temperatures. The microstructure analysis shows the presence of precipitates (laves phase) in WAAM IN718 alloy. Finally, the effect of precipitation on the mechanical properties of the WAAM IN718 alloy was discussed in detail.Funding: This project received funding from the European Union’s Marie Skłodowska–Curie Actions (MSCA) Innovative Training Networks (ITN) H2020-MSCA-ITN-2017 under the grant agreement No. 764979 and Basque Government QUALYFAM project, ELKARTEK 2020 program (KK-2020/00042) and HARIPLUS project, HAZITEK 2019 program (ZL-2019/00352) This project received funding from the European Union?s Marie Sk?odowska?Curie Actions (MSCA) Innovative Training Networks (ITN) H2020-MSCA-ITN-2017 under the grant agreement No. 764979 and Basque Government QUALYFAM project, ELKARTEK 2020 program (KK-2020/00042) and HARIPLUS project, HAZITEK 2019 program (ZL-2019/00352) The authors want to thanks to Ivan Tabernero for helping in experiment, support and expertise on additive manufacturing.Peer reviewe
Validation of the Mechanical Behavior of an Aeronautical Fixing Turret Produced by a Design for Additive Manufacturing (DfAM)
No full textThe design of parts in such critical sectors as the manufacturing of aeronautical parts is awaiting a paradigm shift due to the introduction of additive manufacturing technologies. The manufacture of parts designed by means of the design-oriented additive manufacturing methodology (DfAM) has acquired great relevance in recent years. One of the major gaps in the application of these technologies is the lack of studies on the mechanical behavior of parts manufactured using this methodology. This paper focuses on the manufacture of a turret for the clamping of parts for the aeronautical industry. The design of the lightened turret by means of geometry optimization, the manufacture of the turret in polylactic acid (PLA) and 5XXX series aluminum alloy by means of Wire Arc Additive Manufacturing (WAAM) technology and the analysis by means of finite element analysis (FEA) with its validation by means of a tensile test are presented. The behavior of the part manufactured with both materials is compared. The conclusion allows to establish which are the limitations of the part manufactured in PLA for its orientation to the final application, whose advantages are its lower weight and cost. This paper is novel as it presents a holistic view that covers the process in an integrated way from the design and manufacture to the behaviour of the component in use
