Estudio y optimización del proceso de soldadura por fricción batida (FSW) de materiales compuestos de matriz metálica (MMC) con elevado contenido de refuerzo

La soldadura por fricción batida (FSW, del inglés Friction Stir Welding) es una técnica que, por ser en estado sólido, resulta interesante para unir compuestos de matriz metálica (MMC, del inglés Metal Matrix Composite). Especialmente aquellos que presentan excelentes propiedades mecánicas pero se consideran «no soldables» por técnicas tradicionales de fusión. La principal aplicación de la soldadura por FSW se encuentra en aleaciones de aluminio. A pesar de que en la última década se ha extendido el uso a otros materiales (aceros, aleaciones de titanio, polímeros, etc.) la principal fuente de conocimiento sobre el proceso de FSW sigue siendo el campo de las aleaciones de aluminio. En la implementación del proceso de FSW en los MMC con alto contenido de refuerzo surgen nuevas dificultades relacionadas con la presencia de partículas cerámicas en el material. Por un lado, la mayor resistencia al flujo plástico de estos materiales dificulta la deformación plástica severa que ocurre durante la soldadura por FSW. Por otro lado, la presencia de partículas cerámicas abrasivas hace que la resistencia al desgaste de las herramientas de FSW utilizadas en aleaciones de aluminio no sea suficiente para realizar el proceso de manera reproducible. Por lo tanto, se deben utilizar herramientas con formas simples y fabricadas en materiales resistentes al desgaste (e. g. WC-Co). A su vez, los parámetros del proceso se ven condicionados por la utilización de dichas herramientas; de tal manera que se reduce la ventana de condiciones que permite obtener uniones sin defectos macroscópicos. Además, muchas de las estrategias comúnmente utilizadas para la eliminación de defectos en uniones de aleaciones de aluminio pierden validez cuando se aplican a los MMCs. Por lo tanto, las dificultades que surgen de la aplicación de la soldadura por FSW a los compuestos de este trabajo requieren de un estudio específico. Ya que éstas no pueden ser superadas simplemente aplicando los conocimientos adquiridos para aleaciones de aluminio. En este trabajo se proponen estrategias de eliminación de defectos basadas en la utilización de herramientas no roscadas y resistentes al desgaste. Inclusive, una de estas estrategias saca provecho de la asimetría del flujo de material característico del FSW, para hacer que las zonas críticas de la soldadura reciban mayor nivel de deformación..

Mass Production Processes

It is always hard to set manufacturing systems to produce large quantities of standardized parts. Controlling these mass production lines needs deep knowledge, hard experience, and the required related tools as well. The use of modern methods and techniques to produce a large quantity of products within productive manufacturing processes provides improvements in manufacturing costs and product quality. In order to serve these purposes, this book aims to reflect on the advanced manufacturing systems of different alloys in production with related components and automation technologies. Additionally, it focuses on mass production processes designed according to Industry 4.0 considering different kinds of quality and improvement works in mass production systems for high productive and sustainable manufacturing. This book may be interesting to researchers, industrial employees, or any other partners who work for better quality manufacturing at any stage of the mass production processes

Dislocation Density-Based Finite Element Method Modeling of Ultrasonic Consolidation

A dislocation density-based constitutive model has been developed and implemented into a crystal plasticity quasi-static finite element framework. This approach captures the statistical evolution of dislocation structures and grain fragmentation at the bonding interface when sufficient boundary conditions pertaining to the Ultrasonic Consolidation (UC) process are prescribed. The hardening is incorporated using statistically stored and geometrically necessary dislocation densities (SSDs and GNDs), which are dislocation analogs of isotropic and kinematic hardening, respectively. Since the macroscopic global boundary conditions during UC involves cyclic sinosuidal simple shear loading along with constant normal pressure, the cross slip mechanism has been included in the evolution equation for SSDs. The inclusion of cross slip promotes slip irreversibility, dislocation storage, and hence, cyclic hardening during the UC. The GND considers strain-gradient and thus renders the model size-dependent. The model is calibrated using experimental data from published refereed literature for simple shear deformation of single crystalline pure aluminum alloy and uniaxial tension of polycrystalline Aluminum 3003-H18 alloy. The model also incorporates various local and global effects such as (1) friction, (2) thermal softening, (3) acoustic softening, (4) surface texture of the sonotrode and initial mating surfaces, and (6) presence of oxide-scale at the mating surfaces, which further contribute significantly specifically to the grain substructure evolution at the interface and to the anisotropic bulk deformation away from the interface during UC in general. The model results have been predicted for Al-3003 alloy undergoing UC. A good agreement between the experimental and simulated results has been observed for the evolution of linear weld density and anisotropic global strengths macroscopically. Similarly, microscopic observations such as embrittlement due to grain substructure evolution at the UC interface have been also demonstrated by the simulation. In conclusion, the model was able to predict the effects of macroscopic global boundary conditions on bond quality. It has been found that the normal pressure enhances good bonding characteristics at the interface, though beyond a certain magnitude enhances dynamic failure. Similarly, lower oscillation amplitudes result in a lower rate of gap closure, whereas higher oscillation amplitude results in an enhanced rate of gap relaxation at the interface. Henceforth, good bonding characteristics between the constituent foils are found at an optimum oscillation amplitude. A similar analogy is also true for weld speed where the longitudinal locations behind the sonotrode rip open when higher weld speeds are implemented in the UC machine, leading to lower linear weld density and poor bonding characteristics

Testing, simulation and optimisation of additively manufactured structural hollow sections

Additive manufacturing (AM) is gaining increasing prominence in the construction industry, offering the potential for enhanced design freedom and reduced material use. However, the performance of additively manufactured metallic structural elements and the possible benefits associated with the attainable optimised geometries have seldom been investigated. The primary aim of this study is therefore to conduct an experimental and numerical investigation of additively manufactured metallic components, considering material behaviour, welded components and optimised tubular profiles. An experimental investigation was first conducted to examine the microstructural and mechanical properties of AM materials. Two grades of powder bed fusion (PBF) stainless steel (316L and CX) were considered, and the weldability and joining characteristics of PBF 316L stainless steel were also examined. The underlying microstructures were characterised and correlated with the measured mechanical properties from tensile coupon tests. At the cross-sectional level, axial compression tests were carried out on PBF circular hollow sections; advanced measuring techniques, including 3D laser-scanning and digital image correlation, were employed in the tests. Finite element (FE) models were developed to replicate the test results and to generate supplementary cross-sectional resistance data. Comparisons between design predictions and the test and FE data were made to evaluate the applicability of the existing codified design rules to additively manufactured cross-sections. In order to increase the axial compressive resistance and to reduce the imperfection sensitivity of very slender circular cross-sections (or cylindrical shells), optimised corrugated shells were sought through the use of the Particle Swarm Optimisation algorithm in conjunction with cross-section profile generation and numerical analyses. An experimental investigation into the cross-sectional behaviour of the resulting optimised shells, additively manufactured by PBF in 316L and CX stainless steels, was undertaken. The test results verified that the corrugated cylindrical shells achieved significantly higher capacities than their circular counterparts and with reduced imperfection sensitivity.Open Acces

Proceedings of the 4th International Conference on Innovations in Automation and Mechatronics Engineering (ICIAME2018)

The Mechatronics Department (Accredited by National Board of Accreditation, New Delhi, India) of the G H Patel College of Engineering and Technology, Gujarat, India arranged the 4th International Conference on Innovations in Automation and Mechatronics Engineering 2018, (ICIAME 2018) on 2-3 February 2018. The papers presented during the conference were based on Automation, Optimization, Computer Aided Design and Manufacturing, Nanotechnology, Solar Energy etc and are featured in this book

Structural Framework for Flight II: NASAs Role in Development of Advanced Composite Materials for Aircraft and Space Structures

This monograph is organized to highlight the successful application of light alloys on aircraft and space launch vehicles, the role of NASA in enabling these applications for each different class of flight vehicles, and a discussion of the major advancements made in discipline areas of research. In each section, key personnel and selected references are included. These references are intended to provide additional information for technical specialists and others who desire a more in-depth discussion of the contributions. Also in each section, lessons learned and future challenges are highlighted to help guide technical personnel either in the conduct or management of current and future research projects related to light-weighting advanced air and space vehicles

Additive Manufacturing Technologies and Applications

The present Special Issue proposes articles in the area of Additive Manufacturing with particular attention to the different employed technologies and the several possible applications. The main investigated technologies are the Selective Laser Sintering (SLS) and the Fused Deposition Modelling (FDM). These methodologies, combined with the Computer Aided Design (CAD), provide important advantages. Numerical, analytical and experimental knowledge and models are proposed to exploit the potential advantages given by 3D printing for the production of modern systems and structures in aerospace, mechanical, civil and biomedical engineering fields. The 11 selected papers propose different additive manufacturing methodologies and related applications and studies

Implementación de gramáticas evolutivas sobre GPUs

En el presente trabajo se ha realizado la implementación y análisis de resultados de la ejecución de un algoritmo que utiliza gramáticas evolutivas sobre una tarjeta de procesamiento gráfico o GPU, y su comparación con una implementación equivalente sobre CPU. El problema sobre el que se ha aplicado es el conocido como de regresión simbólica, que consiste en obtener una expresión matemática de la forma y=f(x) a partir de un conjunto de pares x/y. Adicionalmente se ha diseñado una implementación de una gramática para resolver un problema de identificación de perfiles de glucosa en pacientes diabéticos para mostrar una posible aplicación

Advanced Powder Metallurgy Technologies

Powder metallurgy is a group of advanced processes used for the synthesis, processing, and shaping of various kinds of materials. Initially inspired by ceramics processing, the methodology comprising the production of a powder and its transformation to a compact solid product has attracted attention since the end of World War II. At present, many technologies are availabe for powder production (e.g., gas atomization of the melt, chemical reduction, milling, and mechanical alloying) and its consolidation (e.g., pressing and sintering, hot isostatic pressing, and spark plasma sintering). The most promising methods can achieve an ultra-fine or nano-grained powder structure, and preserve it during consolidation. Among these methods, mechanical alloying and spark plasma sintering play a key role. This book places special focus on advances in mechanical alloying, spark plasma sintering, and self-propagating high-temperature synthesis methods, as well as on the role of these processes in the development of new materials