Fusion sélective par laser - influence de l'atmosphère et réalisation d'alliage in situ PDF Download
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Author: Baicheng Zhang
Publisher:
ISBN:
Category :
Languages : fr
Pages : 0
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Book Description
Au cours de la dernière décennie, le procédé de fabrication additive par fusion sélective d'un lit de poudre SLM a attiré une grande attention dans le domaine de l'industrie, car il permet de produire rapidement des pièces de formes complexes. Le but de ce travail est d'étendre les performances des procédés SLM en étudiant la possibilité d'élaborer des pièces en atmosphère raréfiée. Pour atteindre cet objectif, une approche théorique et expérimentale a été développée, avec la mise en place d'une machine de fusion sélective par laser capable de travailler dans le domaine de pression de 1 à 10-2 mbar.Le travail sous vide permet d'éviter la formation du "bouclier" de plasma généré à partir de l'atmosphère de gaz ionisé par l'énergie du laser. Ceci permet d'une part d'éviter la contamination chimique du matériau (oxydation, nitruration,...) au cours des processus de fusion et d'autre part de réduire le taux de porosité. L'effet des paramètres du laser et des variables d'environnement sur la qualité de pièces a été étudié en considérant le cas du fer pur, de l'acier Inox 316L et du titane.Par ailleurs nous avons étudié la possibilité d'obtenir des alliages in-situ au cours de la fabrication par la technique SLM à partir de mélanges de poudres.Des essais ont été conduits à partir de mélanges Mg/Al, Fe/Ni et Ti/Ni. Dans tous les cas nous avons pu obtenir des alliages in-situ pour les domaines de composition visés qui correspondent à des applications pratiques (structures légères, alliage magnétique à faible coercivité, alliage à mémoire de forme). Les propriétés des matériaux obtenus, d'après les premières caractérisations effectuées, se comparent de façon favorable par rapport aux techniques classiques d'élaboration et de mise en œuvre.
Author: Baicheng Zhang
Publisher:
ISBN:
Category :
Languages : fr
Pages : 0
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Book Description
Au cours de la dernière décennie, le procédé de fabrication additive par fusion sélective d'un lit de poudre SLM a attiré une grande attention dans le domaine de l'industrie, car il permet de produire rapidement des pièces de formes complexes. Le but de ce travail est d'étendre les performances des procédés SLM en étudiant la possibilité d'élaborer des pièces en atmosphère raréfiée. Pour atteindre cet objectif, une approche théorique et expérimentale a été développée, avec la mise en place d'une machine de fusion sélective par laser capable de travailler dans le domaine de pression de 1 à 10-2 mbar.Le travail sous vide permet d'éviter la formation du "bouclier" de plasma généré à partir de l'atmosphère de gaz ionisé par l'énergie du laser. Ceci permet d'une part d'éviter la contamination chimique du matériau (oxydation, nitruration,...) au cours des processus de fusion et d'autre part de réduire le taux de porosité. L'effet des paramètres du laser et des variables d'environnement sur la qualité de pièces a été étudié en considérant le cas du fer pur, de l'acier Inox 316L et du titane.Par ailleurs nous avons étudié la possibilité d'obtenir des alliages in-situ au cours de la fabrication par la technique SLM à partir de mélanges de poudres.Des essais ont été conduits à partir de mélanges Mg/Al, Fe/Ni et Ti/Ni. Dans tous les cas nous avons pu obtenir des alliages in-situ pour les domaines de composition visés qui correspondent à des applications pratiques (structures légères, alliage magnétique à faible coercivité, alliage à mémoire de forme). Les propriétés des matériaux obtenus, d'après les premières caractérisations effectuées, se comparent de façon favorable par rapport aux techniques classiques d'élaboration et de mise en œuvre.
Author: Igor Yadroitsev
Publisher: Elsevier
ISBN: 0128240903
Category : Technology & Engineering
Languages : en
Pages : 676
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Book Description
Laser powder bed fusion of metals is a technology that makes use of a laser beam to selectively melt metal powder layer-by-layer in order to fabricate complex geometries in high performance materials. The technology is currently transforming aerospace and biomedical manufacturing and its adoption is widening into other industries as well, including automotive, energy, and traditional manufacturing. With an increase in design freedom brought to bear by additive manufacturing, new opportunities are emerging for designs not possible previously and in material systems that now provide sufficient performance to be qualified in end-use mission-critical applications. After decades of research and development, laser powder bed fusion is now enabling a new era of digitally driven manufacturing. Fundamentals of Laser Powder Bed Fusion of Metals will provide the fundamental principles in a broad range of topics relating to metal laser powder bed fusion. The target audience includes new users, focusing on graduate and undergraduate students; however, this book can also serve as a reference for experienced users as well, including senior researchers and engineers in industry. The current best practices are discussed in detail, as well as the limitations, challenges, and potential research and commercial opportunities moving forward. Presents laser powder bed fusion fundamentals, as well as their inherent challenges Provides an up-to-date summary of this advancing technology and its potential Provides a comprehensive textbook for universities, as well as a reference for industry Acts as quick-reference guide
Author: Golla Eranna
Publisher: CRC Press
ISBN: 1482232812
Category : Science
Languages : en
Pages : 432
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Book Description
Silicon, as a single-crystal semiconductor, has sparked a revolution in the field of electronics and touched nearly every field of science and technology. Though available abundantly as silica and in various other forms in nature, silicon is difficult to separate from its chemical compounds because of its reactivity. As a solid, silicon is chemically inert and stable, but growing it as a single crystal creates many technological challenges. Crystal Growth and Evaluation of Silicon for VLSI and ULSI is one of the first books to cover the systematic growth of silicon single crystals and the complete evaluation of silicon, from sand to useful wafers for device fabrication. Written for engineers and researchers working in semiconductor fabrication industries, this practical text: Describes different techniques used to grow silicon single crystals Explains how grown single-crystal ingots become a complete silicon wafer for integrated-circuit fabrication Reviews different methods to evaluate silicon wafers to determine suitability for device applications Analyzes silicon wafers in terms of resistivity and impurity concentration mapping Examines the effect of intentional and unintentional impurities Explores the defects found in regular silicon-crystal lattice Discusses silicon wafer preparation for VLSI and ULSI processing Crystal Growth and Evaluation of Silicon for VLSI and ULSI is an essential reference for different approaches to the selection of the basic silicon-containing compound, separation of silicon as metallurgical-grade pure silicon, subsequent purification, single-crystal growth, and defects and evaluation of the deviations within the grown crystals.
Author: Richard Leach
Publisher: CRC Press
ISBN: 0429791283
Category : Technology & Engineering
Languages : en
Pages : 419
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Book Description
Additive manufacturing (AM) is a fast-growing sector with the ability to evoke a revolution in manufacturing due to its almost unlimited design freedom and its capability to produce personalised parts locally and with efficient material use. AM companies, however, still face technological challenges such as limited precision due to shrinkage, built-in stresses and limited process stability and robustness. Moreover, often post-processing is needed due to high roughness and remaining porosity. Qualified, trained personnel are also in short supply. In recent years, there have been dramatic improvements in AM design methods, process control, post-processing, material properties and material range. However, if AM is going to gain a significant market share, it must be developed into a true precision manufacturing method. The production of precision parts relies on three principles: Production is robust (i.e. all sensitive parameters can be controlled). Production is predictable (for example, the shrinkage that occurs is acceptable because it can be predicted and compensated in the design). Parts are measurable (as without metrology, accuracy, repeatability and quality assurance cannot be known). AM of metals is inherently a high-energy process with many sensitive and inter-related process parameters, making it susceptible to thermal distortions, defects and process drift. The complete modelling of these processes is beyond current computational power, and novel methods are needed to practicably predict performance and inform design. In addition, metal AM produces highly textured surfaces and complex surface features that stretch the limits of contemporary metrology. With so many factors to consider, there is a significant shortage of background material on how to inject precision into AM processes. Shortage in such material is an important barrier for a wider uptake of advanced manufacturing technologies, and a comprehensive book is thus needed. This book aims to inform the reader how to improve the precision of metal AM processes by tackling the three principles of robustness, predictability and metrology, and by developing computer-aided engineering methods that empower rather than limit AM design. Richard Leach is a professor in metrology at the University of Nottingham and heads up the Manufacturing Metrology Team. Prior to this position, he was at the National Physical Laboratory from 1990 to 2014. His primary love is instrument building, from concept to final installation, and his current interests are the dimensional measurement of precision and additive manufactured structures. His research themes include the measurement of surface topography, the development of methods for measuring 3D structures, the development of methods for controlling large surfaces to high resolution in industrial applications and the traceability of X-ray computed tomography. He is a leader of several professional societies and a visiting professor at Loughborough University and the Harbin Institute of Technology. Simone Carmignato is a professor in manufacturing engineering at the University of Padua. His main research activities are in the areas of precision manufacturing, dimensional metrology and industrial computed tomography. He is the author of books and hundreds of scientific papers, and he is an active member of leading technical and scientific societies. He has been chairman, organiser and keynote speaker for several international conferences, and received national and international awards, including the Taylor Medal from CIRP, the International Academy for Production Engineering.
Author: Dongdong Gu
Publisher: Springer
ISBN: 3662460890
Category : Technology & Engineering
Languages : en
Pages : 322
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Book Description
This book entitled “Laser Additive Manufacturing of High-Performance Materials” covers the specific aspects of laser additive manufacturing of high-performance new materials components based on an unconventional materials incremental manufacturing philosophy, in terms of materials design and preparation, process control and optimization and theories of physical and chemical metallurgy. This book describes the capabilities and characteristics of the development of new metallic materials components by laser additive manufacturing process, including nanostructured materials, in situ composite materials, particle reinforced metal matrix composites, etc. The topics presented in this book, similar as laser additive manufacturing technology itself, show a significant interdisciplinary feature, integrating laser technology, materials science, metallurgical engineering and mechanical engineering. This is a book for researchers, students, practicing engineers and manufacturing industry professionals interested in laser additive manufacturing and laser materials processing. Dongdong Gu is a Professor at College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics (NUAA), PR China.
Author: O. Pironneau
Publisher: Springer Science & Business Media
ISBN: 3642877222
Category : Science
Languages : en
Pages : 179
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Book Description
The study of optimal shape design can be arrived at by asking the following question: "What is the best shape for a physical system?" This book is an applications-oriented study of such physical systems; in particular, those which can be described by an elliptic partial differential equation and where the shape is found by the minimum of a single criterion function. There are many problems of this type in high-technology industries. In fact, most numerical simulations of physical systems are solved not to gain better understanding of the phenomena but to obtain better control and design. Problems of this type are described in Chapter 2. Traditionally, optimal shape design has been treated as a branch of the calculus of variations and more specifically of optimal control. This subject interfaces with no less than four fields: optimization, optimal control, partial differential equations (PDEs), and their numerical solutions-this is the most difficult aspect of the subject. Each of these fields is reviewed briefly: PDEs (Chapter 1), optimization (Chapter 4), optimal control (Chapter 5), and numerical methods (Chapters 1 and 4).
Author: Martin Philip Bendsoe
Publisher: Springer Science & Business Media
ISBN: 3662050862
Category : Mathematics
Languages : en
Pages : 381
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Book Description
The topology optimization method solves the basic enginee- ring problem of distributing a limited amount of material in a design space. The first edition of this book has become the standard text on optimal design which is concerned with the optimization of structural topology, shape and material. This edition, has been substantially revised and updated to reflect progress made in modelling and computational procedures. It also encompasses a comprehensive and unified description of the state-of-the-art of the so-called material distribution method, based on the use of mathematical programming and finite elements. Applications treated include not only structures but also materials and MEMS.
Author: Milan Brandt
Publisher: Woodhead Publishing
ISBN: 0081004346
Category : Technology & Engineering
Languages : en
Pages : 500
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Book Description
Laser Additive Manufacturing: Materials, Design, Technologies, and Applications provides the latest information on this highly efficient method of layer-based manufacturing using metals, plastics, or composite materials. The technology is particularly suitable for the production of complex components with high precision for a range of industries, including aerospace, automotive, and medical engineering. This book provides a comprehensive review of the technology and its range of applications. Part One looks at materials suitable for laser AM processes, with Part Two discussing design strategies for AM. Parts Three and Four review the most widely-used AM technique, powder bed fusion (PBF) and discuss other AM techniques, such as directed energy deposition, sheet lamination, jetting techniques, extrusion techniques, and vat photopolymerization. The final section explores the range of applications of laser AM. Provides a comprehensive one-volume overview of advances in laser additive manufacturing Presents detailed coverage of the latest techniques used for laser additive manufacturing Reviews both established and emerging areas of application
Author: ASM International
Publisher:
ISBN: 9780871707055
Category :
Languages : en
Pages : 0
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Book Description
Author: Agnes Buka
Publisher: World Scientific
ISBN: 1848167997
Category : Science
Languages : en
Pages : 299
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Book Description
The book intends to give a state-of-the-art overview of flexoelectricity, a linear physical coupling between mechanical (orientational) deformations and electric polarization, which is specific to systems with orientational order, such as liquid crystals. Chapters written by experts in the field shed light on theoretical as well as experimental aspects of research carried out since the discovery of flexoelectricity. Besides a common macroscopic (continuum) description the microscopic theory of flexoelectricity is also addressed. Electro-optic effects due to or modified by flexoelectricity as well as various (direct and indirect) measurement methods are discussed. Special emphasis is given to the role of flexoelectricity in pattern-forming instabilities. While the main focus of the book lies in flexoelectricity in nematic liquid crystals, peculiarities of other mesophases (bent-core systems, cholesterics, and smectics) are also reviewed. Flexoelectricity has relevance to biological (living) systems and can also offer possibilities for technical applications. The basics of these two interdisciplinary fields are also summarized.
