Download or read book The Plasticity of Metals at the Sub micrometer Scale and Dislocation Dynamics in a Thin Film written by Seok Woo Lee and published by Stanford University. This book was released on 2011 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology has played a significant role in the development of useful engineering devices and in the synthesis of new classes of materials. For the reliable design of devices and for structural applications of materials with micro- or nano-sized features, nanotechnology has always called for an understanding of the mechanical properties of materials at small length scales. Thus, it becomes important to develop new experimental techniques to allow reliable mechanical testing at small scales. At the same time, the development of computational techniques is necessary to interpret the experimentally observed phenomena. Currently, microcompression testing of micropillars, which are fabricated by focused-ion beam (FIB) milling, is one of the most popular experimental methods for measuring the mechanical properties at the micrometer scale. Also, dislocation dynamics codes have been extensively developed to study the local evolution of dislocation structures. Therefore, we conducted both experimental and theoretical studies that shed new light on the factors that control the strength and plasticity of crystalline materials at the sub-micrometer scale. In the experimental work, we produced gold nanopillars by focused-ion beam milling, and conducted microcompression tests to obtain the stress-strain curves. Firstly, the size effects on the strength of gold nanopillars were studied, and "Smaller is Stronger" was observed. Secondly, we tried to change the dislocation densities to control the strength of gold nanopillars by prestraining and annealing. The results showed that prestraining dramatically reduces the flow strength of nanopillars while annealing restores the strength to the pristine levels. Transmission electron microscopy (TEM) revealed that the high dislocation density (~1015 m-2) of prestrained nanopillars significantly decreased after heavy plastic deformation. In order to interpret this TEM observation, potential dislocation source structures were geometrically analyzed. We found that the insertion of jogged dislocations before relaxation or enabling cross-slip during plastic flow are prerequisites for the formation of potentially strong natural pinning points and single arm dislocation sources. At the sub-micron scale, these conditions are most likely absent, and we argue that mobile dislocation starvation would occur naturally in the course of plastic flow. Two more outstanding issues have also been studied in this dissertation. The first involves the effects of FIB milling on the mechanical properties. Since micropillars are made by FIB milling, the damage layer at the free surface is always formed and would be expected to affect the mechanical properties at a sub-micron scale. Thus, pristine gold microparticles were produced by a solid-state dewetting technique, and the effects of FIB milling on both pristine and prestrained microparticles were examined via microcompression testing. These experiments revealed that FIB milling significantly reduces the strength of pristine microparticles, but does not alter that of prestrained microparticles. Thus, we confirmed that if there are pre-existing mobile-dislocations present in the crystal, FIB milling does not affect the mechanical properties. The second issue is the scaling law commonly used to describe the strength of micropillars as a function of sample size. For the scaling law, the power-law approximation has been widely used without understanding fundamental physics in it. Thus, we tried to analyze the power-law approximation in a quantitative manner with the well-known single arm source model. Material parameters, such as the friction stress, the anisotropic shear modulus, the magnitude of Burgers vector and the dislocation density, were explored to understand their effects on the scaling behavior. Considering these effects allows one to rationalize the observed material-dependent power-law exponents quantitatively. In another part of the dissertation, a computational study of dislocation dynamics in a free-standing thin film is described. We improved the ParaDiS (Parallel Dislocation Simulator) code, which was originally developed at the Lawrence Livermore National Laboratory, to deal with the free surface of a free-standing thin film. The spectral method was implemented to calculate the image stress field in a thin film. The faster convergence in the image stress calculation were obtained by employing Yoffe's image stress, which removes the singularity of the traction at the intersecting point between a threading dislocation and free surface. Using this newly developed code, we studied the stability of dislocation junctions and jogs, which are the potential dislocation sources, in a free standing thin film of a face-centered-cubic metal and discussed the creation of a dislocation source in a thin film. In summary, we have performed both microcompression tests and dislocation dynamics simulations to understand the dislocation mechanisms at the sub-micron scale and the related mechanical properties of metals. We believe that these experimental and computational studies have contributed to the enhancement of our fundamental knowledge of the plasticity of metals at the sub-micron scale.
Download or read book Advances in Heterogeneous Material Mechanics 2011 written by Jinghong Fan and published by DEStech Publications, Inc. This book was released on 2011 with total page 1205 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Mechanics of Metal Plasticity and Fracturing written by Ronald W. Armstrong and published by MDPI. This book was released on 2020-11-03 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The modern understanding of metal plasticity and fracturing began about 100 years ago, with pioneering work; first, on crack-induced fracturing by Griffith and, second, with the invention of dislocation-enhanced crystal plasticity by Taylor, Orowan and Polanyi. The modern counterparts are fracture mechanics, as invented by Irwin, and dislocation mechanics, as initiated in pioneering work by Cottrell. No less important was the breakthrough development of optical characterization of sectioned polycrystalline metal microstructures started by Sorby in the late 19th century and leading eventually to modern optical, x-ray and electron microscopy methods for assessments of crystal fracture surfaces, via fractography, and particularly of x-ray and electron microscopy techniques applied to quantitative characterizations of internal dislocation behaviors. A major current effort is to match computational simulations of metal deformation/fracturing behaviors with experimental measurements made over extended ranges of microstructures and over varying external conditions of stress-state, temperature and loading rate. The relation of such simulations to the development of constitutive equations for a hoped-for predictive description of material deformation/fracturing behaviors is an active topic of research. The present collection of articles provides a broad sampling of research accomplishments on the two subjects.
Download or read book Nanostructures Synthesis Functional Properties and Application written by Thomas Tsakalakos and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Advanced Study Institute on Synthesis, Functional Properties and Applications of Nanostructures, held at the Knossos Royal Village, Heraklion, Crete, Greece, July 26, 2002 - August 4, 2002, successfully reviewed the state-of-the-art of nanostructures and nanotechnology. It was concluded that Nanotechnology is widely agreed to be the research focus that will lead to the next generation of breakthroughs in science and engineering. There are three cornerstones to the expectation that Nanotechnology will yield revolutionary advances in understanding and application: • Breakthroughs in properties that arise from materials fabricated from the nanoscale. • Synergistic behavior that arise from the combination of disparate types of materials (soft vs. hard, organic vs. inorganic, chemical vs. biological vs. solid state) at the nanoscale. • Exploitation of natural (e.g. chemical and biological) assembly mechanisms that can accomplish structural control at the nanoscale. It is expected that this will lead to paradigms for assembling bio-inspired functional systems that accomplish desirable properties that are either unavailable or prohibitively expensive using top-down approaches.
Download or read book Modeling and Simulation of Thin Film Processing Volume 389 written by David J. Srolovitz and published by . This book was released on 1995-10-02 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: A diverse set of materials science communities come together in this volume to review the extraordinary progress made in the development of computer simulation and modeling techniques for the prediction of film morphology, microstructure, composition, profile and structure. These techniques are rapidly moving out of the area of academic research and into technological and production design areas of thin-film-based industries. The book is loosely organized in ascending order of modeling-length scales - from atomic, up to the entire deposition reactor. Topics include: deposition and growth modeling; film morphology and topology; film microstructure; failure mechanisms; etching; process modeling and control and reactor-scale modeling.
Download or read book Multiscale Materials Modeling for Nanomechanics written by Christopher R. Weinberger and published by Springer. This book was released on 2016-08-30 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a unique combination of chapters that together provide a practical introduction to multiscale modeling applied to nanoscale materials mechanics. The goal of this book is to present a balanced treatment of both the theory of the methodology, as well as some practical aspects of conducting the simulations and models. The first half of the book covers some fundamental modeling and simulation techniques ranging from ab-inito methods to the continuum scale. Included in this set of methods are several different concurrent multiscale methods for bridging time and length scales applicable to mechanics at the nanoscale regime. The second half of the book presents a range of case studies from a varied selection of research groups focusing either on a the application of multiscale modeling to a specific nanomaterial, or novel analysis techniques aimed at exploring nanomechanics. Readers are also directed to helpful sites and other resources throughout the book where the simulation codes and methodologies discussed herein can be accessed. Emphasis on the practicality of the detailed techniques is especially felt in the latter half of the book, which is dedicated to specific examples to study nanomechanics and multiscale materials behavior. An instructive avenue for learning how to effectively apply these simulation tools to solve nanomechanics problems is to study previous endeavors. Therefore, each chapter is written by a unique team of experts who have used multiscale materials modeling to solve a practical nanomechanics problem. These chapters provide an extensive picture of the multiscale materials landscape from problem statement through the final results and outlook, providing readers with a roadmap for incorporating these techniques into their own research.
Download or read book Crystal Plasticity Finite Element Methods written by Franz Roters and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Download or read book Fundamental Aspects of Dislocation Interactions written by G. Kostorz and published by Elsevier. This book was released on 2013-09-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III covers the papers presented at a European Research Conference on Plasticity of Materials-Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III, held on August 30-September 4, 1992 in Ascona, Switzerland. The book focuses on the processes, technologies, reactions, transformations, and approaches involved in dislocation interactions. The selection first offers information on work softening and Hall-Petch hardening in extruded mechanically alloyed alloys and dynamic origin of dislocation structures in deformed solids. Discussions focus on stress-strain behavior in relation to composition, structure, and annealing; comparison of stress-strain curves with work softening theory; sweeping and trapping mechanism; and model of dipolar wall structure formation. The text then ponders on plastic instabilities and their relation to fracture and dislocation and kink dynamics in f.c.c. metals studied by mechanical spectroscopy. The book takes a look at misfit dislocation generation mechanisms in heterostructures and evolution of dislocation structure on the interfaces associated with diffusionless phase transitions. Discussions focus on dislocation representation of a wall of elastic domains; equation of equilibrium of an elastic domain; transformation of dislocations; and theoretical and experimental background. The selection is a valuable reference for readers interested in dislocation interactions.
Download or read book Diffusion Processes in Advanced Technological Materials written by Devendra Gupta and published by Springer Science & Business Media. This book was released on 2013-01-15 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new game book for understanding atoms at play aims to document diffusion processes and various other properties operative in advanced technological materials. Diffusion in functional organic chemicals, polymers, granular materials, complex oxides, metallic glasses, and quasi-crystals among other advanced materials is a highly interactive and synergic phenomenon. A large variety of atomic arrangements are possible. Each arrangement affects the performance of these advanced, polycrystalline multiphase materials used in photonics, MEMS, electronics, and other applications of current and developing interest. This book is written by pioneers in industry and academia for engineers, chemists, and physicists in industry and academia at the forefront of today's challenges in nanotechnology, surface science, materials science, and semiconductors.
Download or read book Strengthening Mechanisms in Crystal Plasticity written by Ali Argon and published by Oxford University Press on Demand. This book was released on 2008 with total page 425 pages. Available in PDF, EPUB and Kindle. Book excerpt: Technologically important metals and alloys have been strengthened throughout history by empirical means. The scientific bases of the central mechanisms of such forms of strengthening, developed over the past several decades are presented here through mechanistic models and associated experimental results.
Download or read book Heterostructured Materials written by Xiaolei Wu and published by CRC Press. This book was released on 2021-11-24 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heterostructured (HS) materials represent an emerging class of materials that are expected to become a major research field for the communities of materials, mechanics, and physics in the next couple of decades. One of the biggest advantages of HS materials is that they can be produced by large-scale industrial facilities and technologies and therefore can be commercialized without the scaling up and high-cost barriers that are often encountered by other advanced materials. This book collects recent papers on the progress in the field of HS materials, especially their fundamental physics. The papers are arranged in a sequence of chapters that will help new researchers entering the field to have a quick and comprehensive understanding of HS materials, including the fundamentals and recent progress in their processing, characterization, and properties.
Download or read book Continuum Scale Simulation of Engineering Materials written by Dierk Raabe and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 885 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book fills a gap by presenting our current knowledge and understanding of continuum-based concepts behind computational methods used for microstructure and process simulation of engineering materials above the atomic scale. The volume provides an excellent overview on the different methods, comparing the different methods in terms of their respective particular weaknesses and advantages. This trains readers to identify appropriate approaches to the new challenges that emerge every day in this exciting domain. Divided into three main parts, the first is a basic overview covering fundamental key methods in the field of continuum scale materials simulation. The second one then goes on to look at applications of these methods to the prediction of microstructures, dealing with explicit simulation examples, while the third part discusses example applications in the field of process simulation. By presenting a spectrum of different computational approaches to materials, the book aims to initiate the development of corresponding virtual laboratories in the industry in which these methods are exploited. As such, it addresses graduates and undergraduates, lecturers, materials scientists and engineers, physicists, biologists, chemists, mathematicians, and mechanical engineers.
Download or read book Metals Abstracts written by and published by . This book was released on 1996 with total page 1628 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computer Simulations of Dislocations written by Vasily Bulatov and published by Oxford University Press. This book was released on 2006-11-02 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents a variety of methods for computer simulations of crystal defects in the form of "numerical recipes", complete with computer codes and analysis tools. By working through numerous case studies and problems, this book provides a useful starter kit for further method development in the computational materials sciences.
Download or read book The Journal of the Iron and Steel Institute written by Iron and Steel Institute and published by . This book was released on 1969 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes sect. "A survey of literature on the manufacture and properties of iron and steel, and kindred subjects" (title varies)
Download or read book Mechanical Behavior of Materials written by Marc A. Meyers and published by . This book was released on 2008 with total page 856 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes numerous examples and problems for student practice, this textbook is ideal for courses on the mechanical behaviour of materials taught in departments of mechanical engineering and materials science.
Download or read book Electron Tomography written by Joachim Frank and published by Springer Science & Business Media. This book was released on 2008-03-05 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This definitive work provides a comprehensive treatment of the mathematical background and working methods of three-dimensional reconstruction from tilt series. Special emphasis is placed on the problems presented by limitations of data collection in the transmission electron microscope. The book, extensively revised and updated, takes the reader from biological specimen preparation to three-dimensional images of the cell and its components.
