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Author: Murat Demiral
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Owing to continuous miniaturization, many modern high-technology applications such as medical and optical devices, thermal barrier coatings, electronics, micro- and nano-electro mechanical systems (MEMS and NEMS), gems industry and semiconductors increasingly use components with sizes down to a few micrometers and even smaller. Understanding their deformation mechanisms and assessing their mechanical performance help to achieve new insights or design new material systems with superior properties through controlled microstructure at the appropriate scales. However, a fundamental understanding of mechanical response in surface-dominated structures, different than their bulk behaviours, is still elusive. In this thesis, the size effect in a single-crystal Ti alloy (Ti15V3Cr3Al3Sn) is investigated. To achieve this, nanoindentation and micropillar (with a square cross-section) compression tests were carried out in collaboration with Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland. Three-dimensional finite element models of compression and indentation with an implicit time-integration scheme incorporating a strain-gradient crystal-plasticity (SGCP) theory were developed to accurately represent deformation of the studied body-centered cubic metallic material. An appropriate hardening model was implemented to account for strain-hardening of the active slip systems, determined experimentally. The optimized set of parameters characterizing the deformation behaviour of Ti alloy was obtained based on a direct comparison of simulations and the experiments. An enhanced model based on the SGCP theory (EMSGCP), accounting for an initial microstructure of samples in terms of different types of dislocations (statistically stored and geometrically necessary dislocations), was suggested and used in the numerical analysis. This meso-scale continuum theory bridges the gap between the discrete-dislocation dynamics theory, where simulations are performed at strain rates several orders of magnitude higher than those in experiments, and the classical continuum-plasticity theory, which cannot explain the dependence of mechanical response on a specimen s size since there is no length scale in its constitutive description. A case study was performed using a cylindrical pillar to examine, on the one hand, accuracy of the proposed EMSGCP theory and, on the other hand, its universality for different pillar geometries. An extensive numerical study of the size effect in micron-size pillars was also implemented. On the other hand, an anisotropic character of surface topographies around indents along different crystallographic orientations of single crystals obtained in numerical simulations was compared to experimental findings. The size effect in nano-indentation was studied numerically. The differences in the observed hardness values for various indenter types were investigated using the developed EMSGCP theory.
Author: Murat Demiral
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Owing to continuous miniaturization, many modern high-technology applications such as medical and optical devices, thermal barrier coatings, electronics, micro- and nano-electro mechanical systems (MEMS and NEMS), gems industry and semiconductors increasingly use components with sizes down to a few micrometers and even smaller. Understanding their deformation mechanisms and assessing their mechanical performance help to achieve new insights or design new material systems with superior properties through controlled microstructure at the appropriate scales. However, a fundamental understanding of mechanical response in surface-dominated structures, different than their bulk behaviours, is still elusive. In this thesis, the size effect in a single-crystal Ti alloy (Ti15V3Cr3Al3Sn) is investigated. To achieve this, nanoindentation and micropillar (with a square cross-section) compression tests were carried out in collaboration with Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland. Three-dimensional finite element models of compression and indentation with an implicit time-integration scheme incorporating a strain-gradient crystal-plasticity (SGCP) theory were developed to accurately represent deformation of the studied body-centered cubic metallic material. An appropriate hardening model was implemented to account for strain-hardening of the active slip systems, determined experimentally. The optimized set of parameters characterizing the deformation behaviour of Ti alloy was obtained based on a direct comparison of simulations and the experiments. An enhanced model based on the SGCP theory (EMSGCP), accounting for an initial microstructure of samples in terms of different types of dislocations (statistically stored and geometrically necessary dislocations), was suggested and used in the numerical analysis. This meso-scale continuum theory bridges the gap between the discrete-dislocation dynamics theory, where simulations are performed at strain rates several orders of magnitude higher than those in experiments, and the classical continuum-plasticity theory, which cannot explain the dependence of mechanical response on a specimen s size since there is no length scale in its constitutive description. A case study was performed using a cylindrical pillar to examine, on the one hand, accuracy of the proposed EMSGCP theory and, on the other hand, its universality for different pillar geometries. An extensive numerical study of the size effect in micron-size pillars was also implemented. On the other hand, an anisotropic character of surface topographies around indents along different crystallographic orientations of single crystals obtained in numerical simulations was compared to experimental findings. The size effect in nano-indentation was studied numerically. The differences in the observed hardness values for various indenter types were investigated using the developed EMSGCP theory.
Author: George Z. Voyiadjis
Publisher: Elsevier
ISBN: 0128177675
Category : Technology & Engineering
Languages : en
Pages : 405
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Book Description
Gradient-Enhanced Continuum Plasticity provides an expansive review of gradient-enhanced continuum plasticity from the initial stage to current research trends in experimental, theoretical, computational and numerical investigations. Starting with an overview of continuum mechanics and classical plasticity, the book then delves into concise lessons covering basic principles and applications, such as outlining the use of the finite element method to solve problems with size effects, mesh sensitivity and high velocity impact loading. All major theories are explored, providing readers with a guide to understanding the various concepts of and differences between an array of gradient-enhanced continuum plasticity models. - Outlines the concepts of, and differences between, various gradient-enhanced continuum plasticity models - Provides guidance on problem-solving for size effects, mesh-sensitivity tests and thermo-mechanical coupling - Reviews experimental, numerical and theoretical issues in gradient-enhanced continuum plasticity - Describes micromechanical aspects from experimental observations
Author: Franz Roters
Publisher: John Wiley & Sons
ISBN: 3527642099
Category : Technology & Engineering
Languages : en
Pages : 188
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Book Description
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.
Author: Uday Basheer Al-Naib
Publisher: BoD – Books on Demand
ISBN: 1789846862
Category : Technology & Engineering
Languages : en
Pages : 204
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Book Description
Metallurgy is a field of material science and engineering that studies the chemical and physical behavior of metallic elements, intermetallic compounds, and their mixtures, which are called alloys. These metals are widely used in this kind of engineering because they have unique combinations of mechanical properties (strength, toughness, and ductility) as well as special physical characteristics (thermal and electrical conductivity), which cannot be achieved with other materials. In addition to thousands of traditional alloys, many exciting new materials are under development for modern engineering applications. Metallurgical engineering is an area concerned extracting minerals from raw materials and developing, producing, and using mineral materials. It is based on the principles of science and engineering, and can be divided into mining processes, which are concerned with the extraction of metals from their ores to make refined alloys, and physical metallurgy, which includes the fabrication, alloying, heat treatment, joining and welding, corrosion protection, and different testing methods of metals. Conventional metal forming/shaping techniques include casting and forging, which remains an important processing route. Electrodeposition is one of the most used methods for metal and metallic alloy film preparation in many technological processes. Alloy metal coatings offer a wider range of properties than those obtained by a single metal film and can be applied to improve the properties of the substrate/coating system. This book covers a wide range of topics related to recent advancements in metallurgical engineering and electrodeposition such as metallurgy forming, structure, microstructure properties, testing and characterizations, and electrodeposition techniques. It also highlights the progress of metallurgical engineering, the ferrous and non-ferrous materials industries, and the electrodeposition of nanomaterials and composites.
Author: Vadim V. Silberschmidt
Publisher: Springer
ISBN: 3319171186
Category : Technology & Engineering
Languages : en
Pages : 205
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Book Description
The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc. The last decades have seen a large extension of types of materials employed in various applications. In many cases these materials demonstrate mechanical properties and performance that vary significantly from those of their traditional counterparts. Such uniqueness is sought – or even specially manufactured – to meet increased requirements on modern components and structures related to their specific use. As a result, mechanical behaviors of these materials under different loading and environmental conditions are outside the boundaries of traditional mechanics of materials, presupposing development of new characterization techniques, theoretical descriptions and numerical tools. The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.
Author: Atul Tiwari
Publisher: John Wiley & Sons
ISBN: 1119084520
Category : Technology & Engineering
Languages : en
Pages : 708
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Book Description
Research in the area of nanoindentation has gained significant momentum in recent years, but there are very few books currently available which can educate researchers on the application aspects of this technique in various areas of materials science. Applied Nanoindentation in Advanced Materials addresses this need and is a comprehensive, self-contained reference covering applied aspects of nanoindentation in advanced materials. With contributions from leading researchers in the field, this book is divided into three parts. Part one covers innovations and analysis, and parts two and three examine the application and evaluation of soft and ceramic-like materials respectively. Key features: A one stop solution for scholars and researchers to learn applied aspects of nanoindentation Contains contributions from leading researchers in the field Includes the analysis of key properties that can be studied using the nanoindentation technique Covers recent innovations Includes worked examples Applied Nanoindentation in Advanced Materials is an ideal reference for researchers and practitioners working in the areas of nanotechnology and nanomechanics, and is also a useful source of information for graduate students in mechanical and materials engineering, and chemistry. This book also contains a wealth of information for scientists and engineers interested in mathematical modelling and simulations related to nanoindentation testing and analysis.
Author: R.M. Latanision
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Guruprasad Padubidri Janardhanachar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The goal of this research work is to further the understanding of crystal plasticity, particularly at reduced structural and material length scales. Fundamental understanding of plasticity is central to various challenges facing design and manufacturing of materials for structural and electronic device applications. The development of microstructurally tailored advanced metallic materials with enhanced mechanical properties that can withstand extremes in stress, strain, and temperature, will aid in increasing the efficiency of power generating systems by allowing them to work at higher temperatures and pressures. High specific strength materials can lead to low fuel consumption in transport vehicles. Experiments have shown that enhanced mechanical properties can be obtained in materials by constraining their size, microstructure (e.g. grain size), or both for various applications. For the successful design of these materials, it is necessary to have a thorough understanding of the influence of different length scales and evolving microstructure on the overall behavior. In this study, distinction is made between the effect of structural and material length scale on the mechanical behavior of materials. A length scale associated with an underlying physical mechanism influencing the mechanical behavior can overlap with either structural length scales or material length scales. If it overlaps with structural length scales, then the material is said to be dimensionally constrained. On the other hand, if it overlaps with material length scales, for example grain size, then the material is said to be microstructurally constrained. The objectives of this research work are: (1) to investigate scale and size effects due to dimensional constraints; (2) to investigate size effects due to microstructural constraints; and (3) to develop a size dependent hardening model through coarse graining of dislocation dynamics. A discrete dislocation dynamics (DDD) framework where the scale of analysis is intermediate between a fully discretized (e.g. atomistic) and fully continuum is used for this study. This mesoscale tool allows to address all the stated objectives of this study within a single framework. Within this framework, the effect of structural and the material length scales are naturally accounted for in the simulations and need not be specified in an ad hoc manner, as in some continuum models. It holds the promise of connecting the evolution of the defect microstructure to the effective response of the crystal. Further, it provides useful information to develop physically motivated continuum models to model size effects in materials. The contributions of this study are: (a) provides a new interpretation of mechanical size effect due to only dimensional constraint using DDD; (b) a development of an experimentally validated DDD simulation methodology to model Cu micropillars; (c) a coarse graining technique using DDD to develop a phenomenological model to capture size effect on strain hardening; and (d) a development of a DDD framework for polycrystals to investigate grain size effect on yield strength and strain hardening.
Author: R.M. Latanision
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 972
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Book Description
John Keats, writing to Fanny Brawne [1], said "I long to believe in immortality ••••• I wish to believe in immortality - I wish to live with you forever". So much of this talk will be concerned with the ductile behaviour of crystals, plasticity in its narrower sense. We shall consider a crystal which is deforming by slip, and shall expose a surface in this crystal. We first think of the sur face as a simple mathematical cut along a low-index plane. Then we allow for the relaxation of the newly-exposed atoms, and for surface irregularities, and we consider the effect of lattice va cancies which can enter at the surface. We consider the effect of dissolving off the surface layers, either intermittently or contin uously. Then the effects of adsorption or oxidation by normal con stituents of the atmosphere must be considered, the effects of sur face alloying, and finally those of special surface-active agents. But "All/Life death does end and each day dies with sleep" [2], and plasticity in its broader sense includes the fracture ~'1hich term inates flow. Here there is a bewildering array of effects. The medium in which the crystal flows may enhance its ductility enor mously, or it may cause it to break almost without plastic deform ation, or under a load which it has already supported.
Author: Angelos P. Markopoulos
Publisher: CRC Press
ISBN: 1315305259
Category : Technology & Engineering
Languages : en
Pages : 271
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Book Description
Modeling and machining are two terms closely related. The benefits of the application of modeling on machining are well known. The advances in technology call for the use of more sophisticated machining methods for the production of high-end components. In turn, more complex, more suitable, and reliable modeling methods are required. This book pertains to machining and modeling, but focuses on the special aspects of both. Many researchers in academia and industry, who are looking for ways to refine their work, make it more detailed, increase their accuracy and reliability, or implement new features, will gain access to knowledge in this book that is very scare to find elsewhere.
