Download or read book Multiscale Modelling and Simulation of Deformation and Strength of Nanoscale Metallic Multilayer Systems written by Niaz Abdolrahim and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research is to investigate the deformation behaviors of two types of NMMs at lower length scales: 1) One dimensional Cu-Ni, Au-Ni nanowires with coherent interfaces and 2) Two dimensional Cu-Nb multilayers with incoherent interfaces.

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 Multiscale Analysis of Deformation and Failure of Materials written by Jinghong Fan and published by John Wiley & Sons. This book was released on 2011-06-28 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting cutting-edge research and development within multiscale modeling techniques and frameworks, Multiscale Analysis of Deformation and Failure of Materials systematically describes the background, principles and methods within this exciting new & interdisciplinary field. The author’s approach emphasizes the principles and methods of atomistic simulation and its transition to the nano and sub-micron scale of a continuum, which is technically important for nanotechnology and biotechnology. He also pays close attention to multiscale analysis across the micro/meso/macroscopy of a continuum, which has a broad scope of applications encompassing different disciplines and practices, and is an essential extension of mesomechanics. Of equal interest to engineers, scientists, academics and students, Multiscale Analysis of Deformation and Failure of Materials is a multidisciplinary text relevant to those working in the areas of materials science, solid and computational mechanics, bioengineering and biomaterials, and aerospace, automotive, civil, and environmental engineering. Provides a deep understanding of multiscale analysis and its implementation Shows in detail how multiscale models can be developed from practical problems and how to use the multiscale methods and software to carry out simulations Discusses two interlinked categories of multiscale analysis; analysis spanning from the atomistic to the micro-continuum scales, and analysis across the micro/meso/macro scale of continuum.

Download or read book Size Effects and Deformation Mechanisms in Nanoscale Metallic Multilayered Composites written by Firas Akasheh and published by . This book was released on 2007 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, size effects and deformation mechanisms in nanoscale metallic multilayered (NMM) composites were studied. Existing models for the prediction of the dependence of strength of NMM composites on the individual layer thickness do not capture the experimentally observed dependence. Dislocation interactions have been suggested as a significant contributor to this discrepancy. Due to the complexity and multiplicity of dislocation interaction in real systems, the study started by examining the hardening effect and implications on the dislocation structure of two known-to-be significant dislocation interactions in NMM composites. The first is the interaction between a threading dislocation and orthogonally intersection interfacial dislocations. Dislocation dynamics (DD) analysis was employed and it was found that the strongest interaction occurs when the interacting dislocations are collinear and involves annihilation reactions and the formation of 90° dislocation bends at the interfaces, as commonly observed in experiments. The strength predictions indicate a strengthen increase of about 50%; however, they do not follow the experimentally observed trend. The second interaction to study was that between a threading dislocation and parallel interfacial dislocations. A semi-analytical energetic approach was employed and it was found that parallel interactions can lead to softening effect, as well as hardening effect depending on the relative sign of the Burgers vector of the threading and the parallel dislocations. It was also found that when the Burgers vectors are collinear, the interaction is stronger. A comparison with the measured strength of real multilayered system shows that accounting for parallel interactions improves the strength predictions for an isolated glide dislocation, however that does not offer answers regarding the observed strength saturation when the individual layer thickness in the few nanometer range. Finally, large-scale DD simulations of NMM composites were performed. Such simulations naturally accounts for all the possible and complex interactions in a real system. The strength predictions of such simulations are in better qualitative agreement with experimental trends than any of the unit process. Nevertheless, more work is needed to validate the results by investigating different relaxation models to accomplish the initial dislocations structure used in subsequent loading. The simulations were also valuable in identifying dislocation mechanisms which can take place during the deformation.

Download or read book Atomistic Studies of Deformation Mechanisms in Nanoscale Multilayered Metallic Composites written by Shuai Shao and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this thesis is to understand the interaction between dislocations and various metallic interfaces in nanoscale metallic multilayers (NMM). At lower strain rates, this mean understanding the effect of interfaces to the strain hardening of the NMMs; at higher strain rates, this means the effect of the interfaces on the spallation strengths of the NMMs. NMMs possess ultra-high strength level which is owing to the interactions between single dislocations (i.e. no pile-up) and interfaces. In this thesis, aiming at the goal, using atomistic simulations several nanoscale metallic multilayers subjected to different loading conditions and strain rates are being considered.

Download or read book Trends in Nanoscale Mechanics written by Vasyl Michael Harik and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: An outstanding feature of this book is a collection of state-of-the-art reviews written by leading researchers in the nanomechanics of carbon nanotubes, nanocrystalline materials, biomechanics and polymer nanocomposites. The structure and properties of carbon nanotubes, polycrystalline metals, and coatings are discussed in great details. The book is an exceptional resource on multi-scale modelling of metals, nanocomposites, MEMS materials and biomedical applications. An extensive bibliography concerning all these topics is included. Highlights on bio-materials, MEMS, and the latest multi-scale methods (e.g., molecular dynamics and Monte Carlo) are presented. Numerous illustrations of inter-atomic potentials, nanotube deformation and fracture, grain rotation and growth in solids, ceramic coating structures, blood flows and cell adhesion are discussed. This book provides a comprehensive review of latest developments in the analysis of mechanical phenomena in nanotechnology and bio-nanotechnology.

Download or read book Handbook of Nanomaterials Properties written by Bharat Bhushan and published by Springer Science & Business Media. This book was released on 2014-03-13 with total page 1467 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials attract tremendous attention in recent researches. Although extensive research has been done in this field it still lacks a comprehensive reference work that presents data on properties of different Nanomaterials. This Handbook of Nanomaterials Properties will be the first single reference work that brings together the various properties with wide breadth and scope.

Download or read book Multiscale Modeling and Simulation of Composite Materials and Structures written by Young Kwon and published by Springer Science & Business Media. This book was released on 2007-12-04 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the state-of-the-art in multiscale modeling and simulation techniques for composite materials and structures. It focuses on the structural and functional properties of engineering composites and the sustainable high performance of components and structures. The multiscale techniques can be also applied to nanocomposites which are important application areas in nanotechnology. There are few books available on this topic.

Download or read book Multiscale Phenomena in Materials Experiments and Modeling Related to Mechanical Behavior written by Hussein M. Zbib and published by Cambridge University Press. This book was released on 2014-06-05 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years there has been increasing interest in using what are termed 'multiscale modeling' approaches to understand the effects of composition and microstructure on mechanical behavior of materials. It is of utmost importance that these modeling efforts and simulations at the various length scales be coupled with experimental work. This 2003 volume focuses on experimentally validated multiscale modeling of ductile metals and alloys. The areas of atomistic, mesoscopic and continuum modeling are featured. Topics include: multiscale modeling of plastic deformation; dislocation phenomena at the atomistic-length scale; multiscale modeling of thin films and nanoindentation; multiscale modeling of dislocation phenomena and plastic deformation; multiscale modeling of microstructures and experiments; and models and experiments in nanostructured materials.

Download or read book Computational Multiscale Modeling of Multiphase Nanosystems written by Alexander V. Vakhrushev and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "5. Numerical Simulation Of Nanosystem Properties "--"Bibliography "--"Epilogue

Download or read book The Effects of Length Scale on the Deformation Behavior of Metallic Multilayers Part II written by and published by . This book was released on 2002 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: The experimental observations described in a companion presentation of the same title by Misra et al. highlight that unique, non-bulk rolling textures are achieved in nanoscale multilayered thin films. Specifically, Cu/Nb multilayers deposited with an initial Kudjumov-Sachs orientation relation between Cu and Nb grains and with an initial individual layer thickness of 75nm preserve that relation during rolling. In contrast, samples with micron-scale individual layer thickness do not. To help understand this layer-dependent response, a crystal plasticity model is presented in which the Cu and Nb phases respond by slip on {l_brace}111{r_brace}/110 systems in the fcc Cu case, and {l_brace}110{r_brace} / 111 systems in the bcc Nb phase. Grains within each layered phase are required to plastically deform by a reduction in thickness and corresponding elongation in the rolling direction, with zero plastic strain along the transverse axis. The model also adopts the observation for nano-scale multilayers that the Kudjumov-Sachs orientation relation is preserved; in particular, the e 1 11> Cu and e1 10> Nb directions remain parallel to the interface normal during rolling. The crystal plasticity model then furnishes the minimum plastic work to deform a grain, as a function of grain orientation. For Cu grains, the plastic work is invariant of grain orientation, provided the critical resolved shear stress is uniform on all fcc slip systems. However, the corresponding plastic work in Nb grains is very dependent on grain orientation and has a strong minimum. This large anisotropy serves as a driving force for Nb grains to rotate around their 110 interface normal, toward the minimum. The resulting prediction for rolling texture in Nb layers agrees well with experimental observations in nanoscale Cu/Nb multilayers.

Download or read book Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano wear Testing written by and published by . This book was released on 2016 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 [mu]m). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally, the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.

Download or read book Investigating Deformation and Failure Mechanisms in Nanoscale Multilayer Metallic Composites written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the history of materials science there are many examples of materials discoveries that have made superlative materials; the strongest, lightest, or toughest material is almost always a goal when we invent new materials. However, often these have been a result of enormous trial and error approaches. A new methodology, one in which researchers design, from the atoms up, new ultra-strong materials for use in energy applications, is taking hold within the science and engineering community. This project focused on one particular new classification of materials; nanolaminate metallic composites. These materials, where two metallic materials are intimately bonded and layered over and over to form sheets or coatings, have been shown over the past decade to reach strengths over 10 times that of their constituents. However, they are not yet widely used in part because while extremely strong (they don't permanently bend), they are also not particularly tough (they break relatively easily when notched). Our program took a coupled approach to investigating new materials systems within the laminate field. We used computational materials science to explore ways to institute new deformation mechanisms that occurred when a tri-layer, rather than the more common bi-layer system was created. Our predictions suggested that copper-nickel or copper-niobium composites (two very common bi-layer systems) with layer thicknesses on the order of 20 nm and then layered 100's of times, would be less tough than a copper-nickel-niobium metallic composite of similar thicknesses. In particular, a particular mode of permanent deformation, cross-slip, could be activated only in the tri-layer system; the crystal structure of the other bi-layers would prohibit this particular mode of deformation. We then experimentally validated this predication using a wide range of tools. We utilized a DOE user facility, the Center for Integrated Nanotechnology (CINT), to fabricate, for the first time, these tri-layer composites. CINT formed nanolaminate composites were tested in tension, with bulge testing, using nanoindentation, and using micro-compression testing to demonstrate that the tri-layer films were indeed tougher and hardened more during deformation (they got stronger as we deformed them) than equivalent bi-layers. The seven graduate students, 4 post-docs and research faculty, and the two faculty co-PI's were able to create a collaborated computational prediction and experimental validation team to demonstrate the benefits of this class of materials to the community. The computational work crossed from atomistic to bulk simulations, and the experiments coupled form nm-scale to the mm scale; closely matching the simulations. The simulations provided viable mechanisms that explained the observed results, and new experimental results were used to push the boundaries of the simulation tools. Over the life of the 7 years of this program we proved that tri-layer nanolaminate metallic composite systems exceeded the mechanical performance of bi-layer systems if the right materials were chosen, and that the mechanism responsible for this was tied to the cross slip of dislocations. With 30 journal publications resulting from this work we have broadly disseminated this family of results to the scientific community.

Download or read book An Adaptive Multi scale Computational Method for Modeling Nonlinear Deformation in Nanoscale Materials written by Wenming Wang and published by . This book was released on 2006 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation a coupled multi-scale computational model for simulating nonlinear deformation processes in crystalline metals at finite temperatures is developed. The computational model uses the finite element method to model the coarse scale response of the material. The constitutive response in the finite element will be modeled through interatomic potentials acting on the underlying homogeneous crystal lattice that characterizes its nanostructure. An adaptive remeshing technique is proposed to automatically delineate regions of severe deformation where homogeneity of the microstructure/deformation is violated. In these regions the finite element will be replaced by a set of deformed atoms which interact with each other through the interatomic potential. The resulting coupled multi-scale model will be used to study defect generation and growth, through a computational nanoindentation experiment, in practical 2D and 3D problems.

Download or read book Mechanics of Nanoscale Metallic Multilayers written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Layered composites of Cu/Nb with incoherent interfaces achieve very high strength levels. Interfaces play a crucial role in materials strength by acting as barriers to slip. Atomistic models of Cu/Nb bilayers are used to explore the origins of this resistance. The models clearly show that dislocations near an interface experience an attraction toward the interface. This attraction is caused by shear of the interface induced by the stress field of the dislocation. More importantly, atomistic simulations also reveal that interfacial dislocations easily move in interfaces by both glide and climb. Integrating these findings into a micro-scale model, we develop a three-dimensional crystal elastic-plastic model to describe the mechanical behavior of nanoscale metallic multi layers.

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 Multiscale modeling of contact plasticity and nanoindentation in nanostructured FCC metals written by Virginie Dupont and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT Nanocrystalline thin films are materials with a grain size less than 100 nm which are commonly used to fabricate microscale electro-mechanical devices. At such small scale, nanoindentation is the only standard experimental technique to study the mechanical properties of thin films. However, it is unclear if the continuum laws commonly used in nanoindentation analysis of polycrystalline materials are still valid for nano-grained metals. It is therefore critical to better understand the behavior of nanocrystalline materials under nanoscale contact. This dissertation summarizes the results of atomistic simulations aimed at modeling the nanoindentation of nanocrystalline metal thin films for which the grain size is smaller than the indenter diameter. The nanoindentation of aluminum thin films was first studied using the Quasicontinuum method, which is a concurrent multiscale model where regions of small gradients of deformations are represented as a continuum medium by finite elements, and regions of high gradients of deformation are fully-treated atomistically. Two embeddedatom- method potentials for aluminum were used in order to study the effect of the potential on the nanoindentation behavior. The aim is to better understand the effects of a grain boundary network on the plasticity and the underlying mechanisms from an atomistic perspective. Our results show that a grain boundary network is the primary medium of plasticity at the nanoscale, via shear banding that causes flow serration. We also show that although the dislocation mechanisms are the same, the mechanisms involving grain boundaries are different depending on the interatomic potential. In a second part, abnormal grain growth in aluminum thin films under nanoindentation is studied using both the Quasicontinuum method and parallel molecular dynamics simulations. The effects of the potential, the nature of the indenter and of its size on the grain growth under nanoindentation are investigated. Our results show that the potential used, which can be related to the purity of the material, can reduce grain growth. We also show that the size and material used for the indenter both have significant effects on grain growth. More specifically, grain growth under the indenter is found to occur via atom diffusion if the indenter is of the same material as the thin film. Finally, the sample size effects were studied using parallel molecular dynamics simulations on nickel thin films and nanowires. Single crystals with different sizes are modeled in order to investigate the effects of the free boundaries as well as of the thickness of the samples. It is shown that the yield point and the incipient plasticity mechanisms are similar for all simulations. However, the hardness of the nanowires is found to decrease with the nanowire size during nanoindentation, due to the interaction of prismatic loops and dislocations with the free boundaries. This dissertation has shed light on the plastic deformation mechanisms under nanoscale contact. The results obtained will help the scientific community gain a better understanding of the behavior of nanomaterials, which will lead to the fabrication of more reliable nanodevices.