Download or read book Resolving the Contribution of Interfaces in the Deformation of Nanocrystalline Copper with Atomistic Simulations written by and published by . This book was released on 2012 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantifying the Influence of Twin Boundaries on the Deformation of Nanocrystalline Copper Using Atomistic Simulations written by and published by . This book was released on 2014 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade, numerous efforts have sought to understand the influence of twin boundaries on the behavior of polycrystalline materials. Early results suggested that twin boundaries within nanocrystalline face-centered cubic metals have a considerable effect on material behavior by altering the activated deformation mechanisms. In this work, we employ molecular dynamics simulations to elucidate the role of twin boundaries on the deformation of 100 columnar nanocrystalline copper at room temperature under uniaxial strain. We leverage non-local kinematic metrics, formulated from continuum mechanics theory, to compute atomically-resolved rotational and strain fields during plastic deformation. These results are then utilized to compute the distribution of various nanoscale mechanisms during straining, and quantitatively resolve their contribution to the total strain accommodation within the microstructure, highlighting the fundamental role of twin boundaries. Our results show that nanoscale twins influence nanocrystalline copper by altering the cooperation of fundamental deformation mechanisms and their contributed role in strain accommodation, and we present new methods for extracting useful information from atomistic simulations. The simulation results suggest a tension-compression asymmetry in the distribution of deformation mechanisms and strain accommodation by either dislocations or twin boundary mechanisms. In highly twinned microstructures, twin boundary migration can become a significant deformation mode, in comparison to lattice dislocation plasticity in non-twinned columnar microstructures, especially during compression.
Download or read book Atomistic Simulations of Defect Nucleation and Free Volume in Nanocrystalline Materials written by Garritt J. Tucker and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomistic simulations are employed in this thesis to investigate defect nucleation and free volume of grain boundaries and nanocrystalline materials. Nanocrystalline materials are of particular interest due to their improved mechanical properties and alternative strain accommodation processes at the nanoscale. These processes, or deformation mechanisms, within nanocrystalline materials are strongly dictated by the larger volume fraction of grain boundaries and interfaces due to smaller average grain sizes. The behavior of grain boundaries within nanocrystalline materials is still largely unknown. One reason is that experimental investigation at this scale is often difficult, time consuming, expensive, or impossible with current resources. Atomistic simulations have shown the potential to probe fundamental behavior at these length scales and provide vital insight into material mechanisms. Therefore, work conducted in this thesis will utilize atomistic simulations to explore structure-property relationships of face-centered-cubic grain boundaries, and investigate the deformation of nanocrystalline copper as a function of average grain size. Volume-averaged kinematic metrics are formulated from continuum mechanics theory to estimate nonlocal deformation fields and probe the nanoscale features unique to strain accommodation mechanisms in nanocrystalline metals. The kinematic metrics are also leveraged to explore the tensile deformation of nanocrystalline copper at 10K. The distribution of different deformation mechanisms is calculated and we are able to partition the role of competing mechanisms in the overall strain of the nanocrystalline structure as a function of grain size. Grain boundaries are observed to be influential in smaller grained structures, while dislocation glide is more influential as grain size increases. Under compression, however, the resolved compressive normal stress on interfaces hinders grain boundary plasticity, leading to a tension-compression asymmetry in the strength of nanocrystalline copper. The mechanisms responsible for the asymmetry are probed with atomistic simulations and the volume-averaged metrics. Finally, the utility of the metrics in capturing nonlocal nanoscale deformation behavior and their potential to inform higher-scaled models is discussed.
Download or read book Investigating the Mechanics and Deformation in Multi layered Copper and Niobium Nanowires Using Atomistic Simulations written by Dana Jaclynn Bronen and published by . This book was released on 2016 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis employed atomistic simulations to investigate the role of layer thickness in multi-layered metallic nanowires. Nanowires are of great interest due to their unique mechanical properties and deformation mechanisms. The mechanisms controlling nanowire deformation are highly dependent on the volume fraction and interface orientation between materials within these structures. The behavior all of these variables have on nanowires still widely unknown. Experimental research has not been investigated greatly because of the difficulty, expense and time consuming nature of the fabrication and testing processes. It has been shown that atomistic simulations can probe these fundamental questions while providing vital insight on deformation mechanisms. Therefore, the work performed will exploit atomistic simulations to investigate the deformation mechanisms associated with multi-layered copper and niobium metallic nanowires. An embedded atom method potential was used during molecular statics to generate the alternating face-centered cubic and body-centered cubic interface. The potential was later employed during molecular dynamics compression simulations to accurately portray the behavior of individual atoms. These structures are rst molded into nanowire structures before deformation at 10K under uniaxial compression at a constant strain rate to evaluate the role of layer thickness and interface. The presence of interfaces (e.g., grain boundaries and free surface), and their role in dislocation nucleation within con ned volumes (i.e., nanowires) was then evaluated. Additionally, nanolaminate simulations with identical compositions were compressed using the same parameters to provide a comparison to structures without free surfaces. The simulation data was later applied to provide insightful results on atomic scale deformation. Plastic deformation mechanisms common to nanowires and nanolaminates were analyzed with various metric criteria. The unique deformation mechanisms within each layer and the interaction with the interface drove the compression response. Deformation induced dislocation movement and twin boundary development were specific to individual material layers. Therefore, these mechanisms were responsible for the differing material properties across all combinations. Finally, the rule of mixtures was evaluated to determine whether the unique nanoscale mechanisms were accounted for in the hypothesized material properties.
Download or read book Damage Tolerance and Mechanics of Interfaces in Nanostructured Metals written by Daniel J. Foley and published by . This book was released on 2017 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The concept of interface driven properties in crystalline metals has been one of the most intensely discussed topics in materials science for decades. Since the 1980s researchers have been exploring the concept of grain boundary engineering as route for tuning properties such as fracture toughness and irradiation resistance. This is especially true in ultra-fine grained and nanocrystalline materials where grain boundary mediated properties become dominant. More recently, materials composed of hierarchical nanostructures, such as amorphous-crystalline nanolaminates, have attracted considerable attention due to their favorable properties, ease of manufacture and highly tunable microstructure. While both grain boundary engineering and hierarchical nanostructures have shown promise there are still questions remaining regarding the role of specific attributes of the microstructure (such as grain boundaries, grain/layer size and inter/intralayer morphology) in determining material properties. This thesis attempts to address these questions by using atomistic simulations to perform deformation and damage loading studies on a series of nanolaminate and bicrystalline structures. During the course of this thesis the roles of layer thickness, interlayer structure and interlayer chemistry on the mechanical properties of Ni-NiX amorphous-crystalline nanolaminates were explored using atomistic simulations. This thesis found that layer thickness/thickness ratio and amorphous layer chemistry play a crucial role in yield strength and Young's modulus. Analysis of the deformation mechanisms at the atomic scale revealed that structures containing single crystalline, crystalline layers undergo plastic deformation when shear transformation zones form in the amorphous layer and impinge on the amorphous-crystalline interface, leading to dislocation emission. However, structures containing nanocrystalline, crystalline layers (both equiaxed and columnar nanocrystalline) undergo plastic deformation through a combination of grain boundary sliding and grain boundary mediated dislocation nucleation. Since grain boundaries were found to play a critical role as sources and sinks for dislocations in amorphous-crystalline nanolaminates a follow-up study on the effect of grain boundary character on damage accumulation/accommodation in copper symmetric tilt grain boundaries was performed. This study found that grain boundaries will become saturated with damage, a state where grain boundary energy and grain boundary free volume oscillate about a plateau during continuous defect loading (vacancy, interstitial and frenkel pair loading were all considered). Further, grain boundary character (specifically equilibrium grain boundary energy) was strongly correlated to the damage accommodation behavior of grain boundaries in copper. Finally, a study that attempted to link grain boundary damage saturation behavior to variations in grain boundary mechanical properties was performed. This study found no direct relationships between grain boundary damage saturation behavior and variations in grain boundary properties. The results of this thesis provide researchers with several strategies for tuning the properties of amorphous-crystalline nanolaminates. These strategies include manipulated bulk attributes such as layer thickness and morphology as well as manipulation of microscale attributes such as grain boundary engineering. Finally, this thesis provides valuable insight into the damage loading/accommodation behavior of FCC symmetric tilt grain boundaries.
Download or read book Atomistic and Continuum Modeling of Nanocrystalline Materials written by Laurent Capolungo and published by Springer Science & Business Media. This book was released on 2010-03-17 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomistic and Continuum Modeling of Nanocrystalline Materials develops a complete and rigorous state-of-the-art analysis of the modeling of the mechanical behavior of nanocrystalline (NC) materials. Among other key topics, the material focuses on the novel techniques used to predict the behavior of nanocrystalline materials. Particular attention is given to recent theoretical and computational frameworks combining atomistic and continuum approaches. Also, the most relevant deformation mechanisms governing the response of nanocrystalline materials are addressed and discussed in correlation with available experimental data.
Download or read book Atomistic Simulation Studies of Grain Boundary Segregation and Strengthening Mechanisms in Nanocrystalline Nanotwinned Silver Copper Alloys written by Xing Ke and published by . This book was released on 2019 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silver (Ag) is a precious metal with a low stacking fault energy that is known to form copious nanoscale coherent twin boundaries during magnetron sputtering synthesis. Nanotwinned Ag metals are potentially attractive for creating new interface-dominated nanomaterials with unprecedented mechanical and physical properties. Grain-boundary segregation of solute elements has been found to increase the stability of interfaces and hardness of nanocrystalline metals. However, heavily alloying inevitably complicates the underlying deformation mechanisms due to the hardening effects of solutes, or a change of stacking fault energies in Ag caused by alloying. For the above reasons, we developed a microalloying (or doping) strategy by carefully selecting Cu as the primary impurity--a solute that is predicted to have no solid-solution strengthening effect in Ag when its content is below 3.0 wt.%. Neither will Cu affect the stacking fault energy of Ag at a concentration
Download or read book Atomistic Simulations Based Study of Nanoscale Deformation in Copper written by Ajith K. Ukwattage and published by . This book was released on 2014 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Mechanistic Role of Grain Boundaries on the Strength and Deformation of Nanocrystalline Metals Using Atomistic Simulations written by Satish Rajaram and published by . This book was released on 2019 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline (NC) materials, defined structurally by having average grain sizes less than 100nm, exhibit a number of enhanced mechanical properties such as ultrahigh strength, improved wear resistance and greater resistance to fatigue crack initiation compared to coarser grained polycrystalline (PC) materials. NC materials exhibit these improved properties, in part, due to the increased grain boundary (GB) volume fraction. NC materials strength increases with decreasing grain size, known as the Hall-Petch (HP) effect often resulting in a peak strength between 10-20nm. Studies have shown that NC materials strength decreases due to the shift from dislocation-dominant to GB-dominant deformation mechanisms in the plastic flow regime as average grain size decreases below 10-20nm. While the potential improved properties are of interest, the application of NC materials are hindered due to microstructural instability i.e., grain growth to reduce the total energy of the system, thus degrading desired mechanical properties. Numerous studies have looked at avenues to stabilize NC microstructure, namely through thermodynamics and kinetics, alloying has been one significant strategy used to stabilize NC materials. As these processes are used to stabilize NC microstructures to thermally-induce grain growth, they add additional uncertainty as the deformation and GB behavior of pure NC materials are still not fully understood. Experimental work on NC materials is difficult due to the length scale being investigated as it is difficult to manufacture and can be time consuming to analyze with current technology. Atomistic simulations have shown the potential to investigate fundamental behavior at the nanoscale and provide important insight in the mechanisms that drive the mechanical behavior of NC materials. This thesis will use atomistic simulations to study the structure-property relationship of face-centered-cubic (fcc) metals by focusing on GBs to investigate the strength of NC nickel. During the course of this thesis, four aspects that govern NC behavior will be studied, yielding, plasticity, thermal effects, and GB disorder to elucidate deeper insight into the underlying deformation mechanisms that control the strength of FCC NC metals i.e., flow stress, in the grain size regime 6 to 20nm.
Download or read book Shear Deformation of Amorphous and Nanocrystalline Copper Microstructures Via Atomistic Simulation written by David R. Gandy and published by . This book was released on 2007 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the well-known Hall-Petch behavior, yield and flow stresses in polycrystalline metals increase with a decrease in grain size. As grain size continues to decrease, mechanical strength peaks. As grain size further decreases, mechanical strength begins to decrease. As grain size approaches zero, the total structure is composed of an increasingly high percentage of grain boundaries, which exhibit the properties of an amorphous structure. Molecular dynamics simulations, with the goal of exploring this behavior, were performed on nanocrystalline and amorphous microstructures using the embedded atom potential developed by Mishin et al. A 0.2 shear strain was applied to each of the nanocrystalline and amorphous samples. From these simulations, we have observed the inverse Hall-Petch behavior of nanocrystalline structures. We have also shown that the amorphous structure as zero grain size is reasonable as the limiting case for the inverse Hall-Petch trends in nanocrystalline structures.
Download or read book MY RESEARCH PUBLICATIONS PROJECTS LIST ENGINEERING SOCIAL WORLD ONE GOVERNMENT SCIENCE LAWS MODIFIED COMBINED TURBINE GENERATOR Niagara source FOR ALL written by Prof.Dr.MURUGAVEL.Rathinam and published by Prof.Dr.MURUGAVEL.Rathinam. This book was released on 2024-08-31 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: MY RESEARCH PUBLICATIONS,PROJECTS LIST(ENGINEERING,SOCIAL, WORLD ONE GOVERNMENT),SCIENCE LAWS MODIFIED,COMBINED TURBINE GENERATOR,Niagara source(FOR ALL)
Download or read book Proceedings of the National Academy of Sciences of the United States of America written by National Academy of Sciences (U.S.) and published by . This book was released on 2007 with total page 1280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Metals Abstracts written by and published by . This book was released on 1999-04 with total page 972 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Mechanics of Materials written by Siegfried Schmauder and published by Springer. This book was released on 2019-05-09 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive reference for the studies of mechanical properties of materials over multiple length and time scales. The topics include nanomechanics, micromechanics, continuum mechanics, mechanical property measurements, and materials design. The handbook employs a consistent and systematic approach offering readers a user friendly reference ideal for frequent consultation. It is appropriate for an audience at of graduate students, faculties, researchers, and professionals in the fields of Materials Science, Mechanical Engineering, Civil Engineering, Engineering Mechanics, and Aerospace Engineering.
Download or read book Classical And Quantum Dynamics In Condensed Phase Simulations Proceedings Of The International School Of Physics written by Bruce J Berne and published by World Scientific. This book was released on 1998-06-17 with total page 881 pages. Available in PDF, EPUB and Kindle. Book excerpt: The school held at Villa Marigola, Lerici, Italy, in July 1997 was very much an educational experiment aimed not just at teaching a new generation of students the latest developments in computer simulation methods and theory, but also at bringing together researchers from the condensed matter computer simulation community, the biophysical chemistry community and the quantum dynamics community to confront the shared problem: the development of methods to treat the dynamics of quantum condensed phase systems.This volume collects the lectures delivered there. Due to the focus of the school, the contributions divide along natural lines into two broad groups: (1) the most sophisticated forms of the art of computer simulation, including biased phase space sampling schemes, methods which address the multiplicity of time scales in condensed phase problems, and static equilibrium methods for treating quantum systems; (2) the contributions on quantum dynamics, including methods for mixing quantum and classical dynamics in condensed phase simulations and methods capable of treating all degrees of freedom quantum-mechanically.
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.
