Download or read book Improving Atomistic Simulations to Predict Deformation and Fracture written by Kristopher Learion Baker and published by . This book was released on 2012 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomistic simulations can illuminate detailed mechanisms of brittle and ductile fracture and plasticity. However, there are many limitations to these simulations like short timescales, small spatial scales, and limitations of the discretization. Using molecular dynamics (MD) and multiscale methods, adaptations can be made to allow MD to answer problems relevant to engineers. In the first of three examples, MD is adapted to simulate brittle fracture by changing the discretization and allowing permanent damage between particles. By changing the discretization, specific mechanisms inherent to MD can be suppressed to allow accurate, macroscopic simulations of dynamic fragmentation of brittle materials. Second, the timescale available to MD is extended in a concurrent multiscale method (CADD) combined with accelerated MD. This combined approach allows for microseconds of simulation time at experimentally achievable loading rates. The method is applied to crack opening in aluminum alloys, and the effect of the loading rate on crack growth mechanisms is observed. From the results, it is clear that crack growth mechanisms depend greatly on the rate of the far-field loading. Third, the effect of aging on fatigue crack growth is studied by varying the resistance to dislocation motion in the dislocation dynamics region of CADD. Only in a multiscale simulation like CADD, can dislocation pileups reaching microns into the material interact with the atomic-scale mechanisms at a crack tip. The results of the simulations indicated that increasing the friction force raises the fatigue crack threshold. Also, a transition from stage I fatigue crack growth to stage II fatigue crack growth occurs by dislocations shielding dislocation nucleation on the primary slip plane. These observations support the conclusion that the fatigue crack growth threshold is controlled by the spacing between obstacles to dislocation glide, which is consistent with experimental observations.
Download or read book Atomistic Simulations of Deformation in Metallic Nanolayered Composites written by Sixie Huang and published by . This book was released on 2019 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The mechanical behavior of Metallic Nanolayered Composites (MNCs) is governed by their underlying microstructure. In this dissertation, the roles of the interlayer spacing (grain size, d) and the intralayer biphase spacing (layer thickness, h) on mechanical response of Cu/Nb MNCs are examined by Molecular Dynamics (MD) simulations. The study of the strength of MNCs show that small changes in both d and h play a profound role in the relative plastic contributions from grain boundary sliding and dislocation glide. The interplay of d and h leads to a very broad transition region from grain boundary sliding dominated flow, where the strength of the material is weak and insensitive to changes in h, to grain boundary dislocation emission and glide dominated flow, where the strength of the material is strong and sensitive to changes in h. The study of the fracture behavior of MNCs shows that cracks in Cu and Nb layers may exhibit different propagation paths and distances under the same external loading. Interfaces can improve the fracture resistance of the Nb layer in Cu/Nb MNCs by providing mobile dislocation sources to generate the plastic strain at the crack tip necessary for crack blunting. Increasing the layer thickness can further enhance the fracture resistance of both Cu and Nb layers, since the critical stress for activating dislocation motion decreases with increasing the layer thickness. A novel atomistic-informed interface-dislocation dynamics (I-DD) model has been developed to study Metal-Ceramic Nanolayered Composites (MCNCs) based on the key deformation process and microstructure features revealed by MD simulations. The I-DD predicted results match well with the prior experimental results where both yield stress and strain hardening rate increase as the layer thickness decreases. This I-DD model shows great potential in predicting and optimizing the mechanical properties of MNCs"--Abstract, page iv.
Download or read book Multiscale Materials Modeling written by Siegfried Schmauder and published by Walter de Gruyter GmbH & Co KG. This book was released on 2016-08-22 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents current spatial and temporal multiscaling approaches of materials modeling. Recent results demonstrate the deduction of macroscopic properties at the device and component level by simulating structures and materials sequentially on atomic, micro- and mesostructural scales. The book covers precipitation strengthening and fracture processes in metallic alloys, materials that exhibit ferroelectric and magnetoelectric properties as well as biological, metal-ceramic and polymer composites. The progress which has been achieved documents the current state of art in multiscale materials modelling (MMM) on the route to full multi-scaling. Contents: Part I: Multi-time-scale and multi-length-scale simulations of precipitation and strengthening effects Linking nanoscale and macroscale Multiscale simulations on the coarsening of Cu-rich precipitates in α-Fe using kinetic Monte Carlo, Molecular Dynamics, and Phase-Field simulations Multiscale modeling predictions of age hardening curves in Al-Cu alloys Kinetic Monte Carlo modeling of shear-coupled motion of grain boundaries Product Properties of a two-phase magneto-electric composite Part II: Multiscale simulations of plastic deformation and fracture Niobium/alumina bicrystal interface fracture Atomistically informed crystal plasticity model for body-centred cubic iron FE2AT ・ finite element informed atomistic simulations Multiscale fatigue crack growth modeling for welded stiffened panels Molecular dynamics study on low temperature brittleness in tungsten single crystals Multi scale cellular automata and finite element based model for cold deformation and annealing of a ferritic-pearlitic microstructure Multiscale simulation of the mechanical behavior of nanoparticle-modified polyamide composites Part III: Multiscale simulations of biological and bio-inspired materials, bio-sensors and composites Multiscale Modeling of Nano-Biosensors Finite strain compressive behaviour of CNT/epoxy nanocomposites Peptide・zinc oxide interaction
Download or read book Starch Based Materials in Food Packaging written by Silvia Elena Barbosa and published by Academic Press. This book was released on 2017-06-14 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starch-Based Materials in Food Packaging: Processing, Characterization and Applications comprises an experimental approach related to the processing and characterization of biopolymers derived from different starches. The book includes fundamental knowledge and practical applications, and it also covers valuable experimental case studies. The book not only provides a comprehensive overview concerning biodegradable polymers, but also supplies the new trends in their applications in food packaging. The book is focused toward an ecological proposal to partially replace synthetics polymers arising from non-renewable sources for specific applications. This tender implies the protection of natural resources. Thus, the use of starch as feedstock to develop biodegradable materials is a good and promissory alternative. With the contributions and collaboration of experts in the development and study of starch based materials, this book demonstrates the versatility of this polysaccharide and its potential use. Brings the latest advances in the development of biomaterials from different starches, applying several technologies at laboratory and semi-industrial scales Examines the effect of formulations and processing conditions on structural and final properties of starch-based materials (blends and composites) Discusses the potential applications of starch materials in different fields, especially in food packaging Includes chapters on active and intelligent food packages
Download or read book Atomistic Simulations of Defect Nucleation and Intralayer Fracture in Molybdenum Disulphide MoS3 During Nanoindentation written by James A. Stewart and published by . This book was released on 2012 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molybdenum disulphide (MoS2) is a layered, hexagonal crystal that has a very low coefficient of friction. Due to this low coefficient of friction, MoS2 has become a well-known solid lubricant and liquid lubricant additive. As such, nanoparticles of MoS2 have been proposed as an additive to traditional liquid lubricants to provide frictional properties that are sensitive to different temperature and pressure regimes. However, to properly design these MoS2 nanoparticles to be sensitive to different temperature and pressure regimes, it is necessary to understand the mechanical response of crystalline MoS2 under mechanical loading. Specifically, the fundamental mechanism associated with the nucleation and interaction of defects as well as intralayer fracture. This thesis addressed the mechanical response of crystalline MoS2 via contact deformation (nanoindentation) simulations, which is representative of the loading conditions experienced by these nanoparticles during synthesis and application. There are two main tasks to this thesis. First, a Mo-S interatomic potential (a combination of the reactive empirical bond-order (REBO) interatomic potential and the Lennard-Jones 12-6 interatomic potential) that has been parameterized specifically to investigate the tribological properties of MoS2 was implemented into the classical molecular simulation package, LAMMPS, and refined to provide improved predictions for the mechanical properties of MoS2 via molecular statics calculations. Second, using this newly implemented interatomic potential, molecular statics calculations were performed to investigate the mechanical response of MoS2 via nanoindentation with specific focus on the nucleation of defects. Nanoindentation force - displacement curves were compared to the Hertzian contact theory prediction. It was shown that MoS2 does not follow the Hertzian prediction due it anisotropic nature. In addition, it was shown that the initial sudden force drop event in the force - displacement curves corresponds to plastic deformation. It was hypothesized that the mechanism associated with plastic failure of MoS 2 was the occurrence of broken bonds. However, it was proven that this initial plastic yield does not correspond to the occurrence of broken bonds in the MoS2 lattice; instead, a permanent slip occurred within or between the MoS2 layers.
Download or read book Forcefields for Atomistic Scale Simulations Materials and Applications written by Akarsh Verma and published by Springer Nature. This book was released on 2022-08-19 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the forcefields/interatomic potentials that are used in the atomistic-scale and molecular dynamics simulations. It covers mechanisms, salient features, formulations, important aspects and case studies of various forcefields utilized for characterizing various materials (such as nuclear materials and nanomaterials) and applications. This book gives many help to students and researchers who are studying the forcefield potentials and introduces various applications of atomistic-scale simulations to professors who are researching molecular dynamics.
Download or read book Advances in Interdisciplinary Mathematical Research written by Bourama Toni and published by Springer Science & Business Media. This book was released on 2014-07-08 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the invited contributions to the Spring 2012 seminar series at Virginia State University on Mathematical Sciences and Applications. It is a thematic continuation of work presented in Volume 24 of the Springer Proceedings in Mathematics & Statistics series. Contributors present their own work as leading researchers to advance their specific fields and induce a genuine interdisciplinary interaction. Thus all articles therein are selective, self-contained, and are pedagogically exposed to foster student interest in science, technology, engineering and mathematics, stimulate graduate and undergraduate research, as well as collaboration between researchers from different areas. The volume features new advances in mathematical research and its applications: anti-periodicity; almost stochastic difference equations; absolute and conditional stability in delayed equations; gamma-convergence and applications to block copolymer morphology; the dynamics of collision and near-collision in celestial mechanics; almost and pseudo-almost limit cycles; rainbows in spheres and connections to ray, wave and potential scattering theory; null-controllability of the heat equation with constraints; optimal control for systems subjected to null-controllability; the Galerkin method for heat transfer in closed channels; wavelet transforms for real-time noise cancellation; signal, image processing and machine learning in medicine and biology; methodology for research on durability, reliability, damage tolerance of aerospace materials and structures at NASA Langley Research Center. The volume is suitable and valuable for mathematicians, scientists and research students in a variety of interdisciplinary fields, namely physical and life sciences, engineering and technology including structures and materials sciences, computer science for signal, image processing and machine learning in medicine.
Download or read book Shape Casting written by Murat Tiryakioğlu and published by Springer. This book was released on 2019-02-08 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a collection of papers on the science, engineering, and technology of shape casting, with contributions from researchers worldwide. Among the topics that are addressed are the structure-property-performance relationships, modeling of casting processes, and the effect of casting defects on the mechanical properties of cast alloys.
Download or read book The Physics of Deformation and Fracture of Polymers written by A. S. Argon and published by Cambridge University Press. This book was released on 2013-03-07 with total page 535 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physical, mechanism-based presentation of the plasticity and fracture of polymers, covering industrial scale applications through to nanoscale biofluidic devices.
Download or read book Multiscaling in Molecular and Continuum Mechanics Interaction of Time and Size from Macro to Nano written by G.C. Sih and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 467 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the first time, a book is being edited to address how results from one scale can be shifted or related to another scale, say from macro to micro or vice versa. The new approach retains the use of the equilibrium mechanics within a scale level such that cross scale results can be connected by scale invariant criteria. Engineers in different disciplines should be able to understand and use the results.
Download or read book Computational Methods for Fracture written by Timon Rabczuk and published by MDPI. This book was released on 2019-10-28 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a collection of 17 scientific papers about the computational modeling of fracture. Some of the manuscripts propose new computational methods and/or how to improve existing cutting edge methods for fracture. These contributions can be classified into two categories: 1. Methods which treat the crack as strong discontinuity such as peridynamics, scaled boundary elements or specific versions of the smoothed finite element methods applied to fracture and 2. Continuous approaches to fracture based on, for instance, phase field models or continuum damage mechanics. On the other hand, the book also offers a wide range of applications where state-of-the-art techniques are employed to solve challenging engineering problems such as fractures in rock, glass, concrete. Also, larger systems such as fracture in subway stations due to fire, arch dams, or concrete decks are studied.
Download or read book Applied Computational Materials Modeling written by Guillermo Bozzolo and published by Springer Science & Business Media. This book was released on 2007-12-19 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scope of this book is to identify and emphasize the successful link between computational materials modeling as a simulation and design tool and its synergistic application to experimental research and alloy development. The book provides a more balanced perspective of the role that computational modeling can play in every day research and development efforts. Each chapter describes one or more particular computational tool and how they are best used.
Download or read book Fatigue and Fracture Mechanics written by Kenneth L. Jerina and published by ASTM International. This book was released on 2000 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Atomistic Simulations of Borosilicate Glassess written by Kuo Hao Lee and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been challenging to understand the cracking behavior of oxide glasses under sharp contact due to the complicated stress state in the samples and compositional dependence of the mechanical behavior of glasses. Molecular dynamics (MD) is a powerful technique to study materials structure and properties. By taking advantage of its capability of providing the time-dependent trajectories of all atoms in the system, the in-situ observation of mechanical deformation can be achieved. In this research, we used MD simulations to study the mechanical response of two commercial multi-component borosilicate glasses, Borofloat®33 (Boro33) and N-BK7® (N-BK7), under different loading conditions to obtain a more complete picture of the deformation mechanism of the indented glass from the perspective of atomic scale. This dissertation can be divided into five parts. In the first part, the performances of two sets of classical interatomic potentials for borosilicate glasses were evaluated in terms of structural and elastic properties for the two glass compositions. The results were also compared with available experimental data. It was found that the potential by Wang et al. [M. Wang, N.M. Anoop Krishnan, B. Wang, M.M. Smedskjaer, J.C. Mauro, and M. Bauchy, J. Non. Cryst. Solids, 498 294--304 (2018)] provides a closer N4 value for Boro33 but underpredicts the N4 value for N-BK7. In contrast, the N4 value of N-BK7 using the potential of Deng and Du [L. Deng and J. Du, J. Am. Ceram. Soc., 102 [5] 2482--2505 (2019)] agrees well with the experimental data, but that of Boro33 is overpredicted. Our result also indicates that Wang's potential gives a better prediction in the short-range structure, while Du's potential provides a closer medium-range structure compared with the experimental data. Neither set of potentials is able to provide accurate predictions of elastic moduli. Wang's potential predicts lower elastic modulus due to the underpredicted N4 value, whereas Du's potential yields higher elastic modulus compared with the experimental values, resulting from its overpredicted N4 value. The second part presents the results from cold compression-decompression MD simulations of the borosilicate glasses. Our results suggest that the densification of these two borosilicate glasses involves different types of structural changes. The fraction of permanent densification can be correlated to the change in intermediate-range structure. By performing Voronoi analysis, the contributions to densification from different cation types in these two multicomponent borosilicate glasses were qualified. It was found that 3-coordinated cations facilitate the densification process, and higher-coordinated cations are relatively stable and can even show a slight expansion in their Voronoi volume. The third part describes the shear behaviors of the borosilicate glasses under different pressures. It was found that the addition of alkali ions lowers the yield stress and changes the pressure dependence of shear modulus. Moreover, shear-induced densification was observed in both glasses. The results show that the decreases of the oxygen-centered bond angle and the coordination number change of B are responsible for the density changes at low pressures, and the increase of 5-coordinated Si is the dominant mechanism for densification at high pressures. The atomic shear stress was calculated the results suggest that B is able to relax mechanical stress more easily under pressurized shear compared to other element types. By analyzing the nonaffine displacement of atoms, it was found that N-BK7 exhibits more localized plastic deformation compared to Boro33 at low pressures and the local rearrangements in both glasses become more homogeneous with increasing pressure. The mean squared nonaffine displacement curves show that alkali ions have the highest mobility induced by shear compared to the network formers and B is more mobile than Si for both glasses. It was also observed that plastic deformation tends to take place around boron atoms for Boro33, whereas it occurs in the alkali-rich regions for N-BK7, indicating that these two glasses have different atomic-scale deformation mechanisms. In the fourth part, the plasticity of the two glasses under tension was investigated by implementing a uniaxial tension test using MD simulations. A bond-switching mechanism is found to be responsible for the plastic response of both glasses and is governed by the increasing rate of non-bridging oxygen (NBO) production during the uniaxial tension. It was found that the amount of B4OSi4 linkages in the glass governs the stress drop after yielding, due to its higher tendency to create NBOs compared to Si4OSi4. Also, the initial existence of NBOs weakens the critical stress for breaking the B4-O bond in B4OSi4, which in turn lowers the yield strength of the glass. The last part describes the effects of pressure on elastic properties, surface energy, and fracture toughness (K_IC) of the borosilicate glasses. It was found that the impact on K_IC is mainly dominated by the change of Young's modulus under pressure, which is proportional to the relative change in density. Between the two glasses under investigation, K_IC can be improved more effectively by the hot-compression process for Boro33, due to its higher concentration of 3-coordinated boron (B3), which facilitates densification via B3 to B4 conversion under compression.
Download or read book Atomistic Simulation of Anistropic Crystal Structures at Nanoscale written by Jia Fu and published by BoD – Books on Demand. This book was released on 2019-05-10 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiscale simulations of atomistic/continuum coupling in computational materials science, where the scale expands from macro-/micro- to nanoscale, has become a hot research topic. These small units, usually nanostructures, are commonly anisotropic. The development of molecular modeling tools to describe and predict the mechanical properties of structures reveals an undeniable practical importance. Typical anisotropic structures (e.g. cubic, hexagonal, monoclinic) using DFT, MD, and atomic finite element methods are especially interesting, according to the modeling requirement of upscaling structures. It therefore connects nanoscale modeling and continuous patterns of deformation behavior by identifying relevant parameters from smaller to larger scales. These methodologies have the prospect of significant applications. I would like to recommend this book to both beginners and experienced researchers.
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 Deformation and Fracture in Materials written by Anoop Kumar Mukhopadhyay and published by CRC Press. This book was released on 2024-08-27 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides information on the basics of deformation and fracture in materials and on current, state-of-the-art experimental and numerical/theoretical methods, including data-driven approaches in the deformation and fracture study of materials. The blend of experimental test methods and numerical techniques to study deformation and fracture in materials is discussed. In addition, the application of data-driven approaches in predicting material performance in different types of loading and loading environments is illustrated. Features: Includes clear insights on deformation and fracture in materials, with clear explanations of mechanics and defects relating to them Provides effective treatments of modern numerical simulation methods Explores applications of data-driven approaches such as artificial intelligence, machine learning, and computer vision Reviews simple and basic experimental techniques to understand the concepts of deformation and fracture in materials Details modeling and simulation strategies of mechanics of materials at different scales This book is aimed at researchers and graduate students in fracture mechanics, finite element methods, and materials science.
