Download or read book A Continuum Model of Deformation and Damage in Metals Coated with Nanolaminate Metallic Systems for Applications in High Energy Environments written by Mohammed Hamood Anazi and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research develops a continuum model of deformation and damage in metals coated with nanolaminate metallic systems (NMS) for potential applications in high-energy environments. The model is developed based on continuum mechanics within the elastic/viscoplastic framework that comprises constitutive equations which include dislocation density, size effect, strain hardening, strain rate effect, and damage. In addition, evolution laws for damage and dislocation density are considered. The model investigates the deformation behavior and strength in such materials and provides a predictive capability for designing engineering structures. The model is then implemented into a user subroutine in a commercial finite element analysis subroutine. Several numerical investigations are performed for steel and NMS at various individual layer thicknesses and compared with experimental data found in the literature. The deformation model developed for X70 steel and Copper/Niobium Cu/Nb NMS which is deformed variously based on its individual layer thickness. For X70, a modified Taylor equation is considered for hardening behavior, while for NMS, the confined layer slip (CLS) mechanism obeys a combined formula composed of Orwan's mechanism, interface stress, and dislocation density when the individual layer thickness is between 5 nm and 100 nm. Meanwhile, the nucleation (Nu) mechanism is controlled by the nucleation of a dislocation mechanism when the individual layer thickness is less than 5 nm. Next, the model is extended to consider softening or ductile failure based on an isotropic damage model that considers voids nucleation and growth. Finally, this research conducted an extensive numerical study on X70 and NMS. Then, X70 was coated with NMS to create a new composite called a X70 NMS composite. Likewise, the X70 NMS composite was studied based on a free damage state and damage state. A tension test according to ASTM standards was simulated to study the materials numerically. The models of the materials show good agreement with experimental results found in the literature, suggesting that the NMS coating is a good strength and ductility addition to X70 based on the X70 NMS composite study.

Download or read book Deformation and Failure in Metallic Materials written by Kolumban Hutter and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to the deformation and failure in metallic materials, summarizing the results of a research programme financed by the "Deutsche Forschungsgemeinschaft". It presents the recent engineering as well as mathematical key aspects of this field for a broad community. Its main focus is on the constitutive behaviour as well as the damage and fracture of metallic materials, covering their mathematical foundation, modelling and numerics, but also relevant experiments and their verification.

Download or read book Continuum Damage Mechanics and Numerical Applications written by Wohua Zhang and published by Springer Science & Business Media. This book was released on 2010-11-19 with total page 937 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Continuum Damage Mechanics and Numerical Applications" presents a systematic development of the theory of Continuum Damage Mechanics and its numerical engineering applications using a unified form of the mathematical formulations in anisotropic and isotropic damage models. The theoretical framework is based on the thermodynamic theory of energy and material dissipation and is described by a set of fundamental formulations of constitutive equations of damaged materials, development equations of the damaged state, and evolution equations of micro-structures. According to concepts of damage-dissipation of the material state and effective evolution of material properties, all these advanced equations, which take nonsymmetrized effects of damage aspects into account, are developed and modified from the traditional general failure models so they are more easily applied and verified in a wide range of engineering practices by experimental testing. Dr. Wohua Zhang is a Professor at Engineering Mechanics Research Center in Zhejiang University of China. Dr. Yuanqiang Cai is a Professor at Department of Civil Engineering in Zhejiang University of China.

Download or read book Continuum Damage Mechanics of Materials and Structures written by O. Allix and published by Elsevier. This book was released on 2002-08-13 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: Created in 1975, LMT-Cachan is a joint laboratory École Normale Superieure de Cachan, Pierre & Marie Curie (Paris 6) University and the French Research Council CNRS (Department of Engineering Sciences).The Year 2000 marked the 25th anniversary of LMT. On this occasion, a series of lectures was organized in Cachan in September-October, 2000. This publication contains peer-reviewed proceedings of these lectures and is aimed to present engineers and scientists with an overview of the latest developments in the field of damage mechanics. The formulation of damage models and their identification procedures were discussed for a variety of materials.

Download or read book Physico Mathematical Theory of High Irreversible Strains in Metals written by V.M. Greshnov and published by CRC Press. This book was released on 2019-02-06 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a new physical and mathematical theory of irreversible deformations and ductile fracture of metals that acknowledges the continuous change in the structure of materials during deformation and the accumulation of deformation damage. Plastic deformation, viscous destruction, evolution of structure, creep processes, and long-term strength of metals and stress relaxation are described in the framework of a unified approach and model. The author then expands this into a mathematical model for determining the mechanical characteristics of quasi-samples of standard mechanical properties in deformed semi-finished products.

Download or read book Shock Waves and High Strain Rate Phenomena in Metals written by Mare Meyers and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 1084 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scientific understanding of high-velocity deformation has advanced substantially during the past decade. On the one hand, the framework for a theory explaining the metallurgical effects of shock waves is beginning to take shape; on the other hand, the technological applications of high strain-rate processes have found their way into industries in countries around the world. Ex plosive cladding, welding, forming, compaction and consolidation, cutting, and hardening, in addition to high energy-rate deformation processes using other energy sources, are some of the topics of contemporary technological importance. Metallurgical effects are of the utmost importance in both the scientific understanding of the phenomena involved, and in the successful development and utilization of the associated applications. The international conference upon which this book is based had as its major objectives the acceleration of progress in the field of high-strain rate deformation and fabrication, including applications, by providing a forum for the exchange of state-of-the art information on the metallurgical effects of high strain-rate deformation and fabrication; and the organization of this informa tion into a timely and coherent body of knowledge focused around significant areas and applications. This volume is a manifestation of these objectives. In addition, the contents of this book were organized to provide for a somewhat logical perspective of the fundamentals, development, and state-of-the-art applications of high strain-rate and shock phenomena.

Download or read book A Contribution to the Modeling of Metal Plasticity and Fracture written by Shyam Mohan Keralavarma and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this dissertation is to further the understanding of inelastic behavior in metallic materials. Despite the increasing use of polymeric composites in aircraft structures, high specific strength metals continue to be used in key components such as airframe, fuselage, wings, landing gear and hot engine parts. Design of metallic structures subjected to thermomechanical extremes in aerospace, automotive and nuclear applications requires consideration of the plasticity, creep and fracture behavior of these materials. Consideration of inelasticity and damage processes is also important in the design of metallic components used in functional applications such as thin films, flexible electronics and micro electro mechanical systems. Fracture mechanics has been largely successful in modeling damage and failure phenomena in a host of engineering materials. In the context of ductile metals, the Gurson void growth model remains one of the most successful and widely used models. However, some well documented limitations of the model in quantitative prediction of the fracture strains and failure modes at low triaxialities may be traceable to the limited representation of the damage microstructure in the model. In the first part of this dissertation, we develop an extended continuum model of void growth that takes into account details of the material microstructure such as the texture of the plastically deforming matrix and the evolution of the void shape. The need for such an extension is motivated by a detailed investigation of the effects of the two types of anisotropy on the materials' effective response using finite element analysis. The model is derived using the Hill-Mandel homogenization theory and an approximate limit analysis of a porous representative volume element. Comparisons with several numerical studies are presented towards a partial validation of the analytical model. Inelastic phenomena such as plasticity and creep result from the collective behavior of a large number of nano and micro scale defects such as dislocations, vacancies and grain boundaries. Continuum models relate macroscopically observable quantities such as stress and strain by coarse graining the discrete defect microstructure. While continuum models provide a good approximation for the effective behavior of bulk materials, several deviations have been observed in experiments at small scales such as an intrinsic size dependence of the material strength. Discrete dislocation dynamics (DD) is a mesoscale method for obtaining the mechanical response of a material by direct simulation of the motion and interactions of dislocations. The model incorporates an intrinsic length scale in the dislocation Burgers vector and potentially allows for size dependent mechanical behavior to emerge naturally from the dynamics of the dislocation ensemble. In the second part of this dissertation, a simplified two dimensional DD model is employed to study several phenomena of practical interest such as strain hardening under homogeneous deformation, growth of microvoids in a crystalline matrix and creep of single crystals at elevated temperatures. These studies have been enabled by several recent enhancements to the existing two-dimensional DD framework described in Chapter V. The main contributions from this research are: (i) development of a fully anisotropic continuum model of void growth for use in ductile fracture simulations and (ii) enhancing the capabilities of an existing two-dimensional DD framework for large scale simulations in complex domains and at elevated temperatures.

Download or read book Strained Metallic Surfaces written by Valim Levitin and published by John Wiley & Sons. This book was released on 2009-01-20 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing students as well as engineers and researchers with a must-have insight into the complexities of surface structure and behavior, this monograph extends beyond the usual introductory books, presenting concentrated knowledge on the surface science of metals, and connecting fundamentals with actual applications. Beginning with explanations of the intricacies of surfaces and their differences to bulk, it takes the reader through the vital steps towards macroscopic metallic components as well as surface nanostructuring. In so doing, it makes use of theory, experimental techniques, examples, and modeling to facilitate a firm understanding.

Download or read book Unraveling the Role of Interfaces in the Deformation and Failure Behavior of Metallic Materials Under Dynamic Loading Conditions written by Jie Chen and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Design of next-generation high strength metallic materials for damage-resistant applications relies on a fundamental understanding of the deformation mechanisms and failure behavior of these materials under dynamic loading conditions. The dynamic strength of metals is typically characterized based on the "spall strength" defined as the peak tensile pressure the metal can withstand prior to failure. For pure FCC metals, the capability to increase the spall strength is limited due to insufficient microstructural features that can be used to tailor/modify the deformation and failure behavior under dynamic loading conditions. The current understanding of the role of grain boundaries and deformation twinning in BCC metals, however, is still in its infancy. Another promising strategy to design high strength microstructures is the engineering of nanoscale interfaces in alloy microstructures that may alter the nucleation and evolution of defects/damage. Such strategies have been successfully demonstrated experimentally in FCC/BCC alloy microstructures. A critical challenge in engineering these microstructures, however, is the lack of understanding on the role of interfaces on the spall failure behavior. Such an understanding is particularly challenging using experimental techniques due to the short time and length scales of the processes of nucleation and evolution of defects/damage. Therefore, the goal of this dissertation is to carry out a systematic study using classical molecular dynamics (MD) simulations to investigate the role of structure and energies of grain boundaries in BCC microstructures as well as the structure, size and distribution of FCC/BCC interfaces on the twinning/de-twinning behavior as well as the damage nucleation (void nucleation and growth) behavior under shock loading conditions. Such understanding will enable to identify key microstructural descriptors of the interfaces that determine the spall strength, and aid in the design of nanocrystalline Ta and Cu/Ta microstructures with enhanced spall strengths for damage-tolerant applications.

Download or read book Response of Metals to High Velocity Deformation written by Metallurgical Society of AIME. Physical Metallurgy Committee and published by . This book was released on 1961 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Inelastic Deformation and Fatigue Damage in Metals at High Homologous Temperatures written by James Robert Wilcox and published by . This book was released on 1990 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Deformation Processing written by John J. Burke and published by Springer. This book was released on 1978-02 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Army Materials and Mechanics Research Center has con ducted the Sagamore Army Materials Research Conference in coop eration with the Materials Science Group of the Department of Chemical Engineering and Materials Science of Syracuse University since 1954. The purpose of the conference has been to gather to gether scientists and engineers from academic institutions, in dustry and government who are uniquely qualified to explore in depth a subject of importance to the Army, the Department of Defense and the scientific community. This volume, Advances in Deformation Processing, addresses the areas of Analytical Advances, Workability, Processing to Optimize Properties, Advanced Applications - Materials, and Advanced Applications - Processes. The dedicated assistance of Mr. Joseph Bernier of the Army Materials and Mechanics Research Center throughout the stages of the conference planning and finally the publication of the Sagamore Conference Proceedings is deeply appreciated. The support of Helen Brown DeMascio of Syracuse University in p- paring the final manuscript is acknowledged. The continued active interest and support of these conferences by Dr. A. E. Gorum, Director of the Army Materials and Mechanics Research Center, is appreciated. Syracuse University Syracuse, New York The Editors vii Contents SESSION I INTRODUCTION A. E. Gorum, Moderator Continuum Mechanics and Deformation Processing 1.

Download or read book Deformation and Damage Process in Nanostructured Metallic Systems written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this reporting period, processing of nanostructured powders, consolidation of nanostructured powders, computer simulation, micro structural characterization, and mechanical deformation tests were carried out. The nanostructured powders and bulk nanostructured materials were produced successfully via optimization of processing parameters. The observed highly grain stability can be explained by a grain boundary pinning mechanism arising from the dispersoid particles as well as impurity segregation. The microstructures of the as- extruded and the deformed bulk nanocrystalline aluminum alloys were investigated using transmission electron microscopy. A nanoindentation technique and traditional mechanical tests as well as computer simulation were also used to evaluate the mechanical performance. A discrete dislocation dynamics model has been developed to bridge the gap between atomic simulations and continuum approaches. It has the potential to provide a rigorous description of the complex relationships between the macroscopic mechanical behavior of materials and the underlying fundamental physical mechanisms. The tensile test results showed that grain size effects, solid solution strengthening, Orowan strengthening and dislocation strengthening contribute significantly to the properties of the cryomilled Al alloys. The future work for the next period is also discussed in the report.

Download or read book Notes fournies au Comit de salut public par les Commissaires de Saint Domingue written by and published by . This book was released on 1792* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Atomistic Modeling of Nanowires Small scale Fatigue Damage in Cast Magnesium and Materials for MEMS written by David Carl Miller and published by . This book was released on 2006 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lightweight and miniaturized weapon systems are driving the use of new materials in design such as microscale materials and ultra low-density metallic materials. Reliable design of future weapon components and systems demands a thorough understanding of the deformation modes in these materials that comprise the components and a robust methodology to predict their performance during service or storage. Traditional continuum models of material deformation and failure are not easily extended to these new materials unless microstructural characteristics are included in the formulation. For example, in LIGA Ni and Al-Si thin films, the physical size is on the order of microns, a scale approaching key microstructural features. For a new potential structural material, cast Mg offers a high stiffness-to-weight ratio, but the microstructural heterogeneity at various scales requires a structure-property continuum model. Processes occurring at the nanoscale and microscale develop certain structures that drive material behavior. The objective of the work presented in this report was to understand material characteristics in relation to mechanical properties at the nanoscale and microscale in these promising new material systems. Research was conducted primarily at the University of Colorado at Boulder to employ tightly coupled experimentation and simulation to study damage at various material size scales under monotonic and cyclic loading conditions. Experimental characterization of nano/micro damage will be accomplished by novel techniques such as in-situ environmental scanning electron microscopy (ESEM), 1 MeV transmission electron microscopy (TEM), and atomic force microscopy (AFM). New simulations to support experimental efforts will include modified embedded atom method (MEAM) atomistic simulations at the nanoscale and single crystal micromechanical finite element simulations. This report summarizes the major research and development accomplishments for the LDRD project titled 'Atomistic Modeling of Nanowires, Small-scale Fatigue Damage in Cast Magnesium, and Materials for MEMS'. This project supported a strategic partnership between Sandia National Laboratories and the University of Colorado at Boulder by providing funding for the lead author, Ken Gall, and his students, while he was a member of the University of Colorado faculty.

Download or read book Thermally Activated Defect Processes in Metallic Materials written by Yifan Wang (Researcher of metallic materials) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the mechanical strength of metals and alloys under different temperatures is essential in materials design for modern technology applications. Predicting temperature-dependent mechanical properties requires detailed knowledge of the elementary thermally activated defect processes governing plasticity. These microstructural mechanisms contribute to the plastic flow stress through (a) the 'intrinsic energy barrier' due to unfavorable atomic structures; (b) the long-range elastic interactions between these defects and other obstacles. Both aspects provide crucial inputs to mesoscale modeling methods for plasticity, such as dislocation dynamics (DD). This thesis includes three major projects. The first two focus mainly on (a), in which we combine atomistic simulation with statistical mechanical analysis to develop predictive kinetic theories of defect dynamics under stress. The third project focuses on (b), in which we develop a fast elasticity solver for solving long-range dislocation-void interactions. The first part of the thesis discusses the cross slip of screw dislocations in fcc metals, an essential mechanism for the temperature-dependent stage-III strain hardening. Cross slip of screw dislocations in crystalline solids is a stress-driven thermally activated process essential to many phenomena during plastic deformation, including dislocation pattern formation, strain hardening, and dynamic recovery. Molecular dynamics (MD) simulation has played an important role in determining the microscopic mechanisms of cross slip, but due to its limited timescale, predicting cross slip rate from MD is only possible at high-stress or high-temperature conditions. The transition state theory (TST) can predict the cross-slip rate over a wide range of stress and temperature conditions, but its predictions have been found to be several orders of magnitude too low in comparison to MD results. This discrepancy can be expressed by a large activation entropy whose physical origin remains unclear. Here we resolve this discrepancy by showing that the large activation entropy results from anharmonic effects, including thermal softening, thermal expansion, and soft vibrational modes of the dislocation. We expect these anharmonic effects to be significant when determining the rate of a wide range of stress-driven thermally activated processes in solids. The second part investigates how shear-transformation (ST) events respond to applied stress and thermal activation in CuZr metallic glasses. Understanding how shear transformation (ST) events respond to applied stress and thermal activation remains challenging for glassy materials due to their amorphous structure. Using MD simulation of early-stage deformation of CuZr metallic glasses, we find an anomalous temperature dependence of the elastic limit. We present the energy-strain landscape (ESL) based on high-throughput NEB calculations to probe the strain dependence on activation energies of multiple competitive ST events. A quantitative description is obtained from ESL analyses for the ST dynamics in metallic glasses, which reveals that the reversibility of ST events governs the elastic limit. We discover a strain-independent quantity eigen barrier that characterizes the reversibility of ST events and thus predicts the elastic limit of metallic glasses. We believe that the ESL picture brings a new perspective to understanding ST events' dynamics in glassy materials under external loading. Finally, we introduce a fast numerical methods we developed based on spherical harmonics for solving elasticity problems with any arbitrary boundary conditions defined on a sphere. We develop an efficient numerical method for calculating the image stress field induced by spherical voids in materials, and applied the method to dislocation-void interactions. The method is constructed based on a complete set of basis functions for the displacement potential of the elastic boundary value problem for a spherical hole, as well as the corresponding displacement, stress, and traction fields, all in terms of linear combinations of spherical harmonics. Using the fast transformation between the real and spherical-harmonics spaces provided by the {\it SHTOOLS} package, the method is more efficient than other image stress solvers such as the finite-element method. This method can be readily extended for solving elasticity problems involving inclusions and inhomogeneities, as well as contact between spheres. The tools developed here can also be useful for fast solution of differential equations with spherical boundaries beyond elasticity. The method is applied to long-range elastic interactions between dislocations and voids in crystalline solids and a biomechanical application in the force microscope for measuring immune cell-target interactions.