Unraveling the Role of Interfaces in the Deformation and Failure Behavior of Metallic Materials Under Dynamic Loading Conditions
Unraveling the Role of Interfaces in the Deformation and Failure Behavior of Metallic Materials Under Dynamic Loading Conditions

Author: Jie Chen

Publisher:

Published: 2019

Total Pages:

ISBN-13:

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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.

Deformation and Failure in Metallic Materials
Deformation and Failure in Metallic Materials

Author: Kolumban Hutter

Publisher: Springer Science & Business Media

Published: 2013-11-11

Total Pages: 413

ISBN-13: 3540365648

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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.

Mesoscale Modeling of Defect and Damage Evolution in Lightweight Metallic Materials Under Shock Loading Conditions
Mesoscale Modeling of Defect and Damage Evolution in Lightweight Metallic Materials Under Shock Loading Conditions

Author: Garvit Agarwal

Publisher:

Published: 2019

Total Pages:

ISBN-13:

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The capability to predict the impact tolerance of next generation lightweight metallic materials for protective armor application requires fundamental understanding of the deformation and failure behavior of these materials under dynamic loading conditions. Loading conditions of impact/shock result in complex stress states that range from uniaxial compression to tension at high strain rates ranging from 105 s-1 to 1010s-1. The deformation response of these materials is determined by the capability of the microstructures to nucleate dislocations and failure response is determined by the creation of weak sites for void nucleation during uniaxial expansion. A critical challenge in the understanding of mechanisms of plastic deformation and onset of dynamic failure (spallation) is the short time scales associated with these phenomena that limit the capabilities of experimental characterization methods to investigate these mechanisms. As a result, this dissertation focuses on investigation of micromechanisms of interaction, evolution and accumulation of defects and damage during shock compression and spall failure at atomic scale using molecular dynamics (MD) simulations. The MD simulations, due to their high computational cost, are limited to system sizes that are upto a few hundred nanometers and timescales of tens of picoseconds. These limitations result in strain rates of ~1010 s-1 under shock loading conditions using reasonable computing resources. The dissertation demonstrates the capability of newly developed quasi-coarse-grained dynamics (QCGD) method to retain atomistic mechanisms of evolution of microstructure during shock compression and spall failure at time and length scales which are beyond the capability of MD simulations i.e at mesoscales.

Surfaces and Interfaces II
Surfaces and Interfaces II

Author: John Burke

Publisher: Springer Science & Business Media

Published: 2013-03-09

Total Pages: 493

ISBN-13: 1475701780

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The Army Materials and Mechanics Research Center has conducted the Sagamore Army Materials Research Conferences, in cooperation with the Metallurgical Research Laboratories of the Department of Chemical Engineering and Metallurgy of Syracuse University, since 1954. The purpose of the conferences has been to gather together scientists and engineers from academic institutions, industry, and government who are uniquely qualified to explore in depth a subject of importance to the Army, the Department of Defense and the scientific corr.munity. This volume, Surfaces and Interfaces ll: Physical and Mechanical Properties, can be considered a continuation, or perhaps an extension, of the information contained in Surfaces and Interfaces I: Chemical and Physical Characteristics. The emphasis in this volume is focused on: the technological significance of surfaces and interfaces; surface sensitive mechanical properties; environment-sensitive properties; control of grain structure; and composite materials. It is felt that the rather ambitious undertaking of the program committee to place the role of "surfaces and interfaces" in its proper context has been achieved. The balance between basic research findings and more applied research allows the reader a certain degree of latitude in the use of the two volumes. The continued active interest and support of these conferences by Col. C. T. Riordan, Commanding Officer, Dr. E. Scala, Technical Di rector, and J. F. Sullivan, Deputy Technical Director, of the Army Materials and Mechanics Research Center is appreciated.

Inelastic Deformation of Metals
Inelastic Deformation of Metals

Author: Donald C. Stouffer

Publisher: John Wiley & Sons

Published: 1996-01-05

Total Pages: 522

ISBN-13: 9780471021438

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Using a totally new approach, this groundbreaking book establishesthe logical connections between metallurgy, materials modeling, andnumerical applications. In recognition of the fact that classicalmethods are inadequate when time effects are present, or whencertain types of multiaxial loads are applied, the new, physicallybased state variable method has evolved to meet these needs.Inelastic Deformation of Metals is the first comprehensivepresentation of this new technology in book form. It developsphysically based, numerically efficient, and accurate methods forpredicting the inelastic response of metals under a variety ofloading and environmental conditions. More specifically, Inelastic Deformation of Metals: * Demonstrates how to use the metallurgical information to developmaterial models for structural simulations and low cyclic fatiguepredictions. It presents the key features of classical and statevariable modeling, describes the different types of models andtheir attributes, and provides methods for developing models forspecial situations. This book's innovative approach covers such newtopics as multiaxial loading, thermomechanical loading, and singlecrystal superalloys. * Provides comparisons between data and theory to help the readermake meaningful judgments about the value and accuracy of aparticular model and to instill an understanding of how metalsrespond in real service environments. * Analyzes the numerical methods associated with nonlinearconstitutive modeling, including time independent, time dependentnumerical procedures, time integration schemes, inversiontechniques, and sub-incrementing. Inelastic Deformation of Metals is designed to give theprofessional engineer and advanced student new and expandedknowledge of metals and modeling that will lead to more accuratejudgments and more efficient designs. In contrast to existing plasticity books, which discuss few if anycorrelations between data and models, this breakthrough volumeshows engineers and advanced students how materials and modelsactually do behave in real service environments. As greater demandsare placed on technology, the need for more meaningful judgmentsand more efficient designs increases dramatically. Incorporatingthe state variable approach, Inelastic Deformation of Metals: * Provides an overview of a wide variety of metal responsecharacteristics for rate dependent and rate independent loadingconditions * Shows the correlations between the mechanical response propertiesand the deformation mechanisms, and describes how to use thisinformation in constitutive modeling * Presents different modeling options and discusses the usefulnessand limitations of each modeling approach, with material parametersfor each model * Offers numerous examples of material response and correlationwith model predictions for many alloys * Shows how to implement nonlinear material models in stand-aloneconstitutive model codes and finite element codes An innovative, comprehensive, and essential book, InelasticDeformation of Metals will help practicing engineers and advancedstudents in mechanical, aerospace, civil, and metallurgicalengineering increase their professional skills in the moderntechnological environment.

Dynamic Failure of Materials and Structures
Dynamic Failure of Materials and Structures

Author: Arun Shukla

Publisher: Springer Science & Business Media

Published: 2009-10-20

Total Pages: 416

ISBN-13: 1441904468

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Dynamic Failure of Materials and Structures discusses the topic of dynamic loadings and their effect on material and structural failure. Since dynamic loading problems are very difficult as compared to their static counterpart, very little information is currently available about dynamic behavior of materials and structures. Topics covered include the response of both metallic as well as polymeric composite materials to blast loading and shock loadings, impact loadings and failure of novel materials under more controlled dynamic loads. These include response of soft materials that are important in practical use but have very limited information available on their dynamic response. Dynamic fragmentation, which has re-emerged in recent years has also been included. Both experimental as well as numerical aspects of material and structural response to dynamic loads are discussed. Written by several key experts in the field, Dynamic Failure of Materials and Structures will appeal to graduate students and researchers studying dynamic loadings within mechanical and civil engineering, as well as in physics and materials science.

Effects of Dynamic Material Strength on Hydrodynamic Instability and Damage Evolution in Shock Loaded Copper
Effects of Dynamic Material Strength on Hydrodynamic Instability and Damage Evolution in Shock Loaded Copper

Author: Sudrishti Gautam

Publisher:

Published: 2016

Total Pages: 133

ISBN-13:

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Characterization and modeling of deformation and failure in metallic materials under extreme conditions, such as the high loads and strain rates found under shock loading due to explosive detonation and high velocity-impacts, are extremely important for a wide variety of military and industrial applications. When a shock wave causes stress in a material that exceeds the elastic limit, plasticity and eventually spallation occur in the material. The process of spall fracture, which in ductile materials stems from strain localization, void nucleation, growth and coalescence, can be caused by microstructural heterogeneity. The analysis of void nucleation performed from a microstructurally explicit simulation of a spall damage evolution in a multicrystalline copper indicated triple junctions as the preferred sites for incipient damage nucleation revealing 75% of them with at least two grain boundaries with misorientation angle between 20-55°. The analysis suggested the nature of the boundaries connecting at a triple junction is an indicator of their tendency to localize spall damage. The results also showed that damage propagated preferentially into one of the high angle boundaries after voids nucleate at triple junctions. Recently the Rayleigh-Taylor Instability (RTI) and the Richtmyer-Meshkov Instability (RMI) have been used to deduce dynamic material strength at very high pressures and strain rates. The RMI is used in this work since it allows using precise diagnostics such as Transient Imaging Displacement Interferometry (TIDI) due to its slower linear growth rate. The Preston-Tonks-Wallace (PTW) model is used to study the effects of dynamic strength on the behavior of samples with a fed-thru RMI, induced via direct laser drive on a perturbed surface, on stability of the shock front and the dynamic evolution of the amplitudes and velocities of the perturbation imprinted on the back (flat) surface by the perturbed shock front. Simulation results clearly showed that the amplitude of the hydrodynamic instability increases with a decrease in strength and vice versa and that the amplitude of the perturbed shock front produced by the fed-thru RMI is also affected by strength in the same way, which provides an alternative to amplitude measurements to study strength effects under dynamic conditions. Simulation results also indicate the presence of second harmonics in the surface perturbation after a certain time, which were also affected by the material strength.

Critical Conditions for Failure in Materials Subjected to High Rates of Loading
Critical Conditions for Failure in Materials Subjected to High Rates of Loading

Author: R. J. Clifton

Publisher:

Published: 1985

Total Pages: 39

ISBN-13:

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Mechanisms of the plastic deformation and failure of steels under dynamic loading conditions have been examined through investigations in three area: dynamic plasticity, shear bands, and fracture initiation. The dynamic plastic response of 4340 VAR steel has been measured in torsion experiments at strain rates from 10 to the minus 4th power minus 1 sec and in pressure-shear experiments at strain rates of 10 to the 5th power minus 1 sec. Torsion experiments were conducted at temperatures from -190C to 23C on three tempers (HRC 55,44,33). Relatively weak strain-rate sensitvity obtained in these experiments has been related to the high athermal stress barrier that must be overcome for plastic deformation at low temperatures. Temperature profiles in the vicinity of the shear bands were measured using a ten-element, infrared detector system. Numerical simulations were used to assess the roles of strain hardening, strain-rate sensitivity, thermal softening and heat conduction on shear band formation. Finite element methods were developed for rate dependent plasticity and applied to calculations of failure through shear band propagation and ductile fracture. The effects of microstructure on dynamic and quasi-static fracture initiation of AISI 1020 steel were investigated by means of our notched-round bar experiment. The results cover the temperature range -150C to 100C. For static loading under ductile conditions the results are now being supplemented by a detailed study to determine tthe instant of fracture initiation.