Two-Temperature Thermodynamics for Metal Viscoplasticity: Continuum Modeling and Numerical Experiments

2016 ◽  
Vol 84 (1) ◽  
Author(s):  
Shubhankar Roy Chowdhury ◽  
Gurudas Kar ◽  
Debasish Roy ◽  
J. N. Reddy
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Internal Variable ◽  
Thermodynamic System ◽  
Internal Variables ◽  
Face Centered Cubic ◽  
Dynamic Simulations ◽  
Face Centered ◽  
Atomic Lattices ◽  
Two Temperature

A physics-based model for dislocation mediated thermoviscoplastic deformation in metals is proposed. The modeling is posited in the framework of internal-variables theory of thermodynamics, wherein an effective dislocation density, which assumes the role of the internal variable, tracks permanent changes in the internal structure of metals undergoing plastic deformation. The thermodynamic formulation involves a two-temperature description of viscoplasticity that appears naturally if one considers the thermodynamic system to be composed of two weakly interacting subsystems, namely, a kinetic-vibrational subsystem of the vibrating atomic lattices and a configurational subsystem of the slower degrees-of-freedom (DOFs) of defect motion. Starting with an idealized homogeneous setup, a full-fledged three-dimensional (3D) continuum formulation is set forth. Numerical exercises, specifically in the context of impact dynamic simulations, are carried out and validated against experimental data. The scope of the present work is, however, limited to face-centered cubic (FCC) metals only.

scholarly journals Three-dimensional superlattice engineering with block copolymer epitaxy

2020 ◽  
Vol 6 (24) ◽  
pp. eaaz0002 ◽  
Author(s):  
Jiaxing Ren ◽  
Tamar Segal-Peretz ◽  
Chun Zhou ◽  
Gordon S. W. Craig ◽  
Paul F. Nealey
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Honeycomb Lattice ◽  
Lattice Stability ◽  
Face Centered Cubic ◽  
Precise Control ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Face Centered ◽  
Atomic Lattices

Three-dimensional (3D) structures at the nanometer length scale play a crucial role in modern devices, but their fabrication using traditional top-down approaches is complex and expensive. Analogous to atomic lattices, block copolymers (BCPs) spontaneously form a rich variety of 3D nanostructures and have the potential to substantially simplify 3D nanofabrication. Here, we show that the 3D superlattice formed by BCP micelles can be controlled by lithographically defined 2D templates matching a crystallographic plane in the 3D superlattice. Using scanning transmission electron microscopy tomography, we demonstrate precise control over the lattice symmetry and orientation. Excellent ordering and substrate registration can be achieved, propagating through 284-nanometer-thick films. BCP epitaxy also showed exceptional lattice tunability, with a continuous Bain transformation from a body-centered cubic to a face-centered cubic lattice. Lattice stability was mediated by molecular packing frustration, and surface-induced lattice reconstruction was observed, leading to the formation of a unique honeycomb lattice.

Epitaxial Ni nanoparticles on CaF2(001), (110) and (111) surfaces studied by three-dimensional RHEED, GIXD and GISAXS reciprocal-space mapping techniques

2017 ◽  
Vol 50 (3) ◽  
pp. 830-839 ◽  
Author(s):  
S. M. Suturin ◽  
V. V. Fedorov ◽  
A. M. Korovin ◽  
N. S. Sokolov ◽  
A. V. Nashchekin ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
High Energy ◽  
Reciprocal Space ◽  
Mapping Technique ◽  
Face Centered Cubic ◽  
X Ray ◽  
Cubic Lattice ◽  
Face Centered

The development of growth techniques aimed at the fabrication of nanoscale heterostructures with layers of ferroic 3dmetals on semiconductor substrates is very important for their potential usage in magnetic media recording applications. A structural study is presented of single-crystal nickel island ensembles grown epitaxially on top of CaF2/Si insulator-on-semiconductor heteroepitaxial substrates with (111), (110) and (001) fluorite surface orientations. The CaF2buffer layer in the studied multilayer system prevents the formation of nickel silicide, guides the nucleation of nickel islands and serves as an insulating layer in a potential tunneling spin injection device. The present study, employing both direct-space and reciprocal-space techniques, is a continuation of earlier research on ferromagnetic 3dtransition metals grown epitaxially on non-magnetic and magnetically ordered fluorides. It is demonstrated that arrays of stand-alone faceted nickel islands with a face-centered cubic lattice can be grown controllably on CaF2surfaces of (111), (110) and (001) orientations. The proposed two-stage nickel growth technique employs deposition of a thin seeding layer at low temperature followed by formation of the islands at high temperature. The application of an advanced three-dimensional mapping technique exploiting reflection high-energy electron diffraction (RHEED) has proved that the nickel islands tend to inherit the lattice orientation of the underlying fluorite layer, though they exhibit a certain amount of {111} twinning. As shown by scanning electron microscopy, grazing-incidence X-ray diffraction (GIXD) and grazing-incidence small-angle X-ray scattering (GISAXS), the islands are of similar shape, being faceted with {111} and {100} planes. The results obtained are compared with those from earlier studies of Co/CaF2epitaxial nanoparticles, with special attention paid to the peculiarities related to the differences in lattice structure of the deposited metals: the dual-phase hexagonal close-packed/face-centered cubic lattice structure of cobalt as opposed to the single-phase face-centered cubic lattice structure of nickel.

scholarly journals Interactions between dislocations and three-dimensional annealing twins in face centered cubic metals

2019 ◽  
Vol 161 ◽  
pp. 371-378 ◽  
Author(s):  
Yanxiang Liang ◽  
Xiaofang Yang ◽  
Mingyu Gong ◽  
Guisen Liu ◽  
Qing Liu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Face Centered Cubic ◽  
Cubic Metals ◽  
Annealing Twins ◽  
Face Centered

Towards a Virtual Laboratory for Grain Boundaries and Dislocations

2009 ◽  
Vol 1224 ◽  
Author(s):  
Sebastián Echeverri Restrepo ◽  
Barend J. Thijsse
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundaries ◽  
Systematic Study ◽  
Degrees Of Freedom ◽  
Minimum Energy ◽  
Local Symmetry ◽  
Virtual Laboratory ◽  
Face Centered Cubic ◽  
Face Centered ◽  
Edge Dislocations

AbstractIn order to perform a systematic study of the interaction between grain boundaries (GBs) and dislocations using molecular dynamics (MD), several tools need to be available. A combination of computational geometry and MD was used to build the foundations of what we call a virtual laboratory. First, an algorithm to generate GBs on face-centered cubic bicrystals was developed. Two crystals with different orientations are placed together. Then, by applying “microscopic” rigid body translations along the GB plane to one of the crystals and removing overlapping atoms, a set of initial configurations is sampled and a minimum energy configuration is found. Second, to classify the geometry of the GBs a local symmetry type (LST) describing the angular environment of each atom is calculated. It is found that for a given relaxed GB the number of atoms with different LSTs is not very large and that it is possible to find unique geometrical patterns in each GB. For instance, the LSTs of two GBs having the same “macroscopic” configuration but different “microscopic” degrees of freedom can be dissimilar: the configurations with higher GB energy tend to have a higher number of atoms with different LSTs. Third, edge dislocations are introduced into the bicrystals. We see that full edge dislocations split into Shockley partials. Finally, by loading the bicrystals with tensile stresses the edge dislocations are put into motion. Various examples of dislocation-GB interactions in Cu are presented.

Electromagnetic Thermal Energy Transfer in Nanoparticle Assemblies Below Diffraction Limit

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Anil Yuksel ◽  
Edward T. Yu ◽  
Michael Cullinan ◽  
Jayathi Murthy
Keyword(s):  
Three Dimensional ◽  
Close Packing ◽  
Face Centered Cubic ◽  
Copper Nanoparticle ◽  
Colloidal Solutions ◽  
Plasmonic Coupling ◽  
Nanoparticle Assemblies ◽  
Enhanced Absorption ◽  
Face Centered ◽  
Insight Into

Abstract Fabrication of micro- and nanoscale electronic components has become increasingly demanding due to device and interconnect scaling combined with advanced packaging and assembly for electronic, aerospace, and medical applications. Recent advances in additive manufacturing have made it possible to fabricate microscale, 3D interconnect structures but heat transfer during the fabrication process is one of the most important phenomena influencing the reliable manufacturing of these interconnect structures. In this study, optical absorption and scattering by three-dimensional (3D) nanoparticle packings are investigated to gain insight into micro/nano heat transport within the nanoparticles. Because drying of colloidal solutions creates different configurations of nanoparticles, the plasmonic coupling in three different copper nanoparticle packing configurations was investigated: simple cubic (SC), face-centered cubic (FCC), and hexagonal close packing (HCP). Single-scatter albedo (ω) was analyzed as a function of nanoparticle size, packing density, and configuration to assess effect for thermo-optical properties and plasmonic coupling of the Cu nanoparticles within the nanoparticle packings. This analysis provides insight into plasmonically enhanced absorption in copper nanoparticle particles and its consequences for laser heating of nanoparticle assemblies.

Design and locomotion analysis of a novel deformable mobile robot with two spatial reconfigurable platforms and three kinematic chains

2016 ◽  
Vol 231 (8) ◽  
pp. 1481-1499 ◽  
Author(s):  
Wan Ding ◽  
Qiang Ruan ◽  
Yan-an Yao
Keyword(s):  
Mobile Robot ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Dynamic Simulations ◽  
Gait Planning ◽  
Plane Symmetric ◽  
Kinematic Chains ◽  
Reconfigurable Platforms ◽  
Actuation Systems

A novel five degrees of freedom deformable mobile robot composed of two spatial reconfigurable platforms and three revolute–prismatic–spherical kinematic chains acting in parallel to link the two platforms is proposed to realize large deformation capabilities and multiple locomotion modes. Each platform is an improved deployable single degrees of freedom three-plane-symmetric Bricard linkage. By taking advantage of locomotion collaborating among platforms and kinematic chains, the mobile robot can fold into stick-like shape and possess omnidirectional rolling and worm-like motions. The mechanism design, kinematics, and locomotion feasibility are the main focus. Through kinematics and gait planning, the robot is analyzed to have the capabilities of rolling and turning. Based on its deformation, the worm-like motion performs the ability to overcome narrow passages (such as pipes, holes, gaps, etc.) with large range of variable size. Dynamic simulations with detailed three-dimensional model are carried out to verify the gait planning and provide the variations of essential motion and dynamic parameters in each mode. An experimental robotic system with servo and pneumatic actuation systems is built, experiments are carried out to verify the validity of the theoretical analysis and the feasibility of the different locomotion functions, and its motion performances are compared and analyzed with collected data.

scholarly journals Structure and stacking order in crystals of asymmetric dumbbell-like colloids

2015 ◽  
Vol 48 (1) ◽  
pp. 238-243 ◽  
Author(s):  
Antara Pal ◽  
Janne-Mieke Meijer ◽  
Joost R. Wolters ◽  
Willem K. Kegel ◽  
Andrei V. Petukhov
Keyword(s):  
Crystalline Structure ◽  
Diffuse Scattering ◽  
Colloidal Particles ◽  
Three Dimensional ◽  
Stacking Faults ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Stacking Order ◽  
X Ray Scattering ◽  
Face Centered

The crystalline structure assembled out of charge-stabilized asymmetric dumbbell-like colloidal particles in ethyl alcohol by sedimentation has been probed using small-angle X-ray scattering with microradian resolution. The existence of plastic face-centered cubic crystals was inferred from the observed Bragg peaks. The presence of stacking faults and the mosaic structure of the sample lead to the appearance of diffuse scattering, forming Bragg scattering cylinders in the three-dimensional reciprocal space. The quality of the crystalline structure, as ascertained from a detailed analysis of the diffuse scattering intensity distribution, indicates the presence of only 1.5% of stacking faults between the hexagonal close-packed layers.

SITE- AND BOND-DIFFUSION ON REGULAR LATTICES

2009 ◽  
Vol 23 (24) ◽  
pp. 4943-4952
Author(s):  
LASKO BASNARKOV ◽  
VIKTOR URUMOV
Keyword(s):  
Transition Probability ◽  
Three Dimensional ◽  
Diffusion Constant ◽  
Single Step ◽  
Face Centered Cubic ◽  
Periodic Orbit Theory ◽  
Regular Lattices ◽  
Orbit Theory ◽  
Face Centered ◽  
Theoretical Results

We consider two types of motion, one with particle occupying only the sites on a given regular lattice and another when the bonds between neighboring lattice sites are displaced to the positions of the neighboring bonds. We refer to these models as site- and bond-diffusion. The latter is equivalent to site-diffusion on a lattice constructed from the middle points on each bond of the original lattice. The transition probability is assumed equal to all neighboring positions. The diffusion constant is obtained by periodic orbit theory for all Archimedean lattices, as well as some three-dimensional lattices (cubic, diamond, body centered cubic and face centered cubic lattice). Every single step of bond-motion is expressed through two site-motion steps. Analytic results for the diffusion constant for bond-diffusion for square, triangular and Kagomé lattice are also obtained. Kurtosis is calculated for site-diffusion on square and (4, 82)-lattice, to estimate the deviation of the distribution of displacements from the Gaussian. All theoretical results are verified with numerical simulation.

A three-dimensional photonic crystal model: Hollow-spherical non-closed-packed face-centered cubic structure

2006 ◽  
Vol 381 (1-2) ◽  
pp. 289-293 ◽  
Author(s):  
Hong-Bo Chen ◽  
Yan-Ling Cao ◽  
Yong-Zheng Zhu ◽  
Yan-Ping Wang ◽  
Yuan-Bin Chi
Keyword(s):  
Photonic Crystal ◽  
Three Dimensional ◽  
Face Centered Cubic ◽  
Dimensional Photonic Crystal ◽  
Crystal Model ◽  
Cubic Structure ◽  
Face Centered
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