Dynamics Of Grain Boundaries Under Applied Mechanical Stress

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Dynamics of grain boundary motion coupled to shear

A. Zero-temperature dynamics At 0 K and in the absence of applied stresses, the GB is initially in a particular equilibrium position. Suppose a shear stress is applied to the bicrystal by holding the lower grain and moving the upper grain with a constant velocity v par-allel to t #Fig. 1!a $. The force acting on the upper grain is

Effect of stress state on deformation and fracture of

boundaries are correlated with normal stress acting on the interface. Spearot et al. [23, 24] have recently examined a range of geometries of single crystal Cu and symmetric tilt grain boundaries loaded on tension, and thus, the stress state on the active slip system was indirectly varied as crystallographic orientation changed.

Stress-assisted grain growth in nanocrystalline metals: Grain

Grain growth Grain boundaries Nanoindentation Molecular dynamics abstract The mechanisms of stress-assisted grain growth are explored using molecular dynamics simulations of nanoindentation in nanocrystalline Ni and Ni-1 at.% P as a function of grain size and deformation temperature.

Uniaxial stress-driven coupled grain boundary motion in

grain boundaries accompanying the lattice reorientation under uniaxial compression. An ideal 90 GB model with crystallographic orientations, ð1010Þ Grain2 // ð0001Þ Grain2 // interface plane and ½1210 Grain1 // ½1210 Grain2 is constructed as shown in Fig. 1b. The quasi-static compression stress is applied to the GBs by displacing the

Molecular dynamics investigation of the grain boundary

Jun 14, 2019 distribution [5] or a gradient grain size structure [6 8], have been applied to overcome this dilemma. While material strength under monotonic loading conditions is of significant interest, the mechanical response of nanocrystalline materials under cyclic loading conditions is also an important issue [9].

J ournal of Soli d Mechanics an d Materials Engineering

geometric relationship between two grains and a GB, and the stress state applied to the near-field of a GB. This value and the others so far proposed were calculated for <110>, <100>, and <111> symmetric tilt grain boundaries under uniaxial compression normal to the GB. The dynamic transfer and incorporation of the

Stick slip dynamics of coherent twin boundaries in copper

motion under applied stress. Kizuka et al. observed that shearing of nanometer-sized gold contacts results in coher-enttwinboundary(CTB)coupledmotion[5].Usingchannel die deformation and imaging, Field et al. experimentally observed CTB migration in copper during severe deforma-tion [6] and concluded that twin boundaries are sources of dislocations.

Dynamic Failure of Advanced Ceramics using Molecular Dynamics

behavior of advanced ceramics under shock loading conditions using Molecular Dynamics simulations. These objectives include: learning about the software to perform the simulations, and studying the dynamic failure of Al 2O 3 and its mechanical properties to find applications for materials design.

Molecular dynamics study on the grain boundary dislocation

Molecular dynamics study on the grain boundary dislocation source in nanocrystalline copper under tensile loading Abstract Grain boundary (GB) is the interface between different oriented crystals of the same material, and it can have a significant effect on the many properties of materials. When the average or entire range of grain size is

1,*, C. R. Feng 2 and Bhakta B. Rath 2 - MDPI

Dec 31, 2020 each grain deforms by different amounts, depe nding on its orientation and the constraints imposed by neighboring grains. If each grain were forced to undergo the same uniform strain, voids would form at grain boundaries. To avoid the creation of voids, and ensure strain compatibility, dislocations are introduced.

Plasticity of metal wires in torsion Molecular dynamics and

computes the image stress and interactions with free surfaces. The dislocation dynamics simulations are further modified to account for the applied torque. From elasticity theory, a torque applied to a circular shaft can be related to the shear stress as s zy ¼tr=J where tis the applied torque, r is radius of

in Nano-Crystalline Aluminum Molecular-Dynamics Study of

esting observation is the sudden drop in the flow stress for larger grain sizes, which indicates that fracture has occurred. An analysis of the atomic positions indeed shows that inter-grain fracture, i.e., fracture along the grain boundaries, has taken place. [21] Samples with larger grain sizes tend to exhibit

Atomistic Simulation Studies Of Grain-Boundary Segregation

Nov 06, 2018 facilitates the segregation of Cu into high-energy interface sites such as grain-boundaries and twin-boundary defects. In this thesis, large-scale hybrid Monte-Carlo and molecular dynamics simulations are used to study the unexplored mechanical behavior of Cu-segregated nanocrystalline nanotwinned Ag.

Mechanical behavior of R tilt grain boundaries in nanoscale

of grain boundaries (GBs) under simple shear. The energetics and mechanical strength of 18 R Æ110æ symmetric tilt GBs and two R Æ110æ asymmetric tilt GBs are investigated in Cu and Al. Special emphasis is placed on the evolution of far-field shear stresses under applied strain and related deformation mechanisms at zero temperature.

Void-dynamics in nano-wires and the role of microstructure

solves electromigration at the global scale (entire interconnect), and a 2D local model simulates void dynamics considering the impact of elec-tron wind, void surface energy, and stress gradients. The role of copper texture, i.e., grain boundaries, grain orientation and anisotropic proper-ties is thoroughly investigated.

Dynamics of Nanoscale Grain-Boundary Decohesion in Aluminum

The dynamics and energetics of intergranular crack growth along a flat grain boundary in aluminum is studied by a molecular-dynamics simulation model for crack propagation under steady-state conditions. Using the ability of the molecular-dynamics simulation to identify atoms

Slip of shuffle screw dislocations through tilt grain

Slip of shuffle screw dislocations through tilt grain boundaries in silicon Abstract In this paper, molecular dynamics (MD) simulations of the interaction between tilt grain boundaries (GBs) and a shuffle screw dislocation in silicon are performed. Results show that dislocations transmit into the neighboring grain for all GBs in silicon.

Molecular Dynamics Study of Uniaxial Deformation in Perfect

stress-strain curves obtained from the MD simulations agree well with those obtained by first principles calculations. The strength and ductility of Al decrease with the occurrence of void and grain boundaries. The effect of void size on the uniaxial stress-strain relations is investigated.

Experimental Observations of Stress-Driven Grain Boundary

recent theories of coupled grain boundary migration (13,14)and confirming that grain boundaries are not static structures as traditionally assumed. It is widely acknowledged that shear stresses drive dislocation motion. The motion of low-angle grain boundaries, which consist of dislo-cation arrays, under shear stress can be described

Molecular dynamics study on the atomic mechanisms of coupling

Recent research has revealed that some grain boundaries (GBs) can migrate coupled to applied shear stress. In this paper, molecular dynamics (MD) simu-lations were performed on sixteen [0 0 1] symmetric tilt GBs of bicrystal Cu to identify atomic-scale GB migration mechanisms and investigate their depen-dence on GB structure.

Ductile vs. brittle fracture

effect of stress concentrationat microscopic flaws. The applied stress is amplified at the tips of micro-cracks, voids, notches, surface scratches, corners, etc. that are called stress raisers. The magnitude of this amplification depends on micro-crack orientations, geometry and dimensions. Stress Concentration Figure by N. Bernstein & D. Hess, NRL

The Behavior of Copper Nanoparticle Chain Aggregates under

0.344 respectively, while the maximum stress is close to 4 GPa (strain rate: 0.625 m/s). Both structures fail at the low-angle grain boundaries developed during the sintering process, while the higher strain for fracture for the kinked configuration is associated with interface sliding not observed in the linear case. INTRODUCTION

Thermodynamics of coherent interfaces under mechanical

terize mechanical, mechanochemical, thermomechanical and thermochemical responses of the boundary. In Sec. V,we summarize our work and draw conclusions. II. THERMODYNAMICS OF GRAIN BOUNDARIES A. Grain-boundary symmetry considerations When the grains separated by a GB are stress free, they are thermodynamically identical and form a single-phase

Molecular dynamics (MD) simulation of uniaxial tension of

formulation to perform MD simulations on systems under external stress. Using this method, they applied uniaxial stress to a FCC cubic lattice (Ni) with periodic boundary conditions at 350K. Under uniaxial compression, they suggested a transformation in the crystal structure from FCC to HCP. The maximum tensile strength under uniaxial tension

Structure and motion of junctions between coherent and

The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal anneal-ing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent R ¼ 3½110ð 112Þ twin boundary (ITB), pinned between two R ¼ 3½110ð 111Þ twin boundaries, is

Molecular Dynamics Simulation of Ga Penetration along Al

penetrates along the grain boundaries with and without an applied stress. The simulation study proposed a mechanism of LME and clarified how it is affected by applied stresses. The interplay of stress and Ga penetration leads to the nucleation of a train of dislocations on the grain boundary below the liquid groove root which climbs down the grain

Molecular Dynamics Simulation of Ga Penetration along Grain

applied stress, the rate at which Ga penetrates down the grain boundary (slope in Fig. 2) gradually decreases with time. However, when stress is applied, the Ga penetration rate becomes nearly time independent. Clearly, stress changes the fundamental nature of Ga penetration down grain boundaries in Al: the constant Ga penetration rate

Tuning the mechanical properties of silicene nanosheet by

of a great importance to investigate the mechanical behavior of silicene under applied strain. Even though the pristine structure of silicene has a very high fracture strength,28,29 fracture toughness of silicene is signi -cantly lower than most of the conventional engineering mate-rials.30 This offers a challenge in the fabrication of silicene

Stress-driven migration of simple low-angle mixed grain

We investigated the stress-induced migration of a class of simple low-angle mixed grain boundaries (LAMGBs) using a combination of discrete dislocation dynamics simulations and analytical arguments. The migration of LAMGBs under an externally applied stress can

Continuum mesoscale modelling of nanocrystalline fcc metals

with Hall-Petch grain size dependence and Steinbe rg-Guinan pressure dependence of the ow stress for slip activation; b) for grain boundaries: isotropic viscoplasticity with ow stress independent of grain size, and Mohr-Coulomb pressure dependence. The length-scale of the problem is given by the GB thickness, taken to be 1 nm.

A phase-field model of stress effect on grain boundary migration

We studied the migration of planar and curved grain boundaries under an applied stress. The relation between grain boundary migration velocity and driving force is found to be linear in the steady-state regime. Our study shows that the stress distribution depends on the relative misorientation between the grains and the nature of the applied load.

Twin-size effects on the deformation of nanotwinned copper

and interface motion under applied mechanical loading. We present here studies of dislocation and interface motion in single crystal and nanotwinned copper, utilizing molecular dynamics simulations. Motion of twin boundary interfaces themselves is dictated by the stress state at the interface, and is found to be maximum for

Molecular Dynamics Simulation on 5 Grain Boundaries of Copper

Molecular Dynamics simulation are employed to investigate the structures and mechanical behavior of both symmetric and asymmetric ∑5[0 0 1] tilt grain boundaries (GBs) of copper bicrystal under uniaxial tension and shear deformation. Simulation results indicate that

Lattice shearing in nano-grained graphene sheets: a molecular

and the atomic behavior in grain boundaries is crucial to mechanical deformation in nanocrystalline graphene sheets. In this paper, a set of three-grain models are established and molecular dynamics (MD) simulation is carried out to investi-gate mechanical deformation near GBs under tensile loading.

Disconnection description of triple-junction motion

Atomistic simulation permits an examination of grain growth free of any of the normal grain growth theory assumptions described above. We performed MD simulations of polycrys-talline embedded atom method nickel (84) in an NPT ensemble (Nos`e Hoover thermostat) at 1,200 K ( ˘0:85T m) under zero external stress.

Self-healing of Radiation Damage by Coupled Motion of Grain

FIG. 2: Demonstration of the self-healing mechanism. A threshold stress for activation of the grain boundary motion is decreased with introduction of the interstitials into the grain boundary. The grain boundary migrates under an applied stress. It sweeps vacancies on its way up, leaving behind clean material without the defects. The top and

Shear Properties of Graphene Containing Nitrogen Atoms and

[3], grain boundaries (GBs) [4] and heteroatoms [5]. It is crucial to clarify the relations between those defects and the mechanical properties of graphene to develop high-performance carbon fibers. Carbon fibers derived from raw materials often contain impurities such as oxygen, nitrogen, or hydrogen atoms, and

Molecular dynamics simulation of fracture behaviors of 110

Abstract: Molecular dynamics (MD) simulations were carried out to study the fracture behaviors of several symmetric tilt grain boundaries in γ-TiAl bicrystals with 〈110〉 misorientation axes. Tensile deformation along direction perpendicular to grain boundary was simulated under various strain rates and temperatures.