scholarly journals Anisotropic shock responses of nanoporous Al by molecular dynamics simulations

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0247172
Author(s):  
Xia Tian ◽  
Kaipeng Ma ◽  
Guangyu Ji ◽  
Junzhi Cui ◽  
Yi Liao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Molecular Dynamics Simulations ◽  
Dislocation Nucleation ◽  
Shape Evolution ◽  
Mechanical Responses ◽  
Slip Planes ◽  
Dynamics Simulations ◽  
Collapse Rate ◽  
Crystallographic Orientations

Mechanical responses of nanoporous aluminum samples under shock in different crystallographic orientations (<100>, <111>, <110>, <112> and <130>) are investigated by molecular dynamics simulations. The shape evolution of void during collapse is found to have no relationship with the shock orientation. Void collapse rate and dislocation activities at the void surface are found to strongly dependent on the shock orientation. For a relatively weaker shock, void collapses fastest when shocked along the <100> orientation; while for a relatively stronger shock, void collapses fastest in the <110> orientation. The dislocation nucleation position is strongly depended on the impacting crystallographic orientation. A theory based on resolved shear stress is used to explain which slip planes the earliest-appearing dislocations prefer to nucleate on under different shock orientations.

scholarly journals Shape Stability of Metallic Nanoplates: A Molecular Dynamics Study

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Xiwen Chen ◽  
Rao Huang ◽  
Tien-Mo Shih ◽  
Yu-Hua Wen
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Molecular Dynamics Simulations ◽  
Shape Evolution ◽  
Body Centered Cubic ◽  
Shape Stability ◽  
Subsequent Formation ◽  
Dynamics Simulations ◽  
Saddle Shape ◽  
Functional Versatility

AbstractMetallic nanoplates have attracted widespread interests owing to their functional versatility, which relies heavily on their morphologies. In this study, the shape stability of several metallic nanoplates with body-centered-cubic (bcc) lattices is investigated by employing molecular dynamics simulations. It is found that the nanoplate with (110) surface planes is the most stable compared to the ones with (111) and (001) surfaces, and their shapes evolve with different patterns as the temperature increases. The formation of differently orientated facets is observed in the (001) nanoplates, which leads to the accumulation of shear stress and thus results in the subsequent formation of saddle shape. The associated shape evolution is quantitatively characterized. Further simulations suggest that the shape stability could be tuned by facet orientations, nanoplate sizes (including diameter and thickness), and components.

scholarly journals Shear-rate dependence of thermodynamic properties of the Lennard-Jones truncated and shifted fluid by molecular dynamics simulations

2021 ◽  
Author(s):  
Martin P. Lautenschlaeger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Molecular Dynamics Simulations ◽  
Local Structure ◽  
Rate Dependence ◽  
Lennard Jones ◽  
Fluid Properties ◽  
Dynamics Simulations ◽  
Shear Rate Dependence

It was shown recently that using the two-gradient method, thermal, caloric, and transport properties of fluids under quasi-equilibrium conditions can be determined simultaneously from nonequilibrium molecular dynamics simulations. It is shown here that the influence of shear stresses on these properties can also be studied using the same method. The studied fluid is described by the Lennard-Jones truncated and shifted potential with the cut-off radius r*c = 2.5σ. For a given temperature T and density ρ, the influence of the shear rate on the following fluid properties is determined: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, shear viscosity η, and self-diffusion coefficient D. Data for 27 state points in the range of T ∈ [0.7, 8.0] and ρ ∈ [0.3, 1.0] are reported for five different shear rates (γ ̇ ∈ [0.1,1.0]). Correlations for all properties are provided and compared with literature data. An influence of the shear stress on the fluid properties was found only for states with low temperature and high density. The shear-rate dependence is caused by changes in the local structure of the fluid which were also investigated in the present work. A criterion for identifying the regions in which a given shear stress has an influence on the fluid properties was developed. It is based on information on the local structure of the fluid. For the self-diffusivity, shear-induced anisotropic effects were observed and are discussed.

Dislocation Nucleation and Propagation During Deposition of Cubic Metal Thin Films

2001 ◽  
Vol 677 ◽  
Author(s):  
W. C. Liu ◽  
Y. X. Wang ◽  
C. H. Woo ◽  
Hanchen Huang
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Three Dimensional ◽  
Thin Film Deposition ◽  
Dislocation Nucleation ◽  
Film Deposition ◽  
Film Material ◽  
Metal Thin Films ◽  
Dynamics Simulations

ABSTRACTIn this paper we present three-dimensional molecular dynamics simulations of dislocation nucleation and propagation during thin film deposition. Aiming to identify mechanisms of dislocation nucleation in polycrystalline thin films, we choose the film material to be the same as the substrate – which is stressed. Tungsten and aluminum are taken as representatives of BCC and FCC metals, respectively, in the molecular dynamics simulations. Our studies show that both glissile and sessile dislocations are nucleated during the deposition, and surface steps are preferential nucleation sites of dislocations. Further, the results indicate that dislocations nucleated on slip systems with large Schmid factors more likely survive and propagate into the film. When a glissile dislocation is nucleated, it propagates much faster horizontally than vertically into the film. The mechanisms and criteria of dislocation nucleation are essential to the implementation of the atomistic simulator ADEPT.

Molecular Dynamics Simulations of Dislocation Nucleation From Bicrystal Interfaces in FCC Metals

Materials ◽  
2005 ◽  
Author(s):  
Douglas E. Spearot ◽  
Karl I. Jacob ◽  
David L. McDowell
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Tensile Deformation ◽  
Dislocation Nucleation ◽  
Atomistic Simulations ◽  
Structural Units ◽  
Fcc Metals ◽  
Deformation Response ◽  
Dynamics Simulations

Atomistic simulations are used to study dislocation nucleation from &lt;001&gt; tilt bicrystal interfaces in copper subjected to a tensile deformation. Specifically, three interface misorientations are examined, including the Σ5 (310) interface, which has a high density of coincident atomic sites. The initial interface configurations, which are discussed in terms of structural units, are refined using energy minimization techniques. Molecular dynamics simulations are then used to deform each interface in tension. The role of boundary conditions and their effect on the inelastic deformation response is discussed in detail. Molecular dynamics simulations show that the interface structural units are directly involved in the partial dislocation nucleation process. The maximum tensile strength of the Σ5 (310) interface shows a modest increase in the case where lateral confinement of the interface is an important consideration.

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