scholarly journals Effect of Temperature on the Deformation Behavior of Copper Nickel Alloys under Sliding

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 60
Author(s):  
Stefan J. Eder ◽  
Philipp G. Grützmacher ◽  
Manel Rodríguez Ripoll ◽  
Daniele Dini ◽  
Carsten Gachot
Keyword(s):  
Microstructural Evolution ◽  
Large Scale ◽  
Mechanical Energy ◽  
Normal Pressure ◽  
Effect Of Temperature ◽  
Near Surface ◽  
Dislocation Activity ◽  
Deformation Response ◽  
Sliding Interface ◽  
Dynamics Simulations

The microstructural evolution in the near-surface regions of a dry sliding interface has considerable influence on its tribological behavior and is driven mainly by mechanical energy and heat. In this work, we use large-scale molecular dynamics simulations to study the effect of temperature on the deformation response of FCC CuNi alloys of several compositions under various normal pressures. The microstructural evolution below the surface, marked by mechanisms spanning grain refinement, grain coarsening, twinning, and shear layer formation, is discussed in depth. The observed results are complemented by a rigorous analysis of the dislocation activity near the sliding interface. Moreover, we define key quantities corresponding to deformation mechanisms and analyze the time-independent differences between 300 K and 600 K for all simulated compositions and normal pressures. Raising the Ni content or reducing the temperature increases the energy barrier to activate dislocation activity or promote plasticity overall, thus increasing the threshold stress required for the transition to the next deformation regime. Repeated distillation of our quantitative analysis and successive elimination of spatial and time dimensions from the data allows us to produce a 3D map of the dominating deformation mechanism regimes for CuNi alloys as a function of composition, normal pressure, and homologous temperature.

scholarly journals Elucidating the Onset of Plasticity in Sliding Contacts Using Differential Computational Orientation Tomography

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
S. J. Eder ◽  
P. G. Grützmacher ◽  
M. Rodríguez Ripoll ◽  
J. F. Belak
Keyword(s):  
Grain Boundary ◽  
Large Scale ◽  
Surface Deformation ◽  
Boundary Migration ◽  
Material Design ◽  
Lattice Rotation ◽  
Time Resolved ◽  
Near Surface ◽  
Color Saturation ◽  
Dynamics Simulations

Abstract Depending on the mechanical and thermal energy introduced to a dry sliding interface, the near-surface regions of the mated bodies may undergo plastic deformation. In this work, we use large-scale molecular dynamics simulations to generate “differential computational orientation tomographs” (dCOT) and thus highlight changes to the microstructure near tribological FCC alloy surfaces, allowing us to detect subtle differences in lattice orientation and small distances in grain boundary migration. The analysis approach compares computationally generated orientation tomographs with their undeformed counterparts via a simple image analysis filter. We use our visualization method to discuss the acting microstructural mechanisms in a load- and time-resolved fashion, focusing on sliding conditions that lead to twinning, partial lattice rotation, and grain boundary-dominated processes. Extracting and laterally averaging the color saturation value of the generated tomographs allows us to produce quantitative time- and depth-resolved maps that give a good overview of the progress and severity of near-surface deformation. Corresponding maps of the lateral standard deviation in the color saturation show evidence of homogenization processes occurring in the tribologically loaded microstructure, frequently leading to the formation of a well-defined separation between deformed and undeformed regions. When integrated into a computational materials engineering framework, our approach could help optimize material design for tribological and other deformation problems. Graphic Abstract .

Exploring secondary interactions and the role of temperature in moisture-contaminated polymer networks through molecular simulations

Soft Matter ◽  
2021 ◽  
Vol 17 (10) ◽  
pp. 2942-2956
Author(s):  
Rishabh D. Guha ◽  
Ogheneovo Idolor ◽  
Katherine Berkowitz ◽  
Melissa Pasquinelli ◽  
Landon R. Grace
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Temperature Variation ◽  
Polymer Networks ◽  
Molecular Simulations ◽  
Effect Of Temperature ◽  
Secondary Interactions ◽  
Dynamics Simulations ◽  
Secondary Bonding

We investigated the effect of temperature variation on the secondary bonding interactions between absorbed moisture and epoxies with different morphologies using molecular dynamics simulations.

scholarly journals Influence of the Upstream Terrain on the Formation of a Cold Frontal Snowband in Northeast China

2021 ◽  
Author(s):  
Na Li ◽  
Baofeng Jiao ◽  
Lingkun Ran ◽  
Zongting Gao ◽  
Shouting Gao
Keyword(s):  
Gravity Waves ◽  
Northeast China ◽  
Large Scale ◽  
Control Experiment ◽  
Vertical Motion ◽  
Near Surface ◽  
Inertial Instability ◽  
Two Factors ◽  
Negative Effect ◽  
Conditional Instability

AbstractWe investigated the influence of upstream terrain on the formation of a cold frontal snowband in Northeast China. We conducted numerical sensitivity experiments that gradually removed the upstream terrain and compared the results with a control experiment. Our results indicate a clear negative effect of upstream terrain on the formation of snowbands, especially over large-scale terrain. By thoroughly examining the ingredients necessary for snowfall (instability, lifting and moisture), we found that the release of mid-level conditional instability, followed by the release of low-level or near surface instabilities (inertial instability, conditional instability or conditional symmetrical instability), contributed to formation of the snowband in both experiments. The lifting required for the release of these instabilities was mainly a result of frontogenetic forcing and upper gravity waves. However, the snowband in the control experiment developed later and was weaker than that in the experiment without upstream terrain. Two factors contributed to this negative topographic effect: (1) the mountain gravity waves over the upstream terrain, which perturbed the frontogenetic circulation by rapidly changing the vertical motion and therefore did not favor the release of instabilities in the absence of persistent ascending motion; and (2) the decrease in the supply of moisture as a result of blocking of the upstream terrain, which changed both the moisture and instability structures leeward of the mountains. A conceptual model is presented that shows the effects of the instabilities and lifting on the development of cold frontal snowbands in downstream mountains.

scholarly journals Adsorption in Mixtures with Competing Interactions

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4532
Author(s):  
Marek Litniewski ◽  
Alina Ciach
Keyword(s):  
Short Range ◽  
Selective Adsorption ◽  
Similar Amount ◽  
Particle Interactions ◽  
Near Surface ◽  
Gas Density ◽  
Short Range Repulsion ◽  
Adsorbed Layers ◽  
Dynamics Simulations ◽  
Oppositely Charged

A binary mixture of oppositely charged particles with additional short-range attraction between like particles and short-range repulsion between different ones in the neighborhood of a substrate preferentially adsorbing the first component is studied by molecular dynamics simulations. The studied thermodynamic states correspond to an approach to the gas–crystal coexistence. Dependence of the near-surface structure, adsorption and selective adsorption on the strength of the wall–particle interactions and the gas density is determined. We find that alternating layers or bilayers of particles of the two components are formed, but the number of the adsorbed layers, their orientation and the ordered patterns formed inside these layers could be quite different for different substrates and gas density. Different structures are associated with different numbers of adsorbed layers, and for strong attraction the thickness of the adsorbed film can be as large as seven particle diameters. In all cases, similar amount of particles of the two components is adsorbed, because of the long-range attraction between different particles.

scholarly journals Properties of Steady Geostrophic Turbulence with Isopycnal Outcropping

2012 ◽  
Vol 42 (1) ◽  
pp. 18-38 ◽  
Author(s):  
G. Roullet ◽  
J. C. McWilliams ◽  
X. Capet ◽  
M. J. Molemaker
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Mechanical Energy ◽  
Baroclinic Instability ◽  
Three Dimensional ◽  
Primary Source ◽  
Eddy Diffusivity ◽  
Energy Cycle ◽  
Geostrophic Turbulence ◽  
Pv Gradient

Abstract High-resolution simulations of β-channel, zonal-jet, baroclinic turbulence with a three-dimensional quasigeostrophic (QG) model including surface potential vorticity (PV) are analyzed with emphasis on the competing role of interior and surface PV (associated with isopycnal outcropping). Two distinct regimes are considered: a Phillips case, where the PV gradient changes sign twice in the interior, and a Charney case, where the PV gradient changes sign in the interior and at the surface. The Phillips case is typical of the simplified turbulence test beds that have been widely used to investigate the effect of ocean eddies on ocean tracer distribution and fluxes. The Charney case shares many similarities with recent high-resolution primitive equation simulations. The main difference between the two regimes is indeed an energization of submesoscale turbulence near the surface. The energy cycle is analyzed in the (k, z) plane, where k is the horizontal wavenumber. In the two regimes, the large-scale buoyancy forcing is the primary source of mechanical energy. It sustains an energy cycle in which baroclinic instability converts more available potential energy (APE) to kinetic energy (KE) than the APE directly injected by the forcing. This is due to a conversion of KE to APE at the scale of arrest. All the KE is dissipated at the bottom at large scales, in the limit of infinite resolution and despite the submesoscales energizing in the Charney case. The eddy PV flux is largest at the scale of arrest in both cases. The eddy diffusivity is very smooth but highly nonuniform. The eddy-induced circulation acts to flatten the mean isopycnals in both cases.

scholarly journals Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth

2016 ◽  
Vol 34 (4) ◽  
pp. 041509 ◽  
Author(s):  
Daniel Edström ◽  
Davide G. Sangiovanni ◽  
Lars Hultman ◽  
Ivan Petrov ◽  
J. E. Greene ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Large Scale ◽  
Epitaxial Film ◽  
Film Growth ◽  
Dynamics Simulations ◽  
Epitaxial Film Growth
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