A MOLECULAR DYNAMICS-CONTINUUM CONCURRENT MULTISCALE MODEL FOR QUASI-STATIC NANOSCALE CONTACT PROBLEMS

2012 ◽  
Vol 10 (4) ◽  
pp. 307-326 ◽  
Author(s):  
Tianxiang Liu ◽  
Peter Wriggers ◽  
Geng Liu
Keyword(s):  
Molecular Dynamics ◽  
Contact Problems ◽  
Multiscale Model

Molecular Dynamics and Multiscale Simulations of Nanoindentation and Nanoscratch

2010 ◽  
Author(s):  
Peng-zhe Zhu ◽  
Hui Wang ◽  
Yuan-zhong Hu
Keyword(s):  
Molecular Dynamics ◽  
Computational Cost ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Md Simulations ◽  
System Size ◽  
Multiscale Simulations ◽  
First Case ◽  
Chip Volume ◽  
Indenter Shape

Three-dimensional molecular dynamics (MD) simulations have been performed to investigate behaviors of nanoindentation and nano-scratch. The first case concerns the effects of material defect on the nanoindentation of nickel thin film. The defect is modeled by a spherical void embedded in the substrate and located under the surface of indentation. The simulation results reveal that compared to the case without defect, the presence of the void softens the material and allows for larger indentation depth at a given load. MD simulations are then performed for nano-scratch of single crystal copper, with emphasis on the effect of indenter shape (sharp and blunt) on the substrate deformation. The results show that the blunt indenter causes larger deformation region and much more dislocations at both the indentation and scratch stages. It is also found that during the scratching stage the blunt indenter results in larger chip volume in front of the indenter and gives rise to more friction than the sharp indenter. The scope of the simulations has been extended by introducing a multiscale model which couples MD simulations with Finite Element Method (FEM), and multiscale simulations are performed for two-dimensional nanoindentation of copper. The model has been validated by well-consistent load-depth curves obtained from both multiscale and full MD simulations, and by good continuity of deformation observed in the handshake region. The simulations also reveal that indenter radius and indentation velocity significantly affect the nanoindentation behavior. By use of multiscale method, the system size to be explored can be greatly expanded without increasing much computational cost.

scholarly journals Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

2021 ◽  
Author(s):  
Daniele Savio ◽  
Jannik Hamann ◽  
Pedro A. Romero ◽  
Christoph Klingshirn ◽  
Ravindrakumar Bactavatchalou ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Contact Mechanics ◽  
Adsorbed Water ◽  
Multiscale Model ◽  
Md Simulations ◽  
Constitutive Law ◽  
Multiscale Approach ◽  
Friction Coefficients ◽  
Ether Ether Ketone ◽  
Poly Ether Ether Ketone

Abstract This work elucidates friction in Poly-Ether-Ether-Ketone (PEEK) sliding contacts through multiscale simulations. At the nanoscale, non-reactive classical molecular dynamics (MD) simulations of dry and water-lubricated amorphous PEEK-PEEK interfaces are performed. During a short running-in phase, we observe structural transformations at the sliding interface that result in flattening of the initial nanotopographies accompanied by strong polymer chain alignment in the shearing direction. Our MD simulations reveal a linear pressure-dependence of the shear stress τMD (P,σH2o) [MPa]=0.18P + 50.5 - 1.25σH2o, where σH2o [nm-2] is the surface number density of adsorbed water molecules. This constitutive law is of central importance for our multiscale approach, since it forms a link between MD and elastoplastic contact mechanics calculations. An integration of τMD (P,σH2o) over the real area of contact yields a macroscopic friction coefficient μmacro (σH2o) that allows for a meaningful comparison with friction coefficients μexp≈0.5-0.7 which are in good agreement with the calculated dry friction coefficients μmacro(σH2o=0).For milder experimental loads, our multiscale model suggests that the lower friction states with μexp≈0.2 originate in the presence of physisorbed molecules (e.g. water), which significantly reduce interfacial adhesion.

Finite-Temperature Multiscale Simulations for 3D Nanoscale Contacts

2016 ◽  
Vol 846 ◽  
pp. 288-293 ◽  
Author(s):  
Jie Zhang ◽  
Liang Zhang ◽  
Ahn Kiet Tieu ◽  
Guillaume Michal ◽  
Hong Tao Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Finite Element ◽  
Contact Area ◽  
Finite Temperature ◽  
Multiscale Model ◽  
Area Ratio ◽  
Multiscale Simulations ◽  
Mean Square ◽  
Temperature Analysis ◽  
Contact Area Ratio

A finite-temperature analysis of a multiscale model, which couples finite element and molecular dynamics, is presented in this paper. The model is evaluated by the patch test and demonstrates its capacity. Then, the multiscale scheme is used to study 3D nanoscale contacts. The linear relationship between the contact area ratio and load is observed at small loads, but the temperature effect is small. However, the change in the root mean square (RMS) of heights depends on the temperature at high loads.

Multiscale modeling of organic-inorganic interface: From molecular dynamics simulation to finite element modeling

2012 ◽  
Vol 1466 ◽  
Author(s):  
Denvid Lau ◽  
Oral Büyüköztürk ◽  
Markus J. Buehler
Keyword(s):  
Molecular Dynamics ◽  
Finite Element ◽  
Adhesive Bonding ◽  
Multiscale Model ◽  
Inorganic Materials ◽  
Dynamics Simulation ◽  
Structural Behavior ◽  
Zone Model ◽  
Material Systems ◽  
Separation Relation

ABSTRACTBi-layer material systems are found in various engineering applications ranging from nanoscale components, such as thin films in circuit boards, to macroscale structures, such as adhesive bonding in aerospace and civil infrastructure. They are also found in many natural and biological materials such as nacre or bone. The structural integrity of a bi-layer system depends on properties of both the interface and the constitutive materials. In particular, interfacial delamination has been observed as a major integrity issue. Here we present a multiscale model, which can predict the macroscale structural behavior at the interface between organic and inorganic materials, based on a molecular dynamics (MD) simulation approach combined with the metadynamics method used to reconstruct the free energy surface (FES) between attached and detached states of the bonded system. We apply this technique to model an epoxy-silica system that primarily features non-bonded and non-directional van der Waals and Coulombic interactions. The reconstructed FES of the epoxy-silica system derived from the molecular level is used to quantify the traction-separation relation at epoxy-silica interface. In this paper, two different approaches in deriving the traction-separation relation based on the reconstructed FES are described. With the derived traction-separation relation, a finite element approach using cohesive zone model (CZM) can be implemented such that the structural behavior of epoxy-silica interface at the macroscopic length scale can be predicted. The prediction from our multiscale model shows a good agreement with experimental data of the interfacial fracture toughness. The method used here provides a powerful new approach to link nano to macro for complex heterogeneous material systems.

A Comparison of Coupling Molecular Dynamics to General Finite Elements

2009 ◽  
Author(s):  
Michael F. Macri
Keyword(s):  
Molecular Dynamics ◽  
Finite Element ◽  
Finite Elements ◽  
Finite Element Methods ◽  
Continuum Model ◽  
Partition Of Unity ◽  
Multiscale Model ◽  
Moving Least Squares ◽  
Interpolation Functions ◽  
The Continuum

In this paper, we assess the ability of three interpolation functions in a discretized continuum model to capture and accurately represent the solution. In particular we examine the differences between the partition of unity, moving least squares and finite element methods in the continuum part of the multiscale model.

scholarly journals A multiscale model linking ion-channel molecular dynamics and electrostatics to the cardiac action potential

2009 ◽  
Vol 106 (27) ◽  
pp. 11102-11106 ◽  
Author(s):  
J. R. Silva ◽  
H. Pan ◽  
D. Wu ◽  
A. Nekouzadeh ◽  
K. F. Decker ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Action Potential ◽  
Ion Channel ◽  
Multiscale Model ◽  
Cardiac Action Potential ◽  
Cardiac Action
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