Multiscale calculation based on dual domain material point method combined with molecular dynamics
Abstract
This dissertation combines the dual domain material point method (DDMP) with molecular dynamics (MD) in an attempt to create a multiscale numerical method to simulate materials undergoing large deformations with high strain rates. In these types of problems, the material is often in a thermodynamically nonequilibrium state, and conventional constitutive relations are often not available. In this method, the closure quantities, such as stress, at each material point are calculated from a MD simulation of a group of atoms surrounding the material point. Rather than restricting the multiscale simulation in a small spatial region, such as phase interfaces, or crack tips, this multiscale method can be used to consider nonequilibrium thermodynamic e ects in a macroscopic domain. This method takes advantage that the material points only communicate with mesh nodes, not among themselves; therefore MD simulations for material points can be performed independently in parallel. First, using a onedimensional shock problem as an example, the numerical properties of the original material point method (MPM), the generalized interpolation material point (GIMP) method, the convected particle domain interpolation (CPDI) method, and the DDMP method are investigated. Among these methods, only the DDMP method converges as the number of particles increases, but themore »
 Authors:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Publication Date:
 Research Org.:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1345173
 Report Number(s):
 LAUR1721607
 DOE Contract Number:
 AC5206NA25396
 Resource Type:
 Technical Report
 Country of Publication:
 United States
 Language:
 English
 Subject:
 74 ATOMIC AND MOLECULAR PHYSICS
Citation Formats
Dhakal, Tilak Raj. Multiscale calculation based on dual domain material point method combined with molecular dynamics. United States: N. p., 2017.
Web. doi:10.2172/1345173.
Dhakal, Tilak Raj. Multiscale calculation based on dual domain material point method combined with molecular dynamics. United States. doi:10.2172/1345173.
Dhakal, Tilak Raj. Mon .
"Multiscale calculation based on dual domain material point method combined with molecular dynamics". United States.
doi:10.2172/1345173. https://www.osti.gov/servlets/purl/1345173.
@article{osti_1345173,
title = {Multiscale calculation based on dual domain material point method combined with molecular dynamics},
author = {Dhakal, Tilak Raj},
abstractNote = {This dissertation combines the dual domain material point method (DDMP) with molecular dynamics (MD) in an attempt to create a multiscale numerical method to simulate materials undergoing large deformations with high strain rates. In these types of problems, the material is often in a thermodynamically nonequilibrium state, and conventional constitutive relations are often not available. In this method, the closure quantities, such as stress, at each material point are calculated from a MD simulation of a group of atoms surrounding the material point. Rather than restricting the multiscale simulation in a small spatial region, such as phase interfaces, or crack tips, this multiscale method can be used to consider nonequilibrium thermodynamic e ects in a macroscopic domain. This method takes advantage that the material points only communicate with mesh nodes, not among themselves; therefore MD simulations for material points can be performed independently in parallel. First, using a onedimensional shock problem as an example, the numerical properties of the original material point method (MPM), the generalized interpolation material point (GIMP) method, the convected particle domain interpolation (CPDI) method, and the DDMP method are investigated. Among these methods, only the DDMP method converges as the number of particles increases, but the large number of particles needed for convergence makes the method very expensive especially in our multiscale method where we calculate stress in each material point using MD simulation. To improve DDMP, the subpoint method is introduced in this dissertation, which provides high quality numerical solutions with a very small number of particles. The multiscale method based on DDMP with subpoints is successfully implemented for a one dimensional problem of shock wave propagation in a cerium crystal. The MD simulation to calculate stress in each material point is performed in GPU using CUDA to accelerate the computation. The numerical properties of the multiscale method are investigated as well as the results from this multiscale calculation are compared of particles needed for convergence makes the method very expensive especially in our multiscale method where we calculate stress in each material point using MD simulation. To improve DDMP, the subpoint method is introduced in this dissertation, which provides high quality numerical solutions with a very small number of particles. The multiscale method based on DDMP with subpoints is successfully implemented for a one dimensional problem of shock wave propagation in a cerium crystal. The MD simulation to calculate stress in each material point is performed in GPU using CUDA to accelerate the computation. The numerical properties of the multiscale method are investigated as well as the results from this multiscale calculation are compared with direct MD simulation results to demonstrate the feasibility of the method. Also, the multiscale method is applied for a two dimensional problem of jet formation around copper notch under a strong impact.},
doi = {10.2172/1345173},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Feb 27 00:00:00 EST 2017},
month = {Mon Feb 27 00:00:00 EST 2017}
}

For problems involving large material deformation rate, the material deformation time scale can be shorter than the material takes to reach a thermodynamical equilibrium. For such problems, it is difficult to obtain a constitutive relation. History dependency become important because of thermodynamic nonequilibrium. Our goal is to build a multiscale numerical method which can bypass the need for a constitutive relation. In conclusion, multiscale simulation method is developed based on the dual domain material point (DDMP). Molecular dynamics (MD) simulation is performed to calculate stress. Since the communication among material points is not necessary, the computation can be done embarrassinglymore »

Shock waves simulated using the dual domain material point method combined with molecular dynamics
Here in this work we combine the dual domain material point method with molecular dynamics in an attempt to create a multiscale numerical method to simulate materials undergoing large deformations with high strain rates. In these types of problems, the material is often in a thermodynamically nonequilibrium state, and conventional constitutive relations or equations of state are often not available. In this method, the closure quantities, such as stress, at each material point are calculated from a molecular dynamics simulation of a group of atoms surrounding the material point. Rather than restricting the multiscale simulation in a small spatial region,more » 