Probabilistic Analysis and Design of HCP Nanowires: An Efficient Surrogate Based Molecular Dynamics Simulation Approach

Abstract

We investigate the dependency of strain rate, temperature and size on yield strength of hexagonal close packed (HCP) nanowires based on large-scale molecular dynamics (MD) simulation. A variance-based analysis has been proposed to quantify relative sensitivity of the three controlling factors on the yield strength of the material. One of the major drawbacks of conventional MD simulation based studies is that the simulations are computationally very intensive and economically expensive. Large scale molecular dynamics simulation needs supercomputing access and the larger the number of atoms, the longer it takes time and computational resources. For this reason it becomes practically impossible to perform a robust and comprehensive analysis that requires multiple simulations such as sensitivity analysis, uncertainty quantification and optimization. We propose a novel surrogate based molecular dynamics (SBMD) simulation approach that enables us to carry out thousands of virtual simulations for different combinations of the controlling factors in a computationally efficient way by performing only few MD simulations. Following the SBMD simulation approach an efficient optimum design scheme has been developed to predict optimized size of the nanowire to maximize the yield strength. Subsequently the effect of inevitable uncertainty associated with the controlling factors has been quantified using Monte Carlo simulation. Though we have confined our analyses in this article for Magnesium nanowires only, the proposed approach can be extended to other materials for computationally intensive nano-scale investigation involving multiple factors of influence.

Rebuilding the Strain Hardening at a Large Strain in Twinned Au Nanowires

“…A unique deformation behavior and strain hardening behavior are observed in the NT Au nanowires with θ = 54.47°. For this type of NT nanowires, the serrated stress increases to its maximum in a large strain range of 0.21 to 0.31, which is far away from the yield point, and then drops until failure, as indicated in Figure 4 c. In contrast, for the NT Au nanowires with θ = 0°, 19.47°, and 90°, the stress sharply drops beyond the ultimate strength until failure, as shown in Figure 4 a,b,d, which agrees well with what was generally observed in single nanowires [ 4 , 5 , 17 , 35 ] and NT Cu nanowires [ 14 , 15 ]. It is worth noting that this unique hardening behavior in the NT Au nanowires with θ = 54.47° is very different from that in NT nanowire with θ = 0° and θ = 90° where the strain hardening occurs in the initial stage of plastic deformation and before the first stress drop.…”

“…Moreover, the obvious torsion of sample can be found, which is a result of the migration of CTBs. The above atomic-scale analysis shows that strain softening in NT Au nanowires with θ = 19.47° is related to partial dislocation sliding controlled plastic deformation, which is just the plastic deformation mechanism for the single crystal nanowires with FCC lattice where the strain softening was observed [ 5 , 19 ].…”

“…However, although such nanowires fail at higher stresses, they may exhibit either limited or no strain hardening capability at all. For example, the whisker-like mechanical behavior, in which the stress strain curves indicate a sharp yield point, followed by severe strain-softening, is generally observed in the deformation of single crystalline metal nanowires, where dislocation or deformation twinning or lattice reorientation sustains the plastic deformation [ 5 , 6 , 7 , 8 ].…”

Probing the shear modulus of two-dimensional multiplanar nanostructures and heterostructures

“…Such development can help to bring about the much-needed impetus in the research of two-dimensional materials, which is often hindered due to the need for carrying out computationally expensive and time consuming simulations/ laboratory experiments and availability of interatomic potentials. Besides deterministic analysis of shear moduli, as presented in this paper, the efficient closed-form formulae could be an attractive option for carrying out uncertainty analysis [99][100][101][102][103][104] following a Monte Carlo simulation based approach.…”

Probing the Effective Young's Modulus of ‘Magic Angle’ Inspired Multi‐Functional Twisted Nano‐Heterostructures

“…Noteworthy feature of such an analytical framework is the inexpensive and computationally efficient nature compared to conducting molecular dynamics simulations or nano‐scale experiments. Besides in‐depth deterministic analysis of Young's moduli, as presented here, the efficient analytical approach could be an attractive alternative for performing uncertainty quantification, [ 54–56 ] which is increasingly getting recognized as one of the most crucial aspects of nano‐scale analyses.…”