Characterization of nanoporous silver mechanical properties by molecular dynamics simulation
Authors: Li Jie-Jie  , Lu Bin-Bin  , Xian Yue-Hui  , Hu Guo-Ming  , Xia Re  ,   Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China;,   Hubei Key Laboratory of Waterjet Theory and New Technology, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China
Published: December 2020

Nanoporous metals (NPMs) have great potential applications in many technological areas, such as catalysis, sensing, actuation, and fuel cells, because of their unique physical and chemical properties. The cognition of related mechanical properties is one of the important bases for achieving functionalized applications. A series of large-scale molecular dynamics (MD) simulations is performed to study the mechanical properties of nanoporous sliver (NPS) under uniaxial tension. Three different topology architectures of NPS, including cube, gyroid and diamond structures, are constructed and investigated. The effects of topology architecture and relative density on the mechanical properties are discussed. The LAMMPS is used to perform MD simulations and the embedded atom method potential is utilized to describe the interatomic interactions. The applied strain rate is 109 s-1 and the applied strain increment is 0.001 in each loading step. The results show that the plastic properties of NPS mainly depend on those of ligaments and the breakage of NPS mainly occurs in ligament areas. Meanwhile, the gyroid structure has better plasticity than other structures, due to the existence of ligament in spiral form. For one structure, the ultimate strength and the Young's modulus increase with the increase of relative density. Analysis shows that the basic mechanical properties of NPS largely depend on the relative density, similar to those of porous materials. The modulus as a function of relative density displays a power-law relation and the exponents depend on the topology architectures. The exponents of three structures are in a range between 1 and 2, showing that the bending of ligament and the tension of ligament are both included during the deformation. The variation trends of modulus of diamond and gyroid structures are similar to the variation of relative density, whose possible reason is that diamond and gyroid structures are both constructed by triply periodic minimal surfaces. With the same relative density, the modulus of diamond structure is in good agreement with that of gyroid structure, and the modulus of cube structure is the minimum. The strength shows a linear relation with the relative density, indicating that the yielding behavior of NPS is dominated by the axial yielding of ligament. When three types of NPSs have the same relative density, the strength of diamond structure is the maximum, cube structure second, and gyroid structure is the minimum. In diamond structure NPS, the structure of triangular framework is formed between ligaments, resulting in a relatively higher strength. The present study will provide an atomistic insight into the understanding of deformation mechanisms of nanoporous metals, and it will provide data support for designing NPMs with optimal mechanical properties by controlling geometric structure.