Abstract

Molecular dynamic simulations of defect nanosized beams of single-crystal Cu, loaded in displacement controlled tension until rupture, have been performed. The defects are square-shaped, through-the-thickness voids of different sizes, placed centrally in the beams. Three different cross section sizes and two different crystallographic orientations are investigated. As expected, the sizes of the beam cross section and the void as well as the crystal orientation strongly influence both the elastic and the plastic behaviors of the beams. It was seen that the strain at plastic initiation increases with beam cross section size as well as with decreasing void size. It is further observed that the void deformed in different ways depending on cross section and void size. Sometimes void closure, leading to necking of the beam cross section followed by rupture occurred. In other cases, the void elongated leading to that the two ligaments above and below the void ruptured independently.

Highlights

  • Since it is an experimentally verified fact that nanosized structures respond differently on mechanical loading than macroscopic structures of the same material, design and dimensioning of nanocomponents lack a solid ground corresponding to traditional dimensioning handbook rules at the macroscale

  • The reason for traditional engineering dimensioning rules becoming obsolete at small enough metric scales is that, with decreasing structural size, the number of surface close atoms as compared to number of bulk atoms increases and, at some point, no longer is negligible

  • The strain at plastic initiation, εi, the strain εmc at eventual closure of the mid-section of the void, the strain at eventual total void closure, εc and the strain at rupture were determined through monitoring the instantaneous CSP values for all atoms during the loading process

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Summary

Introduction

Nanotechnology provides applications in an increasing number of engineering fields, with tailor manufactured products for everyday use. The reason for traditional engineering dimensioning rules becoming obsolete at small enough metric scales is that, with decreasing structural size, the number of surface close atoms as compared to number of bulk atoms increases and, at some point, no longer is negligible. Electron redistribution close to the surfaces will leave the surface close atoms in energy states deviating from those of bulk atoms. This influences the interatomic bonding forces and, thereby, the material response to mechanical loading as discussed by e.g., [1–3]. This effect is accentuated if the atoms are placed at, or close to, corners and edges of the structure, e.g., [4]. The material properties will vary with size for small enough structures, and the effects become obvious below about 50–100 nm

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