A Molecular Dynamics Simulations Study of the Influence of Prestrain on the Pop-In Behavior and Indentation Size Effect in Cu Single Crystals

Rong-Guang Xu,Hengxu Song,Yongsheng Leng,Stefanos Papanikolaou

doi:10.3390/ma14185220

Abstract

The pop-in effect in nanoindentation of metals represents a major collective dislocation phenomenon that displays sensitivity in the local surface microstructure and residual stresses. To understand the deformation mechanisms behind pop-ins in metals, large scale molecular dynamics simulations are performed to investigate the pop-in behavior and indentation size effect in undeformed and deformed Cu single crystals. Tensile loading, unloading, and reloading simulations are performed to create a series of samples subjected to a broad range of tensile strains with/without pre-existing dislocations. The subsequent nanoindentation simulations are conducted to investigate the coupled effects of prestrain and the presence of resulting dislocations and surface morphology, as well as indenter size effects on the mechanical response in indentation processes. Our work provides detailed insights into the deformation mechanisms and microstructure-property relationships of nanoindentation in the presence of residual stresses and strains.

Highlights

Nanoindentation is a widely used technique to investigate mechanical responses of small volumes of materials at micro- and nano-length scales [1]
The pioneering theoretical work dated back to 1998, when Nix and Gao explained Indentation size effect (ISE) by utilizing the concept of geometrically necessary dislocations (GND) to construct a mesoscale theory of strain-gradient plasticity based on the model of Taylor hardening [2]
We introduce the dislocations in nanoindentation samples through a very natural manner by uniaxial straining a face-centered cubic (FCC) single crystal Cu to the plastic regime

Summary

Introduction

Nanoindentation is a widely used technique to investigate mechanical responses of small volumes of materials at micro- and nano-length scales [1]. Subsequent MD simulations of nanoindentation investigated the mechanism of incipient plasticity in terms of the mutual interaction of the existing dislocations. Subsequent MD simulations of indentation are carried out to explore the coupled effects of prestrain, the presence of the resulting dislocations, and the indenter size on the nanoindentation response of the Cu single crystal.

Results

Conclusion