Discrete Dislocation Dynamics Simulations of Nanoindentation with Pre-stress: Hardness and Statistics of Abrupt Plastic Events

TL;DR

This study uses 2D discrete dislocation simulations to explore how tensile pre-stress influences nanoindentation hardness and the statistics of sudden plastic events in single crystals, revealing pre-stress effects at small indentation depths.

Contribution

It introduces a discrete dislocation model to analyze the impact of tensile pre-stress on nanoindentation hardness and plastic event statistics, highlighting the detection of plasticity at small depths.

Findings

Higher tensile pre-stress reduces measured hardness at small indentation depths.

Pre-stress has minimal effect on hardness at larger indentation depths.

Pre-stress influences the statistics of abrupt plastic events during nanoindentation.

Abstract

The yield surface in crystal plasticity can be approached from various directions during mechanical loading. We consider the competition between nanoindentation and tensile loading towards plastic yielding. For this purpose, we develop a two-dimensional discrete dislocation model that is then utilized to investigate the hardness and pop-in event statistics during nanoindentation of single crystal under tensile pre-stress. Indentation is performed by using cylindrical (circular in 2D) indentation with varying radius and under both displacement and load control. Tensile in-plane stress, varying from zero to yield strength, is assigned to investigate the effect of pre-stress on hardness and pop-in statistics. At small indentation depths, the measured hardness is found to be smaller for larger tensile pre-stress; therefore, we conclude that nanoindentation can be used to detect plasticity. When indentation depth is larger, the effect of pre-stress is barely seen. Moreover, we discuss event statistics and the related effect of pre-stress.