Effect of Pile-Up on the Mechanical Characteristics of Steel by Depth Sensing Indentation

Abstract

Mechanical properties by depth sensing indentation are derived from the indentation load-displacement data used a micromechanical model developed by Oliver & Pharr (O&P). However, O&P analysis on the indentation unloading curve is developed from a purely elastic contact mechanics (sink-in). The applicability of O&P analysis is limited by the materials pile-up. However, when it does, the contact area is larger than that predicted by elastic contact theory (material sinks-in during purely elastic contact), and both hardness H and Youngs modulus E are overestimated, because their evaluation depends on the contact area deduced from the load-displacement data. H can be overestimated by up to 60 % and E by up to 30 % depending on the extent of pile-up [1,2]. It is therefore important to determine the effect of pile-up on obtained mechanical characteristics of the material by depth sensing indentation. The work experimentally analyses the effect of pile-up height on mechanical characteristics H and E, which are determined by O&P analysis. Pile-up height was measured by atomic force microscopy (AFM).