Establishment of relationships to evaluate mechanical properties of material by indentation: numerical simulation based approach

Abstract

In this study, new relationships are established to predict the mechanical properties of the material such as Young’s modulus, yield strength, residual strain, fatigue strength and hardness numbers. The resistance of a material to deformation, indentation, or penetration by means such as abrasion, drilling, impact, scratching, or wear is measured by hardness or indentation tests. Hardness is a characteristic of a material, not a fundamental physical property. The indentation test can be carried out in macro (10⁻³), micro (10⁻⁶), and nano (10⁻⁹) scales according to the specimen sizes. Three-dimensional (3D) and axisymmetric (2D) nonlinear Finite Element (FE) simulations are used to represent the macro and nano- indentation. ABAQUS software is selected as the FE simulation platform. This study contains two main parts: (1) numerical simulation of macro-indentation and (2) numerical simulation of nano-indention. In structural health monitoring, detecting the material properties of damaged members of structures is a key item. At present, we need to conduct a series of laboratory tests to detect a set of material properties of a target material sample. It is difficult to find a single test that can be used to detect important material properties. The main focus of the first part of this study is to develop a macro- indentation testing method for evaluation of mechanical properties of metals based on numerical simulation of macro-indentation. When we consider the Nano-indentation, it leads to identifying the hardness properties of micro and nanoscale objects such as thin films, integrated circuits (IC) and, etc. The pile-up or sink-in effects can be observed in both macro and nano-indentation, which depends on the strain hardening coefficient of the target material sample. This pile-up or sink-in effect cannot be neglected in the nano- level as it obtains a considerable change of volume relative to the specimen dimensions. This leads to errors when extracting the hardness number and material properties. There are no direct relationships between the pile-up or sink-in effect and mechanical properties in nano-scale. The main focus of the second part of this study is to understand the behavior of the pile-up effect on nano-indentation by using 2D and 3D numerical simulations.