Theory of Nanoindentation
Recent developments in science and technology have advanced the capability to fabricate and control materials and devices with nanometer grain/feature sizes to achieve better mechanical properties in materials and more reliable performance in microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) (Bhushan, 1999; Miller and Tadmor, 2002; Vashishta et al., 2003; Tambe and Bhushan, 2004; Liu et al., 2005; Jian et al., 2006). Nanoindentation instrument provides a valid approach to investigate the mechanical characterizations of nanomaterials, such as the hardness, dislocation motion, and Young’s modulus, which are required to design structural/functional elements in micro-and nanoscale devices. Many powerful capabilities in in situ and ex situ imaging, acoustic emission detection, and high-temperature testing are now being used to probe nanoscale phenomena such as defect nucleation and dynamics, mechanical instabilities or strain localization, and phase transformations (Wang et al., 2003; Aouadia, 2006; Schuh, 2006; Gouldstone et al., 2007; Lin et al., 2007; Snyders et al., 2007; Szlufarska et al., 2007). With the same pace of experimental work, analytical theory and computer simulation, especially the latter, are developed to reproduce or even predict the intrinsic
phenomena during nanoindentation (Vashishta et al., 2003; Szlufarska, 2006). Among these simulation methods, šrst principles calculations (FP) (Aouadia, 2006; Snyders et al., 2007), molecular dynamics (MD) (Noreyan et al., 2005; Liu et al., 2007), šnite element method (FEM) (Liu et al., 2005; Feng et al., 2007; Zhong and Zhu, 2008), and their hybrid methods such as šrst principle molecular dynamics (FPMD) (Schneider et al., 2007) and quasicontinuum method (QC) (Miller and Tadmor, 2002; Dupuy et al., 2005), from the trade-o£ between eÀciency and accuracy point of view, are mostly applied to investigate the evolution of structure and properties in di£erent spatial and temporal scales during nanoindentation.