Chapter 9 - Temperature- and rate-dependent indentation size effects and material length scales

Abstract

This chapter addresses the temperature and rate indentation size effects (TRISE) encountered in nanoindentation experiments and the corresponding material intrinsic length scales at different strain rates. The same value for the material length scale cannot be used for different rate, temperature, and accumulated plastic-strain conditions. A variable length scale is introduced in this chapter. This chapter also addresses the hardening effect in close proximity of a grain boundary during nanoindentation experiments. Indentation experiments are performed on single-crystal, bicrystal, and polycrystalline samples for various metals at different strain rates. The existing theories describing the indentation size effects and length scales are reviewed, and a physically based model that depends on strain rate, accumulated plastic strain, and temperature that were scaled with hardness experiments results is proposed for length scales. Furthermore, numerical simulations are performed by using the ABAQUS software and a physically based viscoplasticity constitutive model.