구리 단결정의 나노 압입 실험 및 전산해석

Abstract

This thesis investigates deformation behaviors of Cu single crystals such as the indentation size effect (ISE), hardening behaviors, and pile-up pattern experimentally during nanoindentation. The experiment that has been used in the deformation behaviors analysis of Cu single crystal can be largely divided into two as simple compression and nanoindentation. The numerical simulation is formulated based on the phenomenological crystal plasticity hardening model and implemented into the user subroutines of the commercial finite element program ABAQUS. The time integration of the constitutive model uses the fully implicit backward Euler method. The simple compression experiment are performed in Cu single crystals with (100), (110) and (111) crystallograhpic orientation and compared with the crystal plasticity finite element (CPFEM) results. The deformed shape, hardening response, and rotation of crystallographic orientation of the Cu single crystal are presented using the INSTRON 8521 and the electron backscattered diffraction (EBSD) system. The macroscopic shape changes are explained by the slip system. The experimental resultants presented in this paper are reasonably good agreement as well as numerical results. This shows the validity of the current constitutive modeling at the single crystal level. The nanoindentation experiment are conducted in three different crystallographic orientations, i.e., (100), (110) and (111), by using a three different indenter tips (Vikers, Berkovich, Conical). The MTS Nano Indenter Xp system and VEECO Dimension 3100 was used for the elastic modulus- displacement relationship, the hardness-displacement relationships, and the surface topography near the nanoindents. The scattering of the elastic modulus in Cu single crystal is due to the thermal drift effect. The ISE of Cu single is characterized by various parameters such as the indentation depth, geometry of the indenter tips and the crystallographic orientations and analysed by the strain gradient model. The pile-up patterns observed near the nanoindents are measured by atomic force microscopy (AFM). These surface deformation patterns explained by the crystallographic slip systems. The resultant of nanoindentation reflects the crystallographic orientation. It also display the crystallographic orientation of material has more strong influence on the nanoindentation results than the loading components such as the azimutal orientation, the geometry of the indenter tips.