Application of Parallel Molecular Dynamics Simulation to Nano-Indentation Tests

• Main Authors: Chen-Lai Lim, 林敬淶
• Other Authors: Chang-Hung Kuo
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/27204088657300334365

碩士 === 國立暨南國際大學 === 土木工程學系 === 98 === In this study, a parallel molecular dynamics simulation is applied to investigate the effects of sample size, indentation depth and the radius of indenter tip on the nanoindentation measurement of monocrystalline copper. The indenter is assumed rigid and the periodic boundary conditions are set along the X and Y-directions of the model. The initial velocity for each atom is assigned by using the Gaussian random generator, and the Morse potential is used to model the interaction forces between the Cu - Cu atoms and C - Cu atoms. The Gear’s fifth predictor-corrector algorithm is used to calculate the displacement, velocity and acceleration for the atoms at each time step. The hardness and Young’s modulus are calculated by using the simulated loading-unloading curve during the indentation process and the Oliver-Pharr theory. Numerical results show that the system temperature can be raised during the simulation by the boundaries of the model. For the smaller size of the model, the temperature increments appear higher during the nano-indentation test. The results show that, for the size of the model smaller than 45.6x45.6x12.3nm3, a readjustment of the system temperature is needed for a certain time steps while the adjustment is only needed in the initial equilibrium when the size of the model is greater than 45.6x45.6x12.3nm3. In addition, a cone indenter with 60 degree angle and a Berkovich indenter are employed to study the effect of indentation depth and radius of indenter tip on the hardness and Young’s modulus. The results show that both planar size and thickness could affect the measurement of hardness and Young’s modulus. In general, the substrate effect becomes more evident as the indentation depth is over 10% of sample thickness.