Atomistic simulation of deformation under extreme loading conditions

• Main Author: Sharuz Farooque Rahmatullah
• Other Authors: Upadrasta Ramamurty
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials; Engineering::Mechanical engineering; Engineering::Manufacturing
• Online Access: https://hdl.handle.net/10356/140877
• Institution: Nanyang Technological University

Shot Peening (SP) and Laser Shock Peening (LSP) are two processes used to improve the fatigue life of a component. One of the most prominent differences between them is that they operate over very different timescales. Past experimental data and observation showed that the LSP process produces more planar dislocation structures as compared to SP, where the process produces shear bands and dislocation structures which are more multi-directional in nature. The reason for this vast difference in the dislocation structure has been hypothesized to be due to the difference in strain rates. Although there have been many studies, experiments and simulations were done to understand the differences in deformation mechanisms due to strain rate, this is something that is still not well understood. This project simulates the effects of LSP by performing molecular dynamics simulations of shock loading on pure Nickel to help develop an understanding of plasticity at high strain rates deformation during laser shock peening. The simulations are carried out using LAMMPS and the results are visualised using OVITO. From the simulations, it was found that different strain rates showed a vast difference in the dislocation patterns. Shock is applied to the metal by applying an impact with a surface at a specified velocity. The strain rates were varied by changing the impact velocity of the sample. There were 2 simulations with different impact velocities with the same strain rate which showed a completely different result. Therefore, impact velocity could also be theorised to be a significant factor.