Multi-scale simulation study on the evolution of stress waves and dislocations in Ti alloy during laser shock peening processing

This study investigates the effect of laser shock peening (LSP) on the evolution of stress waves and dislocations in Ti-6Al-4V alloy by multi-scale simulation. The finite element model on the macroscale and molecular dynamics model on the microscale were built, and multi-scale simulations based on the finite element and molecular dynamics were performed. Under the high pressure on material induced by LSP, elastic deformation and plastic deformation are generated. With the increase of stress wave traveling distance, its intensity gradually decays. The stress wave in the material completely vanishes eventually. The macroscale simulation shows that the average velocity of the stress wave equals 6.0 km/s and does not change much with the loading pressure. The microscale simulation shows that the average velocity of the stress wave in single crystal α-Ti is in the range of 7.1∼7.8 km/s. The average velocity of stress wave in polycrystals is always lower than that in the single crystal and has a trend to decrease with the increase of grain number until a stable value of around 6.0 km/s. Considering the induced shock pressure, the piston velocity should be below 0.4 km/s to recreate the LSP process. This paper provides a comprehensive understanding of the effect of LSP on the evolution of stress waves and dislocations and also provides a new numerical method to further study laser shock peening processing.