Multi-Scale Modeling and Experimental Validation of Thermo-Mechanical Responses in Femtosecond Laser Micromachining of Copper.

Abstract

Femtosecond laser micromachining is a cornerstone of high-precision manufacturing, yet its multi-scale dynamics require a self-consistent bridging from atomic transitions to macroscopic morphology. This study establishes a multi-scale framework where Density Functional Theory (DFT) calculates temperature-dependent electronic thermal properties to inform both Two-Temperature Model-Molecular Dynamics (TTM-MD) and Finite Element Method (TTM-FEM) simulations. By comparing atomistic and macroscopic results, we systematically investigate the thermal-mechanical responses of copper ablation. The macroscopic TTM-FEM model, employing a removal criterion based on the enthalpy of vaporization, achieves high predictive accuracy for ablation depths in the low-to-medium power range up to 300 mW. However, a significant divergence at higher powers (>400 mW) highlights the physical transition from surface evaporation to phase explosion. Concurrently, the TTM-MD simulations provide microscopic insights into the transient temperature and stress evolution, establishing a physically synchronized link between atomic-scale dynamics and macroscopic results. This work defines the applicability boundaries of evaporation-based macroscopic models and provides a validated predictive tool for optimizing laser processing parameters in precision engineering.