Micro Scale Laser Shock Processing of Metallic Components

TLDR

Laser shock processing of copper with a ~10‑µm focused laser beam is investigated to impart beneficial residual stress distributions and improve fatigue life. The study models micro‑scale shock pressure, strain, and stress at high strain rates and ultrahigh pressures, and validates numerical solutions against measured plastic deformation geometry and in‑depth strain profiles on copper surfaces. Validated models show that micro‑scale laser shock can tailor residual stress distributions, with effects modulated by shock location and spacing, and the technique is applicable to MEMS micro‑gears and can complement laser micromachining to mitigate machining‑induced residual stresses.

Abstract

Laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material. Shock pressure and strain/stress are properly modeled to reflect the micro scale involved, and the high strain rate and ultrahigh pressure involved. Numerical solutions of the model are experimentally validated in terms of the geometry of the shock-generated plastic deformation on target material surfaces as well as the average in-depth strains under various conditions. The residual stress distributions can be further influenced by shocking at different locations with certain spacing. The potential of applying the technique to micro components, such as micro gears fabricated using MEMS is demonstrated. The investigation also lays groundwork for possible combination of the micro scale laser shock processing with laser micromachining processes to offset the undesirable residual stress often induced by such machining processes.