Expansion dynamics of the plume induced by a doughnut laser beam under the rigid confinement layer

Laser shock peening (LSP) utilizes laser-induced shock wave pressure to enhance the surface properties of metal sheets. This study simulates the plume expansion from a doughnut laser beam between a rigid confinement layer and an aluminum target, analyzing the resulting shock wave pressure distribution. The influence of the laser beam's inner and outer diameters, fluence distribution, and fluence magnitude is explored through numerical simulations. It is found that the self-interaction of the doughnut beam generates complex pressure fields, leading to multiple, time-varying shock wave pressure peaks on the target surface. The number, magnitude, and location of these peaks are significantly influenced by the inner diameter of the doughnut beam, as well as the distribution and magnitude of its fluence. Additionally, asymmetric fluence distribution results in distinct plume interactions and pressure profiles. The findings suggest that these pressure peaks can be controlled by adjusting the beam parameters.