Time shaping of laser pulses for Laser Shock Peening technology

Abstract:

Laser Shock Peening (LSP) is a multidisciplinary process that lies at the intersection of laser physics, plasma physics, and materials engineering. It uses high-energy nanosecond laser pulses to generate compressive residual stresses in metallic materials. These materials are then characterized by longer fatigue life and generally higher resistance to cracks of all kinds.

In the LSP process, the laser pulse is focused by a lens onto the target material, where it is rapidly absorbed. This creates a rapidly expanding plasma, which leads to the formation of a strong pressure wave propagating through the material. The time course of the pulse plays a crucial role in the absorption of the pulse and the formation of plasma. By choosing the appropriate pulse shape, we can, for example, achieve higher power density limits, which results in higher generated pressure and thus a more efficient process.

The state-of-the-art experimental laser system Bivoj, located at the HiLASE center, serves this purpose. Using variable voltage on Pockels cells, Bivoj enables advanced laser pulse shaping, from basic shapes such as Gaussian, rectangular, and triangular to more complex shapes such as double pulses.

The aim of the work is to utilize the possibility of time shaping Bivoje pulses in the LSP process and to determine the relationship between the pulse shape and the achievable processing parameters. The main output should then be an optimized laser pulse shape that could be used in future LSP experiments.

The LSP effect of selected pulse shapes will be evaluated by means of residual stresses generated in the material, which will be measured using an X-ray diffractometer and a drill. At the same time, the influence of the pulse shape on the degree of plastic deformation of the sample surface will also be measured.

During the work, the student will become familiar with the process of pulse shaping in detail and is expected to actively participate in working with the Bivoj laser system and in evaluating the results of the experiment.

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