Concept of laser peening

Fatigue life comparison of parts

(laser peening vs. shot peening and machined)

The goal of this project area is to provide a complete physical understanding of the laser peening process and to develop a comprehensive predictive model, which will enable optimization of the process to achieve desired residual stress specifications. Specific objectives of the research include:

• Study the fundamentals of laser-material-plasma interaction during laser peening processes.
• Develop comprehensive predictive modeling capability for laser peening processes.
• Find operating conditions that globally optimize the process in order to:
  • maximize laser peening rate
  • achieve desired residual stress distributions.
• Study the laser peening mechanism for various workpiece materials.
• Develop guidelines to determine materials for which laser peening is best suited.
• Develop an economic analysis of laser peening against current practice.

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The study of laser shock peening at Purdue is based on the simultaneous experimental and numerical investigation of the process. The experiments are performed using a ns solid state laser integrated with a positioning system.   Modeling efforts aim at developing a comprehensive predictive model, which allows the prediction of residual stress profiles in terms of laser operating parameters, coating material and thickness, and workpiece material, while accounting for the existing stress distribution.   This allows the underlying physics to be determined while increasing the laser shock peening knowledge-base.

Research Progress:

• A comprehensive 1D thermal model of laser peening process has been developed.   The model is capable of predicting plasma pressure, laser-plasma interaction, electron densities, etc. (figures in the top row below)
• The water breakdown plasma phenomenon has been successfully modeled.   This can provide the limit of laser peening processes in terms of laser power.
• A 3D finite element modeling procedure of predicting residual stresses with given plasma recoil pressure has been developed.  This can provide the resultant residual stress distributions (figure in bottom row below)
• Laser-based monitoring techniques are being developed to monitor various conditions such as plasma plume size, plasma temperature and electron density during laser shock peening processes.

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National Science Foundation
Purdue Research Foundation
Indiana 21st Century Research and Technology
Industrial partners