Improvement of Laser Induced Residual Stress Distributions via Shock Waves

Laser materials processing normally induces a certain residual stress distribution in the target material. Distributions favoring microcrack propagation lead to reduced fatigue life of the material. This paper investigates the feasibility of altering the stress field by using underwater shock waves in the micron scale. Shock pressure was computed and the stress analysis was conducted, in which both pressure and strain rate dependence of the plastic deformation was considered. It was shown that laser induced underwater shock waves could impart compressive stresses about 40 microns into metallic materials such as aluminum when a 12 micron laser beam was used. Experimental results of shock processing and its combination with drilling at micron scale are also presented.