Laser Shock Processing (LSP) When a metallic target is irradiated by an intense (>1 GW/cm2) laser pulse, the surface layer instantaneously vaporizes into a high temperature and high pressure (1~10 GPa) plasma. This plasma induces shock waves during expansion from the irradiated surface, and mechanical impulses are transferred to the target. If the plasma is not confined, i.e., in open air, the pressure can only reach several tenth of one GPa. If it is confined by water or other media, the shock pressure can be magnified by a factor of 5 or more compared with the open-air condition. At the same time, the shock pressure lasts 2 to 3 times longer than the laser pulse duration. In most LSP a coating is used to protect the target from thermal effects so that nearly pure mechanical effects are induced. The coating could be metallic foil, organic paints or adhesives. These coatings can modify the surface loading transmitted to the substrate by acoustic impedance mismatch effects at the coating-substrate interface, and an additional 50% increase in the peak stress values can be achieved. Pressures above 1 GPa are above the yield stress of most metals, thus plastic deformation can be induced. As a result, if the peak shock pressure is over the HEL (Hugoniot Elastic Limit) of the target material for a suitable time duration, compressive stress distribution in the irradiated volume can be formed.Quicktime animation of laser shock processing
Parameters Al, preexist hole Cu, flat plate Stress: Mises movie movie Stress: S11 movie movie Stress: S22 movie movie Stress: S33 movie movie Strain: E11 movie movie Strain: E22 movie movie Strain: E33 movie movie Note: Mises stress is defined as equivalent yield stress of metal:
Sij is defined as ij component of Stress. Eij is the ij component of strain.
To better understand what is laser shock process and interpret the results, please take a look at the explanation in detail...
An example of Quicktime movie of Mises stress during laser shock processing