Objective: Develop a model for the distribution of the residual stress generated by laser shot peening on a metallic alloy, and identify this model using spatially resolved synchrotron X-ray diffraction measurements.

Context: Laser shot peening (LSP) is a process that introduces compressive residual stresses into the surface of a material or a structure in order to improve its fatigue resistance. The process involves focusing a pulsed, high-energy laser beam (several joules) onto the metallic specimen. The laser spot is a few millimeters in diameter while the pulse lasts for about ten nanoseconds, resulting in a huge power density of the order of GW/cm2. The interaction between the laser beam and the material produces a plasma, the confined expansion of which induces a pressure wave in the material (Figure 1(a)). Pressures in the material can be as high as several hundred GPa, enabling the process to be used to discover unknown crystallographic phases, for example in the interior of planets. In our application of  LSP  to  metallic  materials,  the  pressure  is  voluntarily  limited  to  several  GPa  so  that  the  wave propagation leads to local plastic deformation of the specimen, at a huge strain-rate (106s-1  or even more),  ultimately  resulting  in  a  heterogeneous  field  of  residual  stress  once  static  equilibrium  is reached.

Contact 

Olivier Castelnau 

olivier.castelnau@ensam.eu

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