Laser Peen Bending: Simultaneous Shaping and Property Enhancement

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Micro scale laser peen bending (LPB) combines the fatigue performance enhancement effects of laser shock processing with a controlled bending deformation to shape micro scale metallic parts without hard tooling nor external forces. Process conditions under which compressive residual stress is generated at both the irradiated and opposite surfaces of the target will be better understood. Interactions between residual stress generation and bending mechanism will be investigated. The anisotropic behavior of the material and the length scale effect on material properties will be considered since the laser-material in teraction zone is in the same order of magnitude as material grain size. Single crystal FCC metals (Al and Cu) will be used to investigate the anisotropic material response. Spatially resolved characterization of induced residual stresses will be carried out using X ray micro diffraction techniques, and the degrees of plastic deformation and geometrically necessary dislocation (GND) distributions will be measured by Electron Backscatter Diffraction (EBSD). These results will be used to validate the modeling and simulation efforts, in which, an explicit finite element analysis for shock dynamic effects on single crystals will be developed, based on meso-scale single crystal plasticity incorporating the pressure dependent elastic moduli and dynamic hardening caused by length scale.The established principles including anisotropy, hardening from length scale, and process dynamics, and developed techniques for LPB can be extended to other micro-scale manufacturing processes. Expected results will help micro manufacturing processes to make higher quality micro components more effectively and flexibly. The significantly improved understanding of process capability and limitations will open up opportunities for new micro part designs. Personnel development and dissemination of results will improve national competitiveness in micro manufacturing.