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Concept
Laser peening
Résumé
Laser peening (LP), or laser shock peening (LSP), is a surface engineering process used to impart beneficial residual stresses in materials. The deep, high-magnitude compressive residual stresses induced by laser peening increase the resistance of materials to surface-related failures, such as fatigue, fretting fatigue, and stress corrosion cracking. Laser shock peening can also be used to strengthen thin sections, harden surfaces, shape or straighten parts (known as laser peen forming), break up hard materials, compact powdered metals and for other applications where high-pressure, short duration shock waves offer desirable processing results.
Initial scientific discoveries towards modern-day laser peening began in the early 1960s as pulsed-laser technology began to proliferate around the world. In an early investigation of the laser interaction with materials by Gurgen Askaryan and E.M. Moroz, they documented pressure measurements on a targeted surface using a pulsed laser. The pressures observed were much larger than could be created by the force of the laser beam alone. Research into the phenomenon indicated the high-pressure resulted from a momentum impulse generated by material vaporization at the target surface when rapidly heated by the laser pulse. Throughout the 1960s, a number of investigators further defined and modeled the laser beam pulse interaction with materials and the subsequent generation of stress waves. These, and other studies, observed that stress waves in the material were generated from the rapidly expanding plasma created when the pulsed laser beam struck the target. Subsequently, this led to interest in achieving higher pressures to increase the stress wave intensity. To generate higher pressures it was necessary to increase the power density and focus the laser beam (concentrate the energy), requiring that the laser beam-material interaction occur in a vacuum chamber to avoid dielectric breakdown within the beam in air.
Source officielle
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