Laser Shock Peening has shown in the past decades its efficiency over other techniques to enhance the fatigue resistance of parts. However, its use is still limited to certain applications as it is complex to implement (high-footprint, free-space propagation, sacrificial layer management).
In this publication, we introduce the Fibered Laser Shock Peening System (FLASP), which consists of a fiber coupling module, an optical head to focus the beam on the part, and an optical fiber to link both modules.
Energetic laser beam transmission through optical fibers requires specific beam shaping as it is necessary to suppress spatial profile modulations caused by speckle. For this matter, the spatial coherence of the beam was reduced in order to obtain a smooth circular beam profile at the fiber entrance. Such a setup made it possible to couple a record 380mJ in a 1.5mm core optical fiber which corresponds to a peak power of 63MW at a pulse duration of 6ns. Such energy levels have not damaged a 5m fiber for more than 50 million shots.
The FLASP system successfully treated aluminum, titanium and steel parts for which compression peaks reached -400MPa while the affected depth exceeded 1mm.
|