RESUMEN
In this paper, residual stress and plastic deformation of TC4 titanium alloys and AA7075 aluminum alloys after laser shock peening (LSP) with the laser pulses that have the same energy and peak intensity but different time profiles have been studied. The results show that the time profile of the laser pulse has a significant influence on LSP. The difference between the results of LSP with varying laser input mode has been contributed to the shock wave caused by different laser pulse. In LSP, the laser pulse with a positive-slope triangular time profile could induce a more intense and deeper residual stress distribution in metal targets. Residual stress distribution changing with laser time profiles suggests that shaping the laser time profile is a potential residual stress control strategy for LSP. This paper comprises the first step of this strategy.
RESUMEN
In this study, stress wave and damage morphology on the rear surface of silica during laser induced damage with cumulative UV pump shots is investigated. Time resolved imaging system, along with stress induced birefringence detecting, is used to demonstrate the development of stress wave. The properties of three types of stress waves, namely, compressive wave (P-wave), shear wave (S-wave), and Rayleigh wave (R-wave) are recorded and studied during the damage process. The experimental and simulated results indicated that R-wave exhibits the highest intensity among all the three stress waves. Because the R-wave is mainly localized at the region near the surface, it is responsible for the mechanical damage along the surface; in addition, it rapidly increases the damage diameter, which was observed from the front view of the damage.
RESUMEN
The liquid crystal spatial light modulator (SLM) is an effective active beam-shaping device through adjusting each pixel transmittance to improve the spatial beam quality of the output laser, which can also be used as a binary optical element (BOE) with each pixel transmittance 0 or 1 to realize spatial beam shaping for high-power lasers. We present and demonstrate an efficient shaping method of the SLM used as BOE based on diffraction principle. The method can be used to control the output nearfield actively by compensating the spatial nonuniformity of transmission and amplification in the high-power laser system. Results show the output nearfield beam quality improves significantly after shaping by using this method with the fluence contrast changing from 22% to 11.3% within only two shots in the single-shot operation laser.