13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 3.4 Effect of thickness of water layer In experimental set-up (b), impact forces during laser shock peening process were obtained from detected AE waveforms by deconvolution technique, which is plotted in Fig. 12 as a function of water layer thickness. When the water layer was thinner than 2 mm, impact forces of laser irradiation and a bubble collapse were very small. Impact force by a bubble collapse showed the maximum value when thickness of water layer was 3-5 mm, while impact force by laser irradiation was a certain value. 4. Conclusions In the present study, the effect of water layer and temperature in laser shock peening was evaluated by AE method and high speed camera, and following conclusions were drawn; (1)Impacts were emitted by not only laser irradiation but also bubble collapsed. (2)Maximum radius of a cavitation bubble increases with temperature of water layer and has a linear relationship with AE event interval time in constant temperature. (3)Impact forces of laser irradiation are not affected by water temperature. Impact forces of bubble collapse decrease with increasing water temperature. The ratio of two impact forces due to laser ablation and bubble collapse decreases with increasing water temperature. (4)Impact forces by laser irradiation and bubble collapse have the maximum value at the of water layer thickness around 4 mm. Acknowledgement This work was partially supported by JSPS KAKENHI Grant Number 23246124. 0 5 10 15 20 0 2 4 6 8 10 12 Laser Ablation Bubble Collapse Impact Force [kN] Water layer thickness [mm] Figure 12. Relationship between water layer thickness and impact
RkJQdWJsaXNoZXIy MjM0NDE=