A basic study for application of laser peening to large-scale steel structure

Abstract

Laser peening can introduce compressive residual stress to the surface and therefore is effective in enhancing fatigue strength. In this study, we conducted laser peening in air with a water film formed by a nozzle and examined whether the distribution of residual stress along the thickness was different from that achieved by laser peening in water in our previous studies. We also assessed the resultant residual stress and fatigue life when the pulse energy was reduced for developing a simple method to conduct laser peening on large structures. Compressive residual stress equivalent to that observed after laser peening in water was obtained in nozzle-type laser peening in terms of magnitude and depth. With the reduction of pulse energy, it was observed that the depth of the compressive residual stress tended to decrease significantly and the fatigue life also tended to reduce. The results indicate that the depth of the compressive residual stress has a considerable effect on the fatigue life of welded structures as well as the magnitude of the surface residual stress.

Keywords::

• laser peening
• residual stress
• fatigue life
• box-welded joint

Acknowledgements

A part of this study was assisted by a subvention from ‘2009 Seed Unearthing’ and ‘2010 and 2011 Research Results Optimal Development Support Project Feasibility Study (FS) Stage’ programmes of the Japan Science and Technology (JST) Agency, and we wish to express our profound gratitude for this.

Notes

Presented at the Welded Structures Symposium, November 2011.