小型可搬型レーザーピーニング装置による金属材料の残留応力および疲労特性の改善

Abstract

The advantage of laser peening is the possibility of fine execution management and the capability to introduce deep compressive residual stresses on the material surfaces. It is well known to be highly effective in inhibiting stress corrosion cracking and fatigue cracking on material surfaces. In addition, laser peening has an excellent effect on improving the fatigue strength of welds, which compensates for the disadvantage of high strength steels when welded. Laser peening has a high potential for enhancing material surface, but the high-power laser used requires clean room facilities, large equipment and severe operating conditions. Therefore, the application of the laser peening has been limited to the mitigation of high cycle fatigue of jet engine fan blades and stress corrosion cracking of nuclear reactor structures. If microchip lasers, which are small and easy to handle, could be used as a light source for laser peening, it would be possible to apply them not only to production processes in factories but also to existing structures such as bridges, airplanes, etc. to which conventional lasers have been difficult to apply for the above reasons. In this presentation, we report the results of the laser peening treatment of A7075 (aluminum alloy) and HT780 (high strength steel) with the laser pulse energy of less than 10 mJ. Even at such a low pulse energy, compressive residual stress was imparted and fatigue properties were improved.