材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
論文
パルスレーザ照射による疲労き裂進展抑制に関する研究
稲田 健司荒井 正行伊藤 潔洋横田 博紀水津 竜夫
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2020 年 69 巻 10 号 p. 733-739

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It is required to establish a technique for repairing a cracked structural component as well as for evaluating precisely crack initiation life in a main component of land-based gas turbine. It is known that the weld overlay technique is one of repairing processes and is widely applied to aged components in thermal power plants. However, the aged combustor in gas turbine has been replaced with a new one. Expensive alloys such as cobalt based and nickel-based super alloys have been used, which lead to increase of maintenance cost. This gave us motivation to develop an alternative repairing process, fiber laser process, to repair a fatigue crack initiated at the edge of stress concentrated part in thin-walled structures. In this study, residual stress is induced by irradiating a laser ahead of fatigue crack tip, and the delaying effect of residual stress on crack propagation rate is then evaluated. SUS 304 plate specimen with a hole was prepared and fatigue loading was enforced to induce natural cracks at the edge of the hole. Then, the area ahead of crack tip was irradiated by fiber laser and fatigue crack propagation behavior was examined. It was clarified that fatigue crack propagation rate was delayed to approach the laser irradiated area. It was confirmed that tensile residual stress was formed in the laser irradiated area by a hole drilling method. As a result, it was proven that fiber laser can be used as the advanced repairing process to repair a fatigue crack.

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