Some damages were found at the forks of low pressure turbine blades caused by random vibration and steam-flashback vibration. In this study, for the aim of fatigue property improvement, laser peening technology for 12Cr stainless steel was developed and material properties were examined. Laser peening is a process to induce compressive residual stress to the material surface. Fatigue specimens which simulate the stress concentration zone of forks were fabricated and laser peening was applied to the su...
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Development of laser peening technology for low pressure turbine blades to improve fatigue properties

We confirmed the defect detection performance of the eddy current testing (ECT) system in order to inspect the bottom-mounted instrumentation (BMI) nozzle in reactor pressure vessel. We developed the small size cross coil type ECT sensor that has the magnetic cores near the coils and the sensor scanning equipment based on the portable laser peening system. According to the experimental results that measured the sensitivity for the defects on the concave specimen and the relationship between the senso...
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Development of Eddy Current Testing System for Bottom-Mounted Instrumentation Nozzle in Reactor Pressure Vessel

We confirmed the defect detection performance of the eddy current testing (ECT) system in order to inspect the bottom-Mounted instrumentation (BMI) nozzle in reactor pressure vessel. We developed the small size cross coil type ECT sensor that has the magnetic cores near the coils and the sensor driving unit based on the portable laser peening system. According to the experimental result that measured the relationship between the sensor inclined angle and defect detecting sensitivity on the convex surfa...
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Development of Eddy Current Testing System for Bottom-Mounted Instrumentation Nozzle in Reactor Pressure Vessel

Multifunction laser welding head has been developed. The head is able to perform not only underwater laser welding as repair, but also laser peening as preventi ve maintenance and laser ultrasonic testing as inspection. Laser transmission test with multifunction laser welding head and optical fiber was carried out. The result showed that laser power needed for welding was transmitted without any damage to them. Under water laser welding onto EDM slits with this welding head w as carried out. EDM slits were...
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Development of Multifunction Laser Welding Head (1) - Evaluation of Under Water Laser Welding with Multifunction Laser Welding Head -

Multifunction laser welding head has been developed. The head is able to perform not only underwater laser welding as repair, but also laser peening as preventive maintenance and laser ultrasonic testing as inspection. By using the effect of color aberration with optics, laser beam was focused to the ideal spot size on each process. Laser p eening was performed on the material surface with the developed head, and stress improvement ability was confirmed....
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Development of Multifunction Laser Welding Head (2) - Stress Improvement by Laser Peening Technology -

Multifunction laser welding head has been developed. The head is able to perform not only underwater laser welding as repair, but also laser peening as preventive maintenance and laser ultrasonic test ing as inspection. For inspection with multifunction laser welding head, a new method of visualized weld defects in water by laser-ultrasonics has developed. To detect and visualize a surface of weld metal with welding bead, the authors have developed a new detection method by leaky wave induced by interactio...
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Development of Multifunction Laser Welding Head (3) - Surface Inspection Technique by Laser-ultrasonics -

Toshiba has developed various laser-based maintenance and repair technologies and already applied to nuclear power plants. Laser beam welding technology has been developed as an SCC cou ntermeasure for aged components in PWRs and BWRs. This technology can also be used underwater by blowing shielding gas for creating a local dry area. This welding equipment has damage d etecting function of optical elements such as windows and optical fiber cables, and the laser beam spot position and diameter can be adjust...
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Development of Underwater Laser Beam Welding Equipment