| 摘要 |
PROBLEM TO BE SOLVED: To improve fatigue strength by imparting curvature to a metal plate and performing shot peening for a curvature part of the metal plate so as to load bending stress as preload. SOLUTION: A marageing steel belt 12 is made as a material to be processed, a portion to be processed is delivered by rotating rollers 9, 10, 11 and the whole of the belt 12 is processed. A preload level is determined by plate thickness and a radius R2 of the roller 10. A shot 7 is projected to a curvature part of this belt from a nozzle 8 on the roller 10 and shot peening is performed. Because of preload due to bending, compressive residual stress can be concentrated near a surface as compared with preload due to tension. Because a limit of preload due to this bending is determined by yield stress, compressive residual stress can be increased by performing a surface hardening processing capable of increasing yield stress of a surface part.
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