| 摘要 |
PURPOSE:To regulate a shot peening condition in an extremely accurate manner, by attaching a C ring elastically to a pipe inner surface, while measuring a variation in a distance between the gauge marks put to this C ring before and after performing the shot peening to a pipe. CONSTITUTION:Each of three C rings 41-43 removing a part of an annular body having an outer diameter little larger than an inner diameter of a pipe 1 is elastically attached to an inner surface of the pipe 1. Next, a variation in a distance between a two-piece-set pair of gauge marks put to these C rings 41-43 before and after performing the shot peening to the pipe 1 is measured by an optical type displacement measuring instrument 7 being set outward a pipe end. On the basis of this measured value, a shot peening condition optimum to give the extent of depth of a compressed residual stress layer to be formed in and round a pipe outer end of a setting part of each of these C rings 41-43 of the pipe 1 is regulated, so that variations in quality of a product as the pipe being subject to the shot peening can be made smaller.
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