| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for improving residual stress in a pipe inner surface by applying water jet peening to the pipe inner surface, and causing collapse of grown cavitation foam in the pipe inner surface, and to provide a device therefor. SOLUTION: The method is carried out by holding a pipe 40 having openings at both edges with a holding device 9, blocking one of the pipe edges, inserting an ejection nozzle 1 from the other pipe edge into the pipe, and ejecting a liquid fed to the ejection nozzle into the pipe via the ejection nozzle at an inclination of 9°or less with respect to an axis of the pipe, to thereby generate back-flow of the liquid ejected from the ejection nozzle, in the pipe. Thus the residual stress in the pipe inner surface is improved by impact pressure caused by collapse of the cavitation foam accompanying the liquid. According to the method a collision distance from a nozzle ejection hole to the pipe inner surface is set to a value equal to a distance of growth of the cavitation, and the grown cavitation is collided against the pipe inner surface. As a result, the impact pressure generated at the time of collapsing of the cavitation can be applied to the pipe inner surface, and therefore the residual stress in the pipe inner surface can be improved. COPYRIGHT: (C)2006,JPO&NCIPI
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