IMPROVING FOR RESIDUAL STRESS CONDITION ON INNER SURFACE OF SMALL-APERTURE PIPE

摘要

PROBLEM TO BE SOLVED: To reduce tensile residual stress evolved by machining the inner surface of a small-aperture pipe. SOLUTION: So called, the water jet peening method is employed to improve a residual stress state. Where, a cavitation bubbles-containing high-speed water flow is injected from a nozzle at the interior of a small-aperture pipe filled with water, and the cavitation bubbles are collapsed at the vicinity of the inner surface of the small-aperture pipe. The method employs the nozzle having a collision angle between the inner surface of the small-aperture pipe and the high-speed water flow of within the range of 10 to 20 degrees and a distance between the nozzle injection hole and the collided inner surface is within the range of 1/2 to 5 times the diameter of the injection nozzle.