| 摘要 |
PROBLEM TO BE SOLVED: To enhance the internal pressure fatigue strength of the portion of the interior wall of a rail hole around the opening of a branch hole. SOLUTION: Residual compression stresses are produced at the penetration area 15A of the branch hole 15 in the peripheral wall 12 of a rail body 10 and at surrounding areas by imparting radial pressures thereto from a branching cylinder part 13 while receiving the penetration area 15A from its inside by means of a core 27 inserted into the hollow of the rail body 10, prior to penetration of the branch hole 15. Since the residual compression stresses are produced at the penetration area 15A of the branch hole 15 in the peripheral wall 12 and the surrounding areas, tensile stresses caused by the internal pressure of pressurized fuel are restrained by the residual compression stresses at the portion of the interior wall of the rail body 10 around the opening of the branch hole 15 to enhance the internal pressure fatigue strength. |
