| 摘要 |
PURPOSE:To correct out-of-roundness of a pipe of unknown material strength at high accuracy and with minute pipe expanding by providing a displacement meter in the circumferential direction of the end part of piping and determining yield load of the pipe from expanding load and displacement of the pipe during pipe expanding. CONSTITUTION:Signals from sensors 8 installed at four places in the circumferential direction of a pipe 14 are received by an arithmetic section 9, and the initial shape of the pipe 14 is stored in a memory section 10. When a piston 12 is pulled by a hydraulic power source 11, the internal pressure is generated in the pipe 14, and the load and displacement of the pipe 14 are recorded in a recording section 10 by the arithmetic section 9 in terms of relation between the load and displacement. In repeating this operation, a time comes when a fixed proportional relation between the load and displacement of the pipe 14 is lost as the internal pressure grows larger. This load and yield load are determined. Next, a load up to 1.1 times as large as the yield load is given by moving the piston 12. At this time, the internal pressure of the pipe 14 becomes 1.1 times as large as the yield load. The external load that has restrained the maximum deformed part of the pipe 14 is removed at this point of time. Thereafter, pipe expanding is completed by increasing the cylinder load up to 1.3-1.4 times as large as the yield load. When the load is removed, the pipe becomes true circle. |
